/* gtkconstraintlayout.c: Layout manager using constraints
* Copyright 2019 GNOME Foundation
*
* This library is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* License as published by the Free Software Foundation; either
* version 2.1 of the License, or (at your option) any later version.
*
* This library is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public
* License along with this library. If not, see .
*
* Author: Emmanuele Bassi
*/
/**
* GtkConstraintLayout:
*
* A layout manager using constraints to describe relations between widgets.
*
* `GtkConstraintLayout` is a layout manager that uses relations between
* widget attributes, expressed via [class@Gtk.Constraint] instances, to
* measure and allocate widgets.
*
* ### How do constraints work
*
* Constraints are objects defining the relationship between attributes
* of a widget; you can read the description of the [class@Gtk.Constraint]
* class to have a more in depth definition.
*
* By taking multiple constraints and applying them to the children of
* a widget using `GtkConstraintLayout`, it's possible to describe
* complex layout policies; each constraint applied to a child or to the parent
* widgets contributes to the full description of the layout, in terms of
* parameters for resolving the value of each attribute.
*
* It is important to note that a layout is defined by the totality of
* constraints; removing a child, or a constraint, from an existing layout
* without changing the remaining constraints may result in an unstable
* or unsolvable layout.
*
* Constraints have an implicit "reading order"; you should start describing
* each edge of each child, as well as their relationship with the parent
* container, from the top left (or top right, in RTL languages), horizontally
* first, and then vertically.
*
* A constraint-based layout with too few constraints can become "unstable",
* that is: have more than one solution. The behavior of an unstable layout
* is undefined.
*
* A constraint-based layout with conflicting constraints may be unsolvable,
* and lead to an unstable layout. You can use the [property@Gtk.Constraint:strength]
* property of [class@Gtk.Constraint] to "nudge" the layout towards a solution.
*
* ### GtkConstraintLayout as GtkBuildable
*
* `GtkConstraintLayout` implements the [iface@Gtk.Buildable] interface and
* has a custom "constraints" element which allows describing constraints in
* a [class@Gtk.Builder] UI file.
*
* An example of a UI definition fragment specifying a constraint:
*
* ```xml
*
* ```
*
* The definition above will add two constraints to the GtkConstraintLayout:
*
* - a required constraint between the leading edge of "button" and
* the leading edge of the widget using the constraint layout, plus
* 12 pixels
* - a strong, constant constraint making the width of "button" greater
* than, or equal to 250 pixels
*
* The "target" and "target-attribute" attributes are required.
*
* The "source" and "source-attribute" attributes of the "constraint"
* element are optional; if they are not specified, the constraint is
* assumed to be a constant.
*
* The "relation" attribute is optional; if not specified, the constraint
* is assumed to be an equality.
*
* The "strength" attribute is optional; if not specified, the constraint
* is assumed to be required.
*
* The "source" and "target" attributes can be set to "super" to indicate
* that the constraint target is the widget using the GtkConstraintLayout.
*
* There can be "constant" and "multiplier" attributes.
*
* Additionally, the "constraints" element can also contain a description
* of the `GtkConstraintGuides` used by the layout:
*
* ```xml
*
*
*
*
* ```
*
* The "guide" element has the following optional attributes:
*
* - "min-width", "nat-width", and "max-width", describe the minimum,
* natural, and maximum width of the guide, respectively
* - "min-height", "nat-height", and "max-height", describe the minimum,
* natural, and maximum height of the guide, respectively
* - "strength" describes the strength of the constraint on the natural
* size of the guide; if not specified, the constraint is assumed to
* have a medium strength
* - "name" describes a name for the guide, useful when debugging
*
* ### Using the Visual Format Language
*
* Complex constraints can be described using a compact syntax called VFL,
* or *Visual Format Language*.
*
* The Visual Format Language describes all the constraints on a row or
* column, typically starting from the leading edge towards the trailing
* one. Each element of the layout is composed by "views", which identify
* a [iface@Gtk.ConstraintTarget].
*
* For instance:
*
* ```
* [button]-[textField]
* ```
*
* Describes a constraint that binds the trailing edge of "button" to the
* leading edge of "textField", leaving a default space between the two.
*
* Using VFL is also possible to specify predicates that describe constraints
* on attributes like width and height:
*
* ```
* // Width must be greater than, or equal to 50
* [button(>=50)]
*
* // Width of button1 must be equal to width of button2
* [button1(==button2)]
* ```
*
* The default orientation for a VFL description is horizontal, unless
* otherwise specified:
*
* ```
* // horizontal orientation, default attribute: width
* H:[button(>=150)]
*
* // vertical orientation, default attribute: height
* V:[button1(==button2)]
* ```
*
* It's also possible to specify multiple predicates, as well as their
* strength:
*
* ```
* // minimum width of button must be 150
* // natural width of button can be 250
* [button(>=150@required, ==250@medium)]
* ```
*
* Finally, it's also possible to use simple arithmetic operators:
*
* ```
* // width of button1 must be equal to width of button2
* // divided by 2 plus 12
* [button1(button2 / 2 + 12)]
* ```
*/
/**
* GtkConstraintLayoutChild:
*
* `GtkLayoutChild` subclass for children in a `GtkConstraintLayout`.
*/
#include "config.h"
#include "gtkconstraintlayout.h"
#include "gtkconstraintlayoutprivate.h"
#include "gtkconstraintprivate.h"
#include "gtkconstraintexpressionprivate.h"
#include "gtkconstraintguideprivate.h"
#include "gtkconstraintsolverprivate.h"
#include "gtkconstraintvflparserprivate.h"
#include "gtkbuildable.h"
#include "gtkbuilderprivate.h"
#include "gtkdebug.h"
#include "gtklayoutchild.h"
#include "gtkintl.h"
#include "gtkprivate.h"
#include "gtksizerequest.h"
#include "gtkwidgetprivate.h"
#include
#include
enum {
MIN_WIDTH,
MIN_HEIGHT,
NAT_WIDTH,
NAT_HEIGHT,
LAST_VALUE
};
struct _GtkConstraintLayoutChild
{
GtkLayoutChild parent_instance;
int values[LAST_VALUE];
GtkConstraintRef *constraints[LAST_VALUE];
/* HashTable; a hash table of variables,
* one for each attribute; we use these to query and suggest the
* values for the solver. The string is static and does not need
* to be freed.
*/
GHashTable *bound_attributes;
};
struct _GtkConstraintLayout
{
GtkLayoutManager parent_instance;
/* A pointer to the GtkConstraintSolver used by the layout manager;
* we acquire one when the layout manager gets rooted, and release
* it when it gets unrooted.
*/
GtkConstraintSolver *solver;
/* HashTable; a hash table of variables,
* one for each attribute; we use these to query and suggest the
* values for the solver. The string is static and does not need
* to be freed.
*/
GHashTable *bound_attributes;
/* HashSet; the set of constraints on the
* parent widget, using the public API objects.
*/
GHashTable *constraints;
/* HashSet */
GHashTable *guides;
GListStore *constraints_observer;
GListStore *guides_observer;
};
G_DEFINE_TYPE (GtkConstraintLayoutChild, gtk_constraint_layout_child, GTK_TYPE_LAYOUT_CHILD)
GtkConstraintSolver *
gtk_constraint_layout_get_solver (GtkConstraintLayout *self)
{
GtkWidget *widget;
GtkRoot *root;
if (self->solver != NULL)
return self->solver;
widget = gtk_layout_manager_get_widget (GTK_LAYOUT_MANAGER (self));
if (widget == NULL)
return NULL;
root = gtk_widget_get_root (widget);
if (root == NULL)
return NULL;
self->solver = gtk_root_get_constraint_solver (root);
return self->solver;
}
static const char * const attribute_names[] = {
[GTK_CONSTRAINT_ATTRIBUTE_NONE] = "none",
[GTK_CONSTRAINT_ATTRIBUTE_LEFT] = "left",
[GTK_CONSTRAINT_ATTRIBUTE_RIGHT] = "right",
[GTK_CONSTRAINT_ATTRIBUTE_TOP] = "top",
[GTK_CONSTRAINT_ATTRIBUTE_BOTTOM] = "bottom",
[GTK_CONSTRAINT_ATTRIBUTE_START] = "start",
[GTK_CONSTRAINT_ATTRIBUTE_END] = "end",
[GTK_CONSTRAINT_ATTRIBUTE_WIDTH] = "width",
[GTK_CONSTRAINT_ATTRIBUTE_HEIGHT] = "height",
[GTK_CONSTRAINT_ATTRIBUTE_CENTER_X] = "center-x",
[GTK_CONSTRAINT_ATTRIBUTE_CENTER_Y] = "center-y",
[GTK_CONSTRAINT_ATTRIBUTE_BASELINE] = "baseline",
};
G_GNUC_PURE
static const char *
get_attribute_name (GtkConstraintAttribute attr)
{
return attribute_names[attr];
}
static GtkConstraintAttribute
resolve_direction (GtkConstraintAttribute attr,
GtkWidget *widget)
{
GtkTextDirection text_dir;
/* Resolve the start/end attributes depending on the layout's text direction */
if (widget)
text_dir = gtk_widget_get_direction (widget);
else
text_dir = GTK_TEXT_DIR_LTR;
if (attr == GTK_CONSTRAINT_ATTRIBUTE_START)
{
if (text_dir == GTK_TEXT_DIR_RTL)
attr = GTK_CONSTRAINT_ATTRIBUTE_RIGHT;
else
attr = GTK_CONSTRAINT_ATTRIBUTE_LEFT;
}
else if (attr == GTK_CONSTRAINT_ATTRIBUTE_END)
{
if (text_dir == GTK_TEXT_DIR_RTL)
attr = GTK_CONSTRAINT_ATTRIBUTE_LEFT;
else
attr = GTK_CONSTRAINT_ATTRIBUTE_RIGHT;
}
return attr;
}
GtkConstraintVariable *
gtk_constraint_layout_get_attribute (GtkConstraintLayout *layout,
GtkConstraintAttribute attr,
const char *prefix,
GtkWidget *widget,
GHashTable *bound_attributes)
{
const char *attr_name;
GtkConstraintVariable *res;
GtkConstraintSolver *solver = layout->solver;
attr = resolve_direction (attr, widget);
attr_name = get_attribute_name (attr);
res = g_hash_table_lookup (bound_attributes, attr_name);
if (res != NULL)
return res;
res = gtk_constraint_solver_create_variable (solver, prefix, attr_name, 0.0);
g_hash_table_insert (bound_attributes, (gpointer) attr_name, res);
/* Some attributes are really constraints computed from other
* attributes, to avoid creating additional constraints from
* the user's perspective
*/
switch (attr)
{
/* right = left + width */
case GTK_CONSTRAINT_ATTRIBUTE_RIGHT:
{
GtkConstraintExpressionBuilder builder;
GtkConstraintVariable *left, *width;
GtkConstraintExpression *expr;
left = gtk_constraint_layout_get_attribute (layout, GTK_CONSTRAINT_ATTRIBUTE_LEFT, prefix, widget, bound_attributes);
width = gtk_constraint_layout_get_attribute (layout, GTK_CONSTRAINT_ATTRIBUTE_WIDTH, prefix, widget, bound_attributes);
gtk_constraint_expression_builder_init (&builder, solver);
gtk_constraint_expression_builder_term (&builder, left);
gtk_constraint_expression_builder_plus (&builder);
gtk_constraint_expression_builder_term (&builder, width);
expr = gtk_constraint_expression_builder_finish (&builder);
gtk_constraint_solver_add_constraint (solver,
res, GTK_CONSTRAINT_RELATION_EQ, expr,
GTK_CONSTRAINT_STRENGTH_REQUIRED);
}
break;
/* bottom = top + height */
case GTK_CONSTRAINT_ATTRIBUTE_BOTTOM:
{
GtkConstraintExpressionBuilder builder;
GtkConstraintVariable *top, *height;
GtkConstraintExpression *expr;
top = gtk_constraint_layout_get_attribute (layout, GTK_CONSTRAINT_ATTRIBUTE_TOP, prefix, widget, bound_attributes);
height = gtk_constraint_layout_get_attribute (layout, GTK_CONSTRAINT_ATTRIBUTE_HEIGHT, prefix, widget, bound_attributes);
gtk_constraint_expression_builder_init (&builder, solver);
gtk_constraint_expression_builder_term (&builder, top);
gtk_constraint_expression_builder_plus (&builder);
gtk_constraint_expression_builder_term (&builder, height);
expr = gtk_constraint_expression_builder_finish (&builder);
gtk_constraint_solver_add_constraint (solver,
res, GTK_CONSTRAINT_RELATION_EQ, expr,
GTK_CONSTRAINT_STRENGTH_REQUIRED);
}
break;
/* centerX = (width / 2.0) + left*/
case GTK_CONSTRAINT_ATTRIBUTE_CENTER_X:
{
GtkConstraintExpressionBuilder builder;
GtkConstraintVariable *left, *width;
GtkConstraintExpression *expr;
left = gtk_constraint_layout_get_attribute (layout, GTK_CONSTRAINT_ATTRIBUTE_LEFT, prefix, widget, bound_attributes);
width = gtk_constraint_layout_get_attribute (layout, GTK_CONSTRAINT_ATTRIBUTE_WIDTH, prefix, widget, bound_attributes);
gtk_constraint_expression_builder_init (&builder, solver);
gtk_constraint_expression_builder_term (&builder, width);
gtk_constraint_expression_builder_divide_by (&builder);
gtk_constraint_expression_builder_constant (&builder, 2.0);
gtk_constraint_expression_builder_plus (&builder);
gtk_constraint_expression_builder_term (&builder, left);
expr = gtk_constraint_expression_builder_finish (&builder);
gtk_constraint_solver_add_constraint (solver,
res, GTK_CONSTRAINT_RELATION_EQ, expr,
GTK_CONSTRAINT_STRENGTH_REQUIRED);
}
break;
/* centerY = (height / 2.0) + top */
case GTK_CONSTRAINT_ATTRIBUTE_CENTER_Y:
{
GtkConstraintExpressionBuilder builder;
GtkConstraintVariable *top, *height;
GtkConstraintExpression *expr;
top = gtk_constraint_layout_get_attribute (layout, GTK_CONSTRAINT_ATTRIBUTE_TOP, prefix, widget, bound_attributes);
height = gtk_constraint_layout_get_attribute (layout, GTK_CONSTRAINT_ATTRIBUTE_HEIGHT, prefix, widget, bound_attributes);
gtk_constraint_expression_builder_init (&builder, solver);
gtk_constraint_expression_builder_term (&builder, height);
gtk_constraint_expression_builder_divide_by (&builder);
gtk_constraint_expression_builder_constant (&builder, 2.0);
gtk_constraint_expression_builder_plus (&builder);
gtk_constraint_expression_builder_term (&builder, top);
expr = gtk_constraint_expression_builder_finish (&builder);
gtk_constraint_solver_add_constraint (solver,
res, GTK_CONSTRAINT_RELATION_EQ, expr,
GTK_CONSTRAINT_STRENGTH_REQUIRED);
}
break;
/* We do not allow negative sizes */
case GTK_CONSTRAINT_ATTRIBUTE_WIDTH:
case GTK_CONSTRAINT_ATTRIBUTE_HEIGHT:
{
GtkConstraintExpression *expr;
expr = gtk_constraint_expression_new (0.0);
gtk_constraint_solver_add_constraint (solver,
res, GTK_CONSTRAINT_RELATION_GE, expr,
GTK_CONSTRAINT_STRENGTH_REQUIRED);
}
break;
/* These are "pure" attributes */
case GTK_CONSTRAINT_ATTRIBUTE_NONE:
case GTK_CONSTRAINT_ATTRIBUTE_LEFT:
case GTK_CONSTRAINT_ATTRIBUTE_TOP:
case GTK_CONSTRAINT_ATTRIBUTE_BASELINE:
break;
/* These attributes must have been resolved to their real names */
case GTK_CONSTRAINT_ATTRIBUTE_START:
case GTK_CONSTRAINT_ATTRIBUTE_END:
g_assert_not_reached ();
break;
default:
break;
}
return res;
}
static GtkConstraintVariable *
get_child_attribute (GtkConstraintLayout *layout,
GtkWidget *widget,
GtkConstraintAttribute attr)
{
GtkConstraintLayoutChild *child_info;
const char *prefix = gtk_widget_get_name (widget);
child_info = GTK_CONSTRAINT_LAYOUT_CHILD (gtk_layout_manager_get_layout_child (GTK_LAYOUT_MANAGER (layout), widget));
return gtk_constraint_layout_get_attribute (layout, attr, prefix, widget, child_info->bound_attributes);
}
static void
gtk_constraint_layout_child_finalize (GObject *gobject)
{
GtkConstraintLayoutChild *self = GTK_CONSTRAINT_LAYOUT_CHILD (gobject);
g_clear_pointer (&self->bound_attributes, g_hash_table_unref);
G_OBJECT_CLASS (gtk_constraint_layout_child_parent_class)->finalize (gobject);
}
static void
gtk_constraint_layout_child_class_init (GtkConstraintLayoutChildClass *klass)
{
GObjectClass *gobject_class = G_OBJECT_CLASS (klass);
gobject_class->finalize = gtk_constraint_layout_child_finalize;
}
static void
gtk_constraint_layout_child_init (GtkConstraintLayoutChild *self)
{
self->bound_attributes =
g_hash_table_new_full (g_str_hash, g_str_equal,
NULL,
(GDestroyNotify) gtk_constraint_variable_unref);
}
static void gtk_buildable_interface_init (GtkBuildableIface *iface);
G_DEFINE_TYPE_WITH_CODE (GtkConstraintLayout, gtk_constraint_layout, GTK_TYPE_LAYOUT_MANAGER,
G_IMPLEMENT_INTERFACE (GTK_TYPE_BUILDABLE, gtk_buildable_interface_init))
static void
gtk_constraint_layout_finalize (GObject *gobject)
{
GtkConstraintLayout *self = GTK_CONSTRAINT_LAYOUT (gobject);
if (self->constraints_observer)
{
g_list_store_remove_all (self->constraints_observer);
g_object_remove_weak_pointer ((GObject *)self->constraints_observer,
(gpointer *)&self->constraints_observer);
}
if (self->guides_observer)
{
g_list_store_remove_all (self->guides_observer);
g_object_remove_weak_pointer ((GObject *)self->guides_observer,
(gpointer *)&self->guides_observer);
}
g_clear_pointer (&self->bound_attributes, g_hash_table_unref);
g_clear_pointer (&self->constraints, g_hash_table_unref);
g_clear_pointer (&self->guides, g_hash_table_unref);
G_OBJECT_CLASS (gtk_constraint_layout_parent_class)->finalize (gobject);
}
static GtkConstraintVariable *
get_layout_attribute (GtkConstraintLayout *self,
GtkWidget *widget,
GtkConstraintAttribute attr)
{
GtkTextDirection text_dir;
const char *attr_name;
GtkConstraintVariable *res;
/* Resolve the start/end attributes depending on the layout's text direction */
if (attr == GTK_CONSTRAINT_ATTRIBUTE_START)
{
text_dir = gtk_widget_get_direction (widget);
if (text_dir == GTK_TEXT_DIR_RTL)
attr = GTK_CONSTRAINT_ATTRIBUTE_RIGHT;
else
attr = GTK_CONSTRAINT_ATTRIBUTE_LEFT;
}
else if (attr == GTK_CONSTRAINT_ATTRIBUTE_END)
{
text_dir = gtk_widget_get_direction (widget);
if (text_dir == GTK_TEXT_DIR_RTL)
attr = GTK_CONSTRAINT_ATTRIBUTE_LEFT;
else
attr = GTK_CONSTRAINT_ATTRIBUTE_RIGHT;
}
attr_name = get_attribute_name (attr);
res = g_hash_table_lookup (self->bound_attributes, attr_name);
if (res != NULL)
return res;
res = gtk_constraint_solver_create_variable (self->solver, "super", attr_name, 0.0);
g_hash_table_insert (self->bound_attributes, (gpointer) attr_name, res);
/* Some attributes are really constraints computed from other
* attributes, to avoid creating additional constraints from
* the user's perspective
*/
switch (attr)
{
/* right = left + width */
case GTK_CONSTRAINT_ATTRIBUTE_RIGHT:
{
GtkConstraintExpressionBuilder builder;
GtkConstraintVariable *left, *width;
GtkConstraintExpression *expr;
left = get_layout_attribute (self, widget, GTK_CONSTRAINT_ATTRIBUTE_LEFT);
width = get_layout_attribute (self, widget, GTK_CONSTRAINT_ATTRIBUTE_WIDTH);
gtk_constraint_expression_builder_init (&builder, self->solver);
gtk_constraint_expression_builder_term (&builder, left);
gtk_constraint_expression_builder_plus (&builder);
gtk_constraint_expression_builder_term (&builder, width);
expr = gtk_constraint_expression_builder_finish (&builder);
gtk_constraint_solver_add_constraint (self->solver,
res, GTK_CONSTRAINT_RELATION_EQ, expr,
GTK_CONSTRAINT_STRENGTH_REQUIRED);
}
break;
/* bottom = top + height */
case GTK_CONSTRAINT_ATTRIBUTE_BOTTOM:
{
GtkConstraintExpressionBuilder builder;
GtkConstraintVariable *top, *height;
GtkConstraintExpression *expr;
top = get_layout_attribute (self, widget, GTK_CONSTRAINT_ATTRIBUTE_TOP);
height = get_layout_attribute (self, widget, GTK_CONSTRAINT_ATTRIBUTE_HEIGHT);
gtk_constraint_expression_builder_init (&builder, self->solver);
gtk_constraint_expression_builder_term (&builder, top);
gtk_constraint_expression_builder_plus (&builder);
gtk_constraint_expression_builder_term (&builder, height);
expr = gtk_constraint_expression_builder_finish (&builder);
gtk_constraint_solver_add_constraint (self->solver,
res, GTK_CONSTRAINT_RELATION_EQ, expr,
GTK_CONSTRAINT_STRENGTH_REQUIRED);
}
break;
/* centerX = left + (width / 2.0) */
case GTK_CONSTRAINT_ATTRIBUTE_CENTER_X:
{
GtkConstraintExpressionBuilder builder;
GtkConstraintVariable *left, *width;
GtkConstraintExpression *expr;
left = get_layout_attribute (self, widget, GTK_CONSTRAINT_ATTRIBUTE_LEFT);
width = get_layout_attribute (self, widget, GTK_CONSTRAINT_ATTRIBUTE_WIDTH);
gtk_constraint_expression_builder_init (&builder, self->solver);
gtk_constraint_expression_builder_term (&builder, width);
gtk_constraint_expression_builder_divide_by (&builder);
gtk_constraint_expression_builder_constant (&builder, 2.0);
gtk_constraint_expression_builder_plus (&builder);
gtk_constraint_expression_builder_term (&builder, left);
expr = gtk_constraint_expression_builder_finish (&builder);
gtk_constraint_solver_add_constraint (self->solver,
res, GTK_CONSTRAINT_RELATION_EQ, expr,
GTK_CONSTRAINT_STRENGTH_REQUIRED);
}
break;
/* centerY = top + (height / 2.0) */
case GTK_CONSTRAINT_ATTRIBUTE_CENTER_Y:
{
GtkConstraintExpressionBuilder builder;
GtkConstraintVariable *top, *height;
GtkConstraintExpression *expr;
top = get_layout_attribute (self, widget, GTK_CONSTRAINT_ATTRIBUTE_TOP);
height = get_layout_attribute (self, widget, GTK_CONSTRAINT_ATTRIBUTE_HEIGHT);
gtk_constraint_expression_builder_init (&builder, self->solver);
gtk_constraint_expression_builder_term (&builder, height);
gtk_constraint_expression_builder_divide_by (&builder);
gtk_constraint_expression_builder_constant (&builder, 2.0);
gtk_constraint_expression_builder_plus (&builder);
gtk_constraint_expression_builder_term (&builder, top);
expr = gtk_constraint_expression_builder_finish (&builder);
gtk_constraint_solver_add_constraint (self->solver,
res, GTK_CONSTRAINT_RELATION_EQ, expr,
GTK_CONSTRAINT_STRENGTH_REQUIRED);
}
break;
/* We do not allow negative sizes */
case GTK_CONSTRAINT_ATTRIBUTE_WIDTH:
case GTK_CONSTRAINT_ATTRIBUTE_HEIGHT:
{
GtkConstraintExpression *expr;
expr = gtk_constraint_expression_new (0.0);
gtk_constraint_solver_add_constraint (self->solver,
res, GTK_CONSTRAINT_RELATION_GE, expr,
GTK_CONSTRAINT_STRENGTH_REQUIRED);
}
break;
/* These are "pure" attributes */
case GTK_CONSTRAINT_ATTRIBUTE_NONE:
case GTK_CONSTRAINT_ATTRIBUTE_LEFT:
case GTK_CONSTRAINT_ATTRIBUTE_TOP:
case GTK_CONSTRAINT_ATTRIBUTE_BASELINE:
break;
/* These attributes must have been resolved to their real names */
case GTK_CONSTRAINT_ATTRIBUTE_START:
case GTK_CONSTRAINT_ATTRIBUTE_END:
g_assert_not_reached ();
break;
default:
break;
}
return res;
}
/*< private >
* layout_add_constraint:
* @self: a `GtkConstraintLayout`
* @constraint: a [class@Gtk.Constraint]
*
* Turns a `GtkConstraint` into a `GtkConstraintRef` inside the
* constraint solver associated to @self.
*
* If @self does not have a `GtkConstraintSolver`, because it
* has not been rooted yet, we just store the @constraint instance,
* and we're going to call this function when the layout manager
* gets rooted.
*/
static void
layout_add_constraint (GtkConstraintLayout *self,
GtkConstraint *constraint)
{
GtkConstraintVariable *target_attr, *source_attr;
GtkConstraintExpressionBuilder builder;
GtkConstraintExpression *expr;
GtkConstraintSolver *solver;
GtkConstraintAttribute attr;
GtkConstraintTarget *target, *source;
GtkWidget *layout_widget;
if (gtk_constraint_is_attached (constraint))
return;
/* Once we pass the preconditions, we check if we can turn a GtkConstraint
* into a GtkConstraintRef; if we can't, we keep a reference to the
* constraint object and try later on
*/
layout_widget = gtk_layout_manager_get_widget (GTK_LAYOUT_MANAGER (self));
if (layout_widget == NULL)
return;
solver = gtk_constraint_layout_get_solver (self);
if (solver == NULL)
return;
attr = gtk_constraint_get_target_attribute (constraint);
target = gtk_constraint_get_target (constraint);
if (target == NULL || target == GTK_CONSTRAINT_TARGET (layout_widget))
{
/* A NULL target widget is assumed to be referring to the layout itself */
target_attr = get_layout_attribute (self, layout_widget, attr);
}
else if (GTK_IS_WIDGET (target) &&
gtk_widget_get_parent (GTK_WIDGET (target)) == layout_widget)
{
target_attr = get_child_attribute (self, GTK_WIDGET (target), attr);
}
else if (GTK_IS_CONSTRAINT_GUIDE (target))
{
GtkConstraintGuide *guide;
guide = (GtkConstraintGuide*)g_hash_table_lookup (self->guides, target);
target_attr = gtk_constraint_guide_get_attribute (guide, attr);
}
else
{
g_critical ("Unknown target widget '%p'", target);
target_attr = NULL;
}
if (target_attr == NULL)
return;
attr = gtk_constraint_get_source_attribute (constraint);
source = gtk_constraint_get_source (constraint);
/* The constraint is a constant */
if (attr == GTK_CONSTRAINT_ATTRIBUTE_NONE)
{
source_attr = NULL;
}
else
{
if (source == NULL || source == GTK_CONSTRAINT_TARGET (layout_widget))
{
source_attr = get_layout_attribute (self, layout_widget, attr);
}
else if (GTK_IS_WIDGET (source) &&
gtk_widget_get_parent (GTK_WIDGET (source)) == layout_widget)
{
source_attr = get_child_attribute (self, GTK_WIDGET (source), attr);
}
else if (GTK_IS_CONSTRAINT_GUIDE (source))
{
GtkConstraintGuide *guide;
guide = (GtkConstraintGuide*)g_hash_table_lookup (self->guides, source);
source_attr = gtk_constraint_guide_get_attribute (guide, attr);
}
else
{
g_critical ("Unknown source widget '%p'", source);
source_attr = NULL;
return;
}
}
/* Build the expression */
gtk_constraint_expression_builder_init (&builder, self->solver);
if (source_attr != NULL)
{
gtk_constraint_expression_builder_term (&builder, source_attr);
gtk_constraint_expression_builder_multiply_by (&builder);
gtk_constraint_expression_builder_constant (&builder, gtk_constraint_get_multiplier (constraint));
gtk_constraint_expression_builder_plus (&builder);
}
gtk_constraint_expression_builder_constant (&builder, gtk_constraint_get_constant (constraint));
expr = gtk_constraint_expression_builder_finish (&builder);
constraint->solver = solver;
constraint->constraint_ref =
gtk_constraint_solver_add_constraint (self->solver,
target_attr,
gtk_constraint_get_relation (constraint),
expr,
gtk_constraint_get_strength (constraint));
}
static void
update_child_constraint (GtkConstraintLayout *self,
GtkConstraintLayoutChild *child_info,
GtkWidget *child,
int index,
int value)
{
GtkConstraintVariable *var;
int attr[LAST_VALUE] = {
GTK_CONSTRAINT_ATTRIBUTE_WIDTH,
GTK_CONSTRAINT_ATTRIBUTE_HEIGHT,
GTK_CONSTRAINT_ATTRIBUTE_WIDTH,
GTK_CONSTRAINT_ATTRIBUTE_HEIGHT
};
int relation[LAST_VALUE] = {
GTK_CONSTRAINT_RELATION_GE,
GTK_CONSTRAINT_RELATION_GE,
GTK_CONSTRAINT_RELATION_EQ,
GTK_CONSTRAINT_RELATION_EQ
};
if (child_info->values[index] != value)
{
child_info->values[index] = value;
if (child_info->constraints[index])
gtk_constraint_solver_remove_constraint (self->solver,
child_info->constraints[index]);
var = get_child_attribute (self, child, attr[index]);
if (relation[index] == GTK_CONSTRAINT_RELATION_EQ)
{
gtk_constraint_variable_set_value (var, value);
child_info->constraints[index] =
gtk_constraint_solver_add_stay_variable (self->solver,
var,
GTK_CONSTRAINT_STRENGTH_MEDIUM);
}
else
{
child_info->constraints[index] =
gtk_constraint_solver_add_constraint (self->solver,
var,
relation[index],
gtk_constraint_expression_new (value),
GTK_CONSTRAINT_STRENGTH_REQUIRED);
}
}
}
static void
gtk_constraint_layout_measure (GtkLayoutManager *manager,
GtkWidget *widget,
GtkOrientation orientation,
int for_size,
int *minimum,
int *natural,
int *minimum_baseline,
int *natural_baseline)
{
GtkConstraintLayout *self = GTK_CONSTRAINT_LAYOUT (manager);
GtkConstraintVariable *size, *opposite_size;
GtkConstraintSolver *solver;
GtkWidget *child;
int min_value;
int nat_value;
solver = gtk_constraint_layout_get_solver (self);
if (solver == NULL)
return;
gtk_constraint_solver_freeze (solver);
/* We measure each child in the layout and impose restrictions on the
* minimum and natural size, so we can solve the size of the overall
* layout later on
*/
for (child = _gtk_widget_get_first_child (widget);
child != NULL;
child = _gtk_widget_get_next_sibling (child))
{
GtkConstraintLayoutChild *info;
GtkRequisition min_req, nat_req;
if (!gtk_widget_should_layout (child))
continue;
gtk_widget_get_preferred_size (child, &min_req, &nat_req);
info = GTK_CONSTRAINT_LAYOUT_CHILD (gtk_layout_manager_get_layout_child (manager, child));
update_child_constraint (self, info, child, MIN_WIDTH, min_req.width);
update_child_constraint (self, info, child, MIN_HEIGHT, min_req.height);
update_child_constraint (self, info, child, NAT_WIDTH, nat_req.width);
update_child_constraint (self, info, child, NAT_HEIGHT, nat_req.height);
}
gtk_constraint_solver_thaw (solver);
switch (orientation)
{
case GTK_ORIENTATION_HORIZONTAL:
size = get_layout_attribute (self, widget, GTK_CONSTRAINT_ATTRIBUTE_WIDTH);
opposite_size = get_layout_attribute (self, widget, GTK_CONSTRAINT_ATTRIBUTE_HEIGHT);
break;
case GTK_ORIENTATION_VERTICAL:
size = get_layout_attribute (self, widget, GTK_CONSTRAINT_ATTRIBUTE_HEIGHT);
opposite_size = get_layout_attribute (self, widget, GTK_CONSTRAINT_ATTRIBUTE_WIDTH);
break;
default:
g_assert_not_reached ();
}
g_assert (size != NULL && opposite_size != NULL);
nat_value = gtk_constraint_variable_get_value (size);
/* We impose a temporary value on the size and opposite size of the
* layout, with a low weight to let the solver settle towards the
* natural state of the system. Once we get the value out, we can
* remove these constraints
*/
gtk_constraint_solver_add_edit_variable (solver, size, GTK_CONSTRAINT_STRENGTH_STRONG * 2);
if (for_size > 0)
gtk_constraint_solver_add_edit_variable (solver, opposite_size, GTK_CONSTRAINT_STRENGTH_STRONG * 2);
gtk_constraint_solver_begin_edit (solver);
gtk_constraint_solver_suggest_value (solver, size, 0.0);
if (for_size > 0)
gtk_constraint_solver_suggest_value (solver, opposite_size, for_size);
gtk_constraint_solver_resolve (solver);
min_value = gtk_constraint_variable_get_value (size);
gtk_constraint_solver_remove_edit_variable (solver, size);
if (for_size > 0)
gtk_constraint_solver_remove_edit_variable (solver, opposite_size);
gtk_constraint_solver_end_edit (solver);
GTK_NOTE (LAYOUT,
g_print ("layout %p %s size: min %d nat %d (for opposite size: %d)\n",
self,
orientation == GTK_ORIENTATION_HORIZONTAL ? "horizontal" : "vertical",
min_value, nat_value,
for_size));
if (minimum != NULL)
*minimum = min_value;
if (natural != NULL)
*natural = nat_value;
}
static void
gtk_constraint_layout_allocate (GtkLayoutManager *manager,
GtkWidget *widget,
int width,
int height,
int baseline)
{
GtkConstraintLayout *self = GTK_CONSTRAINT_LAYOUT (manager);
GtkConstraintRef *stay_w, *stay_h, *stay_t, *stay_l;
GtkConstraintSolver *solver;
GtkConstraintVariable *layout_top, *layout_height;
GtkConstraintVariable *layout_left, *layout_width;
GtkWidget *child;
solver = gtk_constraint_layout_get_solver (self);
if (solver == NULL)
return;
/* We add required stay constraints to ensure that the layout remains
* within the bounds of the allocation
*/
layout_top = get_layout_attribute (self, widget, GTK_CONSTRAINT_ATTRIBUTE_TOP);
layout_left = get_layout_attribute (self, widget, GTK_CONSTRAINT_ATTRIBUTE_LEFT);
layout_width = get_layout_attribute (self, widget, GTK_CONSTRAINT_ATTRIBUTE_WIDTH);
layout_height = get_layout_attribute (self, widget, GTK_CONSTRAINT_ATTRIBUTE_HEIGHT);
gtk_constraint_variable_set_value (layout_top, 0.0);
stay_t = gtk_constraint_solver_add_stay_variable (solver,
layout_top,
GTK_CONSTRAINT_STRENGTH_REQUIRED);
gtk_constraint_variable_set_value (layout_left, 0.0);
stay_l = gtk_constraint_solver_add_stay_variable (solver,
layout_left,
GTK_CONSTRAINT_STRENGTH_REQUIRED);
gtk_constraint_variable_set_value (layout_width, width);
stay_w = gtk_constraint_solver_add_stay_variable (solver,
layout_width,
GTK_CONSTRAINT_STRENGTH_REQUIRED);
gtk_constraint_variable_set_value (layout_height, height);
stay_h = gtk_constraint_solver_add_stay_variable (solver,
layout_height,
GTK_CONSTRAINT_STRENGTH_REQUIRED);
GTK_NOTE (LAYOUT,
g_print ("Layout [%p]: { .x: %g, .y: %g, .w: %g, .h: %g }\n",
self,
gtk_constraint_variable_get_value (layout_left),
gtk_constraint_variable_get_value (layout_top),
gtk_constraint_variable_get_value (layout_width),
gtk_constraint_variable_get_value (layout_height)));
for (child = _gtk_widget_get_first_child (widget);
child != NULL;
child = _gtk_widget_get_next_sibling (child))
{
GtkConstraintVariable *var_top, *var_left, *var_width, *var_height;
GtkConstraintVariable *var_baseline;
GtkAllocation child_alloc;
int child_baseline = -1;
if (!gtk_widget_should_layout (child))
continue;
/* Retrieve all the values associated with the child */
var_top = get_child_attribute (self, child, GTK_CONSTRAINT_ATTRIBUTE_TOP);
var_left = get_child_attribute (self, child, GTK_CONSTRAINT_ATTRIBUTE_LEFT);
var_width = get_child_attribute (self, child, GTK_CONSTRAINT_ATTRIBUTE_WIDTH);
var_height = get_child_attribute (self, child, GTK_CONSTRAINT_ATTRIBUTE_HEIGHT);
var_baseline = get_child_attribute (self, child, GTK_CONSTRAINT_ATTRIBUTE_BASELINE);
GTK_NOTE (LAYOUT,
g_print ("Allocating child '%s'[%p] with { .x: %g, .y: %g, .w: %g, .h: %g, .b: %g }\n",
gtk_widget_get_name (child), child,
gtk_constraint_variable_get_value (var_left),
gtk_constraint_variable_get_value (var_top),
gtk_constraint_variable_get_value (var_width),
gtk_constraint_variable_get_value (var_height),
gtk_constraint_variable_get_value (var_baseline)));
child_alloc.x = floor (gtk_constraint_variable_get_value (var_left));
child_alloc.y = floor (gtk_constraint_variable_get_value (var_top));
child_alloc.width = ceil (gtk_constraint_variable_get_value (var_width));
child_alloc.height = ceil (gtk_constraint_variable_get_value (var_height));
if (gtk_constraint_variable_get_value (var_baseline) > 0)
child_baseline = floor (gtk_constraint_variable_get_value (var_baseline));
gtk_widget_size_allocate (GTK_WIDGET (child),
&child_alloc,
child_baseline);
}
#ifdef G_ENABLE_DEBUG
if (GTK_DEBUG_CHECK (LAYOUT))
{
GHashTableIter iter;
gpointer key;
g_hash_table_iter_init (&iter, self->guides);
while (g_hash_table_iter_next (&iter, &key, NULL))
{
GtkConstraintGuide *guide = key;
GtkConstraintVariable *var_top, *var_left, *var_width, *var_height;
var_top = gtk_constraint_guide_get_attribute (guide, GTK_CONSTRAINT_ATTRIBUTE_TOP);
var_left = gtk_constraint_guide_get_attribute (guide, GTK_CONSTRAINT_ATTRIBUTE_LEFT);
var_width = gtk_constraint_guide_get_attribute (guide, GTK_CONSTRAINT_ATTRIBUTE_WIDTH);
var_height = gtk_constraint_guide_get_attribute (guide, GTK_CONSTRAINT_ATTRIBUTE_HEIGHT);
g_print ("Allocating guide '%s'[%p] with { .x: %g .y: %g .w: %g .h: %g }\n",
gtk_constraint_guide_get_name (guide), guide,
gtk_constraint_variable_get_value (var_left),
gtk_constraint_variable_get_value (var_top),
gtk_constraint_variable_get_value (var_width),
gtk_constraint_variable_get_value (var_height));
}
}
#endif
/* The allocation stay constraints are not needed any more */
gtk_constraint_solver_remove_constraint (solver, stay_w);
gtk_constraint_solver_remove_constraint (solver, stay_h);
gtk_constraint_solver_remove_constraint (solver, stay_t);
gtk_constraint_solver_remove_constraint (solver, stay_l);
}
static void
gtk_constraint_layout_root (GtkLayoutManager *manager)
{
GtkConstraintLayout *self = GTK_CONSTRAINT_LAYOUT (manager);
GHashTableIter iter;
GtkWidget *widget;
GtkRoot *root;
gpointer key;
widget = gtk_layout_manager_get_widget (manager);
root = gtk_widget_get_root (widget);
self->solver = gtk_root_get_constraint_solver (root);
/* Now that we have a solver, attach all constraints we have */
g_hash_table_iter_init (&iter, self->constraints);
while (g_hash_table_iter_next (&iter, &key, NULL))
{
GtkConstraint *constraint = key;
layout_add_constraint (self, constraint);
}
g_hash_table_iter_init (&iter, self->guides);
while (g_hash_table_iter_next (&iter, &key, NULL))
{
GtkConstraintGuide *guide = key;
gtk_constraint_guide_update (guide);
}
}
static void
gtk_constraint_layout_unroot (GtkLayoutManager *manager)
{
GtkConstraintLayout *self = GTK_CONSTRAINT_LAYOUT (manager);
GHashTableIter iter;
gpointer key;
/* Detach all constraints we're holding, as we're removing the layout
* from the global solver, and they should not contribute to the other
* layouts
*/
g_hash_table_iter_init (&iter, self->constraints);
while (g_hash_table_iter_next (&iter, &key, NULL))
{
GtkConstraint *constraint = key;
gtk_constraint_detach (constraint);
}
g_hash_table_iter_init (&iter, self->guides);
while (g_hash_table_iter_next (&iter, &key, NULL))
{
GtkConstraintGuide *guide = key;
gtk_constraint_guide_detach (guide);
}
self->solver = NULL;
}
static void
gtk_constraint_layout_class_init (GtkConstraintLayoutClass *klass)
{
GtkLayoutManagerClass *manager_class = GTK_LAYOUT_MANAGER_CLASS (klass);
GObjectClass *gobject_class = G_OBJECT_CLASS (klass);
gobject_class->finalize = gtk_constraint_layout_finalize;
manager_class->layout_child_type = GTK_TYPE_CONSTRAINT_LAYOUT_CHILD;
manager_class->measure = gtk_constraint_layout_measure;
manager_class->allocate = gtk_constraint_layout_allocate;
manager_class->root = gtk_constraint_layout_root;
manager_class->unroot = gtk_constraint_layout_unroot;
}
static void
gtk_constraint_layout_init (GtkConstraintLayout *self)
{
/* The bound variables in the solver */
self->bound_attributes =
g_hash_table_new_full (g_str_hash, g_str_equal,
NULL,
(GDestroyNotify) gtk_constraint_variable_unref);
/* The GtkConstraint instances we own */
self->constraints =
g_hash_table_new_full (NULL, NULL,
(GDestroyNotify) g_object_unref,
NULL);
self->guides =
g_hash_table_new_full (NULL, NULL,
(GDestroyNotify) g_object_unref,
NULL);
}
typedef struct {
GtkConstraintLayout *layout;
GtkBuilder *builder;
GList *constraints;
GList *guides;
} ConstraintsParserData;
typedef struct {
char *source_name;
char *source_attr;
char *target_name;
char *target_attr;
char *relation;
char *strength;
double constant;
double multiplier;
} ConstraintData;
typedef struct {
char *name;
char *strength;
struct {
int min, nat, max;
} sizes[2];
} GuideData;
static void
constraint_data_free (gpointer _data)
{
ConstraintData *data = _data;
g_free (data->source_name);
g_free (data->source_attr);
g_free (data->target_name);
g_free (data->target_attr);
g_free (data->relation);
g_free (data->strength);
g_free (data);
}
static void
guide_data_free (gpointer _data)
{
GuideData *data = _data;
g_free (data->name);
g_free (data->strength);
g_free (data);
}
static void
parse_double (const char *string,
double *value_p,
double default_value)
{
double value;
char *endptr;
int saved_errno;
if (string == NULL || string[0] == '\0')
{
*value_p = default_value;
return;
}
saved_errno = errno;
errno = 0;
value = g_ascii_strtod (string, &endptr);
if (errno == 0 && endptr != string)
*value_p = value;
else
*value_p = default_value;
errno = saved_errno;
}
static void
parse_int (const char *string,
int *value_p,
int default_value)
{
gint64 value;
char *endptr;
int saved_errno;
if (string == NULL || string[0] == '\0')
{
*value_p = default_value;
return;
}
saved_errno = errno;
errno = 0;
value = g_ascii_strtoll (string, &endptr, 10);
if (errno == 0 && endptr != string)
*value_p = (int) value;
else
*value_p = default_value;
errno = saved_errno;
}
static GtkConstraint *
constraint_data_to_constraint (const ConstraintData *data,
GtkBuilder *builder,
GHashTable *guides,
GError **error)
{
gpointer source, target;
int source_attr, target_attr;
int relation, strength;
gboolean res;
if (g_strcmp0 (data->source_name, "super") == 0)
source = NULL;
else if (data->source_name == NULL)
{
if (data->source_attr != NULL)
{
g_set_error (error, GTK_BUILDER_ERROR,
GTK_BUILDER_ERROR_INVALID_VALUE,
"Constraints without 'source' must also not "
"have a 'source-attribute' attribute");
return NULL;
}
source = NULL;
}
else
{
if (g_hash_table_contains (guides, data->source_name))
source = g_hash_table_lookup (guides, data->source_name);
else
source = gtk_builder_get_object (builder, data->source_name);
if (source == NULL)
{
g_set_error (error, GTK_BUILDER_ERROR,
GTK_BUILDER_ERROR_INVALID_VALUE,
"Unable to find source '%s' for constraint",
data->source_name);
return NULL;
}
}
if (g_strcmp0 (data->target_name, "super") == 0)
target = NULL;
else
{
if (g_hash_table_contains (guides, data->target_name))
target = g_hash_table_lookup (guides, data->target_name);
else
target = gtk_builder_get_object (builder, data->target_name);
if (target == NULL)
{
g_set_error (error, GTK_BUILDER_ERROR,
GTK_BUILDER_ERROR_INVALID_VALUE,
"Unable to find target '%s' for constraint",
data->target_name);
return NULL;
}
}
if (data->source_attr != NULL)
{
res = _gtk_builder_enum_from_string (GTK_TYPE_CONSTRAINT_ATTRIBUTE,
data->source_attr,
&source_attr,
error);
if (!res)
return NULL;
}
else
source_attr = GTK_CONSTRAINT_ATTRIBUTE_NONE;
res = _gtk_builder_enum_from_string (GTK_TYPE_CONSTRAINT_ATTRIBUTE,
data->target_attr,
&target_attr,
error);
if (!res)
return NULL;
if (data->relation != NULL)
{
res = _gtk_builder_enum_from_string (GTK_TYPE_CONSTRAINT_RELATION,
data->relation,
&relation,
error);
if (!res)
return NULL;
}
else
relation = GTK_CONSTRAINT_RELATION_EQ;
if (data->strength != NULL)
{
res = _gtk_builder_enum_from_string (GTK_TYPE_CONSTRAINT_STRENGTH,
data->strength,
&strength,
error);
if (!res)
return NULL;
}
else
strength = GTK_CONSTRAINT_STRENGTH_REQUIRED;
if (source == NULL && source_attr == GTK_CONSTRAINT_ATTRIBUTE_NONE)
return gtk_constraint_new_constant (target, target_attr,
relation,
data->constant,
strength);
else
return gtk_constraint_new (target, target_attr,
relation,
source, source_attr,
data->multiplier,
data->constant,
strength);
}
static GtkConstraintGuide *
guide_data_to_guide (const GuideData *data,
GtkBuilder *builder,
GError **error)
{
int strength;
gboolean res;
if (data->strength != NULL)
{
res = _gtk_builder_enum_from_string (GTK_TYPE_CONSTRAINT_STRENGTH,
data->strength,
&strength,
error);
if (!res)
return NULL;
}
else
strength = GTK_CONSTRAINT_STRENGTH_MEDIUM;
return g_object_new (GTK_TYPE_CONSTRAINT_GUIDE,
"min-width", data->sizes[GTK_ORIENTATION_HORIZONTAL].min,
"nat-width", data->sizes[GTK_ORIENTATION_HORIZONTAL].nat,
"max-width", data->sizes[GTK_ORIENTATION_HORIZONTAL].max,
"min-height", data->sizes[GTK_ORIENTATION_VERTICAL].min,
"nat-height", data->sizes[GTK_ORIENTATION_VERTICAL].nat,
"max-height", data->sizes[GTK_ORIENTATION_VERTICAL].max,
"strength", strength,
"name", data->name,
NULL);
}
static void
constraints_start_element (GtkBuildableParseContext *context,
const char *element_name,
const char **attr_names,
const char **attr_values,
gpointer user_data,
GError **error)
{
ConstraintsParserData *data = user_data;
if (strcmp (element_name, "constraints") == 0)
{
if (!_gtk_builder_check_parent (data->builder, context, "object", error))
return;
if (!g_markup_collect_attributes (element_name, attr_names, attr_values, error,
G_MARKUP_COLLECT_INVALID, NULL, NULL,
G_MARKUP_COLLECT_INVALID))
_gtk_builder_prefix_error (data->builder, context, error);
}
else if (strcmp (element_name, "constraint") == 0)
{
const char *target_name, *target_attribute;
const char *relation_str = NULL;
const char *source_name = NULL, *source_attribute = NULL;
const char *multiplier_str = NULL, *constant_str = NULL;
const char *strength_str = NULL;
ConstraintData *cdata;
if (!_gtk_builder_check_parent (data->builder, context, "constraints", error))
return;
if (!g_markup_collect_attributes (element_name, attr_names, attr_values, error,
G_MARKUP_COLLECT_STRING, "target", &target_name,
G_MARKUP_COLLECT_STRING, "target-attribute", &target_attribute,
G_MARKUP_COLLECT_STRING, "relation", &relation_str,
G_MARKUP_COLLECT_STRING | G_MARKUP_COLLECT_OPTIONAL, "source", &source_name,
G_MARKUP_COLLECT_STRING | G_MARKUP_COLLECT_OPTIONAL, "source-attribute", &source_attribute,
G_MARKUP_COLLECT_STRING | G_MARKUP_COLLECT_OPTIONAL, "multiplier", &multiplier_str,
G_MARKUP_COLLECT_STRING | G_MARKUP_COLLECT_OPTIONAL, "constant", &constant_str,
G_MARKUP_COLLECT_STRING | G_MARKUP_COLLECT_OPTIONAL, "strength", &strength_str,
G_MARKUP_COLLECT_INVALID))
{
_gtk_builder_prefix_error (data->builder, context, error);
return;
}
cdata = g_new0 (ConstraintData, 1);
cdata->target_name = g_strdup (target_name);
cdata->target_attr = g_strdup (target_attribute);
cdata->relation = g_strdup (relation_str);
cdata->source_name = g_strdup (source_name);
cdata->source_attr = g_strdup (source_attribute);
parse_double (multiplier_str, &cdata->multiplier, 1.0);
parse_double (constant_str, &cdata->constant, 0.0);
cdata->strength = g_strdup (strength_str);
data->constraints = g_list_prepend (data->constraints, cdata);
}
else if (strcmp (element_name, "guide") == 0)
{
const char *min_width, *nat_width, *max_width;
const char *min_height, *nat_height, *max_height;
const char *strength_str;
const char *name;
GuideData *gdata;
if (!_gtk_builder_check_parent (data->builder, context, "constraints", error))
return;
if (!g_markup_collect_attributes (element_name, attr_names, attr_values, error,
G_MARKUP_COLLECT_STRING | G_MARKUP_COLLECT_OPTIONAL, "min-width", &min_width,
G_MARKUP_COLLECT_STRING | G_MARKUP_COLLECT_OPTIONAL, "nat-width", &nat_width,
G_MARKUP_COLLECT_STRING | G_MARKUP_COLLECT_OPTIONAL, "max-width", &max_width,
G_MARKUP_COLLECT_STRING | G_MARKUP_COLLECT_OPTIONAL, "min-height", &min_height,
G_MARKUP_COLLECT_STRING | G_MARKUP_COLLECT_OPTIONAL, "nat-height", &nat_height,
G_MARKUP_COLLECT_STRING | G_MARKUP_COLLECT_OPTIONAL, "max-height", &max_height,
G_MARKUP_COLLECT_STRING | G_MARKUP_COLLECT_OPTIONAL, "strength", &strength_str,
G_MARKUP_COLLECT_STRING | G_MARKUP_COLLECT_OPTIONAL, "name", &name,
G_MARKUP_COLLECT_INVALID))
{
_gtk_builder_prefix_error (data->builder, context, error);
return;
}
gdata = g_new0 (GuideData, 1);
parse_int (min_width, &(gdata->sizes[GTK_ORIENTATION_HORIZONTAL].min), 0);
parse_int (nat_width, &(gdata->sizes[GTK_ORIENTATION_HORIZONTAL].nat), 0);
parse_int (max_width, &(gdata->sizes[GTK_ORIENTATION_HORIZONTAL].max), G_MAXINT);
parse_int (min_height, &(gdata->sizes[GTK_ORIENTATION_VERTICAL].min), 0);
parse_int (nat_height, &(gdata->sizes[GTK_ORIENTATION_VERTICAL].nat), 0);
parse_int (max_height, &(gdata->sizes[GTK_ORIENTATION_VERTICAL].max), G_MAXINT);
gdata->name = g_strdup (name);
gdata->strength = g_strdup (strength_str);
data->guides = g_list_prepend (data->guides, gdata);
}
else
{
_gtk_builder_error_unhandled_tag (data->builder, context,
"GtkConstraintLayout", element_name,
error);
}
}
static void
constraints_end_element (GtkBuildableParseContext *context,
const char *element_name,
gpointer user_data,
GError **error)
{
}
static const GtkBuildableParser constraints_parser = {
constraints_start_element,
constraints_end_element,
NULL,
};
static gboolean
gtk_constraint_layout_custom_tag_start (GtkBuildable *buildable,
GtkBuilder *builder,
GObject *child,
const char *element_name,
GtkBuildableParser *parser,
gpointer *parser_data)
{
if (strcmp (element_name, "constraints") == 0)
{
ConstraintsParserData *data = g_new (ConstraintsParserData, 1);
data->layout = g_object_ref (GTK_CONSTRAINT_LAYOUT (buildable));
data->builder = builder;
data->constraints = NULL;
data->guides = NULL;
*parser = constraints_parser;
*parser_data = data;
return TRUE;
}
return FALSE;
}
static void
gtk_constraint_layout_custom_tag_end (GtkBuildable *buildable,
GtkBuilder *builder,
GObject *child,
const char *element_name,
gpointer data)
{
}
static void
gtk_constraint_layout_custom_finished (GtkBuildable *buildable,
GtkBuilder *builder,
GObject *child,
const char *element_name,
gpointer user_data)
{
ConstraintsParserData *data = user_data;
if (strcmp (element_name, "constraints") == 0)
{
GList *l;
GHashTable *guides;
guides = g_hash_table_new (g_str_hash, g_str_equal);
data->guides = g_list_reverse (data->guides);
for (l = data->guides; l != NULL; l = l->next)
{
const GuideData *gdata = l->data;
GtkConstraintGuide *g;
GError *error = NULL;
const char *name;
g = guide_data_to_guide (gdata, builder, &error);
if (error != NULL)
{
g_critical ("Unable to parse guide definition: %s", error->message);
g_error_free (error);
continue;
}
name = gtk_constraint_guide_get_name (g);
if (g_hash_table_lookup (guides, name))
{
g_critical ("Duplicate guide: %s", name);
g_object_unref (g);
continue;
}
g_hash_table_insert (guides, (gpointer)name, g);
gtk_constraint_layout_add_guide (data->layout, g);
}
data->constraints = g_list_reverse (data->constraints);
for (l = data->constraints; l != NULL; l = l->next)
{
const ConstraintData *cdata = l->data;
GtkConstraint *c;
GError *error = NULL;
c = constraint_data_to_constraint (cdata, builder, guides, &error);
if (error != NULL)
{
g_critical ("Unable to parse constraint definition '%s.%s [%s] %s.%s * %g + %g': %s",
cdata->target_name, cdata->target_attr,
cdata->relation,
cdata->source_name, cdata->source_attr,
cdata->multiplier,
cdata->constant,
error->message);
g_error_free (error);
continue;
}
layout_add_constraint (data->layout, c);
g_hash_table_add (data->layout->constraints, c);
if (data->layout->constraints_observer)
g_list_store_append (data->layout->constraints_observer, c);
}
gtk_layout_manager_layout_changed (GTK_LAYOUT_MANAGER (data->layout));
g_list_free_full (data->constraints, constraint_data_free);
g_list_free_full (data->guides, guide_data_free);
g_object_unref (data->layout);
g_free (data);
g_hash_table_unref (guides);
}
}
static void
gtk_buildable_interface_init (GtkBuildableIface *iface)
{
iface->custom_tag_start = gtk_constraint_layout_custom_tag_start;
iface->custom_tag_end = gtk_constraint_layout_custom_tag_end;
iface->custom_finished = gtk_constraint_layout_custom_finished;
}
/**
* gtk_constraint_layout_new:
*
* Creates a new `GtkConstraintLayout` layout manager.
*
* Returns: the newly created `GtkConstraintLayout`
*/
GtkLayoutManager *
gtk_constraint_layout_new (void)
{
return g_object_new (GTK_TYPE_CONSTRAINT_LAYOUT, NULL);
}
/**
* gtk_constraint_layout_add_constraint:
* @layout: a `GtkConstraintLayout`
* @constraint: (transfer full): a [class@Gtk.Constraint]
*
* Adds a constraint to the layout manager.
*
* The [property@Gtk.Constraint:source] and [property@Gtk.Constraint:target]
* properties of `constraint` can be:
*
* - set to `NULL` to indicate that the constraint refers to the
* widget using `layout`
* - set to the [class@Gtk.Widget] using `layout`
* - set to a child of the [class@Gtk.Widget] using `layout`
* - set to a [class@Gtk.ConstraintGuide] that is part of `layout`
*
* The @layout acquires the ownership of @constraint after calling
* this function.
*/
void
gtk_constraint_layout_add_constraint (GtkConstraintLayout *layout,
GtkConstraint *constraint)
{
g_return_if_fail (GTK_IS_CONSTRAINT_LAYOUT (layout));
g_return_if_fail (GTK_IS_CONSTRAINT (constraint));
g_return_if_fail (!gtk_constraint_is_attached (constraint));
layout_add_constraint (layout, constraint);
g_hash_table_add (layout->constraints, constraint);
if (layout->constraints_observer)
g_list_store_append (layout->constraints_observer, constraint);
gtk_layout_manager_layout_changed (GTK_LAYOUT_MANAGER (layout));
}
static void
list_store_remove_item (GListStore *store,
gpointer item)
{
int n_items;
int i;
n_items = g_list_model_get_n_items (G_LIST_MODEL (store));
for (i = 0; i < n_items; i++)
{
gpointer *model_item = g_list_model_get_item (G_LIST_MODEL (store), i);
g_object_unref (model_item);
if (item == model_item)
{
g_list_store_remove (store, i);
break;
}
}
}
/**
* gtk_constraint_layout_remove_constraint:
* @layout: a `GtkConstraintLayout`
* @constraint: a [class@Gtk.Constraint]
*
* Removes `constraint` from the layout manager,
* so that it no longer influences the layout.
*/
void
gtk_constraint_layout_remove_constraint (GtkConstraintLayout *layout,
GtkConstraint *constraint)
{
g_return_if_fail (GTK_IS_CONSTRAINT_LAYOUT (layout));
g_return_if_fail (GTK_IS_CONSTRAINT (constraint));
g_return_if_fail (gtk_constraint_is_attached (constraint));
gtk_constraint_detach (constraint);
g_hash_table_remove (layout->constraints, constraint);
if (layout->constraints_observer)
list_store_remove_item (layout->constraints_observer, constraint);
gtk_layout_manager_layout_changed (GTK_LAYOUT_MANAGER (layout));
}
/**
* gtk_constraint_layout_remove_all_constraints:
* @layout: a `GtkConstraintLayout`
*
* Removes all constraints from the layout manager.
*/
void
gtk_constraint_layout_remove_all_constraints (GtkConstraintLayout *layout)
{
GHashTableIter iter;
gpointer key;
g_return_if_fail (GTK_IS_CONSTRAINT_LAYOUT (layout));
g_hash_table_iter_init (&iter, layout->constraints);
while (g_hash_table_iter_next (&iter, &key, NULL))
{
GtkConstraint *constraint = key;
gtk_constraint_detach (constraint);
g_hash_table_iter_remove (&iter);
}
if (layout->constraints_observer)
g_list_store_remove_all (layout->constraints_observer);
gtk_layout_manager_layout_changed (GTK_LAYOUT_MANAGER (layout));
}
/**
* gtk_constraint_layout_add_guide:
* @layout: a `GtkConstraintLayout`
* @guide: (transfer full): a [class@Gtk.ConstraintGuide] object
*
* Adds a guide to `layout`.
*
* A guide can be used as the source or target of constraints,
* like a widget, but it is not visible.
*
* The `layout` acquires the ownership of `guide` after calling
* this function.
*/
void
gtk_constraint_layout_add_guide (GtkConstraintLayout *layout,
GtkConstraintGuide *guide)
{
g_return_if_fail (GTK_IS_CONSTRAINT_LAYOUT (layout));
g_return_if_fail (GTK_IS_CONSTRAINT_GUIDE (guide));
g_return_if_fail (gtk_constraint_guide_get_layout (guide) == NULL);
gtk_constraint_guide_set_layout (guide, layout);
g_hash_table_add (layout->guides, guide);
if (layout->guides_observer)
g_list_store_append (layout->guides_observer, guide);
gtk_constraint_guide_update (guide);
gtk_layout_manager_layout_changed (GTK_LAYOUT_MANAGER (layout));
}
/**
* gtk_constraint_layout_remove_guide:
* @layout: a `GtkConstraintLayout`
* @guide: a [class@Gtk.ConstraintGuide] object
*
* Removes `guide` from the layout manager,
* so that it no longer influences the layout.
*/
void
gtk_constraint_layout_remove_guide (GtkConstraintLayout *layout,
GtkConstraintGuide *guide)
{
g_return_if_fail (GTK_IS_CONSTRAINT_LAYOUT (layout));
g_return_if_fail (GTK_IS_CONSTRAINT_GUIDE (guide));
g_return_if_fail (gtk_constraint_guide_get_layout (guide) == layout);
gtk_constraint_guide_detach (guide);
gtk_constraint_guide_set_layout (guide, NULL);
g_hash_table_remove (layout->guides, guide);
if (layout->guides_observer)
list_store_remove_item (layout->guides_observer, guide);
gtk_layout_manager_layout_changed (GTK_LAYOUT_MANAGER (layout));
}
static GtkConstraintAttribute
attribute_from_name (const char *name)
{
if (name == NULL || *name == '\0')
return GTK_CONSTRAINT_ATTRIBUTE_NONE;
/* We sadly need to special case these two because the name does
* not match the VFL grammar rules
*/
if (strcmp (name, "centerX") == 0)
return GTK_CONSTRAINT_ATTRIBUTE_CENTER_X;
if (strcmp (name, "centerY") == 0)
return GTK_CONSTRAINT_ATTRIBUTE_CENTER_Y;
for (int i = 0; i < G_N_ELEMENTS (attribute_names); i++)
{
if (strcmp (attribute_names[i], name) == 0)
return i;
}
return GTK_CONSTRAINT_ATTRIBUTE_NONE;
}
GQuark
gtk_constraint_vfl_parser_error_quark (void)
{
return g_quark_from_static_string ("gtk-constraint-vfl-parser-error-quark");
}
/**
* gtk_constraint_layout_add_constraints_from_descriptionv: (rename-to gtk_constraint_layout_add_constraints_from_description)
* @layout: a `GtkConstraintLayout`
* @lines: (array length=n_lines): an array of Visual Format Language lines
* defining a set of constraints
* @n_lines: the number of lines
* @hspacing: default horizontal spacing value, or -1 for the fallback value
* @vspacing: default vertical spacing value, or -1 for the fallback value
* @views: (element-type utf8 Gtk.ConstraintTarget): a dictionary of `[ name, target ]`
* pairs; the `name` keys map to the view names in the VFL lines, while
* the `target` values map to children of the widget using a `GtkConstraintLayout`,
* or guides
* @error: return location for a `GError`
*
* Creates a list of constraints from a VFL description.
*
* The Visual Format Language, VFL, is based on Apple's AutoLayout [VFL](https://developer.apple.com/library/content/documentation/UserExperience/Conceptual/AutolayoutPG/VisualFormatLanguage.html).
*
* The `views` dictionary is used to match [iface@Gtk.ConstraintTarget]
* instances to the symbolic view name inside the VFL.
*
* The VFL grammar is:
*
* ```
* = ()?
* ()?
* ()*
* ()?
* = 'H' | 'V'
* = '|'
* = '' | '-' '-' | '-'
* = |
* = |
* = '(' (',' )* ')'
* = ()? ()? ('@' )?
* = '==' | '<=' | '>='
* = | | ('.' )?
* = | 'required' | 'strong' | 'medium' | 'weak'
* =
* = ()? ()?
* = [ '*' | '/' ]
* = [ '+' | '-' ]
* = [A-Za-z_]([A-Za-z0-9_]*) // A C identifier
* = [A-Za-z_]([A-Za-z0-9_]*) // A C identifier
* = 'top' | 'bottom' | 'left' | 'right' | 'width' | 'height' |
* 'start' | 'end' | 'centerX' | 'centerY' | 'baseline'
* // A positive real number parseable by g_ascii_strtod()
* // A real number parseable by g_ascii_strtod()
* ```
*
* **Note**: The VFL grammar used by GTK is slightly different than the one
* defined by Apple, as it can use symbolic values for the constraint's
* strength instead of numeric values; additionally, GTK allows adding
* simple arithmetic operations inside predicates.
*
* Examples of VFL descriptions are:
*
* ```
* // Default spacing
* [button]-[textField]
*
* // Width constraint
* [button(>=50)]
*
* // Connection to super view
* |-50-[purpleBox]-50-|
*
* // Vertical layout
* V:[topField]-10-[bottomField]
*
* // Flush views
* [maroonView][blueView]
*
* // Priority
* [button(100@strong)]
*
* // Equal widths
* [button1(==button2)]
*
* // Multiple predicates
* [flexibleButton(>=70,<=100)]
*
* // A complete line of layout
* |-[find]-[findNext]-[findField(>=20)]-|
*
* // Operators
* [button1(button2 / 3 + 50)]
*
* // Named attributes
* [button1(==button2.height)]
* ```
*
* Returns: (transfer container) (element-type GtkConstraint): the list of
* [class@Gtk.Constraint] instances that were added to the layout
*/
GList *
gtk_constraint_layout_add_constraints_from_descriptionv (GtkConstraintLayout *layout,
const char * const lines[],
gsize n_lines,
int hspacing,
int vspacing,
GHashTable *views,
GError **error)
{
GtkConstraintVflParser *parser;
GList *res = NULL;
g_return_val_if_fail (GTK_IS_CONSTRAINT_LAYOUT (layout), NULL);
g_return_val_if_fail (lines != NULL, NULL);
g_return_val_if_fail (views != NULL, NULL);
g_return_val_if_fail (error == NULL || *error == NULL, NULL);
parser = gtk_constraint_vfl_parser_new ();
gtk_constraint_vfl_parser_set_default_spacing (parser, hspacing, vspacing);
gtk_constraint_vfl_parser_set_views (parser, views);
for (gsize i = 0; i < n_lines; i++)
{
const char *line = lines[i];
GError *internal_error = NULL;
gtk_constraint_vfl_parser_parse_line (parser, line, -1, &internal_error);
if (internal_error != NULL)
{
int offset = gtk_constraint_vfl_parser_get_error_offset (parser);
int range = gtk_constraint_vfl_parser_get_error_range (parser);
char *squiggly = NULL;
if (range > 0)
squiggly = g_strnfill (range, '~');
g_set_error (error, GTK_CONSTRAINT_VFL_PARSER_ERROR,
internal_error->code,
"%" G_GSIZE_FORMAT ":%d: %s\n"
"%s\n"
"%*s^%s",
i, offset + 1,
internal_error->message,
line,
offset, " ", squiggly != NULL ? squiggly : "");
g_free (squiggly);
g_error_free (internal_error);
gtk_constraint_vfl_parser_free (parser);
return res;
}
int n_constraints = 0;
GtkConstraintVfl *constraints = gtk_constraint_vfl_parser_get_constraints (parser, &n_constraints);
for (int j = 0; j < n_constraints; j++)
{
const GtkConstraintVfl *c = &constraints[j];
gpointer source, target;
GtkConstraintAttribute source_attr, target_attr;
target = g_hash_table_lookup (views, c->view1);
target_attr = attribute_from_name (c->attr1);
if (c->view2 != NULL)
source = g_hash_table_lookup (views, c->view2);
else
source = NULL;
if (c->attr2 != NULL)
source_attr = attribute_from_name (c->attr2);
else
source_attr = GTK_CONSTRAINT_ATTRIBUTE_NONE;
GtkConstraint *constraint =
gtk_constraint_new (target, target_attr,
c->relation,
source, source_attr,
c->multiplier,
c->constant,
c->strength);
layout_add_constraint (layout, constraint);
g_hash_table_add (layout->constraints, constraint);
if (layout->constraints_observer)
g_list_store_append (layout->constraints_observer, constraint);
res = g_list_prepend (res, constraint);
}
g_free (constraints);
}
gtk_constraint_vfl_parser_free (parser);
gtk_layout_manager_layout_changed (GTK_LAYOUT_MANAGER (layout));
return res;
}
/**
* gtk_constraint_layout_add_constraints_from_description:
* @layout: a `GtkConstraintLayout`
* @lines: (array length=n_lines): an array of Visual Format Language lines
* defining a set of constraints
* @n_lines: the number of lines
* @hspacing: default horizontal spacing value, or -1 for the fallback value
* @vspacing: default vertical spacing value, or -1 for the fallback value
* @error: return location for a `GError`
* @first_view: the name of a view in the VFL description, followed by the
* [iface@Gtk.ConstraintTarget] to which it maps
* @...: a `NULL`-terminated list of view names and [iface@Gtk.ConstraintTarget]s
*
* Creates a list of constraints from a VFL description.
*
* This function is a convenience wrapper around
* [method@Gtk.ConstraintLayout.add_constraints_from_descriptionv], using
* variadic arguments to populate the view/target map.
*
* Returns: (transfer container) (element-type Gtk.Constraint): the list of
* [class@Gtk.Constraint]s that were added to the layout
*/
GList *
gtk_constraint_layout_add_constraints_from_description (GtkConstraintLayout *layout,
const char * const lines[],
gsize n_lines,
int hspacing,
int vspacing,
GError **error,
const char *first_view,
...)
{
GtkConstraintVflParser *parser;
GHashTable *views;
const char *view;
GList *res;
va_list args;
g_return_val_if_fail (GTK_IS_CONSTRAINT_LAYOUT (layout), NULL);
g_return_val_if_fail (lines != NULL, NULL);
g_return_val_if_fail (error == NULL || *error == NULL, NULL);
g_return_val_if_fail (first_view != NULL, NULL);
parser = gtk_constraint_vfl_parser_new ();
gtk_constraint_vfl_parser_set_default_spacing (parser, hspacing, vspacing);
views = g_hash_table_new (g_str_hash, g_str_equal);
va_start (args, first_view);
view = first_view;
while (view != NULL)
{
GtkConstraintTarget *target = va_arg (args, GtkConstraintTarget *);
if (target == NULL)
break;
g_hash_table_insert (views, (gpointer) view, target);
view = va_arg (args, const char *);
}
va_end (args);
res =
gtk_constraint_layout_add_constraints_from_descriptionv (layout, lines, n_lines,
hspacing, vspacing,
views,
error);
g_hash_table_unref (views);
return res;
}
/**
* gtk_constraint_layout_observe_constraints:
* @layout: a `GtkConstraintLayout`
*
* Returns a `GListModel` to track the constraints that are
* part of the layout.
*
* Calling this function will enable extra internal bookkeeping
* to track constraints and emit signals on the returned listmodel.
* It may slow down operations a lot.
*
* Applications should try hard to avoid calling this function
* because of the slowdowns.
*
* Returns: (transfer full) (attributes element-type=GtkConstraint): a
* `GListModel` tracking the layout's constraints
*/
GListModel *
gtk_constraint_layout_observe_constraints (GtkConstraintLayout *layout)
{
GHashTableIter iter;
gpointer key;
if (layout->constraints_observer)
return g_object_ref (G_LIST_MODEL (layout->constraints_observer));
layout->constraints_observer = g_list_store_new (GTK_TYPE_CONSTRAINT);
g_object_add_weak_pointer ((GObject *)layout->constraints_observer,
(gpointer *)&layout->constraints_observer);
g_hash_table_iter_init (&iter, layout->constraints);
while (g_hash_table_iter_next (&iter, &key, NULL))
{
GtkConstraint *constraint = key;
g_list_store_append (layout->constraints_observer, constraint);
}
return G_LIST_MODEL (layout->constraints_observer);
}
/**
* gtk_constraint_layout_observe_guides:
* @layout: a `GtkConstraintLayout`
*
* Returns a `GListModel` to track the guides that are
* part of the layout.
*
* Calling this function will enable extra internal bookkeeping
* to track guides and emit signals on the returned listmodel.
* It may slow down operations a lot.
*
* Applications should try hard to avoid calling this function
* because of the slowdowns.
*
* Returns: (transfer full) (attributes element-type=GtkConstraintGuide): a
* `GListModel` tracking the layout's guides
*/
GListModel *
gtk_constraint_layout_observe_guides (GtkConstraintLayout *layout)
{
GHashTableIter iter;
gpointer key;
if (layout->guides_observer)
return g_object_ref (G_LIST_MODEL (layout->guides_observer));
layout->guides_observer = g_list_store_new (GTK_TYPE_CONSTRAINT_GUIDE);
g_object_add_weak_pointer ((GObject *)layout->guides_observer,
(gpointer *)&layout->guides_observer);
g_hash_table_iter_init (&iter, layout->guides);
while (g_hash_table_iter_next (&iter, &key, NULL))
{
GtkConstraintGuide *guide = key;
g_list_store_append (layout->guides_observer, guide);
}
return G_LIST_MODEL (layout->guides_observer);
}