Add GtkConstraintLayout

A layout manager using GtkConstraintSolver to measure and allocate
children.

1 files changed, 583 insertions, 0 deletions

diff --git a/gtk/gtkconstraint.c b/gtk/gtkconstraint.c
new file mode 100644
index 0000000000..d0c152b56d
--- /dev/null
+++ b/gtk/gtkconstraint.c
@@ -0,0 +1,583 @@
+/* gtkconstraint.c: Constraint between two widgets
+ * 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 <http://www.gnu.org/licenses/>.
+ *
+ * Author: Emmanuele Bassi
+ */
+
+/**
+ * SECTION:gtkconstraint
+ * @Title: GtkConstraint
+ * @Short_description: The description of a constraint
+ *
+ * #GtkConstraint describes a constraint between an attribute on a widget
+ * and another attribute on another widget, expressed as a linear equation
+ * like:
+ *
+ * |[
+ *   target.attr1 = source.attr2 × multiplier + constant
+ * ]|
+ *
+ * Each #GtkConstraint is part of a system that will be solved by a
+ * #GtkConstraintLayout in order to allocate and position each child widget.
+ *
+ * The source and target widgets, as well as their attributes, of a
+ * #GtkConstraint instance are immutable after creation.
+ */
+
+#include "config.h"
+
+#include "gtkconstraintprivate.h"
+#include "gtkconstraintsolverprivate.h"
+#include "gtkintl.h"
+#include "gtktypebuiltins.h"
+#include "gtkwidget.h"
+
+enum {
+  PROP_TARGET_WIDGET = 1,
+  PROP_TARGET_ATTRIBUTE,
+  PROP_RELATION,
+  PROP_SOURCE_WIDGET,
+  PROP_SOURCE_ATTRIBUTE,
+  PROP_MULTIPLIER,
+  PROP_CONSTANT,
+  PROP_STRENGTH,
+
+  N_PROPERTIES
+};
+
+static GParamSpec *obj_props[N_PROPERTIES];
+
+G_DEFINE_TYPE (GtkConstraint, gtk_constraint, G_TYPE_OBJECT)
+
+static void
+gtk_constraint_set_property (GObject      *gobject,
+                             guint         prop_id,
+                             const GValue *value,
+                             GParamSpec   *pspec)
+{
+  GtkConstraint *self = GTK_CONSTRAINT (gobject);
+
+  switch (prop_id)
+    {
+    case PROP_TARGET_WIDGET:
+      self->target_widget = g_value_get_object (value);
+      break;
+
+    case PROP_TARGET_ATTRIBUTE:
+      self->target_attribute = g_value_get_enum (value);
+      break;
+
+    case PROP_RELATION:
+      self->relation = g_value_get_enum (value);
+      break;
+
+    case PROP_SOURCE_WIDGET:
+      self->source_widget = g_value_get_object (value);
+      break;
+
+    case PROP_SOURCE_ATTRIBUTE:
+      self->source_attribute = g_value_get_enum (value);
+      break;
+
+    case PROP_MULTIPLIER:
+      self->multiplier = g_value_get_double (value);
+      break;
+
+    case PROP_CONSTANT:
+      self->constant = g_value_get_double (value);
+      break;
+
+    case PROP_STRENGTH:
+      self->strength = g_value_get_int (value);
+      break;
+
+    default:
+      G_OBJECT_WARN_INVALID_PROPERTY_ID (gobject, prop_id, pspec);
+      break;
+    }
+}
+
+static void
+gtk_constraint_get_property (GObject    *gobject,
+                             guint       prop_id,
+                             GValue     *value,
+                             GParamSpec *pspec)
+{
+  GtkConstraint *self = GTK_CONSTRAINT (gobject);
+
+  switch (prop_id)
+    {
+    case PROP_TARGET_WIDGET:
+      g_value_set_object (value, self->target_widget);
+      break;
+
+    case PROP_TARGET_ATTRIBUTE:
+      g_value_set_enum (value, self->target_attribute);
+      break;
+
+    case PROP_RELATION:
+      g_value_set_enum (value, self->relation);
+      break;
+
+    case PROP_SOURCE_WIDGET:
+      g_value_set_object (value, self->source_widget);
+      break;
+
+    case PROP_SOURCE_ATTRIBUTE:
+      g_value_set_enum (value, self->source_attribute);
+      break;
+
+    case PROP_MULTIPLIER:
+      g_value_set_double (value, self->multiplier);
+      break;
+
+    case PROP_CONSTANT:
+      g_value_set_double (value, self->constant);
+      break;
+
+    case PROP_STRENGTH:
+      g_value_set_int (value, self->strength);
+      break;
+
+    default:
+      G_OBJECT_WARN_INVALID_PROPERTY_ID (gobject, prop_id, pspec);
+      break;
+    }
+}
+
+static void
+gtk_constraint_finalize (GObject *gobject)
+{
+  GtkConstraint *self = GTK_CONSTRAINT (gobject);
+
+  gtk_constraint_detach (self);
+
+  G_OBJECT_CLASS (gtk_constraint_parent_class)->finalize (gobject);
+}
+
+static void
+gtk_constraint_class_init (GtkConstraintClass *klass)
+{
+  GObjectClass *gobject_class = G_OBJECT_CLASS (klass);
+
+  gobject_class->set_property = gtk_constraint_set_property;
+  gobject_class->get_property = gtk_constraint_get_property;
+  gobject_class->finalize = gtk_constraint_finalize;
+
+  /**
+   * GtkConstraint:target-widget:
+   *
+   * The target widget of the constraint.
+   *
+   * The constraint will set the #GtkConstraint:target-attribute of the
+   * target widget using the #GtkConstraint:source-attribute of the source
+   * widget.
+   */
+  obj_props[PROP_TARGET_WIDGET] =
+    g_param_spec_object ("target-widget",
+                         P_("Target Widget"),
+                         P_("The target widget of the constraint"),
+                         GTK_TYPE_WIDGET,
+                         G_PARAM_READWRITE |
+                         G_PARAM_STATIC_STRINGS |
+                         G_PARAM_CONSTRUCT_ONLY);
+  /**
+   * GtkConstraint:target-attribute:
+   *
+   * The attribute of the #GtkConstraint:target-widget set by the constraint.
+   */
+  obj_props[PROP_TARGET_ATTRIBUTE] =
+    g_param_spec_enum ("target-attribute",
+                       P_("Target Attribute"),
+                       P_("The attribute of the target widget set by the constraint"),
+                       GTK_TYPE_CONSTRAINT_ATTRIBUTE,
+                       GTK_CONSTRAINT_ATTRIBUTE_NONE,
+                       G_PARAM_READWRITE |
+                       G_PARAM_STATIC_STRINGS |
+                       G_PARAM_CONSTRUCT_ONLY);
+  /**
+   * GtkConstraint:relation:
+   *
+   * The relation order between the terms of the constraint.
+   */
+  obj_props[PROP_RELATION] =
+    g_param_spec_enum ("relation",
+                       P_("Relation"),
+                       P_("The relation between the source and target attributes"),
+                       GTK_TYPE_CONSTRAINT_RELATION,
+                       GTK_CONSTRAINT_RELATION_EQ,
+                       G_PARAM_READWRITE |
+                       G_PARAM_STATIC_STRINGS |
+                       G_PARAM_CONSTRUCT_ONLY);
+  /**
+   * GtkConstraint:source-widget:
+   *
+   * The source widget of the constraint.
+   *
+   * The constraint will set the #GtkConstraint:target-attribute of the
+   * target widget using the #GtkConstraint:source-attribute of the source
+   * widget.
+   */
+  obj_props[PROP_SOURCE_WIDGET] =
+    g_param_spec_object ("source-widget",
+                         P_("Source Widget"),
+                         P_("The source widget of the constraint"),
+                         GTK_TYPE_WIDGET,
+                         G_PARAM_READWRITE |
+                         G_PARAM_STATIC_STRINGS |
+                         G_PARAM_CONSTRUCT_ONLY);
+  /**
+   * GtkConstraint:source-attribute:
+   *
+   * The attribute of the #GtkConstraint:source-widget read by the constraint.
+   */
+  obj_props[PROP_SOURCE_ATTRIBUTE] =
+    g_param_spec_enum ("source-attribute",
+                       P_("Source Attribute"),
+                       P_("The attribute of the source widget set by the constraint"),
+                       GTK_TYPE_CONSTRAINT_ATTRIBUTE,
+                       GTK_CONSTRAINT_ATTRIBUTE_NONE,
+                       G_PARAM_READWRITE |
+                       G_PARAM_STATIC_STRINGS |
+                       G_PARAM_CONSTRUCT_ONLY);
+  /**
+   * GtkConstraint:multiplier:
+   *
+   * The multiplication factor to be applied to the
+   * #GtkConstraint:source-attribue.
+   */
+  obj_props[PROP_MULTIPLIER] =
+    g_param_spec_double ("multiplier",
+                         P_("Multiplier"),
+                         P_("The multiplication factor to be applied to the source attribute"),
+                         -G_MAXDOUBLE, G_MAXDOUBLE, 1.0,
+                         G_PARAM_READWRITE |
+                         G_PARAM_STATIC_STRINGS |
+                         G_PARAM_CONSTRUCT_ONLY);
+  /**
+   * GtkConstraint:constant:
+   *
+   * The constant value to be added to the #GtkConstraint:source-attribute.
+   */
+  obj_props[PROP_CONSTANT] =
+    g_param_spec_double ("constant",
+                         P_("Constant"),
+                         P_("The constant to be added to the source attribute"),
+                         -G_MAXDOUBLE, G_MAXDOUBLE, 0.0,
+                         G_PARAM_READWRITE |
+                         G_PARAM_STATIC_STRINGS |
+                         G_PARAM_CONSTRUCT_ONLY);
+  /**
+   * GtkConstraint:strength:
+   *
+   * The strength of the constraint.
+   *
+   * The strength can be expressed either using one of the symbolic values
+   * of the #GtkConstraintStrength enumeration, or any positive integer
+   * value.
+   */
+  obj_props[PROP_STRENGTH] =
+    g_param_spec_int ("strength",
+                      P_("Strength"),
+                      P_("The strength of the constraint"),
+                      GTK_CONSTRAINT_STRENGTH_WEAK, G_MAXINT,
+                      GTK_CONSTRAINT_STRENGTH_REQUIRED,
+                      G_PARAM_READWRITE |
+                      G_PARAM_STATIC_STRINGS |
+                      G_PARAM_CONSTRUCT_ONLY);
+
+  g_object_class_install_properties (gobject_class, N_PROPERTIES, obj_props);
+}
+
+static void
+gtk_constraint_init (GtkConstraint *self)
+{
+  self->multiplier = 1.0;
+  self->constant = 0.0;
+
+  self->target_attribute = GTK_CONSTRAINT_ATTRIBUTE_NONE;
+  self->source_attribute = GTK_CONSTRAINT_ATTRIBUTE_NONE;
+  self->relation = GTK_CONSTRAINT_RELATION_EQ;
+  self->strength = GTK_CONSTRAINT_STRENGTH_REQUIRED;
+}
+
+/**
+ * gtk_constraint_new:
+ * @target_widget: (nullable): a #GtkWidget
+ * @target_attribute: the attribute of @target_widget to be set
+ * @relation: the relation equivalence between @target_attribute and @source_attribute
+ * @source_widget: (nullable): a #GtkWidget
+ * @source_attribute: the attribute of @source_widget to be read
+ * @multiplier: a multiplication factor to be applied to @source_attribute
+ * @constant: a constant factor to be added to @source_attribute
+ * @strength: the strength of the constraint
+ *
+ * Creates a new #GtkConstraint representing a relation between a layout
+ * attribute on a source #GtkWidget and a layout attribute on a target
+ * #GtkWidget.
+ *
+ * Returns: the newly created #GtkConstraint
+ */
+GtkConstraint *
+gtk_constraint_new (GtkWidget              *target_widget,
+                    GtkConstraintAttribute  target_attribute,
+                    GtkConstraintRelation   relation,
+                    GtkWidget              *source_widget,
+                    GtkConstraintAttribute  source_attribute,
+                    double                  multiplier,
+                    double                  constant,
+                    int                     strength)
+{
+  g_return_val_if_fail (target_widget == NULL || GTK_IS_WIDGET (target_widget), NULL);
+  g_return_val_if_fail (source_widget == NULL || GTK_IS_WIDGET (source_widget), NULL);
+
+  return g_object_new (GTK_TYPE_CONSTRAINT,
+                       "target-widget", target_widget,
+                       "target-attribute", target_attribute,
+                       "relation", relation,
+                       "source-widget", source_widget,
+                       "source-attribute", source_attribute,
+                       "multiplier", multiplier,
+                       "constant", constant,
+                       "strength", strength,
+                       NULL);
+}
+
+/**
+ * gtk_constraint_new_constant:
+ * @target_widget: (nullable): a #GtkWidget
+ * @target_attribute: the attribute of @target_widget to be set
+ * @relation: the relation equivalence between @target_attribute and @constant
+ * @constant: a constant factor to be set on @target_attribute
+ * @strength: the strength of the constraint
+ *
+ * Creates a new #GtkConstraint representing a relation between a layout
+ * attribute on a target #GtkWidget and a constant value.
+ *
+ * Returns: the newly created #GtkConstraint
+ */
+GtkConstraint *
+gtk_constraint_new_constant (GtkWidget              *target_widget,
+                             GtkConstraintAttribute  target_attribute,
+                             GtkConstraintRelation   relation,
+                             double                  constant,
+                             int                     strength)
+{
+  g_return_val_if_fail (target_widget == NULL || GTK_IS_WIDGET (target_widget), NULL);
+
+  return g_object_new (GTK_TYPE_CONSTRAINT,
+                       "target-widget", target_widget,
+                       "target-attribute", target_attribute,
+                       "relation", relation,
+                       "source-attribute", GTK_CONSTRAINT_ATTRIBUTE_NONE,
+                       "constant", constant,
+                       "strength", strength,
+                       NULL);
+}
+
+/**
+ * gtk_constraint_get_target_widget:
+ * @constraint: a #GtkConstraint
+ *
+ * Retrieves the target widget for the @constraint.
+ *
+ * Returns: (transfer none) (nullable): a #GtkWidget
+ */
+GtkWidget *
+gtk_constraint_get_target_widget (GtkConstraint *constraint)
+{
+  g_return_val_if_fail (GTK_IS_CONSTRAINT (constraint), NULL);
+
+  return constraint->target_widget;
+}
+
+GtkConstraintAttribute
+gtk_constraint_get_target_attribute (GtkConstraint *constraint)
+{
+  g_return_val_if_fail (GTK_IS_CONSTRAINT (constraint), GTK_CONSTRAINT_ATTRIBUTE_NONE);
+
+  return constraint->target_attribute;
+}
+
+/**
+ * gtk_constraint_get_source_widget:
+ * @constraint: a #GtkConstraint
+ *
+ * Retrieves the source widget for the @constraint.
+ *
+ * Returns: (transfer none) (nullable): a #GtkWidget
+ */
+GtkWidget *
+gtk_constraint_get_source_widget (GtkConstraint *constraint)
+{
+  g_return_val_if_fail (GTK_IS_CONSTRAINT (constraint), NULL);
+
+  return constraint->source_widget;
+}
+
+GtkConstraintAttribute
+gtk_constraint_get_source_attribute (GtkConstraint *constraint)
+{
+  g_return_val_if_fail (GTK_IS_CONSTRAINT (constraint), GTK_CONSTRAINT_ATTRIBUTE_NONE);
+
+  return constraint->source_attribute;
+}
+
+GtkConstraintRelation
+gtk_constraint_get_relation (GtkConstraint *constraint)
+{
+  g_return_val_if_fail (GTK_IS_CONSTRAINT (constraint), GTK_CONSTRAINT_RELATION_EQ);
+
+  return constraint->relation;
+}
+
+double
+gtk_constraint_get_multiplier (GtkConstraint *constraint)
+{
+  g_return_val_if_fail (GTK_IS_CONSTRAINT (constraint), 1.0);
+
+  return constraint->multiplier;
+}
+
+double
+gtk_constraint_get_constant (GtkConstraint *constraint)
+{
+  g_return_val_if_fail (GTK_IS_CONSTRAINT (constraint), 0.0);
+
+  return constraint->constant;
+}
+
+int
+gtk_constraint_get_strength (GtkConstraint *constraint)
+{
+  g_return_val_if_fail (GTK_IS_CONSTRAINT (constraint), GTK_CONSTRAINT_STRENGTH_REQUIRED);
+
+  return constraint->strength;
+}
+
+/*< private >
+ * gtk_constraint_get_weight:
+ * @constraint: a #GtkConstraint
+ *
+ * Computes the weight of the @constraint to be used with
+ * #GtkConstraintSolver.
+ *
+ * Returns: the weight of the constraint
+ */
+double
+gtk_constraint_get_weight (GtkConstraint *constraint)
+{
+  if (constraint->strength > 0)
+    return constraint->strength;
+
+  switch (constraint->strength)
+    {
+    case GTK_CONSTRAINT_STRENGTH_REQUIRED:
+      return GTK_CONSTRAINT_WEIGHT_REQUIRED;
+
+    case GTK_CONSTRAINT_STRENGTH_STRONG:
+      return GTK_CONSTRAINT_WEIGHT_STRONG;
+
+    case GTK_CONSTRAINT_STRENGTH_MEDIUM:
+      return GTK_CONSTRAINT_WEIGHT_MEDIUM;
+
+    case GTK_CONSTRAINT_STRENGTH_WEAK:
+      return GTK_CONSTRAINT_WEIGHT_WEAK;
+
+    default:
+      g_assert_not_reached ();
+    }
+
+  return 0;
+}
+
+/**
+ * gtk_constraint_is_required:
+ * @constraint: a #GtkConstraint
+ *
+ * Checks whether the @constraint is a required relation for solving the
+ * constraint layout.
+ *
+ * Returns: %TRUE if the constraint is required
+ */
+gboolean
+gtk_constraint_is_required (GtkConstraint *constraint)
+{
+  g_return_val_if_fail (GTK_IS_CONSTRAINT (constraint), FALSE);
+
+  return constraint->strength == GTK_CONSTRAINT_STRENGTH_REQUIRED;
+}
+
+/**
+ * gtk_constraint_is_attached:
+ * @constraint: a #GtkConstraint
+ *
+ * Checks whether the @constraint is attached to a #GtkConstraintLayout,
+ * and it is contributing to the layout.
+ *
+ * Returns: %TRUE if the constraint is attached
+ */
+gboolean
+gtk_constraint_is_attached (GtkConstraint *constraint)
+{
+  g_return_val_if_fail (GTK_IS_CONSTRAINT (constraint), FALSE);
+
+  return constraint->constraint_ref != NULL;
+}
+
+/**
+ * gtk_constraint_is_constant:
+ * @constraint: a #GtkConstraint
+ *
+ * Checks whether the @constraint describes a relation between an attribute
+ * on the #GtkConstraint:target-widget and a constant value.
+ *
+ * Returns: %TRUE if the constraint is a constant relation
+ */
+gboolean
+gtk_constraint_is_constant (GtkConstraint *constraint)
+{
+  g_return_val_if_fail (GTK_IS_CONSTRAINT (constraint), FALSE);
+
+  return constraint->source_widget == NULL &&
+         constraint->source_attribute == GTK_CONSTRAINT_ATTRIBUTE_NONE;
+}
+
+void
+gtk_constraint_attach (GtkConstraint       *constraint,
+                       GtkConstraintSolver *solver,
+                       GtkConstraintRef    *ref)
+{
+  g_return_if_fail (GTK_IS_CONSTRAINT (constraint));
+  g_return_if_fail (GTK_IS_CONSTRAINT_SOLVER (solver));
+  g_return_if_fail (ref != NULL);
+
+  constraint->constraint_ref = ref;
+  constraint->solver = solver;
+}
+
+void
+gtk_constraint_detach (GtkConstraint *constraint)
+{
+  g_return_if_fail (GTK_IS_CONSTRAINT (constraint));
+
+  if (constraint->constraint_ref == NULL)
+    return;
+
+  gtk_constraint_solver_remove_constraint (constraint->solver, constraint->constraint_ref);
+  constraint->constraint_ref = NULL;
+  constraint->solver = NULL;
+}