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/* Drawing Area
*
* GtkDrawingArea is a blank area where you can draw custom displays
* of various kinds.
*
* This demo has two drawing areas. The checkerboard area shows
* how you can just draw something; all you have to do is set a function
* via gtk_drawing_area_set_draw_func(), as shown here.
*
* The "scribble" area is a bit more advanced, and shows how to handle
* events such as button presses and mouse motion. Click the mouse
* and drag in the scribble area to draw squiggles. Resize the window
* to clear the area.
*/
#include <gtk/gtk.h>
static GtkWidget *window = NULL;
/* Pixmap for scribble area, to store current scribbles */
static cairo_surface_t *surface = NULL;
/* Create a new surface of the appropriate size to store our scribbles */
static void
create_surface (GtkWidget *widget)
{
cairo_t *cr;
if (surface)
cairo_surface_destroy (surface);
surface = cairo_image_surface_create (CAIRO_FORMAT_ARGB32,
gtk_widget_get_width (widget),
gtk_widget_get_height (widget));
/* Initialize the surface to white */
cr = cairo_create (surface);
cairo_set_source_rgb (cr, 1, 1, 1);
cairo_paint (cr);
cairo_destroy (cr);
}
static void
scribble_size_allocate (GtkWidget *widget)
{
create_surface (widget);
}
/* Redraw the screen from the surface */
static void
scribble_draw (GtkDrawingArea *da,
cairo_t *cr,
int width,
int height,
gpointer data)
{
cairo_set_source_surface (cr, surface, 0, 0);
cairo_paint (cr);
}
/* Draw a rectangle on the screen */
static void
draw_brush (GtkWidget *widget,
gdouble x,
gdouble y)
{
GdkRectangle update_rect;
cairo_t *cr;
if (surface == NULL ||
cairo_image_surface_get_width (surface) != gtk_widget_get_width (widget) ||
cairo_image_surface_get_height (surface) != gtk_widget_get_height (widget))
create_surface (widget);
update_rect.x = x - 3;
update_rect.y = y - 3;
update_rect.width = 6;
update_rect.height = 6;
/* Paint to the surface, where we store our state */
cr = cairo_create (surface);
gdk_cairo_rectangle (cr, &update_rect);
cairo_fill (cr);
cairo_destroy (cr);
gtk_widget_queue_draw (widget);
}
static double start_x;
static double start_y;
static void
drag_begin (GtkGestureDrag *gesture,
double x,
double y,
GtkWidget *area)
{
start_x = x;
start_y = y;
draw_brush (area, x, y);
}
static void
drag_update (GtkGestureDrag *gesture,
double x,
double y,
GtkWidget *area)
{
draw_brush (area, start_x + x, start_y + y);
}
static void
drag_end (GtkGestureDrag *gesture,
double x,
double y,
GtkWidget *area)
{
draw_brush (area, start_x + x, start_y + y);
}
static void
checkerboard_draw (GtkDrawingArea *da,
cairo_t *cr,
int width,
int height,
gpointer data)
{
gint i, j, xcount, ycount;
#define CHECK_SIZE 10
#define SPACING 2
/* At the start of a draw handler, a clip region has been set on
* the Cairo context, and the contents have been cleared to the
* widget's background color. The docs for
* gdk_surface_begin_paint_region() give more details on how this
* works.
*/
xcount = 0;
i = SPACING;
while (i < width)
{
j = SPACING;
ycount = xcount % 2; /* start with even/odd depending on row */
while (j < height)
{
if (ycount % 2)
cairo_set_source_rgb (cr, 0.45777, 0, 0.45777);
else
cairo_set_source_rgb (cr, 1, 1, 1);
/* If we're outside the clip, this will do nothing.
*/
cairo_rectangle (cr, i, j, CHECK_SIZE, CHECK_SIZE);
cairo_fill (cr);
j += CHECK_SIZE + SPACING;
++ycount;
}
i += CHECK_SIZE + SPACING;
++xcount;
}
}
static void
close_window (void)
{
window = NULL;
if (surface)
cairo_surface_destroy (surface);
surface = NULL;
}
GtkWidget *
do_drawingarea (GtkWidget *do_widget)
{
GtkWidget *frame;
GtkWidget *vbox;
GtkWidget *da;
GtkWidget *label;
GtkGesture *drag;
if (!window)
{
window = gtk_window_new ();
gtk_window_set_display (GTK_WINDOW (window),
gtk_widget_get_display (do_widget));
gtk_window_set_title (GTK_WINDOW (window), "Drawing Area");
g_signal_connect (window, "destroy",
G_CALLBACK (close_window), NULL);
vbox = gtk_box_new (GTK_ORIENTATION_VERTICAL, 8);
gtk_widget_set_margin_start (vbox, 16);
gtk_widget_set_margin_end (vbox, 16);
gtk_widget_set_margin_top (vbox, 16);
gtk_widget_set_margin_bottom (vbox, 16);
gtk_container_add (GTK_CONTAINER (window), vbox);
/*
* Create the checkerboard area
*/
label = gtk_label_new (NULL);
gtk_label_set_markup (GTK_LABEL (label),
"<u>Checkerboard pattern</u>");
gtk_container_add (GTK_CONTAINER (vbox), label);
frame = gtk_frame_new (NULL);
gtk_frame_set_shadow_type (GTK_FRAME (frame), GTK_SHADOW_IN);
gtk_widget_set_vexpand (frame, TRUE);
gtk_container_add (GTK_CONTAINER (vbox), frame);
da = gtk_drawing_area_new ();
gtk_drawing_area_set_content_width (GTK_DRAWING_AREA (da), 100);
gtk_drawing_area_set_content_height (GTK_DRAWING_AREA (da), 100);
gtk_drawing_area_set_draw_func (GTK_DRAWING_AREA (da), checkerboard_draw, NULL, NULL);
gtk_container_add (GTK_CONTAINER (frame), da);
/*
* Create the scribble area
*/
label = gtk_label_new (NULL);
gtk_label_set_markup (GTK_LABEL (label),
"<u>Scribble area</u>");
gtk_container_add (GTK_CONTAINER (vbox), label);
frame = gtk_frame_new (NULL);
gtk_widget_set_vexpand (frame, TRUE);
gtk_frame_set_shadow_type (GTK_FRAME (frame), GTK_SHADOW_IN);
gtk_container_add (GTK_CONTAINER (vbox), frame);
da = gtk_drawing_area_new ();
gtk_drawing_area_set_content_width (GTK_DRAWING_AREA (da), 100);
gtk_drawing_area_set_content_height (GTK_DRAWING_AREA (da), 100);
gtk_drawing_area_set_draw_func (GTK_DRAWING_AREA (da), scribble_draw, NULL, NULL);
gtk_container_add (GTK_CONTAINER (frame), da);
g_signal_connect (da, "size-allocate",
G_CALLBACK (scribble_size_allocate), NULL);
drag = gtk_gesture_drag_new ();
gtk_gesture_single_set_button (GTK_GESTURE_SINGLE (drag), GDK_BUTTON_PRIMARY);
gtk_widget_add_controller (da, GTK_EVENT_CONTROLLER (drag));
g_signal_connect (drag, "drag-begin", G_CALLBACK (drag_begin), da);
g_signal_connect (drag, "drag-update", G_CALLBACK (drag_update), da);
g_signal_connect (drag, "drag-end", G_CALLBACK (drag_end), da);
}
if (!gtk_widget_get_visible (window))
gtk_widget_show (window);
else
gtk_widget_destroy (window);
return window;
}
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