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#include <gtk/gtk.h>
/* Surface to store current scribbles */
static cairo_surface_t *surface = NULL;
static void
clear_surface (void)
{
cairo_t *cr;
cr = cairo_create (surface);
cairo_set_source_rgb (cr, 1, 1, 1);
cairo_paint (cr);
cairo_destroy (cr);
}
/* Create a new surface of the appropriate size to store our scribbles */
static void
resize_cb (GtkWidget *widget,
int width,
int height,
gpointer data)
{
if (surface)
{
cairo_surface_destroy (surface);
surface = NULL;
}
if (gtk_native_get_surface (gtk_widget_get_native (widget)))
{
surface = cairo_image_surface_create (CAIRO_FORMAT_ARGB32,
gtk_widget_get_width (widget),
gtk_widget_get_height (widget));
/* Initialize the surface to white */
clear_surface ();
}
}
/* Redraw the screen from the surface. Note that the draw
* callback receives a ready-to-be-used cairo_t that is already
* clipped to only draw the exposed areas of the widget
*/
static void
draw_cb (GtkDrawingArea *drawing_area,
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 surface at the given position */
static void
draw_brush (GtkWidget *widget,
double x,
double y)
{
cairo_t *cr;
/* Paint to the surface, where we store our state */
cr = cairo_create (surface);
cairo_rectangle (cr, x - 3, y - 3, 6, 6);
cairo_fill (cr);
cairo_destroy (cr);
/* Now invalidate the drawing area. */
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
pressed (GtkGestureClick *gesture,
int n_press,
double x,
double y,
GtkWidget *area)
{
clear_surface ();
gtk_widget_queue_draw (area);
}
static void
close_window (void)
{
if (surface)
cairo_surface_destroy (surface);
}
static void
activate (GtkApplication *app,
gpointer user_data)
{
GtkWidget *window;
GtkWidget *drawing_area;
GtkGesture *drag;
GtkGesture *press;
window = gtk_application_window_new (app);
gtk_window_set_title (GTK_WINDOW (window), "Drawing Area");
g_signal_connect (window, "destroy", G_CALLBACK (close_window), NULL);
drawing_area = gtk_drawing_area_new ();
/* set a minimum size */
gtk_widget_set_size_request (drawing_area, 100, 100);
gtk_window_set_child (GTK_WINDOW (window), drawing_area);
gtk_drawing_area_set_draw_func (GTK_DRAWING_AREA (drawing_area), draw_cb, NULL, NULL);
g_signal_connect_after (drawing_area, "resize", G_CALLBACK (resize_cb), NULL);
drag = gtk_gesture_drag_new ();
gtk_gesture_single_set_button (GTK_GESTURE_SINGLE (drag), GDK_BUTTON_PRIMARY);
gtk_widget_add_controller (drawing_area, GTK_EVENT_CONTROLLER (drag));
g_signal_connect (drag, "drag-begin", G_CALLBACK (drag_begin), drawing_area);
g_signal_connect (drag, "drag-update", G_CALLBACK (drag_update), drawing_area);
g_signal_connect (drag, "drag-end", G_CALLBACK (drag_end), drawing_area);
press = gtk_gesture_click_new ();
gtk_gesture_single_set_button (GTK_GESTURE_SINGLE (press), GDK_BUTTON_SECONDARY);
gtk_widget_add_controller (drawing_area, GTK_EVENT_CONTROLLER (press));
g_signal_connect (press, "pressed", G_CALLBACK (pressed), drawing_area);
gtk_window_present (GTK_WINDOW (window));
}
int
main (int argc,
char **argv)
{
GtkApplication *app;
int status;
app = gtk_application_new ("org.gtk.example", G_APPLICATION_FLAGS_NONE);
g_signal_connect (app, "activate", G_CALLBACK (activate), NULL);
status = g_application_run (G_APPLICATION (app), argc, argv);
g_object_unref (app);
return status;
}
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