mirror of
https://gitlab.gnome.org/GNOME/gtk.git
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185 lines
4.8 KiB
C
185 lines
4.8 KiB
C
#include <gtk/gtk.h>
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/* Surface to store current scribbles */
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static cairo_surface_t *surface = NULL;
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static void
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clear_surface (void)
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{
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cairo_t *cr;
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cr = cairo_create (surface);
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cairo_set_source_rgb (cr, 1, 1, 1);
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cairo_paint (cr);
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cairo_destroy (cr);
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}
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/* Create a new surface of the appropriate size to store our scribbles */
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static gboolean
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configure_event_cb (GtkWidget *widget,
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GdkEventConfigure *event,
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gpointer data)
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{
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if (surface)
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cairo_surface_destroy (surface);
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surface = gdk_window_create_similar_surface (gtk_widget_get_window (widget),
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CAIRO_CONTENT_COLOR,
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gtk_widget_get_allocated_width (widget),
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gtk_widget_get_allocated_height (widget));
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/* Initialize the surface to white */
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clear_surface ();
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/* We've handled the configure event, no need for further processing. */
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return TRUE;
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}
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/* Redraw the screen from the surface. Note that the ::draw
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* signal receives a ready-to-be-used cairo_t that is already
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* clipped to only draw the exposed areas of the widget
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*/
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static gboolean
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draw_cb (GtkWidget *widget,
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cairo_t *cr,
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gpointer data)
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{
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cairo_set_source_surface (cr, surface, 0, 0);
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cairo_paint (cr);
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return FALSE;
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}
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/* Draw a rectangle on the surface at the given position */
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static void
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draw_brush (GtkWidget *widget,
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gdouble x,
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gdouble y)
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{
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cairo_t *cr;
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/* Paint to the surface, where we store our state */
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cr = cairo_create (surface);
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cairo_rectangle (cr, x - 3, y - 3, 6, 6);
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cairo_fill (cr);
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cairo_destroy (cr);
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/* Now invalidate the affected region of the drawing area. */
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gtk_widget_queue_draw_area (widget, x - 3, y - 3, 6, 6);
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}
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/* Handle button press events by either drawing a rectangle
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* or clearing the surface, depending on which button was pressed.
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* The ::button-press signal handler receives a GdkEventButton
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* struct which contains this information.
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*/
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static gboolean
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button_press_event_cb (GtkWidget *widget,
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GdkEventButton *event,
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gpointer data)
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{
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/* paranoia check, in case we haven't gotten a configure event */
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if (surface == NULL)
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return FALSE;
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if (event->button == GDK_BUTTON_PRIMARY)
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{
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draw_brush (widget, event->x, event->y);
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}
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else if (event->button == GDK_BUTTON_SECONDARY)
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{
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clear_surface ();
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gtk_widget_queue_draw (widget);
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}
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/* We've handled the event, stop processing */
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return TRUE;
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}
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/* Handle motion events by continuing to draw if button 1 is
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* still held down. The ::motion-notify signal handler receives
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* a GdkEventMotion struct which contains this information.
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*/
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static gboolean
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motion_notify_event_cb (GtkWidget *widget,
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GdkEventMotion *event,
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gpointer data)
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{
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/* paranoia check, in case we haven't gotten a configure event */
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if (surface == NULL)
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return FALSE;
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if (event->state & GDK_BUTTON1_MASK)
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draw_brush (widget, event->x, event->y);
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/* We've handled it, stop processing */
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return TRUE;
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}
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static void
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close_window (void)
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{
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if (surface)
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cairo_surface_destroy (surface);
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gtk_main_quit ();
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}
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int
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main (int argc,
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char *argv[])
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{
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GtkWidget *window;
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GtkWidget *frame;
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GtkWidget *da;
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gtk_init (&argc, &argv);
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window = gtk_window_new (GTK_WINDOW_TOPLEVEL);
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gtk_window_set_title (GTK_WINDOW (window), "Drawing Area");
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g_signal_connect (window, "destroy", G_CALLBACK (close_window), NULL);
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gtk_container_set_border_width (GTK_CONTAINER (window), 8);
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frame = gtk_frame_new (NULL);
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gtk_frame_set_shadow_type (GTK_FRAME (frame), GTK_SHADOW_IN);
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gtk_container_add (GTK_CONTAINER (window), frame);
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da = gtk_drawing_area_new ();
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/* set a minimum size */
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gtk_widget_set_size_request (da, 100, 100);
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gtk_container_add (GTK_CONTAINER (frame), da);
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/* Signals used to handle the backing surface */
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g_signal_connect (da, "draw",
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G_CALLBACK (draw_cb), NULL);
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g_signal_connect (da,"configure-event",
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G_CALLBACK (configure_event_cb), NULL);
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/* Event signals */
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g_signal_connect (da, "motion-notify-event",
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G_CALLBACK (motion_notify_event_cb), NULL);
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g_signal_connect (da, "button-press-event",
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G_CALLBACK (button_press_event_cb), NULL);
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/* Ask to receive events the drawing area doesn't normally
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* subscribe to. In particular, we need to ask for the
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* button press and motion notify events that want to handle.
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*/
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gtk_widget_set_events (da, gtk_widget_get_events (da)
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| GDK_BUTTON_PRESS_MASK
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| GDK_POINTER_MOTION_MASK);
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gtk_widget_show_all (window);
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gtk_main ();
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return 0;
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}
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