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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 write
- * a signal handler for expose_event, 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 <config.h>
- #include <gtk/gtk.h>
-
- static GtkWidget *window = NULL;
- /* Pixmap for scribble area, to store current scribbles */
- static GdkPixmap *pixmap = NULL;
-
- /* Create a new pixmap of the appropriate size to store our scribbles */
- static gboolean
- scribble_configure_event (GtkWidget *widget,
- GdkEventConfigure *event,
- gpointer data)
- {
- if (pixmap)
- g_object_unref (pixmap);
-
- pixmap = gdk_pixmap_new (widget->window,
- widget->allocation.width,
- widget->allocation.height,
- -1);
-
- /* Initialize the pixmap to white */
- gdk_draw_rectangle (pixmap,
- widget->style->white_gc,
- TRUE,
- 0, 0,
- widget->allocation.width,
- widget->allocation.height);
-
- /* We've handled the configure event, no need for further processing. */
- return TRUE;
- }
-
- /* Redraw the screen from the pixmap */
- static gboolean
- scribble_expose_event (GtkWidget *widget,
- GdkEventExpose *event,
- gpointer data)
- {
- /* We use the "foreground GC" for the widget since it already exists,
- * but honestly any GC would work. The only thing to worry about
- * is whether the GC has an inappropriate clip region set.
- */
-
- gdk_draw_drawable (widget->window,
- widget->style->fg_gc[GTK_WIDGET_STATE (widget)],
- pixmap,
- /* Only copy the area that was exposed. */
- event->area.x, event->area.y,
- event->area.x, event->area.y,
- event->area.width, event->area.height);
-
- return FALSE;
- }
-
- /* Draw a rectangle on the screen */
- static void
- draw_brush (GtkWidget *widget,
- gdouble x,
- gdouble y)
- {
- GdkRectangle update_rect;
-
- update_rect.x = x - 3;
- update_rect.y = y - 3;
- update_rect.width = 6;
- update_rect.height = 6;
-
- /* Paint to the pixmap, where we store our state */
- gdk_draw_rectangle (pixmap,
- widget->style->black_gc,
- TRUE,
- update_rect.x, update_rect.y,
- update_rect.width, update_rect.height);
-
- /* Now invalidate the affected region of the drawing area. */
- gdk_window_invalidate_rect (widget->window,
- &update_rect,
- FALSE);
- }
-
- static gboolean
- scribble_button_press_event (GtkWidget *widget,
- GdkEventButton *event,
- gpointer data)
- {
- if (pixmap == NULL)
- return FALSE; /* paranoia check, in case we haven't gotten a configure event */
-
- if (event->button == 1)
- draw_brush (widget, event->x, event->y);
-
- /* We've handled the event, stop processing */
- return TRUE;
- }
-
- static gboolean
- scribble_motion_notify_event (GtkWidget *widget,
- GdkEventMotion *event,
- gpointer data)
- {
- int x, y;
- GdkModifierType state;
-
- if (pixmap == NULL)
- return FALSE; /* paranoia check, in case we haven't gotten a configure event */
-
- /* This call is very important; it requests the next motion event.
- * If you don't call gdk_window_get_pointer() you'll only get
- * a single motion event. The reason is that we specified
- * GDK_POINTER_MOTION_HINT_MASK to gtk_widget_set_events().
- * If we hadn't specified that, we could just use event->x, event->y
- * as the pointer location. But we'd also get deluged in events.
- * By requesting the next event as we handle the current one,
- * we avoid getting a huge number of events faster than we
- * can cope.
- */
-
- gdk_window_get_pointer (event->window, &x, &y, &state);
-
- if (state & GDK_BUTTON1_MASK)
- draw_brush (widget, x, y);
-
- /* We've handled it, stop processing */
- return TRUE;
- }
-
-
- static gboolean
- checkerboard_expose (GtkWidget *da,
- GdkEventExpose *event,
- gpointer data)
- {
- gint i, j, xcount, ycount;
- GdkGC *gc1, *gc2;
- GdkColor color;
-
- #define CHECK_SIZE 10
- #define SPACING 2
-
- /* At the start of an expose handler, a clip region of event->area
- * is set on the window, and event->area has been cleared to the
- * widget's background color. The docs for
- * gdk_window_begin_paint_region() give more details on how this
- * works.
- */
-
- /* It would be a bit more efficient to keep these
- * GC's around instead of recreating on each expose, but
- * this is the lazy/slow way.
- */
- gc1 = gdk_gc_new (da->window);
- color.red = 30000;
- color.green = 0;
- color.blue = 30000;
- gdk_gc_set_rgb_fg_color (gc1, &color);
-
- gc2 = gdk_gc_new (da->window);
- color.red = 65535;
- color.green = 65535;
- color.blue = 65535;
- gdk_gc_set_rgb_fg_color (gc2, &color);
-
- xcount = 0;
- i = SPACING;
- while (i < da->allocation.width)
- {
- j = SPACING;
- ycount = xcount % 2; /* start with even/odd depending on row */
- while (j < da->allocation.height)
- {
- GdkGC *gc;
-
- if (ycount % 2)
- gc = gc1;
- else
- gc = gc2;
-
- /* If we're outside event->area, this will do nothing.
- * It might be mildly more efficient if we handled
- * the clipping ourselves, but again we're feeling lazy.
- */
- gdk_draw_rectangle (da->window,
- gc,
- TRUE,
- i, j,
- CHECK_SIZE,
- CHECK_SIZE);
-
- j += CHECK_SIZE + SPACING;
- ++ycount;
- }
-
- i += CHECK_SIZE + SPACING;
- ++xcount;
- }
-
- g_object_unref (gc1);
- g_object_unref (gc2);
-
- /* return TRUE because we've handled this event, so no
- * further processing is required.
- */
- return TRUE;
- }
-
- GtkWidget *
- do_drawingarea (GtkWidget *do_widget)
- {
- GtkWidget *frame;
- GtkWidget *vbox;
- GtkWidget *da;
- GtkWidget *label;
-
- if (!window)
- {
- window = gtk_window_new (GTK_WINDOW_TOPLEVEL);
- gtk_window_set_screen (GTK_WINDOW (window),
- gtk_widget_get_screen (do_widget));
- gtk_window_set_title (GTK_WINDOW (window), "Drawing Area");
-
- g_signal_connect (window, "destroy", G_CALLBACK (gtk_widget_destroyed), &window);
-
- gtk_container_set_border_width (GTK_CONTAINER (window), 8);
-
- vbox = gtk_vbox_new (FALSE, 8);
- gtk_container_set_border_width (GTK_CONTAINER (vbox), 8);
- 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_box_pack_start (GTK_BOX (vbox), label, FALSE, FALSE, 0);
-
- frame = gtk_frame_new (NULL);
- gtk_frame_set_shadow_type (GTK_FRAME (frame), GTK_SHADOW_IN);
- gtk_box_pack_start (GTK_BOX (vbox), frame, TRUE, TRUE, 0);
-
- da = gtk_drawing_area_new ();
- /* set a minimum size */
- gtk_widget_set_size_request (da, 100, 100);
-
- gtk_container_add (GTK_CONTAINER (frame), da);
-
- g_signal_connect (da, "expose_event",
- G_CALLBACK (checkerboard_expose), NULL);
-
- /*
- * Create the scribble area
- */
-
- label = gtk_label_new (NULL);
- gtk_label_set_markup (GTK_LABEL (label),
- "<u>Scribble area</u>");
- gtk_box_pack_start (GTK_BOX (vbox), label, FALSE, FALSE, 0);
-
- frame = gtk_frame_new (NULL);
- gtk_frame_set_shadow_type (GTK_FRAME (frame), GTK_SHADOW_IN);
- gtk_box_pack_start (GTK_BOX (vbox), frame, TRUE, TRUE, 0);
-
- da = gtk_drawing_area_new ();
- /* set a minimum size */
- gtk_widget_set_size_request (da, 100, 100);
-
- gtk_container_add (GTK_CONTAINER (frame), da);
-
- /* Signals used to handle backing pixmap */
-
- g_signal_connect (da, "expose_event",
- G_CALLBACK (scribble_expose_event), NULL);
- g_signal_connect (da,"configure_event",
- G_CALLBACK (scribble_configure_event), NULL);
-
- /* Event signals */
-
- g_signal_connect (da, "motion_notify_event",
- G_CALLBACK (scribble_motion_notify_event), NULL);
- g_signal_connect (da, "button_press_event",
- G_CALLBACK (scribble_button_press_event), NULL);
-
-
- /* Ask to receive events the drawing area doesn't normally
- * subscribe to
- */
- gtk_widget_set_events (da, gtk_widget_get_events (da)
- | GDK_LEAVE_NOTIFY_MASK
- | GDK_BUTTON_PRESS_MASK
- | GDK_POINTER_MOTION_MASK
- | GDK_POINTER_MOTION_HINT_MASK);
-
- }
-
- if (!GTK_WIDGET_VISIBLE (window))
- {
- gtk_widget_show_all (window);
- }
- else
- {
- gtk_widget_destroy (window);
- window = NULL;
- }
-
- return window;
- }
-