3 * GtkDrawingArea is a blank area where you can draw custom displays
6 * This demo has two drawing areas. The checkerboard area shows
7 * how you can just draw something; all you have to do is write
8 * a signal handler for expose_event, as shown here.
10 * The "scribble" area is a bit more advanced, and shows how to handle
11 * events such as button presses and mouse motion. Click the mouse
12 * and drag in the scribble area to draw squiggles. Resize the window
18 static GtkWidget *window = NULL;
19 /* Pixmap for scribble area, to store current scribbles */
20 static GdkPixmap *pixmap = NULL;
22 /* Create a new pixmap of the appropriate size to store our scribbles */
24 scribble_configure_event (GtkWidget *widget,
25 GdkEventConfigure *event,
29 g_object_unref (pixmap);
31 pixmap = gdk_pixmap_new (widget->window,
32 widget->allocation.width,
33 widget->allocation.height,
36 /* Initialize the pixmap to white */
37 gdk_draw_rectangle (pixmap,
38 widget->style->white_gc,
41 widget->allocation.width,
42 widget->allocation.height);
44 /* We've handled the configure event, no need for further processing. */
48 /* Redraw the screen from the pixmap */
50 scribble_expose_event (GtkWidget *widget,
51 GdkEventExpose *event,
54 /* We use the "foreground GC" for the widget since it already exists,
55 * but honestly any GC would work. The only thing to worry about
56 * is whether the GC has an inappropriate clip region set.
59 gdk_draw_drawable (widget->window,
60 widget->style->fg_gc[gtk_widget_get_state (widget)],
62 /* Only copy the area that was exposed. */
63 event->area.x, event->area.y,
64 event->area.x, event->area.y,
65 event->area.width, event->area.height);
70 /* Draw a rectangle on the screen */
72 draw_brush (GtkWidget *widget,
76 GdkRectangle update_rect;
78 update_rect.x = x - 3;
79 update_rect.y = y - 3;
80 update_rect.width = 6;
81 update_rect.height = 6;
83 /* Paint to the pixmap, where we store our state */
84 gdk_draw_rectangle (pixmap,
85 widget->style->black_gc,
87 update_rect.x, update_rect.y,
88 update_rect.width, update_rect.height);
90 /* Now invalidate the affected region of the drawing area. */
91 gdk_window_invalidate_rect (widget->window,
97 scribble_button_press_event (GtkWidget *widget,
98 GdkEventButton *event,
102 return FALSE; /* paranoia check, in case we haven't gotten a configure event */
104 if (event->button == 1)
105 draw_brush (widget, event->x, event->y);
107 /* We've handled the event, stop processing */
112 scribble_motion_notify_event (GtkWidget *widget,
113 GdkEventMotion *event,
117 GdkModifierType state;
120 return FALSE; /* paranoia check, in case we haven't gotten a configure event */
122 /* This call is very important; it requests the next motion event.
123 * If you don't call gdk_window_get_pointer() you'll only get
124 * a single motion event. The reason is that we specified
125 * GDK_POINTER_MOTION_HINT_MASK to gtk_widget_set_events().
126 * If we hadn't specified that, we could just use event->x, event->y
127 * as the pointer location. But we'd also get deluged in events.
128 * By requesting the next event as we handle the current one,
129 * we avoid getting a huge number of events faster than we
133 gdk_window_get_pointer (event->window, &x, &y, &state);
135 if (state & GDK_BUTTON1_MASK)
136 draw_brush (widget, x, y);
138 /* We've handled it, stop processing */
144 checkerboard_expose (GtkWidget *da,
145 GdkEventExpose *event,
148 gint i, j, xcount, ycount;
152 #define CHECK_SIZE 10
155 /* At the start of an expose handler, a clip region of event->area
156 * is set on the window, and event->area has been cleared to the
157 * widget's background color. The docs for
158 * gdk_window_begin_paint_region() give more details on how this
162 /* It would be a bit more efficient to keep these
163 * GC's around instead of recreating on each expose, but
164 * this is the lazy/slow way.
166 gc1 = gdk_gc_new (da->window);
170 gdk_gc_set_rgb_fg_color (gc1, &color);
172 gc2 = gdk_gc_new (da->window);
176 gdk_gc_set_rgb_fg_color (gc2, &color);
180 while (i < da->allocation.width)
183 ycount = xcount % 2; /* start with even/odd depending on row */
184 while (j < da->allocation.height)
193 /* If we're outside event->area, this will do nothing.
194 * It might be mildly more efficient if we handled
195 * the clipping ourselves, but again we're feeling lazy.
197 gdk_draw_rectangle (da->window,
204 j += CHECK_SIZE + SPACING;
208 i += CHECK_SIZE + SPACING;
212 g_object_unref (gc1);
213 g_object_unref (gc2);
215 /* return TRUE because we've handled this event, so no
216 * further processing is required.
227 g_object_unref (pixmap);
232 do_drawingarea (GtkWidget *do_widget)
241 window = gtk_window_new (GTK_WINDOW_TOPLEVEL);
242 gtk_window_set_screen (GTK_WINDOW (window),
243 gtk_widget_get_screen (do_widget));
244 gtk_window_set_title (GTK_WINDOW (window), "Drawing Area");
246 g_signal_connect (window, "destroy", G_CALLBACK (close_window), NULL);
248 gtk_container_set_border_width (GTK_CONTAINER (window), 8);
250 vbox = gtk_vbox_new (FALSE, 8);
251 gtk_container_set_border_width (GTK_CONTAINER (vbox), 8);
252 gtk_container_add (GTK_CONTAINER (window), vbox);
255 * Create the checkerboard area
258 label = gtk_label_new (NULL);
259 gtk_label_set_markup (GTK_LABEL (label),
260 "<u>Checkerboard pattern</u>");
261 gtk_box_pack_start (GTK_BOX (vbox), label, FALSE, FALSE, 0);
263 frame = gtk_frame_new (NULL);
264 gtk_frame_set_shadow_type (GTK_FRAME (frame), GTK_SHADOW_IN);
265 gtk_box_pack_start (GTK_BOX (vbox), frame, TRUE, TRUE, 0);
267 da = gtk_drawing_area_new ();
268 /* set a minimum size */
269 gtk_widget_set_size_request (da, 100, 100);
271 gtk_container_add (GTK_CONTAINER (frame), da);
273 g_signal_connect (da, "expose-event",
274 G_CALLBACK (checkerboard_expose), NULL);
277 * Create the scribble area
280 label = gtk_label_new (NULL);
281 gtk_label_set_markup (GTK_LABEL (label),
282 "<u>Scribble area</u>");
283 gtk_box_pack_start (GTK_BOX (vbox), label, FALSE, FALSE, 0);
285 frame = gtk_frame_new (NULL);
286 gtk_frame_set_shadow_type (GTK_FRAME (frame), GTK_SHADOW_IN);
287 gtk_box_pack_start (GTK_BOX (vbox), frame, TRUE, TRUE, 0);
289 da = gtk_drawing_area_new ();
290 /* set a minimum size */
291 gtk_widget_set_size_request (da, 100, 100);
293 gtk_container_add (GTK_CONTAINER (frame), da);
295 /* Signals used to handle backing pixmap */
297 g_signal_connect (da, "expose-event",
298 G_CALLBACK (scribble_expose_event), NULL);
299 g_signal_connect (da,"configure-event",
300 G_CALLBACK (scribble_configure_event), NULL);
304 g_signal_connect (da, "motion-notify-event",
305 G_CALLBACK (scribble_motion_notify_event), NULL);
306 g_signal_connect (da, "button-press-event",
307 G_CALLBACK (scribble_button_press_event), NULL);
310 /* Ask to receive events the drawing area doesn't normally
313 gtk_widget_set_events (da, gtk_widget_get_events (da)
314 | GDK_LEAVE_NOTIFY_MASK
315 | GDK_BUTTON_PRESS_MASK
316 | GDK_POINTER_MOTION_MASK
317 | GDK_POINTER_MOTION_HINT_MASK);
321 if (!gtk_widget_get_visible (window))
322 gtk_widget_show_all (window);
324 gtk_widget_destroy (window);