/* 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 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 gboolean scribble_configure_event (GtkWidget *widget, GdkEventConfigure *event, gpointer data) { cairo_t *cr; if (surface) cairo_surface_destroy (surface); surface = gdk_window_create_similar_surface (widget->window, CAIRO_CONTENT_COLOR, widget->allocation.width, widget->allocation.height); /* Initialize the surface to white */ cr = cairo_create (surface); cairo_set_source_rgb (cr, 1, 1, 1); cairo_paint (cr); cairo_destroy (cr); /* We've handled the configure event, no need for further processing. */ return TRUE; } /* Redraw the screen from the surface */ static gboolean scribble_expose_event (GtkWidget *widget, GdkEventExpose *event, gpointer data) { cairo_t *cr; cr = gdk_cairo_create (widget->window); cairo_set_source_surface (cr, surface, 0, 0); gdk_cairo_rectangle (cr, &event->area); cairo_fill (cr); cairo_destroy (cr); return FALSE; } /* Draw a rectangle on the screen */ static void draw_brush (GtkWidget *widget, gdouble x, gdouble y) { GdkRectangle update_rect; cairo_t *cr; 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); /* 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 (surface == 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 (surface == 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; cairo_t *cr; #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. */ cr = gdk_cairo_create (da->window); gdk_cairo_rectangle (cr, &event->area); cairo_clip (cr); 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) { 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 event->area, this will do nothing. * It might be mildly more efficient if we handled * the clipping ourselves, but again we're feeling lazy. */ cairo_rectangle (cr, i, j, CHECK_SIZE, CHECK_SIZE); cairo_fill (cr); j += CHECK_SIZE + SPACING; ++ycount; } i += CHECK_SIZE + SPACING; ++xcount; } cairo_destroy (cr); /* return TRUE because we've handled this event, so no * further processing is required. */ return TRUE; } 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; 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 (close_window), NULL); 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), "Checkerboard pattern"); 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), "Scribble area"); 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 surface */ 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_get_visible (window)) gtk_widget_show_all (window); else gtk_widget_destroy (window); return window; }