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at August 6, 2011 21:29 by FArcellier
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#include <string.h> #include <gtk/gtk.h> static GtkWidget *window = NULL; /*! * \brief Pixmap to scribble area, to store our scribbles */ static cairo_surface_t *surface = NULL; /*! * \brief Create a new surface of the appropriate size to store our scribbles */ static gboolean scribble_configure_event (GtkWidget*, GdkEventConfigure*, gpointer); /*! * \brief Redraw the screen from the surface */ static gboolean scribble_expose_event (GtkWidget*, GdkEventExpose*, gpointer); /*! * \brief Draw a rectangle on the screen */ static void draw_brush (GtkWidget *widget, gdouble x, gdouble y); static gboolean scribble_button_press_event (GtkWidget*, GdkEventButton*, gpointer); static gboolean scribble_motion_notify_event (GtkWidget*, GdkEventMotion*, gpointer); static gboolean checkerboard_expose (GtkWidget*, GdkEventExpose*, gpointer); static void close_window (void); GtkWidget * do_drawingarea (); /*! * \brief 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 = NULL; 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; } /*! * \brief Redraw the screen from the surface */ static gboolean scribble_expose_event (GtkWidget *widget, GdkEventExpose *event, gpointer data) { cairo_t *cr = NULL; 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; } /*! * \brief Draw a rectangle on the screen */ static void draw_brush (GtkWidget *widget, gdouble x, gdouble y) { GdkRectangle update_rect; memset(&update_rect, 0, sizeof(GdkRectangle)); cairo_t *cr = NULL; 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 = 0, y = 0; GdkModifierType state = 0; 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 juste 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 = 0, j = 0, xcount = 0, ycount = 0; cairo_t *cr = NULL; #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. 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) { g_object_unref (surface); } surface = NULL; gtk_main_quit(); } GtkWidget * do_drawingarea () { GtkWidget *frame = NULL, *vbox = NULL, *da = NULL, *label = NULL; 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 (G_OBJECT(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), "<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 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; } int main(int argc, char *argv[]) { gtk_init (&argc, &argv); do_drawingarea(); gtk_main(); return 0; }
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Get from the gtk-demo Application. Drawing Area demo It's stand alone program you can modify and compil. It was missing the main in source to be able to use it.
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GTK+ Code Demos : Drawing Area (+ Main)
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C