/* 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 set a function * via gtk_drawing_area_set_draw_func(), 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 void create_surface (GtkWidget *widget) { cairo_t *cr; if (surface) cairo_surface_destroy (surface); surface = cairo_image_surface_create (CAIRO_FORMAT_ARGB32, gtk_widget_get_width (widget), gtk_widget_get_height (widget)); /* Initialize the surface to white */ cr = cairo_create (surface); cairo_set_source_rgb (cr, 1, 1, 1); cairo_paint (cr); cairo_destroy (cr); } static void scribble_size_allocate (GtkWidget *widget) { create_surface (widget); } /* Redraw the screen from the surface */ static void scribble_draw (GtkDrawingArea *da, cairo_t *cr, int width, int height, gpointer data) { cairo_set_source_surface (cr, surface, 0, 0); cairo_paint (cr); } /* Draw a rectangle on the screen */ static void draw_brush (GtkWidget *widget, gdouble x, gdouble y) { GdkRectangle update_rect; cairo_t *cr; if (surface == NULL || cairo_image_surface_get_width (surface) != gtk_widget_get_width (widget) || cairo_image_surface_get_height (surface) != gtk_widget_get_height (widget)) create_surface (widget); 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); gtk_widget_queue_draw (widget); } static double start_x; static double start_y; static void drag_begin (GtkGestureDrag *gesture, double x, double y, GtkWidget *area) { start_x = x; start_y = y; draw_brush (area, x, y); } static void drag_update (GtkGestureDrag *gesture, double x, double y, GtkWidget *area) { draw_brush (area, start_x + x, start_y + y); } static void drag_end (GtkGestureDrag *gesture, double x, double y, GtkWidget *area) { draw_brush (area, start_x + x, start_y + y); } static void checkerboard_draw (GtkDrawingArea *da, cairo_t *cr, int width, int height, gpointer data) { gint i, j, xcount, ycount; #define CHECK_SIZE 10 #define SPACING 2 /* At the start of a draw handler, a clip region has been set on * the Cairo context, and the contents have been cleared to the * widget's background color. The docs for * gdk_surface_begin_paint_region() give more details on how this * works. */ xcount = 0; i = SPACING; while (i < width) { j = SPACING; ycount = xcount % 2; /* start with even/odd depending on row */ while (j < 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 the clip, this will do nothing. */ cairo_rectangle (cr, i, j, CHECK_SIZE, CHECK_SIZE); cairo_fill (cr); j += CHECK_SIZE + SPACING; ++ycount; } i += CHECK_SIZE + SPACING; ++xcount; } } 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; GtkGesture *drag; if (!window) { window = gtk_window_new (); gtk_window_set_display (GTK_WINDOW (window), gtk_widget_get_display (do_widget)); gtk_window_set_title (GTK_WINDOW (window), "Drawing Area"); g_signal_connect (window, "destroy", G_CALLBACK (close_window), NULL); vbox = gtk_box_new (GTK_ORIENTATION_VERTICAL, 8); gtk_widget_set_margin_start (vbox, 16); gtk_widget_set_margin_end (vbox, 16); gtk_widget_set_margin_top (vbox, 16); gtk_widget_set_margin_bottom (vbox, 16); gtk_window_set_child (GTK_WINDOW (window), vbox); /* * Create the checkerboard area */ label = gtk_label_new (NULL); gtk_label_set_markup (GTK_LABEL (label), "Checkerboard pattern"); gtk_container_add (GTK_CONTAINER (vbox), label); frame = gtk_frame_new (NULL); gtk_widget_set_vexpand (frame, TRUE); gtk_container_add (GTK_CONTAINER (vbox), frame); da = gtk_drawing_area_new (); gtk_drawing_area_set_content_width (GTK_DRAWING_AREA (da), 100); gtk_drawing_area_set_content_height (GTK_DRAWING_AREA (da), 100); gtk_drawing_area_set_draw_func (GTK_DRAWING_AREA (da), checkerboard_draw, NULL, NULL); gtk_frame_set_child (GTK_FRAME (frame), da); /* * Create the scribble area */ label = gtk_label_new (NULL); gtk_label_set_markup (GTK_LABEL (label), "Scribble area"); gtk_container_add (GTK_CONTAINER (vbox), label); frame = gtk_frame_new (NULL); gtk_widget_set_vexpand (frame, TRUE); gtk_container_add (GTK_CONTAINER (vbox), frame); da = gtk_drawing_area_new (); gtk_drawing_area_set_content_width (GTK_DRAWING_AREA (da), 100); gtk_drawing_area_set_content_height (GTK_DRAWING_AREA (da), 100); gtk_drawing_area_set_draw_func (GTK_DRAWING_AREA (da), scribble_draw, NULL, NULL); gtk_frame_set_child (GTK_FRAME (frame), da); g_signal_connect (da, "size-allocate", G_CALLBACK (scribble_size_allocate), NULL); drag = gtk_gesture_drag_new (); gtk_gesture_single_set_button (GTK_GESTURE_SINGLE (drag), GDK_BUTTON_PRIMARY); gtk_widget_add_controller (da, GTK_EVENT_CONTROLLER (drag)); g_signal_connect (drag, "drag-begin", G_CALLBACK (drag_begin), da); g_signal_connect (drag, "drag-update", G_CALLBACK (drag_update), da); g_signal_connect (drag, "drag-end", G_CALLBACK (drag_end), da); } if (!gtk_widget_get_visible (window)) gtk_widget_show (window); else gtk_widget_destroy (window); return window; }