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| // This example adds handling stylus input to the Custom Drawing example | |
| // from the GTK4 Getting Started. | |
| // See: https://docs.gtk.org/gtk4/getting_started.html#custom-drawing | |
| #include <gtk/gtk.h> | |
| /* Surface to store current scribbles */ | |
| static cairo_surface_t *surface = NULL; | |
| static void clear_surface(void) { | |
| cairo_t* cr = cairo_create(surface); | |
| cairo_set_source_rgb(cr, 1, 1, 1); | |
| cairo_paint(cr); | |
| cairo_destroy(cr); | |
| } | |
| /* Create a new surface of the appropriate size to store our scribbles */ | |
| static void resize_cb(GtkWidget *widget, int width, int height, gpointer data) { | |
| if (surface) { | |
| cairo_surface_destroy(surface); | |
| surface = NULL; | |
| } | |
| if (gtk_native_get_surface(gtk_widget_get_native(widget))) { | |
| surface = gdk_surface_create_similar_surface( | |
| gtk_native_get_surface(gtk_widget_get_native(widget)), | |
| CAIRO_CONTENT_COLOR, gtk_widget_get_width(widget), | |
| gtk_widget_get_height(widget)); | |
| /* Initialize the surface to white */ | |
| clear_surface(); | |
| } | |
| } | |
| /* Redraw the screen from the surface. Note that the draw | |
| * callback receives a ready-to-be-used cairo_t that is already | |
| * clipped to only draw the exposed areas of the widget | |
| */ | |
| static void draw_cb(GtkDrawingArea *drawing_area, 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 surface at the given position */ | |
| static void draw_brush (GtkWidget *widget, double x, double y, double size = 0.5) { | |
| /* Paint to the surface, where we store our state */ | |
| cairo_t* cr = cairo_create (surface); | |
| double w = 12*size; | |
| cairo_rectangle (cr, x - w*0.5, y - w*0.5, w, w); | |
| cairo_fill (cr); | |
| cairo_destroy (cr); | |
| /* Now invalidate the drawing area. */ | |
| gtk_widget_queue_draw (widget); | |
| } | |
| static double start_x; | |
| static double start_y; | |
| static GtkGesture* stylus; | |
| static void drag_begin(GtkGestureDrag *gesture, double x, double y, | |
| GtkWidget *area) { | |
| // First check if the event sequence is already handled by the stylus gesture; if not | |
| // we will handle is here; if it is deny it | |
| GdkEventSequence* sequence = gtk_gesture_get_last_updated_sequence(GTK_GESTURE(gesture)); | |
| if (gtk_gesture_get_sequence_state(GTK_GESTURE(stylus), sequence) == GTK_EVENT_SEQUENCE_CLAIMED) { | |
| gtk_gesture_set_sequence_state(GTK_GESTURE(gesture), sequence, GTK_EVENT_SEQUENCE_DENIED); | |
| } else { | |
| start_x = x; | |
| start_y = y; | |
| draw_brush(area, x, y); | |
| } | |
| } | |
| static void drag_update(GtkGestureDrag *gesture, double x, double y, | |
| GtkWidget *area) { | |
| // First check if the event sequence is already handled by the stylus gesture; if not | |
| // we will handle is here; if it is deny it | |
| GdkEventSequence* sequence = gtk_gesture_get_last_updated_sequence(GTK_GESTURE(gesture)); | |
| if (gtk_gesture_get_sequence_state(GTK_GESTURE(stylus), sequence) == GTK_EVENT_SEQUENCE_CLAIMED) { | |
| gtk_gesture_set_sequence_state(GTK_GESTURE(gesture), sequence, GTK_EVENT_SEQUENCE_DENIED); | |
| } else { | |
| draw_brush(area, start_x + x, start_y + y); | |
| } | |
| } | |
| static void drag_end(GtkGestureDrag *gesture, double x, double y, | |
| GtkWidget *area) { | |
| // First check if the event sequence is already handled by the stylus gesture; if not | |
| // we will handle is here; if it is deny it | |
| GdkEventSequence* sequence = gtk_gesture_get_last_updated_sequence(GTK_GESTURE(gesture)); | |
| if (gtk_gesture_get_sequence_state(GTK_GESTURE(stylus), sequence) == GTK_EVENT_SEQUENCE_CLAIMED) { | |
| gtk_gesture_set_sequence_state(GTK_GESTURE(gesture), sequence, GTK_EVENT_SEQUENCE_DENIED); | |
| } else { | |
| draw_brush(area, start_x + x, start_y + y); | |
| } | |
| } | |
| static void stylus_down(GtkGestureStylus* gesture, double x, double y, GtkWidget* area) { | |
| double pressure; | |
| gtk_gesture_stylus_get_axis(gesture, GDK_AXIS_PRESSURE, &pressure); | |
| draw_brush(area, x, y, pressure); | |
| // Claim the event sequence; the drag gesture should not handle it | |
| GdkEventSequence* sequence = gtk_gesture_get_last_updated_sequence(GTK_GESTURE(gesture)); | |
| gtk_gesture_set_sequence_state(GTK_GESTURE(gesture), sequence, GTK_EVENT_SEQUENCE_CLAIMED); | |
| } | |
| static void stylus_motion(GtkGestureStylus* gesture, double x, double y, GtkWidget* area) { | |
| double pressure; | |
| gtk_gesture_stylus_get_axis(gesture, GDK_AXIS_PRESSURE, &pressure); | |
| draw_brush(area, x, y, pressure); | |
| // Claim the event sequence; the drag gesture should not handle it | |
| GdkEventSequence* sequence = gtk_gesture_get_last_updated_sequence(GTK_GESTURE(gesture)); | |
| gtk_gesture_set_sequence_state(GTK_GESTURE(gesture), sequence, GTK_EVENT_SEQUENCE_CLAIMED); | |
| } | |
| static void stylus_up(GtkGestureStylus* gesture, double x, double y, GtkWidget* area) { | |
| double pressure; | |
| gtk_gesture_stylus_get_axis(gesture, GDK_AXIS_PRESSURE, &pressure); | |
| draw_brush(area, x, y, pressure); | |
| // Claim the event sequence; the drag gesture should not handle it | |
| GdkEventSequence* sequence = gtk_gesture_get_last_updated_sequence(GTK_GESTURE(gesture)); | |
| gtk_gesture_set_sequence_state(GTK_GESTURE(gesture), sequence, GTK_EVENT_SEQUENCE_CLAIMED); | |
| } | |
| static void pressed (GtkGestureClick *gesture, int n_press, double x, | |
| double y, GtkWidget *area) { | |
| clear_surface (); | |
| gtk_widget_queue_draw (area); | |
| } | |
| static void close_window(void) { | |
| if (surface) cairo_surface_destroy(surface); | |
| } | |
| static void activate(GtkApplication *app, gpointer user_data) { | |
| GtkWidget* window = gtk_application_window_new(app); | |
| gtk_window_set_title(GTK_WINDOW(window), "Drawing Area"); | |
| g_signal_connect(window, "destroy", G_CALLBACK(close_window), NULL); | |
| GtkWidget* frame = gtk_frame_new(NULL); | |
| gtk_window_set_child(GTK_WINDOW(window), frame); | |
| GtkWidget* drawing_area = gtk_drawing_area_new(); | |
| gtk_widget_set_size_request(drawing_area, 500, 500); | |
| gtk_frame_set_child(GTK_FRAME(frame), drawing_area); | |
| gtk_drawing_area_set_draw_func(GTK_DRAWING_AREA(drawing_area), draw_cb, NULL, NULL); | |
| g_signal_connect_after(drawing_area, "resize", G_CALLBACK(resize_cb), NULL); | |
| // Add the drag gesture before the stylus gesture; we want to have the stylus | |
| // gesture handling the events first. | |
| GtkGesture* drag = gtk_gesture_drag_new(); | |
| gtk_gesture_single_set_button(GTK_GESTURE_SINGLE(drag), GDK_BUTTON_PRIMARY); | |
| gtk_widget_add_controller(drawing_area, GTK_EVENT_CONTROLLER(drag)); | |
| g_signal_connect(drag, "drag-begin", G_CALLBACK(drag_begin), drawing_area); | |
| g_signal_connect(drag, "drag-update", G_CALLBACK(drag_update), drawing_area); | |
| g_signal_connect(drag, "drag-end", G_CALLBACK(drag_end), drawing_area); | |
| // We store the stylus gesture globally as it is also needed by the | |
| // drag gesture to check if the stylus gesture has already handled the | |
| // event sequence | |
| stylus = gtk_gesture_stylus_new(); | |
| gtk_widget_add_controller(drawing_area, GTK_EVENT_CONTROLLER(stylus)); | |
| g_signal_connect(stylus, "down", G_CALLBACK(stylus_down), drawing_area); | |
| g_signal_connect(stylus, "up", G_CALLBACK(stylus_up), drawing_area); | |
| g_signal_connect(stylus, "motion", G_CALLBACK(stylus_motion), drawing_area); | |
| // Right click clears the page | |
| GtkGesture* press = gtk_gesture_click_new (); | |
| gtk_gesture_single_set_button (GTK_GESTURE_SINGLE (press), GDK_BUTTON_SECONDARY); | |
| gtk_widget_add_controller (drawing_area, GTK_EVENT_CONTROLLER (press)); | |
| g_signal_connect (press, "pressed", G_CALLBACK (pressed), drawing_area); | |
| gtk_widget_show(window); | |
| } | |
| int main(int argc, char* argv[]) { | |
| GtkApplication* app = gtk_application_new("org.gtk.example", G_APPLICATION_FLAGS_NONE); | |
| g_signal_connect(app, "activate", G_CALLBACK(activate), NULL); | |
| int status = g_application_run(G_APPLICATION(app), argc, argv); | |
| g_object_unref(app); | |
| return status; | |
| } |
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Sorry to bother, it turns out when running the program through the integrated VSCode terminal, the
GDK_BACKEND=x11environment variable is inherited, which breaks everything...