clients/resizor: Use pointer locking for resizing window

Resizes the window using pointer locking when holding the left pointer
button down. The pointer lock cursor position hint is used to warp the
pointer to the same position relative to the bottom right corner.

Signed-off-by: Jonas Ådahl <jadahl@gmail.com>
Reviewed-by: Peter Hutterer <peter.hutterer@who-t.net>

clients/resizor.c

@@ -23,6 +23,7 @@
 
 #include "config.h"
 
+#include <stdbool.h>
 #include <stdint.h>
 #include <stdio.h>
 #include <stdlib.h>
@@ -51,6 +52,10 @@ struct resizor {
 	struct spring width;
 	struct spring height;
 	struct wl_callback *frame_callback;
+	bool pointer_locked;
+	struct input *locked_input;
+	float pointer_x;
+	float pointer_y;
 };
 
 static void
@@ -220,21 +225,158 @@ show_menu(struct resizor *resizor, struct input *input, uint32_t time)
 			 x - 10, y - 10, menu_func, entries, 4);
 }
 
+static void
+locked_pointer_handle_motion(struct window *window,
+			     struct input *input,
+			     uint32_t time,
+			     float dx,
+			     float dy,
+			     void *data)
+{
+	struct resizor *resizor = data;
+
+	resizor->width.current += dx;
+	resizor->width.previous = resizor->width.current;
+	resizor->width.target = resizor->width.current;
+
+	resizor->height.current += dy;
+	resizor->height.previous = resizor->height.current;
+	resizor->height.target = resizor->height.current;
+
+	widget_schedule_resize(resizor->widget,
+			       resizor->width.current,
+			       resizor->height.current);
+}
+
+static void
+handle_pointer_locked(struct window *window, struct input *input, void *data)
+{
+	struct resizor *resizor = data;
+
+	resizor->pointer_locked = true;
+	input_set_pointer_image(input, CURSOR_BLANK);
+}
+
+static void
+handle_pointer_unlocked(struct window *window, struct input *input, void *data)
+{
+	struct resizor *resizor = data;
+
+	resizor->pointer_locked = false;
+	input_set_pointer_image(input, CURSOR_LEFT_PTR);
+}
+
+static const struct wl_callback_listener locked_pointer_frame_listener;
+
+static void
+locked_pointer_frame_callback(void *data,
+			      struct wl_callback *callback,
+			      uint32_t time)
+{
+	struct resizor *resizor = data;
+	struct wl_surface *surface;
+	struct rectangle allocation;
+	float x, y;
+
+	if (resizor->pointer_locked) {
+		widget_get_allocation(resizor->widget, &allocation);
+
+		x = resizor->pointer_x + (allocation.width - allocation.x);
+		y = resizor->pointer_y + (allocation.height - allocation.y);
+
+		widget_set_locked_pointer_cursor_hint(resizor->widget, x, y);
+	}
+
+	wl_callback_destroy(callback);
+
+	surface = window_get_wl_surface(resizor->window);
+	callback = wl_surface_frame(surface);
+	wl_callback_add_listener(callback,
+				 &locked_pointer_frame_listener,
+				 resizor);
+}
+
+static const struct wl_callback_listener locked_pointer_frame_listener = {
+	locked_pointer_frame_callback
+};
+
 static void
 button_handler(struct widget *widget,
 	       struct input *input, uint32_t time,
 	       uint32_t button, enum wl_pointer_button_state state, void *data)
 {
 	struct resizor *resizor = data;
+	struct rectangle allocation;
+	struct wl_surface *surface;
+	struct wl_callback *callback;
 
-	switch (button) {
-	case BTN_RIGHT:
-		if (state == WL_POINTER_BUTTON_STATE_PRESSED)
-			show_menu(resizor, input, time);
-		break;
+	if (button == BTN_RIGHT && state == WL_POINTER_BUTTON_STATE_PRESSED) {
+		show_menu(resizor, input, time);
+	} else if (button == BTN_LEFT &&
+		   state == WL_POINTER_BUTTON_STATE_PRESSED) {
+		window_get_allocation(resizor->window, &allocation);
+
+		resizor->width.current = allocation.width;
+		resizor->width.previous = allocation.width;
+		resizor->width.target = allocation.width;
+
+		resizor->height.current = allocation.height;
+		resizor->height.previous = allocation.height;
+		resizor->height.target = allocation.height;
+
+		window_lock_pointer(resizor->window, input);
+		window_set_pointer_locked_handler(resizor->window,
+						  handle_pointer_locked,
+						  handle_pointer_unlocked);
+		resizor->locked_input = input;
+
+		surface = window_get_wl_surface(resizor->window);
+		callback = wl_surface_frame(surface);
+		wl_callback_add_listener(callback,
+					 &locked_pointer_frame_listener,
+					 resizor);
+	} else if (button == BTN_LEFT &&
+		   state == WL_POINTER_BUTTON_STATE_RELEASED) {
+		input_set_pointer_image(input, CURSOR_LEFT_PTR);
+		window_unlock_pointer(resizor->window);
 	}
 }
 
+static void
+set_cursor_inv_offset(struct resizor *resizor, float x, float y)
+{
+	struct rectangle allocation;
+
+	widget_get_allocation(resizor->widget, &allocation);
+
+	resizor->pointer_x = x - (allocation.width - allocation.x);
+	resizor->pointer_y = y - (allocation.height - allocation.y);
+}
+
+static int
+enter_handler(struct widget *widget,
+	      struct input *input,
+	      float x, float y, void *data)
+{
+	struct resizor *resizor = data;
+
+	set_cursor_inv_offset(resizor, x , y);
+
+	return CURSOR_LEFT_PTR;
+}
+
+static int
+motion_handler(struct widget *widget,
+	       struct input *input, uint32_t time,
+	       float x, float y, void *data)
+{
+	struct resizor *resizor = data;
+
+	set_cursor_inv_offset(resizor, x , y);
+
+	return CURSOR_LEFT_PTR;
+}
+
 static struct resizor *
 resizor_create(struct display *display)
 {
@@ -252,6 +394,12 @@ resizor_create(struct display *display)
 	window_set_keyboard_focus_handler(resizor->window,
 					  keyboard_focus_handler);
 
+	widget_set_enter_handler(resizor->widget, enter_handler);
+	widget_set_motion_handler(resizor->widget, motion_handler);
+
+	window_set_locked_pointer_motion_handler(
+			resizor->window, locked_pointer_handle_motion);
+
 	widget_set_button_handler(resizor->widget, button_handler);
 
 	resizor->height.previous = 400;