interactive: set grab parameters at cursor press

Add interactive_set_grab_context() which is called when the mouse button
is first pressed, before interactive_begin(). This fixes two small issues:

- The cursor origin position for interactive move/resize was slightly
  off (depending on mouse resolution), because it was set after the
  mouse had already moved slightly. Now it's exact.

- If app- or keybind-initiated maximize (etc.) happened after the button
  press but before the mouse was moved, then interactive_begin() would
  still start move/resize even though the view might now be far away
  from the cursor. Now interactive_cancel() works as expected, even if
  called before interactive_begin().

Also, make sure to call interactive_cancel() for un-maximize as well.

include/labwc.h

@@ -414,6 +414,7 @@ void seat_focus_override_end(struct seat *seat, bool restore_focus);
  */
 void interactive_anchor_to_cursor(struct server *server, struct wlr_box *geo);
 
+void interactive_set_grab_context(struct cursor_context *ctx);
 void interactive_begin(struct view *view, enum input_mode mode,
 	enum lab_edge edges);
 void interactive_finish(struct view *view);

src/action.c

@@ -1262,6 +1262,14 @@ run_action(struct view *view, struct server *server, struct action *action,
 		break;
 	case ACTION_TYPE_MOVE:
 		if (view) {
+			/*
+			 * If triggered by mousebind, grab context was already
+			 * set by button press handling. For keybind-triggered
+			 * Move, set it now from current cursor position.
+			 */
+			if (view != server->seat.pressed.ctx.view) {
+				interactive_set_grab_context(ctx);
+			}
 			interactive_begin(view, LAB_INPUT_STATE_MOVE,
 				LAB_EDGE_NONE);
 		}
@@ -1285,9 +1293,13 @@ run_action(struct view *view, struct server *server, struct action *action,
 			 */
 			enum lab_edge resize_edges =
 				action_get_int(action, "direction", LAB_EDGE_NONE);
-			if (resize_edges == LAB_EDGE_NONE) {
-				resize_edges = cursor_get_resize_edges(
-					server->seat.cursor, ctx);
+			/*
+			 * If triggered by mousebind, grab context was already
+			 * set by button press handling. For keybind-triggered
+			 * Resize, set it now from current cursor position.
+			 */
+			if (view != server->seat.pressed.ctx.view) {
+				interactive_set_grab_context(ctx);
 			}
 			interactive_begin(view, LAB_INPUT_STATE_RESIZE,
 				resize_edges);

src/input/cursor.c

@@ -1147,6 +1147,7 @@ cursor_process_button_press(struct seat *seat, uint32_t button, uint32_t time_ms
 	if (ctx.view || ctx.surface) {
 		/* Store cursor context for later action processing */
 		cursor_context_save(&seat->pressed, &ctx);
+		interactive_set_grab_context(&ctx);
 	}
 
 	if (server->input_mode == LAB_INPUT_STATE_MENU) {
@@ -1277,6 +1278,9 @@ cursor_finish_button_release(struct seat *seat, uint32_t button)
 		/* Exit interactive move/resize mode */
 		interactive_finish(server->grabbed_view);
 		return true;
+	} else if (server->grabbed_view) {
+		/* Button was released without starting move/resize */
+		interactive_cancel(server->grabbed_view);
 	}
 
 	return false;

src/interactive.c

@@ -54,9 +54,34 @@ interactive_anchor_to_cursor(struct server *server, struct wlr_box *geo)
 	geo->y = server->grab_box.y + (server->seat.cursor->y - server->grab_y);
 }
 
+/*
+ * Called before interactive_begin() to set the initial grab parameters
+ * (cursor position and view geometry). Once the cursor actually moves,
+ * then interactive_begin() is called.
+ */
+void
+interactive_set_grab_context(struct cursor_context *ctx)
+{
+	if (!ctx->view) {
+		return;
+	}
+	struct server *server = ctx->view->server;
+	if (server->input_mode != LAB_INPUT_STATE_PASSTHROUGH) {
+		return;
+	}
+
+	server->grabbed_view = ctx->view;
+	server->grab_x = server->seat.cursor->x;
+	server->grab_y = server->seat.cursor->y;
+	server->grab_box = ctx->view->current;
+	server->resize_edges =
+		cursor_get_resize_edges(server->seat.cursor, ctx);
+}
+
 void
 interactive_begin(struct view *view, enum input_mode mode, enum lab_edge edges)
 {
+	assert(view);
 	/*
 	 * This function sets up an interactive move or resize operation, where
 	 * the compositor stops propagating pointer events to clients and
@@ -65,7 +90,8 @@ interactive_begin(struct view *view, enum input_mode mode, enum lab_edge edges)
 	struct server *server = view->server;
 	struct seat *seat = &server->seat;
 
-	if (server->input_mode != LAB_INPUT_STATE_PASSTHROUGH) {
+	if (server->input_mode != LAB_INPUT_STATE_PASSTHROUGH
+			|| view != server->grabbed_view) {
 		return;
 	}
 
@@ -108,21 +134,29 @@ interactive_begin(struct view *view, enum input_mode mode, enum lab_edge edges)
 			return;
 		}
 
+		/*
+		 * Override resize edges if specified explicitly.
+		 * Otherwise, they were set already from cursor context.
+		 */
+		if (edges != LAB_EDGE_NONE) {
+			server->resize_edges = edges;
+		}
+
 		/*
 		 * If tiled or maximized in only one direction, reset
 		 * tiled state and un-maximize the relevant axes, but
 		 * keep the same geometry as the starting point.
 		 */
 		enum view_axis maximized = view->maximized;
-		if (edges & LAB_EDGES_LEFT_RIGHT) {
+		if (server->resize_edges & LAB_EDGES_LEFT_RIGHT) {
 			maximized &= ~VIEW_AXIS_HORIZONTAL;
 		}
-		if (edges & LAB_EDGES_TOP_BOTTOM) {
+		if (server->resize_edges & LAB_EDGES_TOP_BOTTOM) {
 			maximized &= ~VIEW_AXIS_VERTICAL;
 		}
 		view_set_maximized(view, maximized);
 		view_set_untiled(view);
-		cursor_shape = cursor_get_from_edge(edges);
+		cursor_shape = cursor_get_from_edge(server->resize_edges);
 		break;
 	}
 	default:
@@ -130,13 +164,6 @@ interactive_begin(struct view *view, enum input_mode mode, enum lab_edge edges)
 		return;
 	}
 
-	server->grabbed_view = view;
-	/* Remember view and cursor positions at start of move/resize */
-	server->grab_x = seat->cursor->x;
-	server->grab_y = seat->cursor->y;
-	server->grab_box = view->current;
-	server->resize_edges = edges;
-
 	seat_focus_override_begin(seat, mode, cursor_shape);
 
 	/*
@@ -293,6 +320,8 @@ snap_to_region(struct view *view)
 void
 interactive_finish(struct view *view)
 {
+	assert(view);
+
 	if (view->server->grabbed_view != view) {
 		return;
 	}
@@ -314,16 +343,27 @@ interactive_finish(struct view *view)
 void
 interactive_cancel(struct view *view)
 {
+	assert(view);
+
 	if (view->server->grabbed_view != view) {
 		return;
 	}
 
+	view->server->grabbed_view = NULL;
+
+	/*
+	 * It's possible that grabbed_view was set but interactive_begin()
+	 * wasn't called yet. In that case, we are done.
+	 */
+	if (view->server->input_mode != LAB_INPUT_STATE_MOVE
+			&& view->server->input_mode != LAB_INPUT_STATE_RESIZE) {
+		return;
+	}
+
 	overlay_finish(&view->server->seat);
 
 	resize_indicator_hide(view);
 
-	view->server->grabbed_view = NULL;
-
 	/* Restore keyboard/pointer focus */
 	seat_focus_override_end(&view->server->seat, /*restore_focus*/ true);
 }

src/view.c

@@ -1433,14 +1433,11 @@ view_maximize(struct view *view, enum view_axis axis)
 	bool store_natural_geometry = !in_interactive_move(view);
 	view_set_shade(view, false);
 
-	if (axis != VIEW_AXIS_NONE) {
-		/*
-		 * Maximize via keybind or client request cancels
-		 * interactive move/resize since we can't move/resize
-		 * a maximized view.
-		 */
-		interactive_cancel(view);
-	}
+	/*
+	 * Maximize/unmaximize via keybind or client request cancels
+	 * interactive move/resize.
+	 */
+	interactive_cancel(view);
 
 	/*
 	 * Update natural geometry for any axis that wasn't already

src/xdg.c

@@ -454,11 +454,11 @@ handle_request_move(struct wl_listener *listener, void *data)
 	 * the provided serial against a list of button press serials sent to
 	 * this client, to prevent the client from requesting this whenever they
 	 * want.
+	 *
+	 * Note: interactive_begin() checks that view == server->grabbed_view.
 	 */
 	struct view *view = wl_container_of(listener, view, request_move);
-	if (view == view->server->seat.pressed.ctx.view) {
-		interactive_begin(view, LAB_INPUT_STATE_MOVE, LAB_EDGE_NONE);
-	}
+	interactive_begin(view, LAB_INPUT_STATE_MOVE, LAB_EDGE_NONE);
 }
 
 static void
@@ -471,12 +471,12 @@ handle_request_resize(struct wl_listener *listener, void *data)
 	 * the provided serial against a list of button press serials sent to
 	 * this client, to prevent the client from requesting this whenever they
 	 * want.
+	 *
+	 * Note: interactive_begin() checks that view == server->grabbed_view.
 	 */
 	struct wlr_xdg_toplevel_resize_event *event = data;
 	struct view *view = wl_container_of(listener, view, request_resize);
-	if (view == view->server->seat.pressed.ctx.view) {
-		interactive_begin(view, LAB_INPUT_STATE_RESIZE, event->edges);
-	}
+	interactive_begin(view, LAB_INPUT_STATE_RESIZE, event->edges);
 }
 
 static void

src/xwayland.c

@@ -288,11 +288,11 @@ handle_request_move(struct wl_listener *listener, void *data)
 	 * the provided serial against a list of button press serials sent to
 	 * this client, to prevent the client from requesting this whenever they
 	 * want.
+	 *
+	 * Note: interactive_begin() checks that view == server->grabbed_view.
 	 */
 	struct view *view = wl_container_of(listener, view, request_move);
-	if (view == view->server->seat.pressed.ctx.view) {
-		interactive_begin(view, LAB_INPUT_STATE_MOVE, LAB_EDGE_NONE);
-	}
+	interactive_begin(view, LAB_INPUT_STATE_MOVE, LAB_EDGE_NONE);
 }
 
 static void
@@ -305,12 +305,12 @@ handle_request_resize(struct wl_listener *listener, void *data)
 	 * the provided serial against a list of button press serials sent to
 	 * this client, to prevent the client from requesting this whenever they
 	 * want.
+	 *
+	 * Note: interactive_begin() checks that view == server->grabbed_view.
 	 */
 	struct wlr_xwayland_resize_event *event = data;
 	struct view *view = wl_container_of(listener, view, request_resize);
-	if (view == view->server->seat.pressed.ctx.view) {
-		interactive_begin(view, LAB_INPUT_STATE_RESIZE, event->edges);
-	}
+	interactive_begin(view, LAB_INPUT_STATE_RESIZE, event->edges);
 }
 
 static void