action: allow SnapToEdge to combine two cardinal directions

This patch adds `combine` argument to (Toggle)SnapToEdge actions.
This allows to snap a window to e.g. up-left by running two actions:
- `<action name="SnapToEdge" direction="left" combine="yes" />`
- `<action name="SnapToEdge" direction="up" combine="yes" />`

Then running `<action name="SnapToEdge" direction="down" combine="yes" />`
snaps it to left again. This behavior is almost the same as KWin, except
that snapping a up-right-tiled window to right doesn't move it to the
right-adjacent output, but makes it right-tiled first.

docs/labwc-actions.5.scd

@@ -92,11 +92,18 @@ Actions are used in menus and keyboard/mouse bindings.
 	Move window relative to its current position. Positive value of x moves
 	it right, negative left. Positive value of y moves it down, negative up.
 
-*<action name="ToggleSnapToEdge" direction="value" />*++
-*<action name="SnapToEdge" direction="value" />*
-	Resize window to fill half the output in the given direction. Supports
-	directions "left", "up", "right", "down", "up-left", "up-right", "down-left",
-	"down-right" and "center".
+*<action name="ToggleSnapToEdge" direction="value" combine="value" />*++
+*<action name="SnapToEdge" direction="value" combine="value" />*
+	Resize window to fill half or quarter the output in the given direction.
+
+	*direction* [up|down|left|right|up-left|up-right|down-left|down-right|center]
+		Direction in which to snap the window.
+
+	*combine* [yes|no]
+		Allows to snap a window to an output corner by combining two
+		directions. For example, snapping a window to *right* and then
+		to *up* places it in the *up-right* quarter of the output.
+		Default is no.
 
 	ToggleSnapToEdge additionally toggles the active window between
 	tiled to the given direction and its untiled position.

include/view.h

@@ -548,7 +548,7 @@ void view_move_to_edge(struct view *view, enum lab_edge direction, bool snap_to_
 void view_grow_to_edge(struct view *view, enum lab_edge direction);
 void view_shrink_to_edge(struct view *view, enum lab_edge direction);
 void view_snap_to_edge(struct view *view, enum lab_edge direction,
-	bool across_outputs, bool store_natural_geometry);
+	bool across_outputs, bool combine, bool store_natural_geometry);
 void view_snap_to_region(struct view *view, struct region *region, bool store_natural_geometry);
 void view_move_to_output(struct view *view, struct output *output);
 

src/action.c

@@ -337,11 +337,6 @@ action_arg_from_xml_node(struct action *action, const char *nodename, const char
 		}
 		break;
 	case ACTION_TYPE_MOVE_TO_EDGE:
-		if (!strcasecmp(argument, "snapWindows")) {
-			action_arg_add_bool(action, argument, parse_bool(content, true));
-			goto cleanup;
-		}
-		/* Falls through */
 	case ACTION_TYPE_TOGGLE_SNAP_TO_EDGE:
 	case ACTION_TYPE_SNAP_TO_EDGE:
 	case ACTION_TYPE_GROW_TO_EDGE:
@@ -358,6 +353,17 @@ action_arg_from_xml_node(struct action *action, const char *nodename, const char
 			}
 			goto cleanup;
 		}
+		if (action->type == ACTION_TYPE_MOVE_TO_EDGE
+				&& !strcasecmp(argument, "snapWindows")) {
+			action_arg_add_bool(action, argument, parse_bool(content, true));
+			goto cleanup;
+		}
+		if ((action->type == ACTION_TYPE_SNAP_TO_EDGE
+					|| action->type == ACTION_TYPE_TOGGLE_SNAP_TO_EDGE)
+				&& !strcasecmp(argument, "combine")) {
+			action_arg_add_bool(action, argument, parse_bool(content, false));
+			goto cleanup;
+		}
 		break;
 	case ACTION_TYPE_SHOW_MENU:
 		if (!strcmp(argument, "menu")) {
@@ -1031,9 +1037,9 @@ run_action(struct view *view, struct server *server, struct action *action,
 				view_apply_natural_geometry(view);
 				break;
 			}
-			view_snap_to_edge(view, edge,
-				/*across_outputs*/ true,
-				/*store_natural_geometry*/ true);
+			bool combine = action_get_bool(action, "combine", false);
+			view_snap_to_edge(view, edge, /*across_outputs*/ true,
+				combine, /*store_natural_geometry*/ true);
 		}
 		break;
 	case ACTION_TYPE_GROW_TO_EDGE:

src/interactive.c

@@ -260,9 +260,8 @@ snap_to_edge(struct view *view)
 		view_maximize(view, VIEW_AXIS_BOTH,
 			/*store_natural_geometry*/ false);
 	} else {
-		view_snap_to_edge(view, edge,
-			/*across_outputs*/ false,
-			/*store_natural_geometry*/ false);
+		view_snap_to_edge(view, edge, /*across_outputs*/ false,
+			/*combine*/ false, /*store_natural_geometry*/ false);
 	}
 
 	return true;

src/view.c

@@ -2126,7 +2126,7 @@ view_placement_parse(const char *policy)
 
 void
 view_snap_to_edge(struct view *view, enum lab_edge edge,
-			bool across_outputs, bool store_natural_geometry)
+		bool across_outputs, bool combine, bool store_natural_geometry)
 {
 	assert(view);
 
@@ -2142,15 +2142,45 @@ view_snap_to_edge(struct view *view, enum lab_edge edge,
 
 	view_set_shade(view, false);
 
-	if (across_outputs && view->tiled == edge && view->maximized == VIEW_AXIS_NONE) {
-		/* We are already tiled for this edge; try to switch outputs */
-		output = output_get_adjacent(view->output, edge, /* wrap */ false);
+	if (lab_edge_is_cardinal(edge) && view->maximized == VIEW_AXIS_NONE) {
+		enum lab_edge invert_edge = lab_edge_invert(edge);
+		/* Represents axis of snapping direction */
+		enum lab_edge parallel_mask = edge | invert_edge;
+		/*
+		 * The vector view->tiled is split to components
+		 * parallel/orthogonal to snapping direction. For example,
+		 * view->tiled=TOP_LEFT is split to parallel_tiled=TOP and
+		 * orthogonal_tiled=LEFT when edge=TOP or edge=BOTTOM.
+		 */
+		enum lab_edge parallel_tiled = view->tiled & parallel_mask;
+		enum lab_edge orthogonal_tiled = view->tiled & ~parallel_mask;
+
+		if (across_outputs && view->tiled == edge) {
+			/*
+			 * E.g. when window is tiled to up and being snapped
+			 * to up again, move it to the output above and tile
+			 * it to down.
+			 */
+			output = output_get_adjacent(view->output, edge,
+				/* wrap */ false);
 			if (!output) {
 				return;
 			}
-
-		/* When switching outputs, jump to the opposite edge */
-		edge = lab_edge_invert(edge);
+			edge = invert_edge;
+		} else if (combine && parallel_tiled == invert_edge
+				&& orthogonal_tiled != LAB_EDGE_NONE) {
+			/*
+			 * E.g. when window is tiled to downleft/downright and
+			 * being snapped to up, tile it to left/right.
+			 */
+			edge = view->tiled & ~parallel_mask;
+		} else if (combine && parallel_tiled == LAB_EDGE_NONE) {
+			/*
+			 * E.g. when window is tiled to left/right and being
+			 * snapped to up, tile it to upleft/upright.
+			 */
+			edge = view->tiled | edge;
+		}
 	}
 
 	if (view->maximized != VIEW_AXIS_NONE) {