ssd: fix resizing on border corners and add <resize><cornerRange>

Eliminate corner extents and instead use cursor position to map SSD
borders and extents to corner contexts, with a size configurable by the
<resize><cornerRange> parameter. This simplifies extent handling,
eliminates bugs in the detection of corner context, and allows users to
expand corner targets if they wish.

Co-authored-by: Andrew J. Hesford <ajh@sideband.org>

src/config/rcxml.c

@@ -1223,6 +1223,8 @@ entry(xmlNode *node, char *nodename, char *content, struct parser_state *state)
 		}
 	} else if (!strcasecmp(nodename, "drawContents.resize")) {
 		set_bool(content, &rc.resize_draw_contents);
+	} else if (!strcasecmp(nodename, "cornerRange.resize")) {
+		rc.resize_corner_range = atoi(content);
 	} else if (!strcasecmp(nodename, "mouseEmulation.tablet")) {
 		set_bool(content, &rc.tablet.force_mouse_emulation);
 	} else if (!strcasecmp(nodename, "mapToOutput.tablet")) {
@@ -1498,6 +1500,7 @@ rcxml_init(void)
 
 	rc.resize_indicator = LAB_RESIZE_INDICATOR_NEVER;
 	rc.resize_draw_contents = true;
+	rc.resize_corner_range = -1;
 
 	rc.workspace_config.popuptime = INT_MIN;
 	rc.workspace_config.min_nr_workspaces = 1;

src/desktop.c

@@ -278,7 +278,8 @@ get_cursor_context(struct server *server)
 			case LAB_NODE_DESC_VIEW:
 			case LAB_NODE_DESC_XDG_POPUP:
 				ret.view = desc->data;
-				ret.type = ssd_get_part_type(ret.view->ssd, ret.node);
+				ret.type = ssd_get_part_type(
+					ret.view->ssd, ret.node, cursor);
 				if (ret.type == LAB_SSD_CLIENT) {
 					ret.surface = lab_wlr_surface_from_node(ret.node);
 				}

src/ssd/ssd-extents.c

@@ -37,17 +37,10 @@ ssd_extents_create(struct ssd *ssd)
 		-(theme->border_width + extended_area),
 		-(ssd->titlebar.height + theme->border_width + extended_area));
 
-	/* Top */
-	add_extent(part_list, LAB_SSD_PART_CORNER_TOP_LEFT, parent);
 	add_extent(part_list, LAB_SSD_PART_TOP, parent);
-	add_extent(part_list, LAB_SSD_PART_CORNER_TOP_RIGHT, parent);
-	/* Sides */
 	add_extent(part_list, LAB_SSD_PART_LEFT, parent);
 	add_extent(part_list, LAB_SSD_PART_RIGHT, parent);
-	/* Bottom */
-	add_extent(part_list, LAB_SSD_PART_CORNER_BOTTOM_LEFT, parent);
 	add_extent(part_list, LAB_SSD_PART_BOTTOM, parent);
-	add_extent(part_list, LAB_SSD_PART_CORNER_BOTTOM_RIGHT, parent);
 
 	/* Initial manual update to keep X11 applications happy */
 	ssd_extents_update(ssd);
@@ -76,11 +69,6 @@ ssd_extents_update(struct ssd *ssd)
 	int full_height = height + theme->border_width * 2 + ssd->titlebar.height;
 	int full_width = width + 2 * theme->border_width;
 	int extended_area = SSD_EXTENDED_AREA;
-	int corner_width = ssd_get_corner_width();
-	int corner_size = extended_area + theme->border_width +
-		MIN(corner_width, width) / 2;
-	int side_width = full_width + extended_area * 2 - corner_size * 2;
-	int side_height = full_height + extended_area * 2 - corner_size * 2;
 
 	struct wlr_box part_box;
 	struct wlr_box result_box;
@@ -120,54 +108,30 @@ ssd_extents_update(struct ssd *ssd)
 	wl_list_for_each(part, &ssd->extents.parts, link) {
 		rect = wlr_scene_rect_from_node(part->node);
 		switch (part->type) {
-		case LAB_SSD_PART_CORNER_TOP_LEFT:
+		case LAB_SSD_PART_TOP:
 			target.x = 0;
 			target.y = 0;
-			target.width = corner_size;
-			target.height = corner_size;
-			break;
-		case LAB_SSD_PART_TOP:
-			target.x = corner_size;
-			target.y = 0;
-			target.width = side_width;
+			target.width = full_width + extended_area * 2;
 			target.height = extended_area;
 			break;
-		case LAB_SSD_PART_CORNER_TOP_RIGHT:
-			target.x = corner_size + side_width;
-			target.y = 0;
-			target.width = corner_size;
-			target.height = corner_size;
-			break;
 		case LAB_SSD_PART_LEFT:
 			target.x = 0;
-			target.y = corner_size;
+			target.y = extended_area;
 			target.width = extended_area;
-			target.height = side_height;
+			target.height = full_height;
 			break;
 		case LAB_SSD_PART_RIGHT:
 			target.x = extended_area + full_width;
-			target.y = corner_size;
+			target.y = extended_area;
 			target.width = extended_area;
-			target.height = side_height;
-			break;
-		case LAB_SSD_PART_CORNER_BOTTOM_LEFT:
-			target.x = 0;
-			target.y = corner_size + side_height;
-			target.width = corner_size;
-			target.height = corner_size;
+			target.height = full_height;
 			break;
 		case LAB_SSD_PART_BOTTOM:
-			target.x = corner_size;
+			target.x = 0;
 			target.y = extended_area + full_height;
-			target.width = side_width;
+			target.width = full_width + extended_area * 2;
 			target.height = extended_area;
 			break;
-		case LAB_SSD_PART_CORNER_BOTTOM_RIGHT:
-			target.x = corner_size + side_width;
-			target.y = corner_size + side_height;
-			target.width = corner_size;
-			target.height = corner_size;
-			break;
 		default:
 			/* not reached */
 			assert(false);

src/ssd/ssd.c

@@ -74,8 +74,69 @@ ssd_max_extents(struct view *view)
 	};
 }
 
+/*
+ * Resizing and mouse contexts like 'Left', 'TLCorner', etc. in the vicinity of
+ * SSD borders, titlebars and extents can have effective "corner regions" that
+ * behave differently from single-edge contexts.
+ *
+ * Corner regions are active whenever the cursor is within a prescribed size
+ * (generally rc.resize_corner_range, but clipped to view size) of the view
+ * bounds, so check the cursor against the view here.
+ */
+static enum ssd_part_type
+get_resizing_type(const struct ssd *ssd, struct wlr_cursor *cursor)
+{
+	struct view *view = ssd ? ssd->view : NULL;
+	if (!view || !cursor || !view->ssd_enabled || view->fullscreen) {
+		return LAB_SSD_NONE;
+	}
+
+	struct wlr_box view_box = view->current;
+	view_box.height = view_effective_height(view, /* use_pending */ false);
+
+	if (!view->ssd_titlebar_hidden) {
+		/* If the titlebar is visible, consider it part of the view */
+		int titlebar_height = view->server->theme->titlebar_height;
+		view_box.y -= titlebar_height;
+		view_box.height += titlebar_height;
+	}
+
+	if (wlr_box_contains_point(&view_box, cursor->x, cursor->y)) {
+		/* A cursor in bounds of the view is never in an SSD context */
+		return LAB_SSD_NONE;
+	}
+
+	int corner_height = MAX(0, MIN(rc.resize_corner_range, view_box.height / 2));
+	int corner_width = MAX(0, MIN(rc.resize_corner_range, view_box.width / 2));
+	bool left = cursor->x < view_box.x + corner_width;
+	bool right = cursor->x > view_box.x + view_box.width - corner_width;
+	bool top = cursor->y < view_box.y + corner_height;
+	bool bottom = cursor->y > view_box.y + view_box.height - corner_height;
+
+	if (top && left) {
+		return LAB_SSD_PART_CORNER_TOP_LEFT;
+	} else if (top && right) {
+		return LAB_SSD_PART_CORNER_TOP_RIGHT;
+	} else if (bottom && left) {
+		return LAB_SSD_PART_CORNER_BOTTOM_LEFT;
+	} else if (bottom && right) {
+		return LAB_SSD_PART_CORNER_BOTTOM_RIGHT;
+	} else if (top) {
+		return LAB_SSD_PART_TOP;
+	} else if (bottom) {
+		return LAB_SSD_PART_BOTTOM;
+	} else if (left) {
+		return LAB_SSD_PART_LEFT;
+	} else if (right) {
+		return LAB_SSD_PART_RIGHT;
+	}
+
+	return LAB_SSD_NONE;
+}
+
 enum ssd_part_type
-ssd_get_part_type(const struct ssd *ssd, struct wlr_scene_node *node)
+ssd_get_part_type(const struct ssd *ssd, struct wlr_scene_node *node,
+		struct wlr_cursor *cursor)
 {
 	if (!node) {
 		return LAB_SSD_NONE;
@@ -121,25 +182,25 @@ ssd_get_part_type(const struct ssd *ssd, struct wlr_scene_node *node)
 		part_list = &ssd->border.inactive.parts;
 	}
 
+	enum ssd_part_type part_type = LAB_SSD_NONE;
+
 	if (part_list) {
 		struct ssd_part *part;
 		wl_list_for_each(part, part_list, link) {
 			if (node == part->node) {
-				return part->type;
+				part_type = part->type;
+				break;
 			}
 		}
 	}
-	return LAB_SSD_NONE;
-}
 
-enum ssd_part_type
-ssd_at(const struct ssd *ssd, struct wlr_scene *scene, double lx, double ly)
-{
-	assert(scene);
-	double sx, sy;
-	struct wlr_scene_node *node = wlr_scene_node_at(
-		&scene->tree.node, lx, ly, &sx, &sy);
-	return ssd_get_part_type(ssd, node);
+	if (part_type == LAB_SSD_NONE) {
+		return part_type;
+	}
+
+	/* Perform cursor-based context checks */
+	enum ssd_part_type resizing_type = get_resizing_type(ssd, cursor);
+	return resizing_type != LAB_SSD_NONE ? resizing_type : part_type;
 }
 
 uint32_t

src/theme.c

@@ -1388,6 +1388,10 @@ post_processing(struct theme *theme)
 		rc.corner_radius = theme->titlebar_height - 1;
 	}
 
+	if (rc.resize_corner_range < 0) {
+		rc.resize_corner_range = theme->titlebar_height / 2;
+	}
+
 	int min_button_hover_radius =
 		MIN(theme->window_button_width, theme->window_button_height) / 2;
 	if (theme->window_button_hover_bg_corner_radius > min_button_hover_radius) {