feat: under-cursor window placement

With under-cursor placement, new top-level windows will be centered
under the cursor rather than centered on the active view.

src/config/rcxml.c

@@ -703,6 +703,12 @@ entry(xmlNode *node, char *nodename, char *content)
 		set_bool(content, &rc.adaptive_sync);
 	} else if (!strcasecmp(nodename, "reuseOutputMode.core")) {
 		set_bool(content, &rc.reuse_output_mode);
+	} else if (!strcmp(nodename, "policy.placement")) {
+		if (!strcmp(content, "cursor")) {
+			rc.placement_policy = LAB_PLACE_CURSOR;
+		} else {
+			rc.placement_policy = LAB_PLACE_CENTER;
+		}
 	} else if (!strcmp(nodename, "name.theme")) {
 		rc.theme_name = xstrdup(content);
 	} else if (!strcmp(nodename, "cornerradius.theme")) {
@@ -949,6 +955,8 @@ rcxml_init(void)
 	}
 	has_run = true;
 
+	rc.placement_policy = LAB_PLACE_CENTER;
+
 	rc.xdg_shell_server_side_deco = true;
 	rc.ssd_keep_border = true;
 	rc.corner_radius = 8;

src/view.c

@@ -678,6 +678,17 @@ view_center(struct view *view, const struct wlr_box *ref)
 	}
 }
 
+void
+view_place_initial(struct view *view)
+{
+	if (rc.placement_policy == LAB_PLACE_CURSOR) {
+		view_move_to_cursor(view);
+		return;
+	}
+
+	view_center(view, NULL);
+}
+
 static void
 view_apply_natural_geometry(struct view *view)
 {

src/xdg.c

@@ -1,4 +1,5 @@
 // SPDX-License-Identifier: GPL-2.0-only
+
 #include <assert.h>
 #include "common/macros.h"
 #include "common/mem.h"
@@ -409,19 +410,18 @@ position_xdg_toplevel_view(struct view *view)
 	struct wlr_xdg_toplevel *parent_xdg_toplevel =
 		xdg_toplevel_from_view(view)->parent;
 
-	if (!parent_xdg_toplevel) {
-		view_center(view, NULL);
-	} else {
-		/*
-		 * If child-toplevel-views, we center-align relative to their
-		 * parents
-		 */
+	if (parent_xdg_toplevel) {
+		/* Child views are center-aligned relative to their parents */
 		struct view *parent = lookup_view_by_xdg_toplevel(
 			view->server, parent_xdg_toplevel);
 		assert(parent);
 		view_set_output(view, parent->output);
 		view_center(view, &parent->pending);
+		return;
 	}
+
+	/* All other views are placed according to a configured strategy */
+	view_place_initial(view);
 }
 
 static const char *

src/xwayland.c

@@ -517,7 +517,7 @@ set_initial_position(struct view *view,
 		}
 	} else {
 		if (view_is_floating(view)) {
-			view_center(view, NULL);
+			view_place_initial(view);
 		} else {
 			/*
 			 * View is maximized/fullscreen. Center the