tree-wide: use die_if_null() for wlr_scene alloc failures

wlr_scene_*_create() functions all allocate memory via calloc() and
return NULL if the allocation fails. Previously, the failures were
handled in any of 3 different ways:

 - sending a wayland protocol error
 - exiting labwc with an error
 - segfault (no NULL check at all)

Since labwc does not attempt to survive heap exhaustion in other
allocation paths (such as `znew`), it seems more consistent to use the
same die_if_null() check used in those paths to exit with an error.

For the three most common create() functions (tree, rect, buffer),
add small lab_wlr_ wrappers to common/scene-helpers.

src/ssd/resize-indicator.c

@@ -3,6 +3,7 @@
 #include <wlr/types/wlr_scene.h>
 #include <wlr/util/box.h>
 #include <wlr/util/log.h>
+#include "common/scene-helpers.h"
 #include "config/rcxml.h"
 #include "labwc.h"
 #include "resize-indicator.h"
@@ -44,10 +45,10 @@ resize_indicator_init(struct view *view)
 	struct resize_indicator *indicator = &view->resize_indicator;
 	assert(!indicator->tree);
 
-	indicator->tree = wlr_scene_tree_create(view->scene_tree);
-	indicator->border = wlr_scene_rect_create(
+	indicator->tree = lab_wlr_scene_tree_create(view->scene_tree);
+	indicator->border = lab_wlr_scene_rect_create(
 		indicator->tree, 0, 0, rc.theme->osd_border_color);
-	indicator->background = wlr_scene_rect_create(
+	indicator->background = lab_wlr_scene_rect_create(
 		indicator->tree, 0, 0, rc.theme->osd_bg_color);
 	indicator->text = scaled_font_buffer_create(indicator->tree);
 

src/ssd/ssd-border.c

@@ -3,6 +3,7 @@
 #include <assert.h>
 #include <wlr/types/wlr_scene.h>
 #include "common/macros.h"
+#include "common/scene-helpers.h"
 #include "labwc.h"
 #include "ssd.h"
 #include "ssd-internal.h"
@@ -22,32 +23,32 @@ ssd_border_create(struct ssd *ssd)
 	int full_width = width + 2 * theme->border_width;
 	int corner_width = ssd_get_corner_width();
 
-	ssd->border.tree = wlr_scene_tree_create(ssd->tree);
+	ssd->border.tree = lab_wlr_scene_tree_create(ssd->tree);
 	wlr_scene_node_set_position(&ssd->border.tree->node, -theme->border_width, 0);
 
 	enum ssd_active_state active;
 	FOR_EACH_ACTIVE_STATE(active) {
 		struct ssd_border_subtree *subtree = &ssd->border.subtrees[active];
-		subtree->tree = wlr_scene_tree_create(ssd->border.tree);
+		subtree->tree = lab_wlr_scene_tree_create(ssd->border.tree);
 		struct wlr_scene_tree *parent = subtree->tree;
 		wlr_scene_node_set_enabled(&parent->node, active);
 		float *color = theme->window[active].border_color;
 
-		subtree->left = wlr_scene_rect_create(parent,
+		subtree->left = lab_wlr_scene_rect_create(parent,
 			theme->border_width, height, color);
 		wlr_scene_node_set_position(&subtree->left->node, 0, 0);
 
-		subtree->right = wlr_scene_rect_create(parent,
+		subtree->right = lab_wlr_scene_rect_create(parent,
 			theme->border_width, height, color);
 		wlr_scene_node_set_position(&subtree->right->node,
 			theme->border_width + width, 0);
 
-		subtree->bottom = wlr_scene_rect_create(parent,
+		subtree->bottom = lab_wlr_scene_rect_create(parent,
 			full_width, theme->border_width, color);
 		wlr_scene_node_set_position(&subtree->bottom->node,
 			0, height);
 
-		subtree->top = wlr_scene_rect_create(parent,
+		subtree->top = lab_wlr_scene_rect_create(parent,
 			MAX(width - 2 * corner_width, 0), theme->border_width, color);
 		wlr_scene_node_set_position(&subtree->top->node,
 			theme->border_width + corner_width,

src/ssd/ssd-button.c

@@ -5,6 +5,7 @@
 #include "config/rcxml.h"
 #include "common/list.h"
 #include "common/mem.h"
+#include "common/scene-helpers.h"
 #include "node.h"
 #include "scaled-buffer/scaled-icon-buffer.h"
 #include "scaled-buffer/scaled-img-buffer.h"
@@ -19,7 +20,7 @@ attach_ssd_button(struct wl_list *button_parts, enum lab_node_type type,
 		struct lab_img *imgs[LAB_BS_ALL + 1],
 		int x, int y, struct view *view)
 {
-	struct wlr_scene_tree *root = wlr_scene_tree_create(parent);
+	struct wlr_scene_tree *root = lab_wlr_scene_tree_create(parent);
 	wlr_scene_node_set_position(&root->node, x, y);
 
 	assert(node_type_contains(LAB_NODE_BUTTON, type));
@@ -31,7 +32,7 @@ attach_ssd_button(struct wl_list *button_parts, enum lab_node_type type,
 
 	/* Hitbox */
 	float invisible[4] = { 0, 0, 0, 0 };
-	wlr_scene_rect_create(root, rc.theme->window_button_width,
+	lab_wlr_scene_rect_create(root, rc.theme->window_button_width,
 		rc.theme->window_button_height, invisible);
 
 	/* Icons */

src/ssd/ssd-extents.c

@@ -2,6 +2,7 @@
 
 #include <pixman.h>
 #include <wlr/types/wlr_scene.h>
+#include "common/scene-helpers.h"
 #include "config/rcxml.h"
 #include "labwc.h"
 #include "output.h"
@@ -17,7 +18,7 @@ ssd_extents_create(struct ssd *ssd)
 
 	int border_width = MAX(0, MAX(rc.resize_minimum_area, theme->border_width));
 
-	ssd->extents.tree = wlr_scene_tree_create(ssd->tree);
+	ssd->extents.tree = lab_wlr_scene_tree_create(ssd->tree);
 	struct wlr_scene_tree *parent = ssd->extents.tree;
 	if (view->fullscreen || view->maximized == VIEW_AXIS_BOTH) {
 		wlr_scene_node_set_enabled(&parent->node, false);
@@ -26,10 +27,10 @@ ssd_extents_create(struct ssd *ssd)
 		-border_width, -(ssd->titlebar.height + border_width));
 
 	float invisible[4] = { 0.0f, 0.0f, 0.0f, 0.0f };
-	ssd->extents.top = wlr_scene_rect_create(parent, 0, 0, invisible);
-	ssd->extents.left = wlr_scene_rect_create(parent, 0, 0, invisible);
-	ssd->extents.right = wlr_scene_rect_create(parent, 0, 0, invisible);
-	ssd->extents.bottom = wlr_scene_rect_create(parent, 0, 0, invisible);
+	ssd->extents.top = lab_wlr_scene_rect_create(parent, 0, 0, invisible);
+	ssd->extents.left = lab_wlr_scene_rect_create(parent, 0, 0, invisible);
+	ssd->extents.right = lab_wlr_scene_rect_create(parent, 0, 0, invisible);
+	ssd->extents.bottom = lab_wlr_scene_rect_create(parent, 0, 0, invisible);
 
 	/* Initial manual update to keep X11 applications happy */
 	ssd_extents_update(ssd);

src/ssd/ssd-shadow.c

@@ -3,6 +3,7 @@
 #include <assert.h>
 #include <wlr/types/wlr_scene.h>
 #include "buffer.h"
+#include "common/scene-helpers.h"
 #include "config/rcxml.h"
 #include "labwc.h"
 #include "ssd.h"
@@ -183,7 +184,7 @@ make_shadow(struct view *view,
 	enum wl_output_transform tx)
 {
 	struct wlr_scene_buffer *scene_buf =
-		wlr_scene_buffer_create(parent, buf);
+		lab_wlr_scene_buffer_create(parent, buf);
 	wlr_scene_buffer_set_transform(scene_buf, tx);
 	scene_buf->point_accepts_input = never_accepts_input;
 	/*
@@ -200,7 +201,7 @@ ssd_shadow_create(struct ssd *ssd)
 	assert(ssd);
 	assert(!ssd->shadow.tree);
 
-	ssd->shadow.tree = wlr_scene_tree_create(ssd->tree);
+	ssd->shadow.tree = lab_wlr_scene_tree_create(ssd->tree);
 
 	struct theme *theme = ssd->view->server->theme;
 	struct view *view = ssd->view;
@@ -218,7 +219,7 @@ ssd_shadow_create(struct ssd *ssd)
 			continue;
 		}
 
-		subtree->tree = wlr_scene_tree_create(ssd->shadow.tree);
+		subtree->tree = lab_wlr_scene_tree_create(ssd->shadow.tree);
 		struct wlr_scene_tree *parent = subtree->tree;
 		struct wlr_buffer *corner_top_buffer =
 			&theme->window[active].shadow_corner_top->base;

src/ssd/ssd-titlebar.c

@@ -7,7 +7,7 @@
 #include <wlr/types/wlr_scene.h>
 #include "buffer.h"
 #include "common/mem.h"
-#include "common/string-helpers.h"
+#include "common/scene-helpers.h"
 #include "config/rcxml.h"
 #include "labwc.h"
 #include "node.h"
@@ -31,14 +31,14 @@ ssd_titlebar_create(struct ssd *ssd)
 	int width = view->current.width;
 	int corner_width = ssd_get_corner_width();
 
-	ssd->titlebar.tree = wlr_scene_tree_create(ssd->tree);
+	ssd->titlebar.tree = lab_wlr_scene_tree_create(ssd->tree);
 	node_descriptor_create(&ssd->titlebar.tree->node,
 		LAB_NODE_TITLEBAR, view, /*data*/ NULL);
 
 	enum ssd_active_state active;
 	FOR_EACH_ACTIVE_STATE(active) {
 		struct ssd_titlebar_subtree *subtree = &ssd->titlebar.subtrees[active];
-		subtree->tree = wlr_scene_tree_create(ssd->titlebar.tree);
+		subtree->tree = lab_wlr_scene_tree_create(ssd->titlebar.tree);
 		struct wlr_scene_tree *parent = subtree->tree;
 		wlr_scene_node_set_enabled(&parent->node, active);
 		wlr_scene_node_set_position(&parent->node, 0, -theme->titlebar_height);
@@ -51,7 +51,7 @@ ssd_titlebar_create(struct ssd *ssd)
 			&theme->window[active].corner_top_right_normal->base;
 
 		/* Background */
-		subtree->bar = wlr_scene_buffer_create(parent, titlebar_fill);
+		subtree->bar = lab_wlr_scene_buffer_create(parent, titlebar_fill);
 		/*
 		 * Work around the wlroots/pixman bug that widened 1px buffer
 		 * becomes translucent when bilinear filtering is used.
@@ -64,11 +64,11 @@ ssd_titlebar_create(struct ssd *ssd)
 		}
 		wlr_scene_node_set_position(&subtree->bar->node, corner_width, 0);
 
-		subtree->corner_left = wlr_scene_buffer_create(parent, corner_top_left);
+		subtree->corner_left = lab_wlr_scene_buffer_create(parent, corner_top_left);
 		wlr_scene_node_set_position(&subtree->corner_left->node,
 			-rc.theme->border_width, -rc.theme->border_width);
 
-		subtree->corner_right = wlr_scene_buffer_create(parent, corner_top_right);
+		subtree->corner_right = lab_wlr_scene_buffer_create(parent, corner_top_right);
 		wlr_scene_node_set_position(&subtree->corner_right->node,
 			width - corner_width, -rc.theme->border_width);
 

src/ssd/ssd.c

@@ -12,6 +12,7 @@
 #include <wlr/types/wlr_cursor.h>
 #include <wlr/types/wlr_scene.h>
 #include "common/mem.h"
+#include "common/scene-helpers.h"
 #include "config/rcxml.h"
 #include "labwc.h"
 #include "node.h"
@@ -145,7 +146,7 @@ ssd_create(struct view *view, bool active)
 	struct ssd *ssd = znew(*ssd);
 
 	ssd->view = view;
-	ssd->tree = wlr_scene_tree_create(view->scene_tree);
+	ssd->tree = lab_wlr_scene_tree_create(view->scene_tree);
 
 	/*
 	 * Attach node_descriptor to the root node so that get_cursor_context()