Add scaled_rect_buffer

scaled_rect_buffer is an implementation of scaled_scene_buffer and shows
an auto-scaling bordered rectangle. This is intended for menu borders,
but can be also useful for other elements like window switcher items.

We will support rounded corners for scaled_rect_buffer in the future.

include/common/scaled-rect-buffer.h

@@ -0,0 +1,31 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+#ifndef LABWC_SCALED_RECT_BUFFER_H
+#define LABWC_SCALED_RECT_BUFFER_H
+
+#include <stdint.h>
+
+struct wlr_scene_tree;
+struct wlr_scene_buffer;
+struct scaled_scene_buffer;
+
+struct scaled_rect_buffer {
+	struct wlr_scene_buffer *scene_buffer;
+	struct scaled_scene_buffer *scaled_buffer;
+	int width;
+	int height;
+	int border_width;
+	float fill_color[4];
+	float border_color[4];
+};
+
+/*
+ * Create an auto scaling borderd-rectangle buffer, providing a wlr_scene_buffer
+ * node for display. It gets destroyed automatically when the backing
+ * scaled_scene_buffer is being destroyed which in turn happens automatically
+ * when the backing wlr_scene_buffer (or one of its parents) is being destroyed.
+ */
+struct scaled_rect_buffer *scaled_rect_buffer_create(
+	struct wlr_scene_tree *parent, int width, int height, int border_width,
+	float fill_color[4], float border_color[4]);
+
+#endif /* LABWC_SCALED_RECT_BUFFER_H */

src/common/meson.build

@@ -14,6 +14,7 @@ labwc_sources += files(
   'parse-bool.c',
   'parse-double.c',
   'scaled-font-buffer.c',
+  'scaled-rect-buffer.c',
   'scaled-scene-buffer.c',
   'scene-helpers.c',
   'set.c',

src/common/scaled-rect-buffer.c

@@ -0,0 +1,113 @@
+// SPDX-License-Identifier: GPL-2.0-only
+#define _POSIX_C_SOURCE 200809L
+#include <assert.h>
+#include <stdlib.h>
+#include <string.h>
+#include <wayland-server-core.h>
+#include <wlr/util/log.h>
+#include "buffer.h"
+#include "common/graphic-helpers.h"
+#include "common/list.h"
+#include "common/macros.h"
+#include "common/mem.h"
+#include "common/scaled-scene-buffer.h"
+#include "common/scaled-rect-buffer.h"
+
+static struct wl_list cached_buffers = WL_LIST_INIT(&cached_buffers);
+
+static void
+draw_rectangle_path(cairo_t *cairo, int width, int height, int border_width)
+{
+	double offset = border_width / 2.0;
+	double right_x = width - offset;
+	double bottom_y = height - offset;
+
+	cairo_move_to(cairo, offset, offset);
+	cairo_line_to(cairo, right_x, offset);
+	cairo_line_to(cairo, right_x, bottom_y);
+	cairo_line_to(cairo, offset, bottom_y);
+	cairo_close_path(cairo);
+}
+
+static struct lab_data_buffer *
+_create_buffer(struct scaled_scene_buffer *scaled_buffer, double scale)
+{
+	struct scaled_rect_buffer *self = scaled_buffer->data;
+	struct lab_data_buffer *buffer = buffer_create_cairo(
+		self->width, self->height, scale);
+	if (!buffer) {
+		return NULL;
+	}
+
+	cairo_t *cairo = buffer->cairo;
+
+	/* Clear background */
+	cairo_set_operator(cairo, CAIRO_OPERATOR_CLEAR);
+	cairo_paint(cairo);
+	cairo_set_operator(cairo, CAIRO_OPERATOR_SOURCE);
+
+	/* Fill rectangle */
+	draw_rectangle_path(cairo, self->width, self->height, 0);
+	set_cairo_color(cairo, self->fill_color);
+	cairo_fill(cairo);
+
+	/* Draw borders */
+	draw_rectangle_path(cairo, self->width, self->height,
+		self->border_width);
+	cairo_set_line_width(cairo, self->border_width);
+	set_cairo_color(cairo, self->border_color);
+	cairo_stroke(cairo);
+
+	return buffer;
+}
+
+static void
+_destroy(struct scaled_scene_buffer *scaled_buffer)
+{
+	struct scaled_rect_buffer *self = scaled_buffer->data;
+	scaled_buffer->data = NULL;
+	free(self);
+}
+
+static bool
+_equal(struct scaled_scene_buffer *scaled_buffer_a, struct scaled_scene_buffer *scaled_buffer_b)
+{
+	struct scaled_rect_buffer *a = scaled_buffer_a->data;
+	struct scaled_rect_buffer *b = scaled_buffer_b->data;
+
+	return a->width == b->width
+		&& a->height == b->height
+		&& a->border_width == b->border_width
+		&& !memcmp(a->fill_color, b->fill_color, sizeof(a->fill_color))
+		&& !memcmp(a->border_color, b->border_color, sizeof(a->border_color));
+}
+
+static const struct scaled_scene_buffer_impl impl = {
+	.create_buffer = _create_buffer,
+	.destroy = _destroy,
+	.equal = _equal,
+};
+
+struct scaled_rect_buffer *scaled_rect_buffer_create(
+	struct wlr_scene_tree *parent, int width, int height, int border_width,
+	float fill_color[4], float border_color[4])
+{
+	/* TODO: support rounded corners for menus and OSDs */
+
+	assert(parent);
+	struct scaled_rect_buffer *self = znew(*self);
+	struct scaled_scene_buffer *scaled_buffer = scaled_scene_buffer_create(
+		parent, &impl, &cached_buffers, /* drop_buffer */ true);
+	scaled_buffer->data = self;
+	self->scaled_buffer = scaled_buffer;
+	self->scene_buffer = scaled_buffer->scene_buffer;
+	self->width = MAX(width, 1);
+	self->height = MAX(height, 1);
+	self->border_width = border_width;
+	memcpy(self->fill_color, fill_color, sizeof(self->fill_color));
+	memcpy(self->border_color, border_color, sizeof(self->border_color));
+
+	scaled_scene_buffer_invalidate_cache(scaled_buffer);
+
+	return self;
+}