Add C++20 RAII wrapper around wlroots 0.20 + scenefx

Wraps wlroots' C ABI behind owning types (Display, Backend, Compositor,
Output, XdgShell/Toplevel, Seat/Cursor/Keyboard, Scene/Node/Tree) with
wl_signal -> std::function callbacks. Links the scenefx effect engine and
ships a wlr::fx animation helper. Includes a runnable tinywl-style compositor
and a scene/blur demo.

License: AGPL-3.0-only.

include/wlr/scene.hpp

@@ -0,0 +1,74 @@
+// SPDX-License-Identifier: AGPL-3.0-only
+#pragma once
+
+#include <pixman.h>
+#include <string>
+
+#include "wlr/wlr.hpp"
+
+namespace wlr {
+
+std::string version();
+
+class Scene {
+public:
+	Scene() : m_scene(wlr_scene_create()) {}
+	~Scene() { if (m_scene) wlr_scene_node_destroy(&m_scene->tree.node); }
+
+	Scene(const Scene&) = delete;
+	Scene& operator=(const Scene&) = delete;
+	Scene(Scene&&) = delete;
+	Scene& operator=(Scene&&) = delete;
+
+	struct wlr_scene* raw() const { return m_scene; }
+	explicit operator bool() const { return m_scene != nullptr; }
+
+	void set_blur_data(int num_passes, int radius, float noise,
+		float brightness, float contrast, float saturation) {
+		wlr_scene_set_blur_data(m_scene, num_passes, radius,
+			noise, brightness, contrast, saturation);
+	}
+	void set_blur_num_passes(int num_passes) { wlr_scene_set_blur_num_passes(m_scene, num_passes); }
+	void set_blur_radius(int radius) { wlr_scene_set_blur_radius(m_scene, radius); }
+	void set_blur_noise(float noise) { wlr_scene_set_blur_noise(m_scene, noise); }
+	void set_blur_brightness(float brightness) { wlr_scene_set_blur_brightness(m_scene, brightness); }
+	void set_blur_contrast(float contrast) { wlr_scene_set_blur_contrast(m_scene, contrast); }
+	void set_blur_saturation(float saturation) { wlr_scene_set_blur_saturation(m_scene, saturation); }
+	struct wlr_scene_tree* root() { return &m_scene->tree; }
+
+private:
+	struct wlr_scene* m_scene;
+};
+
+struct Box {
+	int x = 0, y = 0, width = 0, height = 0;
+	pixman_box32 to_box() const { return {x, y, x + width, y + height}; }
+	static Box from_box(pixman_box32 b) {
+		return {b.x1, b.y1, b.x2 - b.x1, b.y2 - b.y1};
+	}
+};
+
+struct Color {
+	float r = 1.0f, g = 1.0f, b = 1.0f, a = 1.0f;
+	void apply(float out[4]) const {
+		out[0] = r; out[1] = g; out[2] = b; out[3] = a;
+	}
+};
+
+struct CornerRadii {
+	uint16_t top_left = 0, top_right = 0, bottom_right = 0, bottom_left = 0;
+
+	CornerRadii() = default;
+	CornerRadii(uint16_t all) : top_left(all), top_right(all), bottom_right(all), bottom_left(all) {}
+	CornerRadii(uint16_t tl, uint16_t tr, uint16_t br, uint16_t bl)
+		: top_left(tl), top_right(tr), bottom_right(br), bottom_left(bl) {}
+
+	fx_corner_radii raw() const {
+		return fx_corner_radii{top_left, top_right, bottom_right, bottom_left};
+	}
+	static CornerRadii from_radii(fx_corner_radii r) {
+		return {r.top_left, r.top_right, r.bottom_right, r.bottom_left};
+	}
+};
+
+}