add xdg decoration, scene/tree factories, geometry + seat focus

more wrapper soup. xdg decoration manager, scene/tree node factories so
callers stop touching raw wlr_scene_*_create, a box geometry helper, and
seat pointer/keyboard focus clearing. dragging myself through it.

include/wlr/scene.hpp

@@ -1,10 +1,11 @@
 // SPDX-License-Identifier: AGPL-3.0-only
 #pragma once
 
-#include <pixman.h>
 #include <string>
 
 #include "wlr/wlr.hpp"
+#include "wlr/color.hpp"
+#include "wlr/node.hpp"
 
 namespace wlr {
 
@@ -36,39 +37,16 @@ public:
 	void set_blur_saturation(float saturation) { wlr_scene_set_blur_saturation(m_scene, saturation); }
 	struct wlr_scene_tree* root() { return &m_scene->tree; }
 
+	Tree add_tree() { return Tree{wlr_scene_tree_create(&m_scene->tree)}; }
+	Rect add_rect(int w, int h, const Color& c) {
+		float col[4]; c.apply(col);
+		return Rect{wlr_scene_rect_create(&m_scene->tree, w, h, col)};
+	}
+	Buffer add_buffer() { return Buffer{wlr_scene_buffer_create(&m_scene->tree, nullptr)}; }
+	Surface add_surface(struct wlr_surface* s) { return Surface{wlr_scene_surface_create(&m_scene->tree, s)}; }
+
 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};
-	}
-};
-
 }