render: introduce wlr_texture_from_buffer

This adds a a function to create a wlr_texture from a wlr_buffer.

The main motivation for this is to allow the renderer to create a
single wlr_texture per wlr_buffer. This can avoid needless imports
by re-using existing textures.

include/render/wlr_texture.h

@@ -0,0 +1,15 @@
+#ifndef RENDER_WLR_TEXTURE_H
+#define RENDER_WLR_TEXTURE_H
+
+#include <wlr/render/wlr_texture.h>
+
+/**
+ * Create a new texture from a buffer.
+ *
+ * Should not be called in a rendering block like renderer_begin()/end() or
+ * between attaching a renderer to an output and committing it.
+ */
+struct wlr_texture *wlr_texture_from_buffer(struct wlr_renderer *renderer,
+	struct wlr_buffer *buffer);
+
+#endif

include/wlr/render/interface.h

@@ -57,6 +57,8 @@ struct wlr_renderer_impl {
 		struct wl_display *wl_display);
 	int (*get_drm_fd)(struct wlr_renderer *renderer);
 	uint32_t (*get_render_buffer_caps)(void);
+	struct wlr_texture *(*texture_from_buffer)(struct wlr_renderer *renderer,
+		struct wlr_buffer *buffer);
 };
 
 void wlr_renderer_init(struct wlr_renderer *renderer,