Introduce wlr_client_buffer

Split out the client/resource handling out of wlr_buffer by introducing
wlr_client_buffer. Make wlr_buffer an interface so that compositors can
create their own wlr_buffers (e.g. backed by GBM, like glider [1]).

[1]: c66847dd1c/include/gbm_allocator.h (L7)

include/wlr/types/wlr_buffer.h

@@ -13,14 +13,52 @@
 #include <wayland-server-core.h>
 #include <wlr/render/dmabuf.h>
 
+struct wlr_buffer;
+
+struct wlr_buffer_impl {
+	void (*destroy)(struct wlr_buffer *buffer);
+	bool (*get_dmabuf)(struct wlr_buffer *buffer,
+		struct wlr_dmabuf_attributes *attribs);
+};
+
+struct wlr_buffer {
+	const struct wlr_buffer_impl *impl;
+
+	size_t n_refs;
+};
+
+void wlr_buffer_init(struct wlr_buffer *buffer,
+	const struct wlr_buffer_impl *impl);
+/**
+ * Reference the buffer.
+ */
+struct wlr_buffer *wlr_buffer_ref(struct wlr_buffer *buffer);
+/**
+ * Unreference the buffer. After this call, `buffer` may not be accessed
+ * anymore.
+ */
+void wlr_buffer_unref(struct wlr_buffer *buffer);
+/**
+ * Reads the DMA-BUF attributes of the buffer. If this buffer isn't a DMA-BUF,
+ * returns false.
+ */
+bool wlr_buffer_get_dmabuf(struct wlr_buffer *buffer,
+	struct wlr_dmabuf_attributes *attribs);
+
 /**
  * A client buffer.
  */
-struct wlr_buffer {
+struct wlr_client_buffer {
+	struct wlr_buffer base;
+
 	/**
 	 * The buffer resource, if any. Will be NULL if the client destroys it.
 	 */
 	struct wl_resource *resource;
+	/**
+	 * Whether a release event has been sent to the resource.
+	 */
+	bool resource_released;
 	/**
 	 * The buffer's texture, if any. A buffer will not have a texture if the
 	 * client destroys the buffer before it has been released.
@@ -41,23 +79,13 @@ bool wlr_resource_is_buffer(struct wl_resource *resource);
 /**
  * Get the size of a wl_buffer resource.
  */
-bool wlr_buffer_get_resource_size(struct wl_resource *resource,
+bool wlr_resource_get_buffer_size(struct wl_resource *resource,
 	struct wlr_renderer *renderer, int *width, int *height);
-
 /**
  * Upload a buffer to the GPU and reference it.
  */
-struct wlr_buffer *wlr_buffer_create(struct wlr_renderer *renderer,
-	struct wl_resource *resource);
-/**
- * Reference the buffer.
- */
-struct wlr_buffer *wlr_buffer_ref(struct wlr_buffer *buffer);
-/**
- * Unreference the buffer. After this call, `buffer` may not be accessed
- * anymore.
- */
-void wlr_buffer_unref(struct wlr_buffer *buffer);
+struct wlr_client_buffer *wlr_client_buffer_create(
+	struct wlr_renderer *renderer, struct wl_resource *resource);
 /**
  * Try to update the buffer's content. On success, returns the updated buffer
  * and destroys the provided `buffer`. On error, `buffer` is intact and NULL is
@@ -66,13 +94,8 @@ void wlr_buffer_unref(struct wlr_buffer *buffer);
  * Fails if there's more than one reference to the buffer or if the texture
  * isn't mutable.
  */
-struct wlr_buffer *wlr_buffer_apply_damage(struct wlr_buffer *buffer,
-	struct wl_resource *resource, pixman_region32_t *damage);
-/**
- * Reads the DMA-BUF attributes of the buffer. If this buffer isn't a DMA-BUF,
- * returns false.
- */
-bool wlr_buffer_get_dmabuf(struct wlr_buffer *buffer,
-		struct wlr_dmabuf_attributes *attribs);
+struct wlr_client_buffer *wlr_client_buffer_apply_damage(
+	struct wlr_client_buffer *buffer, struct wl_resource *resource,
+	pixman_region32_t *damage);
 
 #endif

include/wlr/types/wlr_surface.h

@@ -59,7 +59,7 @@ struct wlr_surface {
 	 * have a buffer if it has never committed one, has committed a null buffer,
 	 * or something went wrong with uploading the buffer.
 	 */
-	struct wlr_buffer *buffer;
+	struct wlr_client_buffer *buffer;
 	/**
 	 * The buffer position, in surface-local units.
 	 */