Use enum wl_shm_format for gles2 texture formats

Also rephrase the write_pixels comment.

include/render/gles2.h

@@ -19,7 +19,7 @@
 extern PFNGLEGLIMAGETARGETTEXTURE2DOESPROC glEGLImageTargetTexture2DOES;
 
 struct wlr_gles2_pixel_format {
-	uint32_t wl_format;
+	enum wl_shm_format wl_format;
 	GLint gl_format, gl_type;
 	int depth, bpp;
 	bool has_alpha;
@@ -72,7 +72,7 @@ struct wlr_gles2_texture {
 	enum wlr_gles2_texture_type type;
 	int width, height;
 	bool has_alpha;
-	uint32_t wl_format; // used to interpret upload data
+	enum wl_shm_format wl_format; // used to interpret upload data
 	bool inverted_y;
 
 	// Not set if WLR_GLES2_TEXTURE_GLTEX

include/wlr/render/wlr_texture.h

@@ -54,10 +54,9 @@ void wlr_texture_get_size(struct wlr_texture *texture, int *width, int *height);
 bool wlr_texture_is_opaque(struct wlr_texture *texture);
 
 /**
- * Update a texture with raw pixels. The texture must be mutable.
- * The given data is interpreted as being in the format the
- * texture was created with.
- */
+  * Update a texture with raw pixels. The texture must be mutable, and the input
+  * data must have the same pixel format that the texture was created with.
+  */
 bool wlr_texture_write_pixels(struct wlr_texture *texture,
 	uint32_t stride, uint32_t width, uint32_t height,
 	uint32_t src_x, uint32_t src_y, uint32_t dst_x, uint32_t dst_y,

render/gles2/texture.c

@@ -55,8 +55,8 @@ static bool gles2_texture_write_pixels(struct wlr_texture *wlr_texture,
 		return false;
 	}
 
-	const struct wlr_gles2_pixel_format *fmt = get_gles2_format_from_wl(
-		texture->wl_format);
+	const struct wlr_gles2_pixel_format *fmt =
+		get_gles2_format_from_wl(texture->wl_format);
 	assert(fmt);
 
 	// TODO: what if the unpack subimage extension isn't supported?