backend: gl: handle custom shader image property

Signed-off-by: Yuxuan Shui <yshuiv7@gmail.com>

src/backend/gl/gl_common.c

@@ -1994,6 +1994,18 @@ bool gl_image_op(backend_t *base, enum image_operations op, void *image_data,
 	return true;
 }
 
+bool gl_set_image_property(backend_t *backend_data, enum image_properties prop,
+                           void *image_data, void *args) {
+	if (prop != IMAGE_PROPERTY_CUSTOM_SHADER) {
+		return default_set_image_property(backend_data, prop, image_data, args);
+	}
+
+	struct backend_image *img = image_data;
+	auto inner = (struct gl_texture *)img->inner;
+	inner->shader = args;
+	return true;
+}
+
 enum device_status gl_device_status(backend_t *base) {
 	auto gd = (struct gl_data *)base;
 	if (!gd->has_robustness) {

src/backend/gl/gl_common.h

@@ -110,6 +110,8 @@ GLuint gl_create_program(const GLuint *const shaders, int nshaders);
 GLuint gl_create_program_from_str(const char *vert_shader_str, const char *frag_shader_str);
 void *gl_create_window_shader(backend_t *backend_data, const char *source);
 void gl_destroy_window_shader(backend_t *backend_data, void *shader);
+bool gl_set_image_property(backend_t *backend_data, enum image_properties prop,
+                           void *image_data, void *args);
 
 /**
  * @brief Render a region with texture data.

src/backend/gl/glx.c

@@ -534,7 +534,7 @@ struct backend_operations glx_ops = {
     .release_image = gl_release_image,
     .compose = gl_compose,
     .image_op = gl_image_op,
-    .set_image_property = default_set_image_property,
+    .set_image_property = gl_set_image_property,
     .clone_image = default_clone_image,
     .blur = gl_blur,
     .is_image_transparent = default_is_image_transparent,