awesome.load_image(): Return errors instead of "throwing" them

Signed-off-by: Uli Schlachter <psychon@znc.in>

draw.c

@@ -229,23 +229,18 @@ draw_dup_image_surface(cairo_surface_t *surface)
 /** Load the specified path into a cairo surface
  * \param L Lua state
  * \param path file to load
+ * \param error A place to store an error message, if needed
  * \return A cairo image surface or NULL on error.
  */
 cairo_surface_t *
-draw_load_image(lua_State *L, const char *path)
+draw_load_image(lua_State *L, const char *path, GError **error)
 {
-    GError *error = NULL;
     cairo_surface_t *ret;
-    GdkPixbuf *buf = gdk_pixbuf_new_from_file(path, &error);
+    GdkPixbuf *buf = gdk_pixbuf_new_from_file(path, error);
 
-    if (!buf) {
-        luaL_where(L, 1);
-        lua_pushstring(L, error->message);
-        lua_concat(L, 2);
-        g_error_free(error);
-        lua_error(L);
+    if (!buf)
+        /* error was set above */
         return NULL;
-    }
 
     ret = draw_surface_from_pixbuf(buf);
     g_object_unref(buf);

draw.h

@@ -25,6 +25,7 @@
 #include <xcb/xcb.h>
 #include <cairo.h>
 #include <lua.h>
+#include <glib.h> /* for GError */
 
 #include "common/util.h"
 
@@ -70,7 +71,7 @@ a_iso2utf8(const char *str, ssize_t len, char **dest, ssize_t *dlen)
 
 cairo_surface_t *draw_surface_from_data(int width, int height, uint32_t *data);
 cairo_surface_t *draw_dup_image_surface(cairo_surface_t *surface);
-cairo_surface_t *draw_load_image(lua_State *L, const char *path);
+cairo_surface_t *draw_load_image(lua_State *L, const char *path, GError **error);
 
 xcb_visualtype_t *draw_find_visual(const xcb_screen_t *s, xcb_visualid_t visual);
 xcb_visualtype_t *draw_default_visual(const xcb_screen_t *s);

luaa.c

@@ -147,16 +147,24 @@ luaA_restart(lua_State *L)
 /** Load an image from a given path.
  *
  * @param name The file name.
- * @return A cairo surface as light user datum.
+ * @return[1] A cairo surface as light user datum.
+ * @return[2] nil
+ * @treturn[2] string Error message
  * @function load_image
  */
 static int
 luaA_load_image(lua_State *L)
 {
+    GError *error = NULL;
     const char *filename = luaL_checkstring(L, 1);
-    cairo_surface_t *surface = draw_load_image(L, filename);
-    if (!surface)
-        return 0;
+    cairo_surface_t *surface = draw_load_image(L, filename, &error);
+    if (!surface) {
+        lua_pushnil(L);
+        lua_pushstring(L, error->message);
+        g_error_free(error);
+        return 2;
+    }
+
     /* lua has to make sure to free the ref or we have a leak */
     lua_pushlightuserdata(L, surface);
     return 1;