Merge pull request #9265 from jdgleaver/shader-menu-fix

(Menu) Prevent undefined behaviour when failing to load shaders

intl/msg_hash_us.h

@@ -4679,6 +4679,10 @@ MSG_HASH(
     MSG_FAILED_TO_APPLY_SHADER,
     "Failed to apply shader."
     )
+MSG_HASH(
+    MSG_FAILED_TO_APPLY_SHADER_PRESET,
+    "Failed to apply shader preset:"
+    )
 MSG_HASH(
     MSG_FAILED_TO_BIND_SOCKET,
     "Failed to bind socket."

menu/menu_setting.c

@@ -5713,8 +5713,8 @@ void general_write_handler(rarch_setting_t *setting)
                settings->bools.video_shader_enable = false;
             }
          }
-         /* TODO/FIXME - fallthrough here intentional? */
 #endif
+         break;
       case MENU_ENUM_LABEL_VIDEO_THREADED:
          {
             if (*setting->value.target.boolean)

menu/menu_shader.c

@@ -158,7 +158,32 @@ bool menu_shader_manager_set_preset(void *data,
 
    if (!video_driver_set_shader(type, preset_path))
    {
-      configuration_set_bool(settings, settings->bools.video_shader_enable, false);
+      char msg[PATH_MAX_LENGTH];
+      const char *preset_file     = NULL;
+
+      msg[0] = '\0';
+
+      /* Display error message */
+      if (!string_is_empty(preset_path))
+         preset_file = path_basename(preset_path);
+
+      snprintf(msg, sizeof(msg), "%s %s",
+            msg_hash_to_str(MSG_FAILED_TO_APPLY_SHADER_PRESET),
+            string_is_empty(preset_file) ? "(null)" : preset_file);
+
+      runloop_msg_queue_push(
+            msg, 1, 180, true, NULL,
+            MESSAGE_QUEUE_ICON_DEFAULT, MESSAGE_QUEUE_CATEGORY_ERROR);
+
+      /* We don't want to disable shaders entirely here,
+       * just reset number of passes
+       * > Note: Disabling shaders at this point would in
+       *   fact be dangerous, since it changes the number of
+       *   entries in the shader options menu which can in
+       *   turn lead to the menu selection pointer going out
+       *   of bounds. This causes undefined behaviour/segfaults */
+      menu_shader_manager_clear_num_passes();
+
       return false;
    }
 

msg_hash.h

@@ -389,6 +389,7 @@ enum msg_hash_enums
    MSG_STATE_SLOT,
    MSG_STARTING_MOVIE_RECORD_TO,
    MSG_FAILED_TO_APPLY_SHADER,
+   MSG_FAILED_TO_APPLY_SHADER_PRESET,
    MSG_APPLYING_SHADER,
    MSG_SHADER,
    MSG_REDIRECTING_SAVESTATE_TO,