From 9e347ec71fc408fe77b95d39ec91c83b1c57f1ff Mon Sep 17 00:00:00 2001
From: Brad Parker <cbparker@gmail.com>
Date: Thu, 25 Jan 2018 19:09:55 -0500
Subject: [PATCH] detect shader file changes on move and delete as well, and
 wait a few frames before re-applying changes

---
 frontend/drivers/platform_unix.c |  4 ++++
 frontend/frontend_driver.h       |  5 ++++-
 gfx/video_shader_parse.c         |  7 ++++++-
 retroarch.c                      | 27 ++++++++++++++++++++++++++-
 4 files changed, 40 insertions(+), 3 deletions(-)

diff --git a/frontend/drivers/platform_unix.c b/frontend/drivers/platform_unix.c
index daee38d2a3..6f6015ed1a 100644
--- a/frontend/drivers/platform_unix.c
+++ b/frontend/drivers/platform_unix.c
@@ -2357,6 +2357,10 @@ static void frontend_unix_watch_path_for_changes(struct string_list *list, int f
       inotify_mask |= IN_MODIFY;
    if (flags & PATH_CHANGE_TYPE_WRITE_FILE_CLOSED)
       inotify_mask |= IN_CLOSE_WRITE;
+   if (flags & PATH_CHANGE_TYPE_FILE_MOVED)
+      inotify_mask |= IN_MOVE_SELF;
+   if (flags & PATH_CHANGE_TYPE_FILE_DELETED)
+      inotify_mask |= IN_DELETE_SELF;
 
    inotify_data->flags = inotify_mask;
 
diff --git a/frontend/frontend_driver.h b/frontend/frontend_driver.h
index 8e3fe089bf..a2f5ddf966 100644
--- a/frontend/frontend_driver.h
+++ b/frontend/frontend_driver.h
@@ -56,10 +56,13 @@ enum frontend_architecture
    FRONTEND_ARCH_TILE
 };
 
+/* different platforms may only support some of these types */
 enum path_change_type
 {
    PATH_CHANGE_TYPE_MODIFIED = (1 << 0),
-   PATH_CHANGE_TYPE_WRITE_FILE_CLOSED = (1 << 1)
+   PATH_CHANGE_TYPE_WRITE_FILE_CLOSED = (1 << 1),
+   PATH_CHANGE_TYPE_FILE_MOVED = (1 << 2),
+   PATH_CHANGE_TYPE_FILE_DELETED = (1 << 3)
 };
 
 typedef struct path_change_data
diff --git a/gfx/video_shader_parse.c b/gfx/video_shader_parse.c
index 6313cdacbc..d4160fd4a9 100644
--- a/gfx/video_shader_parse.c
+++ b/gfx/video_shader_parse.c
@@ -809,7 +809,12 @@ bool video_shader_read_conf_cgp(config_file_t *conf,
 
    if (settings->bools.video_shader_watch_files)
    {
-      frontend_driver_watch_path_for_changes(file_list, PATH_CHANGE_TYPE_WRITE_FILE_CLOSED, &file_change_data);
+      int flags = PATH_CHANGE_TYPE_MODIFIED |
+                  PATH_CHANGE_TYPE_WRITE_FILE_CLOSED |
+                  PATH_CHANGE_TYPE_FILE_MOVED |
+                  PATH_CHANGE_TYPE_FILE_DELETED;
+
+      frontend_driver_watch_path_for_changes(file_list, flags, &file_change_data);
       string_list_free(file_list);
    }
 
diff --git a/retroarch.c b/retroarch.c
index f07dc16e3a..1c6165f6c3 100644
--- a/retroarch.c
+++ b/retroarch.c
@@ -130,6 +130,8 @@
 #define DEFAULT_EXT ""
 #endif
 
+#define SHADER_FILE_WATCH_DELAY_FRAMES 5
+
 /* Descriptive names for options without short variant.
  *
  * Please keep the name in sync with the option name.
@@ -2996,8 +2998,31 @@ static enum runloop_state runloop_check_state(
 
    if (settings->bools.video_shader_watch_files)
    {
+      static bool need_to_apply = false;
+      static int elapsed_frames = 0;
+
       if (video_shader_check_for_changes())
-         command_event(CMD_EVENT_SHADERS_APPLY_CHANGES, NULL);
+      {
+         need_to_apply = true;
+         elapsed_frames = 0;
+      }
+
+      /* If a file is modified atomically (moved/renamed from a different file), we have no idea how long that might take.
+       * If we're trying to re-apply shaders immediately after changes are made to the original file(s), the filesystem might be in an in-between
+       * state where the new file hasn't been moved over yet and the original file was already deleted. This leaves us no choice
+       * but to wait an arbitrary amount of time and hope for the best.
+       */
+      if (need_to_apply)
+      {
+         if (elapsed_frames > SHADER_FILE_WATCH_DELAY_FRAMES)
+         {
+            need_to_apply = false;
+            elapsed_frames = 0;
+            command_event(CMD_EVENT_SHADERS_APPLY_CHANGES, NULL);
+         }
+         else
+            elapsed_frames++;
+      }
    }
 
    return RUNLOOP_STATE_ITERATE;