overlay_params: Add FPS limit method

README.md

@@ -331,6 +331,7 @@ Parameters that are enabled by default have to be explicitly disabled. These (cu
 | `font_size=`                       | Customizeable font size (default=24)                                                  |
 | `font_size_text=`                  | Customizeable font size for other text like media metadata (default=24)               |
 | `fps_limit`                        | Limit the apps framerate. Comma-separated list of one or more FPS values. `0` means unlimited. |
+| `fps_limit_method`                 | If FPS limiter should wait before or after presenting a frame. Choose `late` (default) for the lowest latency or `early` for the smoothest frametimes. |
 | `fps_only`                         | Show FPS only. ***Not meant to be used with other display params***                   |
 | `frame_count`                      | Display frame count                                                                   |
 | `frametime`                        | Display frametime next to FPS text                                                    |

data/MangoHud.conf

@@ -8,6 +8,9 @@
 ### Limit the application FPS. Comma-separated list of one or more FPS values (e.g. 0,30,60). 0 means unlimited (unless VSynced)
 # fps_limit=
 
+### early = wait before present, late = wait after present
+# fps_limit_method=
+
 ### VSync [0-3] 0 = adaptive; 1 = off; 2 = mailbox; 3 = on
 # vsync=
 

src/overlay.h

@@ -61,6 +61,7 @@ struct fps_limit {
    Clock::duration targetFrameTime;
    Clock::duration frameOverhead;
    Clock::duration sleepTime;
+   enum fps_limit_method method;
 };
 
 struct benchmark_stats {

src/overlay_params.cpp

@@ -188,6 +188,16 @@ parse_fps_limit(const char *str)
    return fps_limit;
 }
 
+static enum fps_limit_method
+parse_fps_limit_method(const char *str)
+{
+   if (!strcmp(str, "early")) {
+      return FPS_LIMIT_METHOD_EARLY;
+   }
+
+   return FPS_LIMIT_METHOD_LATE;
+}
+
 static bool
 parse_no_display(const char *str)
 {
@@ -597,6 +607,7 @@ parse_overlay_config(struct overlay_params *params,
    params->height = 140;
    params->control = -1;
    params->fps_limit = { 0 };
+   params->fps_limit_method = FPS_LIMIT_METHOD_LATE;
    params->vsync = -1;
    params->gl_vsync = -2;
    params->offset_x = 0;
@@ -802,6 +813,8 @@ parse_overlay_config(struct overlay_params *params,
    else
       fps_limit_stats.targetFrameTime = {};
 
+   fps_limit_stats.method = params->fps_limit_method;
+
 #ifdef HAVE_DBUS
    if (params->enabled[OVERLAY_PARAM_ENABLED_media_player]) {
       if (dbusmgr::dbus_mgr.init(dbusmgr::SRV_MPRIS))

src/overlay_params.h

@@ -108,6 +108,7 @@ typedef unsigned long KeySym;
    OVERLAY_PARAM_CUSTOM(no_display)                  \
    OVERLAY_PARAM_CUSTOM(control)                     \
    OVERLAY_PARAM_CUSTOM(fps_limit)                   \
+   OVERLAY_PARAM_CUSTOM(fps_limit_method)            \
    OVERLAY_PARAM_CUSTOM(vsync)                       \
    OVERLAY_PARAM_CUSTOM(gl_vsync)                    \
    OVERLAY_PARAM_CUSTOM(gl_size_query)               \
@@ -200,6 +201,11 @@ enum gl_size_query {
    GL_SIZE_SCISSORBOX, // needed?
 };
 
+enum fps_limit_method {
+   FPS_LIMIT_METHOD_EARLY,
+   FPS_LIMIT_METHOD_LATE
+};
+
 enum overlay_param_enabled {
 #define OVERLAY_PARAM_BOOL(name) OVERLAY_PARAM_ENABLED_##name,
 #define OVERLAY_PARAM_CUSTOM(name)
@@ -215,6 +221,7 @@ struct overlay_params {
    int control;
    uint32_t fps_sampling_period; /* ns */
    std::vector<std::uint32_t> fps_limit;
+   enum fps_limit_method fps_limit_method;
    bool help;
    bool no_display;
    bool full;