Fix vsync for refresh rates of 120hz and 240hz

Author: drhelius

platforms/shared/desktop/application.cpp

@@ -44,6 +44,9 @@ static bool paused_when_focus_lost = false;
 static Uint64 frame_time_start = 0;
 static Uint64 frame_time_end = 0;
 static bool input_updated = false;
+static int monitor_refresh_rate = 60;
+static int vsync_frames_per_emu_frame = 1;
+static int vsync_frame_counter = 0;
 static Uint16 input_last_state[GG_MAX_GAMEPADS] = { };
 static bool input_turbo_toggle_prev[GG_MAX_GAMEPADS][2] = { };
 static bool input_gamepad_shortcut_prev[GG_MAX_GAMEPADS][config_HotkeyIndex_COUNT] = { };
@@ -77,8 +80,10 @@ static void handle_mouse_cursor(void);
 static void handle_menu(void);
 static void handle_single_instance(void);
 static void run_emulator(void);
+static bool should_run_emu_frame(void);
 static void render(void);
 static void frame_throttle(void);
+static void update_frame_pacing(void);
 static void save_window_size(void);
 static void log_sdl_error(const char* action, const char* file, int line);
 static bool check_hotkey(const SDL_Event* event, const config_Hotkey& hotkey, bool allow_repeat);
@@ -139,7 +144,7 @@ int application_init(const char* rom_file, const char* symbol_file, bool force_f
         return 5;
     }
 
-    SDL_GL_SetSwapInterval(config_video.sync ? 1 : 0);
+    application_set_vsync(config_video.sync);
 
     if (config_emulator.fullscreen)
         application_trigger_fullscreen(true);
@@ -322,6 +327,7 @@ void application_trigger_fullscreen(bool fullscreen)
 #endif
 
     mouse_last_motion_time = SDL_GetTicks();
+    update_frame_pacing();
 }
 
 void application_trigger_fit_to_content(int width, int height)
@@ -330,6 +336,12 @@ void application_trigger_fit_to_content(int width, int height)
     SDL_ERROR("SDL_SetWindowSize");
 }
 
+void application_set_vsync(bool enabled)
+{
+    SDL_GL_SetSwapInterval(enabled ? 1 : 0);
+    update_frame_pacing();
+}
+
 void application_update_title_with_rom(const char* rom)
 {
     char final_title[256];
@@ -740,6 +752,11 @@ static void sdl_events_app(const SDL_Event* event)
                     }
                     break;
                 }
+                case SDL_WINDOWEVENT_DISPLAY_CHANGED:
+                {
+                    update_frame_pacing();
+                    break;
+                }
             }
             break;
         }
@@ -1201,6 +1218,9 @@ static bool input_get_button(SDL_GameController* controller, int mapping)
 
 static void run_emulator(void)
 {
+    if (!should_run_emu_frame())
+        return;
+
     config_emulator.paused = emu_is_paused();
     emu_audio_sync = config_audio.sync;
     emu_update();
@@ -1210,6 +1230,20 @@ static void run_emulator(void)
     input_updated = false;
 }
 
+static bool should_run_emu_frame(void)
+{
+    if (config_video.sync && vsync_frames_per_emu_frame > 1 && !config_emulator.ffwd)
+    {
+        bool should_run = (vsync_frame_counter == 0);
+        vsync_frame_counter++;
+        if (vsync_frame_counter >= vsync_frames_per_emu_frame)
+            vsync_frame_counter = 0;
+        return should_run;
+    }
+
+    return true;
+}
+
 static void render(void)
 {
     renderer_begin_render();
@@ -1269,6 +1303,37 @@ static void save_window_size(void)
     }
 }
 
+static void update_frame_pacing(void)
+{
+    int display = SDL_GetWindowDisplayIndex(application_sdl_window);
+    SDL_ERROR("SDL_GetWindowDisplayIndex");
+
+    if (display < 0)
+        display = 0;
+
+    SDL_DisplayMode mode;
+    if (SDL_GetCurrentDisplayMode(display, &mode) == 0 && mode.refresh_rate > 0)
+        monitor_refresh_rate = mode.refresh_rate;
+    else
+    {
+        SDL_ERROR("SDL_GetCurrentDisplayMode");
+        monitor_refresh_rate = 60;
+    }
+
+    const int emu_fps = 60;
+
+    if (monitor_refresh_rate <= emu_fps + 5)
+        vsync_frames_per_emu_frame = 1;
+    else
+        vsync_frames_per_emu_frame = (monitor_refresh_rate + emu_fps / 2) / emu_fps;
+
+    vsync_frames_per_emu_frame = CLAMP(vsync_frames_per_emu_frame, 1, 8);
+
+    vsync_frame_counter = 0;
+
+    Debug("Monitor refresh rate: %d Hz, vsync frames per emu frame: %d", monitor_refresh_rate, vsync_frames_per_emu_frame);
+}
+
 static void log_sdl_error(const char* action, const char* file, int line)
 {
     const char* error = SDL_GetError();

platforms/shared/desktop/application.h

@@ -49,6 +49,7 @@ EXTERN void application_mainloop(void);
 EXTERN void application_trigger_quit(void);
 EXTERN void application_trigger_fullscreen(bool fullscreen);
 EXTERN void application_trigger_fit_to_content(int width, int height);
+EXTERN void application_set_vsync(bool enabled);
 EXTERN void application_update_title_with_rom(const char* rom);
 EXTERN void application_assign_gamepad(int slot, int device_index);
 EXTERN void application_input_pump(void);

platforms/shared/desktop/gui_actions.cpp

@@ -24,6 +24,7 @@
 #include "config.h"
 #include "emu.h"
 #include "geargrafx.h"
+#include "application.h"
 
 void gui_action_reset(void)
 {
@@ -75,12 +76,12 @@ void gui_action_ffwd(void)
     if (config_emulator.ffwd)
     {
         gui_set_status_message("Fast Forward ON", 3000);
-        SDL_GL_SetSwapInterval(0);
+        application_set_vsync(false);
     }
     else
     {
         gui_set_status_message("Fast Forward OFF", 3000);
-        SDL_GL_SetSwapInterval(config_video.sync ? 1 : 0);
+        application_set_vsync(config_video.sync);
         emu_audio_reset();
     }
 }

platforms/shared/desktop/gui_menus.cpp

@@ -737,7 +737,7 @@ static void menu_video(void)
 
         if (ImGui::MenuItem("Vertical Sync", "", &config_video.sync))
         {
-            SDL_GL_SetSwapInterval(config_video.sync ? 1 : 0);
+            application_set_vsync(config_video.sync);
 
             if (config_video.sync)
             {
@@ -1239,7 +1239,7 @@ static void menu_audio(void)
             if (!config_audio.sync)
             {
                 config_video.sync = false;
-                SDL_GL_SetSwapInterval(0);
+                application_set_vsync(false);
             }
         }