keep framerate stable even without vsync (#2165)

src/common/thread.h

@@ -37,6 +37,10 @@ class AccurateTimer {
     void Start();
 
     void End();
+
+    std::chrono::nanoseconds GetTotalWait() const {
+        return total_wait;
+    }
 };
 
 } // namespace Common

src/core/debug_state.h

@@ -165,7 +165,7 @@ class DebugStateImpl {
         debug_message_popup.push(std::move(message));
     }
 
-    bool& ShowingDebugMenuBar() {
+    bool& IsShowingDebugMenuBar() {
         return showing_debug_menu_bar;
     }
 

src/core/devtools/layer.cpp

@@ -253,7 +253,7 @@ void L::DrawAdvanced() {
 
 void L::DrawSimple() {
     const float frameRate = DebugState.Framerate;
-    Text("%d FPS (%.1f ms)", static_cast<int>(std::round(1.0f / frameRate)), frameRate * 1000.0f);
+    Text("%d FPS (%.1f ms)", static_cast<int>(std::round(frameRate)), 1000.0f / frameRate);
 }
 
 static void LoadSettings(const char* line) {
@@ -264,7 +264,7 @@ static void LoadSettings(const char* line) {
         return;
     }
     if (sscanf(line, "show_advanced_debug=%d", &i) == 1) {
-        DebugState.ShowingDebugMenuBar() = i != 0;
+        DebugState.IsShowingDebugMenuBar() = i != 0;
         return;
     }
     if (sscanf(line, "show_frame_graph=%d", &i) == 1) {
@@ -309,7 +309,7 @@ void L::SetupSettings() {
     handler.WriteAllFn = [](ImGuiContext*, ImGuiSettingsHandler* handler, ImGuiTextBuffer* buf) {
         buf->appendf("[%s][Data]\n", handler->TypeName);
         buf->appendf("fps_scale=%f\n", fps_scale);
-        buf->appendf("show_advanced_debug=%d\n", DebugState.ShowingDebugMenuBar());
+        buf->appendf("show_advanced_debug=%d\n", DebugState.IsShowingDebugMenuBar());
         buf->appendf("show_frame_graph=%d\n", frame_graph.is_open);
         buf->appendf("dump_frame_count=%d\n", dump_frame_count);
         buf->append("\n");
@@ -340,7 +340,7 @@ void L::Draw() {
 
     if (IsKeyPressed(ImGuiKey_F10, false)) {
         if (io.KeyCtrl) {
-            DebugState.ShowingDebugMenuBar() ^= true;
+            DebugState.IsShowingDebugMenuBar() ^= true;
         } else {
             show_simple_fps = !show_simple_fps;
         }
@@ -375,7 +375,7 @@ void L::Draw() {
         End();
     }
 
-    if (DebugState.ShowingDebugMenuBar()) {
+    if (DebugState.IsShowingDebugMenuBar()) {
         PushFont(io.Fonts->Fonts[IMGUI_FONT_MONO]);
         PushID("DevtoolsLayer");
         DrawAdvanced();

src/core/libraries/videoout/driver.cpp

@@ -9,6 +9,7 @@
 #include "core/libraries/kernel/time.h"
 #include "core/libraries/videoout/driver.h"
 #include "core/libraries/videoout/videoout_error.h"
+#include "imgui/renderer/imgui_core.h"
 #include "video_core/renderer_vulkan/vk_presenter.h"
 
 extern std::unique_ptr<Vulkan::Presenter> presenter;
@@ -297,10 +298,12 @@ void VideoOutDriver::PresentThread(std::stop_token token) {
         if (vblank_status.count % (main_port.flip_rate + 1) == 0) {
             const auto request = receive_request();
             if (!request) {
-                if (!main_port.is_open) {
-                    DrawBlankFrame();
-                } else {
-                    DrawLastFrame();
+                if (timer.GetTotalWait().count() < 0) { // Dont draw too fast
+                    if (!main_port.is_open) {
+                        DrawBlankFrame();
+                    } else if (ImGui::Core::MustKeepDrawing()) {
+                        DrawLastFrame();
+                    }
                 }
             } else {
                 Flip(request);

src/imgui/renderer/imgui_core.cpp

@@ -187,7 +187,7 @@ ImGuiID NewFrame(bool is_reusing_frame) {
     ImGui::NewFrame();
 
     ImGuiWindowFlags flags = ImGuiDockNodeFlags_PassthruCentralNode;
-    if (!DebugState.ShowingDebugMenuBar()) {
+    if (!DebugState.IsShowingDebugMenuBar()) {
         flags |= ImGuiDockNodeFlags_NoTabBar;
     }
     ImGuiID dockId = DockSpaceOverViewport(0, GetMainViewport(), flags);
@@ -237,6 +237,10 @@ void Render(const vk::CommandBuffer& cmdbuf, const vk::ImageView& image_view,
     }
 }
 
+bool MustKeepDrawing() {
+    return layers.size() > 1 || DebugState.IsShowingDebugMenuBar();
+}
+
 } // namespace Core
 
 void Layer::AddLayer(Layer* layer) {

src/imgui/renderer/imgui_core.h

@@ -31,4 +31,6 @@ ImGuiID NewFrame(bool is_reusing_frame = false);
 void Render(const vk::CommandBuffer& cmdbuf, const vk::ImageView& image_view,
             const vk::Extent2D& extent);
 
+bool MustKeepDrawing(); // Force the emulator redraw
+
 } // namespace ImGui::Core

src/imgui/renderer/imgui_impl_sdl3.cpp

@@ -46,6 +46,11 @@ struct SdlData {
     ImVector<SDL_Gamepad*> gamepads{};
     GamepadMode gamepad_mode{};
     bool want_update_gamepads_list{};
+
+    // Framerate counting (based on ImGui impl)
+    std::array<float, 60> framerateSecPerFrame;
+    int framerateSecPerFrameIdx{};
+    float framerateSecPerFrameAcc{};
 };
 
 // Backend data stored in io.BackendPlatformUserData to allow support for multiple Dear ImGui
@@ -812,12 +817,15 @@ void NewFrame(bool is_reusing_frame) {
                 : 1.0f / 60.0f;
         bd->nonReusedtime = current_time;
         DebugState.FrameDeltaTime = deltaTime;
-        float distribution = 0.016f / deltaTime / 10.0f;
-        if (distribution > 1.0f) {
-            distribution = 1.0f;
-        }
-        DebugState.Framerate =
-            deltaTime * distribution + DebugState.Framerate * (1.0f - distribution);
+
+        int& frameIdx = bd->framerateSecPerFrameIdx;
+        float& framerateSec = bd->framerateSecPerFrame[frameIdx];
+        float& acc = bd->framerateSecPerFrameAcc;
+        int count = bd->framerateSecPerFrame.size();
+        acc += deltaTime - framerateSec;
+        framerateSec = deltaTime;
+        frameIdx = (frameIdx + 1) % count;
+        DebugState.Framerate = acc > 0.0f ? 1.0f / (acc / (float)count) : FLT_MAX;
     }
 
     if (bd->mouse_pending_leave_frame && bd->mouse_pending_leave_frame >= ImGui::GetFrameCount() &&