Implement frame pacing for Windows using D3DKMTWaitForVerticalBlankEvent

2026-06-16 21:51:17 +00:00 · 2018-08-16 01:29:53 -07:00
parent 8e257ab241
commit 404eaa44e4
3 changed files with 160 additions and 7 deletions
@@ -1,10 +1,13 @@
 #include "dxvsyncsource.h"

-#include <dwmapi.h>
+// Useful references:
+// https://bugs.chromium.org/p/chromium/issues/detail?id=467617
+// https://chromium.googlesource.com/chromium/src.git/+/c564f2fe339b2b2abb0c8773c90c83215670ea71/gpu/ipc/service/gpu_vsync_provider_win.cc

 DxVsyncSource::DxVsyncSource(Pacer* pacer) :
    m_Pacer(pacer),
-    m_Thread(nullptr)
+    m_Thread(nullptr),
+    m_Gdi32Handle(nullptr)
 {
    SDL_AtomicSet(&m_Stopping, 0);
 }
@@ -15,10 +18,47 @@ DxVsyncSource::~DxVsyncSource()
        SDL_AtomicSet(&m_Stopping, 1);
        SDL_WaitThread(m_Thread, nullptr);
    }
+
+    if (m_Gdi32Handle != nullptr) {
+        FreeLibrary(m_Gdi32Handle);
+    }
 }

 bool DxVsyncSource::initialize(SDL_Window* window)
 {
+    m_Gdi32Handle = LoadLibraryA("gdi32.dll");
+    if (m_Gdi32Handle == nullptr) {
+        SDL_LogError(SDL_LOG_CATEGORY_APPLICATION,
+                     "Failed to load gdi32.dll: %d",
+                     GetLastError());
+        return false;
+    }
+
+    m_D3DKMTOpenAdapterFromHdc = (PFND3DKMTOPENADAPTERFROMHDC)GetProcAddress(m_Gdi32Handle, "D3DKMTOpenAdapterFromHdc");
+    m_D3DKMTCloseAdapter = (PFND3DKMTCLOSEADAPTER)GetProcAddress(m_Gdi32Handle, "D3DKMTCloseAdapter");
+    m_D3DKMTWaitForVerticalBlankEvent = (PFND3DKMTWAITFORVERTICALBLANKEVENT)GetProcAddress(m_Gdi32Handle, "D3DKMTWaitForVerticalBlankEvent");
+
+    if (m_D3DKMTOpenAdapterFromHdc == nullptr ||
+            m_D3DKMTCloseAdapter == nullptr ||
+            m_D3DKMTWaitForVerticalBlankEvent == nullptr) {
+        SDL_LogError(SDL_LOG_CATEGORY_APPLICATION,
+                     "Missing required function in gdi32.dll");
+        return false;
+    }
+
+    SDL_SysWMinfo info;
+
+    SDL_VERSION(&info.version);
+
+    if (!SDL_GetWindowWMInfo(window, &info)) {
+        SDL_LogError(SDL_LOG_CATEGORY_APPLICATION,
+                     "SDL_GetWindowWMInfo() failed: %s",
+                     SDL_GetError());
+        return false;
+    }
+
+    m_Window = info.info.win.window;
+
    m_Thread = SDL_CreateThread(vsyncThread, "DX Vsync Thread", this);
    if (m_Thread == nullptr) {
        SDL_LogError(SDL_LOG_CATEGORY_APPLICATION,
@@ -36,14 +76,95 @@ int DxVsyncSource::vsyncThread(void* context)

    SDL_SetThreadPriority(SDL_THREAD_PRIORITY_HIGH);

+    D3DKMT_OPENADAPTERFROMHDC openAdapterParams = {};
+    HMONITOR lastMonitor = nullptr;
+    DEVMODEA monitorMode;
+    monitorMode.dmSize = sizeof(monitorMode);
+
    while (SDL_AtomicGet(&me->m_Stopping) == 0) {
-        // FIXME: We should really use D3DKMTWaitForVerticalBlankEvent() instead!
-        // https://bugs.chromium.org/p/chromium/issues/detail?id=467617
-        // https://chromium.googlesource.com/chromium/src.git/+/c564f2fe339b2b2abb0c8773c90c83215670ea71/gpu/ipc/service/gpu_vsync_provider_win.cc
-        DwmFlush();
+        D3DKMT_WAITFORVERTICALBLANKEVENT waitForVblankEventParams;
+        NTSTATUS status;
+
+        // If the monitor has changed from last time, open the new adapter
+        HMONITOR currentMonitor = MonitorFromWindow(me->m_Window, MONITOR_DEFAULTTONEAREST);
+        if (currentMonitor != lastMonitor) {
+            MONITORINFOEXA monitorInfo = {};
+            monitorInfo.cbSize = sizeof(monitorInfo);
+            if (!GetMonitorInfoA(currentMonitor, &monitorInfo)) {
+                SDL_LogError(SDL_LOG_CATEGORY_APPLICATION,
+                             "GetMonitorInfo() failed: %d",
+                             GetLastError());
+                SDL_Delay(10);
+                continue;
+            }
+
+            if (!EnumDisplaySettingsA(monitorInfo.szDevice, ENUM_CURRENT_SETTINGS, &monitorMode)) {
+                SDL_LogError(SDL_LOG_CATEGORY_APPLICATION,
+                             "EnumDisplaySettings() failed: %d",
+                             GetLastError());
+                SDL_Delay(10);
+                continue;
+            }
+
+            SDL_LogInfo(SDL_LOG_CATEGORY_APPLICATION,
+                        "Monitor changed: %s %d Hz",
+                        monitorInfo.szDevice,
+                        monitorMode.dmDisplayFrequency);
+
+            if (openAdapterParams.hAdapter != 0) {
+                D3DKMT_CLOSEADAPTER closeAdapterParams = {};
+                closeAdapterParams.hAdapter = openAdapterParams.hAdapter;
+                me->m_D3DKMTCloseAdapter(&closeAdapterParams);
+            }
+
+            openAdapterParams.hDc = CreateDCA(nullptr, monitorInfo.szDevice, nullptr, nullptr);
+            if (!openAdapterParams.hDc) {
+                SDL_LogError(SDL_LOG_CATEGORY_APPLICATION,
+                             "CreateDC() failed: %d",
+                             GetLastError());
+                SDL_Delay(10);
+                continue;
+            }
+
+            status = me->m_D3DKMTOpenAdapterFromHdc(&openAdapterParams);
+            DeleteDC(openAdapterParams.hDc);
+
+            if (status != STATUS_SUCCESS) {
+                SDL_LogError(SDL_LOG_CATEGORY_APPLICATION,
+                             "D3DKMTOpenAdapterFromHdc() failed: %x",
+                             status);
+                SDL_Delay(10);
+                continue;
+            }
+
+            lastMonitor = currentMonitor;
+        }
+
+        waitForVblankEventParams.hAdapter = openAdapterParams.hAdapter;
+        waitForVblankEventParams.hDevice = 0;
+        waitForVblankEventParams.VidPnSourceId = openAdapterParams.VidPnSourceId;
+
+        status = me->m_D3DKMTWaitForVerticalBlankEvent(&waitForVblankEventParams);
+        if (status != STATUS_SUCCESS) {
+            SDL_LogError(SDL_LOG_CATEGORY_APPLICATION,
+                         "D3DKMTWaitForVerticalBlankEvent() failed: %x",
+                         status);
+            SDL_Delay(10);
+            continue;
+        }
+
+        // Try to delay to the middle of the V-sync period to give the frame
+        // from the host time to arrive.
+        SDL_Delay(500 / monitorMode.dmDisplayFrequency);

        me->m_Pacer->vsyncCallback();
    }

+    if (openAdapterParams.hAdapter != 0) {
+        D3DKMT_CLOSEADAPTER closeAdapterParams = {};
+        closeAdapterParams.hAdapter = openAdapterParams.hAdapter;
+        me->m_D3DKMTCloseAdapter(&closeAdapterParams);
+    }
+
    return 0;
 }