Bump GPU scheduling priority for responsiveness vs background apps

src/config.cpp

@@ -32,6 +32,7 @@ Config ParseConfig(const std::string& text) {
             else if (key == "vsync")            c.vsync = std::stoi(val);
             else if (key == "dwmFlush")         c.dwmFlush = std::stoi(val);
             else if (key == "present")          c.present = val;
+            else if (key == "gpuPriority")      c.gpuPriority = std::stoi(val);
             else if (key == "diagnostics")      c.diagnostics = std::stoi(val);
             else if (key == "cursorSensitivity")  c.cursorSensitivity = std::stod(val);
             else if (key == "cursorSmoothing")    c.cursorSmoothing = std::stod(val);
@@ -78,6 +79,9 @@ Config LoadConfig(const std::wstring& path) {
                "; present: blt=default (blt swapchain + DwmFlush); dcomp=flip-model via DirectComposition\n"
                ";   (experimental, vsync-paced; restart to change)\n"
                "present=blt\n"
+               "; gpuPriority: GPU scheduling priority (-7..7). Higher keeps the zoom responsive when a\n"
+               ";   game runs in the background; lower if it hurts a foreground game (restart to apply)\n"
+               "gpuPriority=7\n"
                "; diagnostics=1 logs frame timing to %TEMP%\\wind_diag.log (restart to apply)\n"
                "diagnostics=0\n"
                "; cursorSensitivity: pan speed per raw count\n"

src/config.h

@@ -25,6 +25,11 @@ struct Config {
     // (default); "dcomp" = flip-model swapchain via DirectComposition, paced by vsync Present
     // (experimental A/B - native flip pacing + lower latency, still click-through via layered).
     std::string present     = "blt";
+    // GPU scheduling priority for the magnifier's device (IDXGIDevice::SetGPUThreadPriority,
+    // clamped to [-7,7]). Higher = the GPU scheduler favors us over other apps, so the zoom
+    // stays responsive when a GPU-heavy app (a game) runs in the background. 0 = OS default.
+    // Lower it if it hurts a foreground game while zoomed.
+    int    gpuPriority      = 7;
     int    diagnostics      = 0;     // 1 = log frame-timing to wind_diag.log
 
     // --- Own GPU renderer ---------------------------------------------------

src/main.cpp

@@ -255,7 +255,7 @@ int WINAPI wWinMain(HINSTANCE hInst, HINSTANCE, PWSTR, int) {
 
     // --- Own GPU renderer (DXGI Desktop Duplication + D3D11) ---
     RenderEngine renderEngine;
-    if (!renderEngine.initialize(sw, sh, cfg.zorderBand, cfg.hdrTonemap != 0, cfg.present == "dcomp")) {
+    if (!renderEngine.initialize(sw, sh, cfg.zorderBand, cfg.hdrTonemap != 0, cfg.present == "dcomp", cfg.gpuPriority)) {
         MessageBoxW(nullptr, L"Could not start the renderer (Direct3D 11 / Desktop Duplication "
                              L"unavailable on this system).", L"Wind", MB_ICONERROR);
         g_input.stop();

src/render_engine.cpp

@@ -447,7 +447,7 @@ void RenderEngine::debugHdr(unsigned& ddaFormat, int& colorSpace, int& bitsPerCo
     ddaFormat = s_->ddaFormat; colorSpace = s_->outColorSpace; bitsPerColor = s_->outBitsPerColor;
 }
 
-bool RenderEngine::initialize(int screenW, int screenH, int zorderBand, bool hdrTonemap, bool useDComp) {
+bool RenderEngine::initialize(int screenW, int screenH, int zorderBand, bool hdrTonemap, bool useDComp, int gpuPriority) {
     s_->sw = screenW;
     s_->sh = screenH;
     s_->wantHdrTonemap = hdrTonemap;   // read before recreateDupl decides the capture format
@@ -513,6 +513,11 @@ bool RenderEngine::initialize(int screenW, int screenH, int zorderBand, bool hdr
     IDXGIDevice1* dxgiDev = nullptr;
     if (FAILED(s_->device->QueryInterface(__uuidof(IDXGIDevice1), (void**)&dxgiDev))) return false;
     dxgiDev->SetMaximumFrameLatency(1);     // cap input-to-photon latency to ~1 frame
+    if (gpuPriority != 0) {                 // favor the magnifier on the GPU vs background apps
+        int p = gpuPriority < -7 ? -7 : (gpuPriority > 7 ? 7 : gpuPriority);
+        dxgiDev->SetGPUThreadPriority(p);
+        RLog("SetGPUThreadPriority(%d)", p);
+    }
     IDXGIAdapter* adapter = nullptr;
     dxgiDev->GetAdapter(&adapter);
 

src/render_engine.h

@@ -36,7 +36,8 @@ class RenderEngine {
     // useDComp: false = blt-model swapchain on the layered HWND (default, paced by DwmFlush);
     // true = flip-model swapchain composed via DirectComposition (still WS_EX_LAYERED for
     // click-through), paced by vsync Present. Opt-in A/B backend.
-    bool initialize(int screenW, int screenH, int zorderBand = 0, bool hdrTonemap = false, bool useDComp = false);
+    bool initialize(int screenW, int screenH, int zorderBand = 0, bool hdrTonemap = false,
+                    bool useDComp = false, int gpuPriority = 0);
     bool renderFrame(const RenderFrameParams& p);  // capture (if changed) + scale + cursor + present
     void setVisible(bool visible);                 // show/hide the overlay (hidden at 1x)
     // Force the next frame to grab a fresh full-desktop capture (release+recreate the

tests/test_config.cpp

@@ -33,10 +33,13 @@ TEST_CASE("renderer knobs have sane defaults") {
     CHECK(c.dwmFlush == 1);                     // DwmFlush pacing on by default (the smooth path)
     CHECK(c.tickHzCap == 0);                    // 0 = auto-detect display refresh rate
     CHECK(c.present == "blt");                   // blt+DwmFlush backend by default
+    CHECK(c.gpuPriority == 7);                    // favor the magnifier on the GPU by default
 }
-TEST_CASE("present backend selects blt or dcomp") {
+TEST_CASE("present backend and gpuPriority parse") {
     CHECK(ParseConfig("present=dcomp\n").present == "dcomp");
     CHECK(ParseConfig("present=blt\n").present == "blt");
+    CHECK(ParseConfig("gpuPriority=0\n").gpuPriority == 0);
+    CHECK(ParseConfig("gpuPriority=-7\n").gpuPriority == -7);
 }
 TEST_CASE("vsync, dwmFlush, tickHzCap can be set") {
     CHECK(ParseConfig("vsync=0\n").vsync == 0);