Headless: Run Vulkan offscreen, without a window

Vulkan no longer needs a hidden window (which on macOS could never work, as
the Metal window description has no data2). It now uses the offscreen mode,
and presents each frame like the app does, as an unpresented frame would
wait forever for its next image. MoltenVK's console logging is limited to
errors, as it mixed into the test output.

Co-Authored-By: Claude Opus 5.5 (1M context) <[email protected]>

headless/Headless.cpp

@@ -271,9 +271,6 @@ static GraphicsContext *CreateGraphicsContext(GPUCore gpuCore, std::string **dev
 	switch (gpuCore) {
 	case GPUCORE_GLES:
 		return new SDLHeadlessGLGraphicsContext();
-	case GPUCORE_VULKAN:
-		*deviceSetting = &g_Config.sVulkanDevice;
-		return new VulkanGraphicsContext();
 	default:
 		return nullptr;
 	}
@@ -287,9 +284,6 @@ static GraphicsContext *CreateGraphicsContext(GPUCore gpuCore, std::string **dev
 	case GPUCORE_DIRECTX11:
 		*deviceSetting = &g_Config.sD3D11Device;
 		return new D3D11Context();
-	case GPUCORE_VULKAN:
-		*deviceSetting = &g_Config.sVulkanDevice;
-		return new VulkanGraphicsContext();
 	case GPUCORE_SOFTWARE:
 	default:
 		return nullptr;
@@ -336,6 +330,16 @@ struct AutoTestOptions {
 	int requiredDisableHLE;
 };
 
+// Ends a frame of the draw context the way the app does, presenting it. With Vulkan, presenting is
+// also what returns a frame's image, and a frame that isn't presented would wait forever for its
+// next one. The other backends present to a hidden window, which could wait for vsync.
+static void EndDrawFrame(Draw::DrawContext *draw) {
+	draw->EndFrame();
+	if (GetGPUBackend() == GPUBackend::VULKAN) {
+		draw->Present(Draw::PresentMode::FIFO);
+	}
+}
+
 static bool RunAutoTest(GraphicsContext *graphicsContext, CoreParameter &coreParameter, const AutoTestOptions &opt) {
 	using namespace Draw;
 
@@ -469,7 +473,7 @@ static bool RunAutoTest(GraphicsContext *graphicsContext, CoreParameter &corePar
 				gpu->EndHostFrame();
 			}
 			if (draw) {
-				draw->EndFrame();
+				EndDrawFrame(draw);
 				draw->BeginFrame(Draw::DebugFlags::NONE);
 			}
 			if (gpu) {
@@ -515,7 +519,7 @@ static bool RunAutoTest(GraphicsContext *graphicsContext, CoreParameter &corePar
 			gpu->CopyDisplayToOutput(g_Config.GetDisplayLayoutConfig(DeviceOrientation::Landscape));
 		}
 
-		draw->EndFrame();
+		EndDrawFrame(draw);
 	}
 
 	if (!g_screenshotSavePath.empty() && !g_screenshotSaved) {
@@ -682,6 +686,11 @@ int main(int argc, const char* argv[]) {
 		perror("Unable to ignore SIGPIPE");
 	}
 #endif
+#if PPSSPP_PLATFORM(MAC)
+	// MoltenVK logs its setup and every unsupported feature to the console, which mixes into the
+	// test output. Only its errors, unless asked for more.
+	setenv("MVK_CONFIG_LOG_LEVEL", "1", 0);
+#endif
 
 	SetupCRT(true);
 
@@ -949,17 +958,25 @@ int main(int argc, const char* argv[]) {
 		fprintf(stderr, "Headless graphics context creation is not supported on this platform.\n");
 		return 1;
 #else
-		// TODO: Will we need a larger window for higher resolutions? Well, not if we use buffered rendering.
-		window = CreateHiddenWindow(480, 272, cmdLineOptions.gpuBackend.value_or(GPUBackend::OPENGL), &windowDesc);
-		if (!windowDesc.Valid()) {
-			fprintf(stderr, "Failed to create a window for graphics context");
-			return 1;
-		}
-		graphicsContext = CreateGraphicsContext(gpuCore, &deviceSetting);
-		if (!graphicsContext) {
-			// If we don't get the desired context, we DO NOT fall back.
-			fprintf(stderr, "Failed to create a graphics context for GPU core");
-			return 1;
+		if (gpuCore == GPUCORE_VULKAN) {
+			// Vulkan renders into images of its own, with no window or swapchain.
+			VulkanGraphicsContext *vulkanContext = new VulkanGraphicsContext();
+			vulkanContext->SetOffscreen(480, 272);
+			graphicsContext = vulkanContext;
+			deviceSetting = &g_Config.sVulkanDevice;
+		} else {
+			// TODO: Will we need a larger window for higher resolutions? Well, not if we use buffered rendering.
+			window = CreateHiddenWindow(480, 272, cmdLineOptions.gpuBackend.value_or(GPUBackend::OPENGL), &windowDesc);
+			if (!windowDesc.Valid()) {
+				fprintf(stderr, "Failed to create a window for graphics context\n");
+				return 1;
+			}
+			graphicsContext = CreateGraphicsContext(gpuCore, &deviceSetting);
+			if (!graphicsContext) {
+				// If we don't get the desired context, we DO NOT fall back.
+				fprintf(stderr, "Failed to create a graphics context for GPU core\n");
+				return 1;
+			}
 		}
 #endif
 	}