OGL: Fix headless frame dumping

Also skips swapping the window system buffers in headless mode, as there
may not be a surface which can be swapped in the first place. Instead,
we call glFlush() at the end of a frame in this case.

Source/Core/VideoBackends/OGL/Render.cpp

@@ -1349,25 +1349,35 @@ void Renderer::SwapImpl(AbstractTexture* texture, const EFBRectangle& xfb_region
   // Flip top and bottom for some reason; TODO: Fix the code to suck less?
   std::swap(flipped_trc.top, flipped_trc.bottom);
 
-  // Copy the framebuffer to screen.
-  glBindFramebuffer(GL_FRAMEBUFFER, 0);
-  BlitScreen(sourceRc, flipped_trc, xfb_texture->GetRawTexIdentifier(),
-             xfb_texture->GetConfig().width, xfb_texture->GetConfig().height);
-
-  // Finish up the current frame, print some stats
-  glEnable(GL_BLEND);
-  glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);
-
-  // Reset viewport for drawing text
-  glViewport(0, 0, GLInterface->GetBackBufferWidth(), GLInterface->GetBackBufferHeight());
-  DrawDebugText();
-
   // Do our OSD callbacks
   OSD::DoCallbacks(OSD::CallbackType::OnFrame);
-  OSD::DrawMessages();
 
-  // Copy the rendered frame to the real window.
-  GLInterface->Swap();
+  // Skip screen rendering when running in headless mode.
+  if (!IsHeadless())
+  {
+    // Copy the framebuffer to screen.
+    glBindFramebuffer(GL_FRAMEBUFFER, 0);
+    BlitScreen(sourceRc, flipped_trc, xfb_texture->GetRawTexIdentifier(),
+               xfb_texture->GetConfig().width, xfb_texture->GetConfig().height);
+
+    // Finish up the current frame, print some stats
+    glEnable(GL_BLEND);
+    glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);
+
+    // Reset viewport for drawing text
+    glViewport(0, 0, GLInterface->GetBackBufferWidth(), GLInterface->GetBackBufferHeight());
+    DrawDebugText();
+    OSD::DrawMessages();
+
+    // Copy the rendered frame to the real window.
+    GLInterface->Swap();
+  }
+  else
+  {
+    // Since we're not swapping in headless mode, ensure all commands are sent to the GPU.
+    // Otherwise the driver could batch several frames togehter.
+    glFlush();
+  }
 
 #ifdef ANDROID
   // Handle surface changes on Android.
@@ -1375,6 +1385,7 @@ void Renderer::SwapImpl(AbstractTexture* texture, const EFBRectangle& xfb_region
   {
     GLInterface->UpdateHandle(m_new_surface_handle);
     GLInterface->UpdateSurface();
+    m_surface_handle = m_new_surface_handle;
     m_new_surface_handle = nullptr;
     m_surface_needs_change.Clear();
     m_surface_changed.Set();
@@ -1431,8 +1442,11 @@ void Renderer::SwapImpl(AbstractTexture* texture, const EFBRectangle& xfb_region
   }
 
   // Clear framebuffer
-  glClearColor(0, 0, 0, 0);
-  glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
+  if (!IsHeadless())
+  {
+    glClearColor(0, 0, 0, 0);
+    glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
+  }
 
   if (s_vsync != g_ActiveConfig.IsVSync())
   {

Source/Core/VideoBackends/Software/SWRenderer.cpp

@@ -45,9 +45,11 @@ void SWRenderer::SwapImpl(AbstractTexture* texture, const EFBRectangle& xfb_regi
 {
   OSD::DoCallbacks(OSD::CallbackType::OnFrame);
 
-  DrawDebugText();
-
-  SWOGLWindow::s_instance->ShowImage(texture, xfb_region);
+  if (!IsHeadless())
+  {
+    DrawDebugText();
+    SWOGLWindow::s_instance->ShowImage(texture, xfb_region);
+  }
 
   UpdateActiveConfig();
 }

Source/Core/VideoBackends/Vulkan/Renderer.cpp

@@ -600,7 +600,6 @@ void Renderer::DrawScreen(VKTexture* xfb_texture, const EFBRectangle& xfb_region
                        VK_SUBPASS_CONTENTS_INLINE);
 
   // Draw
-  TargetRectangle source_rc = xfb_texture->GetConfig().GetRect();
   BlitScreen(m_swap_chain->GetRenderPass(), GetTargetRectangle(), xfb_region,
              xfb_texture->GetRawTexIdentifier());
 
@@ -702,6 +701,7 @@ void Renderer::CheckForSurfaceChange()
 
     // Notify calling thread.
     m_surface_needs_change.Clear();
+    m_surface_handle = m_new_surface_handle;
     m_new_surface_handle = nullptr;
     m_surface_changed.Set();
   }

Source/Core/VideoCommon/RenderBase.cpp

@@ -94,6 +94,7 @@ Renderer::Renderer(int backbuffer_width, int backbuffer_height)
   if (SConfig::GetInstance().bWii)
     m_aspect_wide = Config::Get(Config::SYSCONF_WIDESCREEN);
 
+  m_surface_handle = Host_GetRenderHandle();
   m_last_host_config_bits = ShaderHostConfig::GetCurrent().bits;
 }
 
@@ -400,6 +401,11 @@ float Renderer::CalculateDrawAspectRatio() const
   }
 }
 
+bool Renderer::IsHeadless() const
+{
+  return !m_surface_handle;
+}
+
 std::tuple<float, float> Renderer::ScaleToDisplayAspectRatio(const int width,
                                                              const int height) const
 {
@@ -711,7 +717,7 @@ void Renderer::DoDumpFrame()
 void Renderer::UpdateFrameDumpTexture()
 {
   int target_width, target_height;
-  if (!g_ActiveConfig.bInternalResolutionFrameDumps)
+  if (!g_ActiveConfig.bInternalResolutionFrameDumps && !IsHeadless())
   {
     auto target_rect = GetTargetRectangle();
     target_width = target_rect.GetWidth();

Source/Core/VideoCommon/RenderBase.h

@@ -94,6 +94,7 @@ public:
 
   const TargetRectangle& GetTargetRectangle() const { return m_target_rectangle; }
   float CalculateDrawAspectRatio() const;
+  bool IsHeadless() const;
 
   std::tuple<float, float> ScaleToDisplayAspectRatio(int width, int height) const;
   void UpdateDrawRectangle();
@@ -176,9 +177,10 @@ protected:
 
   static const float GX_MAX_DEPTH;
 
+  void* m_surface_handle = nullptr;
+  void* m_new_surface_handle = nullptr;
   Common::Flag m_surface_needs_change;
   Common::Event m_surface_changed;
-  void* m_new_surface_handle = nullptr;
 
   u32 m_last_host_config_bits = 0;