GPU: Claer interlaced field buffer when enabling

Fixes old frames getting briefly displayed.

src/core/gpu.cpp

@@ -974,6 +974,12 @@ void GPU::WriteGP1(u32 value)
       new_GPUSTAT.reverse_flag = dm.reverse_flag;
       Log_DebugPrintf("Set display mode <- 0x%08X", dm.bits);
 
+      if (!m_GPUSTAT.vertical_interlace && dm.vertical_interlace && !m_force_progressive_scan)
+      {
+        // bit of a hack, technically we should pull the previous frame in, but this may not exist anymore
+        ClearDisplay();
+      }
+
       if (m_GPUSTAT.bits != new_GPUSTAT.bits)
       {
         // Have to be careful when setting this because Synchronize() can modify GPUSTAT.
@@ -1069,6 +1075,8 @@ void GPU::HandleGetGPUInfoCommand(u32 value)
   }
 }
 
+void GPU::ClearDisplay() {}
+
 void GPU::UpdateDisplay() {}
 
 void GPU::ReadVRAM(u32 x, u32 y, u32 width, u32 height) {}

src/core/gpu.h

@@ -427,6 +427,7 @@ protected:
   virtual void CopyVRAM(u32 src_x, u32 src_y, u32 dst_x, u32 dst_y, u32 width, u32 height);
   virtual void DispatchRenderCommand();
   virtual void FlushRender();
+  virtual void ClearDisplay();
   virtual void UpdateDisplay();
   virtual void DrawRendererStats(bool is_idle_frame);
 

src/core/gpu_hw_d3d11.cpp

@@ -549,6 +549,14 @@ void GPU_HW_D3D11::SetScissorFromDrawingArea()
   m_context->RSSetScissorRects(1, &rc);
 }
 
+void GPU_HW_D3D11::ClearDisplay()
+{
+  GPU_HW::ClearDisplay();
+
+  static constexpr std::array<float, 4> clear_color = { 0.0f, 0.0f, 0.0f, 1.0f };
+  m_context->ClearRenderTargetView(m_display_texture.GetD3DRTV(), clear_color.data());
+}
+
 void GPU_HW_D3D11::UpdateDisplay()
 {
   GPU_HW::UpdateDisplay();

src/core/gpu_hw_d3d11.h

@@ -27,6 +27,7 @@ public:
   void UpdateSettings() override;
 
 protected:
+  void ClearDisplay() override;
   void UpdateDisplay() override;
   void ReadVRAM(u32 x, u32 y, u32 width, u32 height) override;
   void FillVRAM(u32 x, u32 y, u32 width, u32 height, u32 color) override;

src/core/gpu_hw_opengl.cpp

@@ -560,6 +560,18 @@ void GPU_HW_OpenGL::UploadUniformBuffer(const void* data, u32 data_size)
   m_renderer_stats.num_uniform_buffer_updates++;
 }
 
+void GPU_HW_OpenGL::ClearDisplay()
+{
+  GPU_HW::ClearDisplay();
+
+  m_display_texture.BindFramebuffer(GL_DRAW_FRAMEBUFFER);
+  glDisable(GL_SCISSOR_TEST);
+  glClearColor(0.0f, 0.0f, 0.0f, 1.0f);
+  glClear(GL_COLOR_BUFFER_BIT);
+  glEnable(GL_SCISSOR_TEST);
+  m_vram_texture.BindFramebuffer(GL_DRAW_FRAMEBUFFER);
+}
+
 void GPU_HW_OpenGL::UpdateDisplay()
 {
   GPU_HW::UpdateDisplay();

src/core/gpu_hw_opengl.h

@@ -23,6 +23,7 @@ public:
   void UpdateSettings() override;
 
 protected:
+  void ClearDisplay() override;
   void UpdateDisplay() override;
   void ReadVRAM(u32 x, u32 y, u32 width, u32 height) override;
   void FillVRAM(u32 x, u32 y, u32 width, u32 height, u32 color) override;

src/core/gpu_hw_vulkan.cpp

@@ -467,6 +467,7 @@ bool GPU_HW_Vulkan::CreateFramebuffer()
     old_vram_texture.Destroy(true);
   }
 
+  ClearDisplay();
   SetFullVRAMDirtyRectangle();
   return true;
 }
@@ -888,6 +889,18 @@ void GPU_HW_Vulkan::SetScissorFromDrawingArea()
   Vulkan::Util::SetScissor(g_vulkan_context->GetCurrentCommandBuffer(), left, top, right - left, bottom - top);
 }
 
+void GPU_HW_Vulkan::ClearDisplay()
+{
+  GPU_HW::ClearDisplay();
+
+  VkCommandBuffer cmdbuf = g_vulkan_context->GetCurrentCommandBuffer();
+  m_display_texture.TransitionToLayout(cmdbuf, VK_IMAGE_LAYOUT_TRANSFER_DST_OPTIMAL);
+
+  static const VkClearColorValue cc = {0.0f, 0.0f, 0.0f, 1.0f};
+  static const VkImageSubresourceRange srr = {VK_IMAGE_ASPECT_COLOR_BIT, 0, 1, 0, 1};
+  vkCmdClearColorImage(cmdbuf, m_display_texture.GetImage(), m_display_texture.GetLayout(), &cc, 1, &srr);
+}
+
 void GPU_HW_Vulkan::UpdateDisplay()
 {
   GPU_HW::UpdateDisplay();

src/core/gpu_hw_vulkan.h

@@ -22,6 +22,7 @@ public:
   void UpdateSettings() override;
 
 protected:
+  void ClearDisplay() override;
   void UpdateDisplay() override;
   void ReadVRAM(u32 x, u32 y, u32 width, u32 height) override;
   void FillVRAM(u32 x, u32 y, u32 width, u32 height, u32 color) override;

src/core/gpu_sw.cpp

@@ -142,6 +142,11 @@ void GPU_SW::CopyOut24Bit(u32 src_x, u32 src_y, u32* dst_ptr, u32 dst_stride, u3
   }
 }
 
+void GPU_SW::ClearDisplay()
+{
+  std::memset(m_display_texture_buffer.data(), 0, sizeof(u32) * m_display_texture_buffer.size());
+}
+
 void GPU_SW::UpdateDisplay()
 {
   // fill display texture

src/core/gpu_sw.h

@@ -51,6 +51,7 @@ protected:
                     bool interleaved);
   void CopyOut24Bit(u32 src_x, u32 src_y, u32* dst_ptr, u32 dst_stride, u32 width, u32 height, bool interlaced,
                     bool interleaved);
+  void ClearDisplay() override;
   void UpdateDisplay() override;
 
   //////////////////////////////////////////////////////////////////////////