GPU: Don't truncate clear colour to 15-bit with true colour on

src/core/gpu.cpp

@@ -667,7 +667,7 @@ void GPU::UpdateDrawingArea() {}
 
 void GPU::ReadVRAM(u32 x, u32 y, u32 width, u32 height, void* buffer) {}
 
-void GPU::FillVRAM(u32 x, u32 y, u32 width, u32 height, u16 color) {}
+void GPU::FillVRAM(u32 x, u32 y, u32 width, u32 height, u32 color) {}
 
 void GPU::UpdateVRAM(u32 x, u32 y, u32 width, u32 height, const void* data) {}
 

src/core/gpu.h

@@ -284,7 +284,7 @@ protected:
   virtual void UpdateDisplay();
   virtual void UpdateDrawingArea();
   virtual void ReadVRAM(u32 x, u32 y, u32 width, u32 height, void* buffer);
-  virtual void FillVRAM(u32 x, u32 y, u32 width, u32 height, u16 color);
+  virtual void FillVRAM(u32 x, u32 y, u32 width, u32 height, u32 color);
   virtual void UpdateVRAM(u32 x, u32 y, u32 width, u32 height, const void* data);
   virtual void CopyVRAM(u32 src_x, u32 src_y, u32 dst_x, u32 dst_y, u32 width, u32 height);
   virtual void DispatchRenderCommand(RenderCommand rc, u32 num_vertices, const u32* command_ptr);

src/core/gpu_commands.cpp

@@ -259,11 +259,7 @@ bool GPU::HandleFillRectangleCommand(const u32*& command_ptr, u32 command_size)
 
   Log_DebugPrintf("Fill VRAM rectangle offset=(%u,%u), size=(%u,%u)", dst_x, dst_y, width, height);
 
-  // Drop higher precision when filling. Bit15 is set to 0.
-  // TODO: Force 8-bit color option.
-  const u16 color16 = RGBA8888ToRGBA5551(color);
-
-  FillVRAM(dst_x, dst_y, width, height, color16);
+  FillVRAM(dst_x, dst_y, width, height, color);
   return true;
 }
 

src/core/gpu_hw_opengl.cpp

@@ -574,7 +574,7 @@ void GPU_HW_OpenGL::ReadVRAM(u32 x, u32 y, u32 width, u32 height, void* buffer)
   m_stats.num_vram_reads++;
 }
 
-void GPU_HW_OpenGL::FillVRAM(u32 x, u32 y, u32 width, u32 height, u16 color)
+void GPU_HW_OpenGL::FillVRAM(u32 x, u32 y, u32 width, u32 height, u32 color)
 {
   // scale coordinates
   x *= m_resolution_scale;
@@ -584,7 +584,11 @@ void GPU_HW_OpenGL::FillVRAM(u32 x, u32 y, u32 width, u32 height, u16 color)
 
   glScissor(x, m_vram_texture->GetHeight() - y - height, width, height);
 
-  const auto [r, g, b, a] = RGBA8ToFloat(RGBA5551ToRGBA8888(color));
+  // drop precision unless true colour is enabled
+  if (!m_true_color)
+    color = RGBA5551ToRGBA8888(RGBA8888ToRGBA5551(color));
+
+  const auto [r, g, b, a] = RGBA8ToFloat(color);
   glClearColor(r, g, b, a);
   glClear(GL_COLOR_BUFFER_BIT);
 

src/core/gpu_hw_opengl.h

@@ -27,7 +27,7 @@ protected:
   void UpdateDisplay() override;
   void UpdateDrawingArea() override;
   void ReadVRAM(u32 x, u32 y, u32 width, u32 height, void* buffer) override;
-  void FillVRAM(u32 x, u32 y, u32 width, u32 height, u16 color) override;
+  void FillVRAM(u32 x, u32 y, u32 width, u32 height, u32 color) override;
   void UpdateVRAM(u32 x, u32 y, u32 width, u32 height, const void* data) override;
   void CopyVRAM(u32 src_x, u32 src_y, u32 dst_x, u32 dst_y, u32 width, u32 height) override;
   void FlushRender() override;

src/core/gpu_sw.cpp

@@ -41,10 +41,11 @@ void GPU_SW::ReadVRAM(u32 x, u32 y, u32 width, u32 height, void* buffer)
   }
 }
 
-void GPU_SW::FillVRAM(u32 x, u32 y, u32 width, u32 height, u16 color)
+void GPU_SW::FillVRAM(u32 x, u32 y, u32 width, u32 height, u32 color)
 {
+  const u16 color16 = RGBA8888ToRGBA5551(color);
   for (u32 yoffs = 0; yoffs < height; yoffs++)
-    std::fill_n(GetPixelPtr(x, y + yoffs), width, color);
+    std::fill_n(GetPixelPtr(x, y + yoffs), width, color16);
 }
 
 void GPU_SW::UpdateVRAM(u32 x, u32 y, u32 width, u32 height, const void* data)

src/core/gpu_sw.h

@@ -37,7 +37,7 @@ protected:
   };
 
   void ReadVRAM(u32 x, u32 y, u32 width, u32 height, void* buffer) override;
-  void FillVRAM(u32 x, u32 y, u32 width, u32 height, u16 color) override;
+  void FillVRAM(u32 x, u32 y, u32 width, u32 height, u32 color) override;
   void UpdateVRAM(u32 x, u32 y, u32 width, u32 height, const void* data) override;
   void CopyVRAM(u32 src_x, u32 src_y, u32 dst_x, u32 dst_y, u32 width, u32 height) override;