GPU/HW: Implement automatic resolution scale from window size

src/core/gpu.cpp

@@ -57,6 +57,8 @@ void GPU::UpdateSettings()
   UpdateCRTCDisplayParameters();
 }
 
+void GPU::UpdateResolutionScale() {}
+
 void GPU::Reset()
 {
   SoftReset();

src/core/gpu.h

@@ -154,12 +154,15 @@ public:
   /// Returns true if a raster scanline or command execution is pending.
   bool IsCommandCompletionPending() const;
 
-  // Synchronizes the CRTC, updating the hblank timer.
+  /// Synchronizes the CRTC, updating the hblank timer.
   void SynchronizeCRTC();
 
-  // Recompile shaders/recreate framebuffers when needed.
+  /// Recompile shaders/recreate framebuffers when needed.
   virtual void UpdateSettings();
 
+  /// Updates the resolution scale when it's set to automatic.
+  virtual void UpdateResolutionScale();
+
   // gpu_hw_d3d11.cpp
   static std::unique_ptr<GPU> CreateHardwareD3D11Renderer();
 

src/core/gpu_hw.cpp

@@ -7,8 +7,8 @@
 #include "pgxp.h"
 #include "settings.h"
 #include "system.h"
-#include <sstream>
 #include <cmath>
+#include <sstream>
 #include <tuple>
 Log_SetChannel(GPU_HW);
 
@@ -38,18 +38,11 @@ bool GPU_HW::Initialize(HostDisplay* host_display)
   if (!GPU::Initialize(host_display))
     return false;
 
-  m_resolution_scale = g_settings.gpu_resolution_scale;
+  m_resolution_scale = CalculateResolutionScale();
   m_render_api = host_display->GetRenderAPI();
   m_true_color = g_settings.gpu_true_color;
   m_scaled_dithering = g_settings.gpu_scaled_dithering;
   m_texture_filtering = g_settings.gpu_texture_filtering;
-  if (m_resolution_scale < 1 || m_resolution_scale > m_max_resolution_scale)
-  {
-    g_host_interface->AddFormattedOSDMessage(5.0f, "Invalid resolution scale %ux specified. Maximum is %u.",
-                                             m_resolution_scale, m_max_resolution_scale);
-    m_resolution_scale = std::clamp<u32>(m_resolution_scale, 1u, m_max_resolution_scale);
-  }
-
   PrintSettingsToLog();
   return true;
 }
@@ -90,13 +83,35 @@ void GPU_HW::UpdateSettings()
 {
   GPU::UpdateSettings();
 
-  m_resolution_scale = std::clamp<u32>(g_settings.gpu_resolution_scale, 1, m_max_resolution_scale);
+  m_resolution_scale = CalculateResolutionScale();
   m_true_color = g_settings.gpu_true_color;
   m_scaled_dithering = g_settings.gpu_scaled_dithering;
   m_texture_filtering = g_settings.gpu_texture_filtering;
   PrintSettingsToLog();
 }
 
+u32 GPU_HW::CalculateResolutionScale() const
+{
+  if (g_settings.gpu_resolution_scale != 0)
+    return std::clamp<u32>(g_settings.gpu_resolution_scale, 1, m_max_resolution_scale);
+
+  // auto scaling
+  const s32 height = (m_crtc_state.display_height != 0) ? static_cast<s32>(m_crtc_state.display_height) : 480;
+  const s32 preferred_scale =
+    static_cast<s32>(std::ceil(static_cast<float>(m_host_display->GetWindowHeight()) / height));
+  Log_InfoPrintf("Height = %d, preferred scale = %d", height, preferred_scale);
+
+  return static_cast<u32>(std::clamp<s32>(preferred_scale, 1, m_max_resolution_scale));
+}
+
+void GPU_HW::UpdateResolutionScale()
+{
+  GPU::UpdateResolutionScale();
+
+  if (CalculateResolutionScale() != m_resolution_scale)
+    UpdateSettings();
+}
+
 void GPU_HW::PrintSettingsToLog()
 {
   Log_InfoPrintf("Resolution Scale: %u (%ux%u), maximum %u", m_resolution_scale, VRAM_WIDTH * m_resolution_scale,

src/core/gpu_hw.h

@@ -35,6 +35,7 @@ public:
   virtual void Reset() override;
   virtual bool DoState(StateWrapper& sw) override;
   virtual void UpdateSettings() override;
+  virtual void UpdateResolutionScale() override;
 
 protected:
   enum : u32
@@ -167,6 +168,8 @@ protected:
   virtual void UploadUniformBuffer(const void* uniforms, u32 uniforms_size) = 0;
   virtual void DrawBatchVertices(BatchRenderMode render_mode, u32 base_vertex, u32 num_vertices) = 0;
 
+  u32 CalculateResolutionScale() const;
+
   void SetFullVRAMDirtyRectangle()
   {
     m_vram_dirty_rect.Set(0, 0, VRAM_WIDTH, VRAM_HEIGHT);

src/duckstation-qt/qthostinterface.cpp

@@ -425,7 +425,10 @@ void QtHostInterface::onHostDisplayWindowResized(int width, int height)
 
   // re-render the display, since otherwise it will be out of date and stretched if paused
   if (!System::IsShutdown())
+  {
+    g_gpu->UpdateResolutionScale();
     renderDisplay();
+  }
 }
 
 void QtHostInterface::redrawDisplayWindow()
@@ -538,7 +541,12 @@ void QtHostInterface::updateDisplayState()
     Panic("Failed to make device context current after updating");
 
   connectDisplaySignals(display_widget);
+
+  if (!System::IsShutdown())
+  {
+    g_gpu->UpdateResolutionScale();
     redrawDisplayWindow();
+  }
   UpdateSpeedLimiterState();
 }
 

src/duckstation-sdl/sdl_host_interface.cpp

@@ -370,6 +370,10 @@ bool SDLHostInterface::SetFullscreen(bool enabled)
   int window_width, window_height;
   SDL_GetWindowSize(m_window, &window_width, &window_height);
   m_display->ResizeRenderWindow(window_width, window_height);
+
+  if (!System::IsShutdown())
+    g_gpu->UpdateResolutionScale();
+
   m_fullscreen = enabled;
   return true;
 }
@@ -523,6 +527,9 @@ void SDLHostInterface::HandleSDLEvent(const SDL_Event* event)
       {
         m_display->ResizeRenderWindow(event->window.data1, event->window.data2);
         UpdateFramebufferScale();
+
+        if (!System::IsShutdown())
+          g_gpu->UpdateResolutionScale();
       }
       else if (event->window.event == SDL_WINDOWEVENT_MOVED)
       {