libretro: Fix runtime aspect ratio changes not applying

src/core/host_display.h

@@ -89,6 +89,7 @@ public:
   virtual void SetVSync(bool enabled) = 0;
 
   const s32 GetDisplayTopMargin() const { return m_display_top_margin; }
+  const float GetDisplayAspectRatio() const { return m_display_aspect_ratio; }
 
   void ClearDisplayTexture()
   {

src/duckstation-libretro/libretro_host_interface.cpp

@@ -103,6 +103,8 @@ bool LibretroHostInterface::Initialize()
   LoadSettings();
   FixIncompatibleSettings(true);
   UpdateLogging();
+
+  m_last_aspect_ratio = Settings::GetDisplayAspectRatioValue(g_settings.display_aspect_ratio);
   return true;
 }
 
@@ -226,7 +228,7 @@ void LibretroHostInterface::GetSystemAVInfo(struct retro_system_av_info* info, b
 
   std::memset(info, 0, sizeof(*info));
 
-  info->geometry.aspect_ratio = Settings::GetDisplayAspectRatioValue(g_settings.display_aspect_ratio);
+  info->geometry.aspect_ratio = m_last_aspect_ratio;
   info->geometry.base_width = 320;
   info->geometry.base_height = 240;
   info->geometry.max_width = GPU::VRAM_WIDTH * resolution_scale;
@@ -334,6 +336,13 @@ void LibretroHostInterface::retro_run_frame()
 
   System::RunFrame();
 
+  const float aspect_ratio = m_display->GetDisplayAspectRatio();
+  if (aspect_ratio != m_last_aspect_ratio)
+  {
+    m_last_aspect_ratio = aspect_ratio;
+    UpdateGeometry();
+  }
+
   m_display->Render();
 }
 

src/duckstation-libretro/libretro_host_interface.h

@@ -97,6 +97,8 @@ private:
   bool m_rumble_interface_valid = false;
   bool m_supports_input_bitmasks = false;
   bool m_interfaces_initialized = false;
+
+  float m_last_aspect_ratio = 4.0f / 3.0f;
 };
 
 extern LibretroHostInterface g_libretro_host_interface;