CommonHostInterface: Add resize window to scale functions

src/frontend-common/common_host_interface.cpp

@@ -2534,6 +2534,28 @@ bool CommonHostInterface::ParseFullscreenMode(const std::string_view& mode, u32*
   return false;
 }
 
+bool CommonHostInterface::RequestRenderWindowSize(s32 new_window_width, s32 new_window_height)
+{
+  return false;
+}
+
+bool CommonHostInterface::RequestRenderWindowScale(float scale)
+{
+  if (!System::IsValid() || scale == 0)
+    return false;
+
+  const float y_scale =
+    (static_cast<float>(m_display->GetDisplayWidth()) / static_cast<float>(m_display->GetDisplayHeight())) /
+    m_display->GetDisplayAspectRatio();
+
+  const u32 requested_width =
+    std::max<u32>(static_cast<u32>(std::ceil(static_cast<float>(m_display->GetDisplayWidth()) * scale)), 1);
+  const u32 requested_height =
+    std::max<u32>(static_cast<u32>(std::ceil(static_cast<float>(m_display->GetDisplayHeight()) * y_scale * scale)), 1);
+
+  return RequestRenderWindowSize(static_cast<s32>(requested_width), static_cast<s32>(requested_height));
+}
+
 #ifdef WITH_DISCORD_PRESENCE
 
 void CommonHostInterface::SetDiscordPresenceEnabled(bool enabled)

src/frontend-common/common_host_interface.h

@@ -183,6 +183,12 @@ public:
   /// Returns true if fast forwarding is currently active.
   bool IsFastForwardEnabled() const { return m_fast_forward_enabled; }
 
+  /// Requests the specified size for the render window. Not guaranteed to succeed (e.g. if in fullscreen).
+  virtual bool RequestRenderWindowSize(s32 new_window_width, s32 new_window_height);
+
+  /// Requests a resize to a multiple of the render window size.
+  bool RequestRenderWindowScale(float scale);
+
 protected:
   enum : u32
   {