2 files changed, 33 insertions, 3 deletions

diff --git a/src/core/frontend/framebuffer_layout.cpp b/src/core/frontend/framebuffer_layout.cpp
index d6d2cf3f0..2dc795d56 100644
--- a/src/core/frontend/framebuffer_layout.cpp
+++ b/src/core/frontend/framebuffer_layout.cpp
@@ -27,9 +27,9 @@ FramebufferLayout DefaultFrameLayout(u32 width, u32 height) {
     // so just calculate them both even if the other isn't showing.
     FramebufferLayout res{width, height};
 
-    const float emulation_aspect_ratio{static_cast<float>(ScreenUndocked::Height) /
-                                       ScreenUndocked::Width};
-    const auto window_aspect_ratio = static_cast<float>(height) / width;
+    const float window_aspect_ratio = static_cast<float>(height) / width;
+    const float emulation_aspect_ratio = EmulationAspectRatio(
+        static_cast<AspectRatio>(Settings::values.aspect_ratio), window_aspect_ratio);
 
     const Common::Rectangle<u32> screen_window_area{0, 0, width, height};
     Common::Rectangle<u32> screen = MaxRectangle(screen_window_area, emulation_aspect_ratio);
@@ -58,4 +58,19 @@ FramebufferLayout FrameLayoutFromResolutionScale(u32 res_scale) {
     return DefaultFrameLayout(width, height);
 }
 
+float EmulationAspectRatio(AspectRatio aspect, float window_aspect_ratio) {
+    switch (aspect) {
+    case AspectRatio::Default:
+        return static_cast<float>(ScreenUndocked::Height) / ScreenUndocked::Width;
+    case AspectRatio::R4_3:
+        return 3.0f / 4.0f;
+    case AspectRatio::R21_9:
+        return 9.0f / 21.0f;
+    case AspectRatio::StretchToWindow:
+        return window_aspect_ratio;
+    default:
+        return static_cast<float>(ScreenUndocked::Height) / ScreenUndocked::Width;
+    }
+}
+
 } // namespace Layout
diff --git a/src/core/frontend/framebuffer_layout.h b/src/core/frontend/framebuffer_layout.h
index d2370adde..1d39c1faf 100644
--- a/src/core/frontend/framebuffer_layout.h
+++ b/src/core/frontend/framebuffer_layout.h
@@ -18,6 +18,13 @@ enum ScreenDocked : u32 {
     HeightDocked = 1080,
 };
 
+enum class AspectRatio {
+    Default,
+    R4_3,
+    R21_9,
+    StretchToWindow,
+};
+
 /// Describes the layout of the window framebuffer
 struct FramebufferLayout {
     u32 width{ScreenUndocked::Width};
@@ -48,4 +55,12 @@ FramebufferLayout DefaultFrameLayout(u32 width, u32 height);
  */
 FramebufferLayout FrameLayoutFromResolutionScale(u32 res_scale);
 
+/**
+ * Convenience method to determine emulation aspect ratio
+ * @param aspect Represents the index of aspect ratio stored in Settings::values.aspect_ratio
+ * @param window_aspect_ratio Current window aspect ratio
+ * @return Emulation render window aspect ratio
+ */
+float EmulationAspectRatio(AspectRatio aspect, float window_aspect_ratio);
+
 } // namespace Layout