Support custom and match display aspect ratios

android/app/src/main/res/values-es/arrays.xml

@@ -45,6 +45,7 @@
     </string-array>
     <string-array name="settings_display_aspect_ratio_names">
         <item>Auto (Nativo del juego)</item>
+        <item>Auto (Match Display)</item>
         <item>4:3</item>
         <item>16:9</item>
         <item>16:10</item>

android/app/src/main/res/values-it/arrays.xml

@@ -45,6 +45,7 @@
     </string-array>
     <string-array name="settings_display_aspect_ratio_names">
         <item>Auto (Game Native)</item>
+        <item>Auto (Match Display)</item>
         <item>4:3</item>
         <item>16:9</item>
         <item>16:10</item>

android/app/src/main/res/values-nl/arrays.xml

@@ -45,6 +45,7 @@
     </string-array>
     <string-array name="settings_display_aspect_ratio_names">
         <item>Auto (Game Native)</item>
+        <item>Auto (Match Display)</item>
         <item>4:3</item>
         <item>16:9</item>
         <item>16:10</item>

android/app/src/main/res/values-pt-rBR/arrays.xml

@@ -45,6 +45,7 @@
     </string-array>
     <string-array name="settings_display_aspect_ratio_names">
        <item>Auto (Nativo)</item>
+        <item>Auto (Match Display)</item>
         <item>4:3</item>
         <item>16:9</item>
         <item>16:10</item>

android/app/src/main/res/values-ru/arrays.xml

@@ -44,8 +44,9 @@
 		<item>Все границы</item>
 	</string-array>
 	<string-array name="settings_display_aspect_ratio_names">
-		<item>Автонастройка (нативное игре)</item>
+    <item>Автонастройка (нативное игре)</item>
-		<item>4:3</item>
+    <item>Auto (Match Display)</item>
+    <item>4:3</item>
 		<item>16:9</item>
 		<item>16:10</item>
 		<item>19:9</item>

android/app/src/main/res/values/arrays.xml

@@ -89,6 +89,7 @@
     </string-array>
     <string-array name="settings_display_aspect_ratio_names">
         <item>Auto (Game Native)</item>
+        <item>Auto (Match Display)</item>
         <item>4:3</item>
         <item>16:9</item>
         <item>16:10</item>
@@ -105,6 +106,7 @@
     </string-array>
     <string-array name="settings_display_aspect_ratio_values">
         <item>Auto (Game Native)</item>
+        <item>Auto (Match Window)</item>
         <item>4:3</item>
         <item>16:9</item>
         <item>16:10</item>

src/core/gpu.cpp

@@ -492,7 +492,7 @@ float GPU::GetDisplayAspectRatio() const
   }
   else
   {
-    return Settings::GetDisplayAspectRatioValue(g_settings.display_aspect_ratio);
+    return g_settings.GetDisplayAspectRatioValue();
   }
 }
 

src/core/gte.cpp

@@ -3,10 +3,13 @@
 #include "common/bitutils.h"
 #include "common/state_wrapper.h"
 #include "cpu_core.h"
+#include "host_display.h"
+#include "host_interface.h"
 #include "pgxp.h"
 #include "settings.h"
 #include <algorithm>
 #include <array>
+#include <numeric>
 
 namespace GTE {
 
@@ -19,6 +22,11 @@ static constexpr s32 IR0_MAX_VALUE = 0x1000;
 static constexpr s32 IR123_MIN_VALUE = -(INT64_C(1) << 15);
 static constexpr s32 IR123_MAX_VALUE = (INT64_C(1) << 15) - 1;
 
+static DisplayAspectRatio s_aspect_ratio = DisplayAspectRatio::R4_3;
+static u32 s_custom_aspect_ratio_numerator;
+static u32 s_custom_aspect_ratio_denominator;
+static float s_custom_aspect_ratio_f;
+
 #define REGS CPU::g_state.gte_regs
 
 ALWAYS_INLINE static u32 CountLeadingBits(u32 value)
@@ -148,6 +156,7 @@ ALWAYS_INLINE static u32 TruncateRGB(s32 value)
 
 void Initialize()
 {
+  UpdateAspectRatio();
   Reset();
 }
 
@@ -162,6 +171,55 @@ bool DoState(StateWrapper& sw)
   return !sw.HasError();
 }
 
+void UpdateAspectRatio()
+{
+  if (!g_settings.gpu_widescreen_hack)
+  {
+    s_aspect_ratio = DisplayAspectRatio::R4_3;
+    return;
+  }
+
+  s_aspect_ratio = g_settings.display_aspect_ratio;
+
+  u32 num, denom;
+  switch (s_aspect_ratio)
+  {
+    case DisplayAspectRatio::MatchWindow:
+    {
+      const HostDisplay* display = g_host_interface->GetDisplay();
+      if (!display)
+      {
+        s_aspect_ratio = DisplayAspectRatio::R4_3;
+        return;
+      }
+
+      num = display->GetWindowWidth();
+      denom = display->GetWindowHeight();
+    }
+    break;
+
+    case DisplayAspectRatio::Custom:
+    {
+      num = g_settings.display_aspect_ratio_custom_numerator;
+      denom = g_settings.display_aspect_ratio_custom_denominator;
+    }
+    break;
+
+    default:
+      return;
+  }
+
+  // (4 / 3) / (num / denom) => gcd((4 * denom) / (3 * num))
+  const u32 x = 4u * denom;
+  const u32 y = 3u * num;
+  const u32 gcd = std::gcd(x, y);
+
+  s_custom_aspect_ratio_numerator = x / gcd;
+  s_custom_aspect_ratio_denominator = y / gcd;
+
+  s_custom_aspect_ratio_f = static_cast<float>((4.0 / 3.0) / (static_cast<double>(num) / static_cast<double>(denom)));
+}
+
 u32 ReadRegister(u32 index)
 {
   DebugAssert(index < countof(REGS.r32));
@@ -614,66 +672,65 @@ static void RTPS(const s16 V[3], u8 shift, bool lm, bool last)
   const s64 result = static_cast<s64>(ZeroExtend64(UNRDivide(REGS.H, REGS.SZ3)));
 
   s64 Sx;
-  if (g_settings.gpu_widescreen_hack)
+  switch (s_aspect_ratio)
   {
-    const DisplayAspectRatio ar = g_settings.display_aspect_ratio;
+    case DisplayAspectRatio::R16_9:
-    switch (ar)
+      Sx = ((((s64(result) * s64(REGS.IR1)) * s64(3)) / s64(4)) + s64(REGS.OFX));
-    {
+      break;
-      case DisplayAspectRatio::R16_9:
-        Sx = ((((s64(result) * s64(REGS.IR1)) * s64(3)) / s64(4)) + s64(REGS.OFX));
-        break;
 
-      case DisplayAspectRatio::R16_10:
+    case DisplayAspectRatio::R16_10:
-        Sx = ((((s64(result) * s64(REGS.IR1)) * s64(5)) / s64(6)) + s64(REGS.OFX));
+      Sx = ((((s64(result) * s64(REGS.IR1)) * s64(5)) / s64(6)) + s64(REGS.OFX));
-        break;
+      break;
 
-      case DisplayAspectRatio::R19_9:
+    case DisplayAspectRatio::R19_9:
-        Sx = ((((s64(result) * s64(REGS.IR1)) * s64(12)) / s64(19)) + s64(REGS.OFX));
+      Sx = ((((s64(result) * s64(REGS.IR1)) * s64(12)) / s64(19)) + s64(REGS.OFX));
-        break;
+      break;
 
-      case DisplayAspectRatio::R20_9:
+    case DisplayAspectRatio::R20_9:
-        Sx = ((((s64(result) * s64(REGS.IR1)) * s64(3)) / s64(5)) + s64(REGS.OFX));
+      Sx = ((((s64(result) * s64(REGS.IR1)) * s64(3)) / s64(5)) + s64(REGS.OFX));
-        break;
+      break;
 
-      case DisplayAspectRatio::R21_9:
+    case DisplayAspectRatio::R21_9:
-        Sx = ((((s64(result) * s64(REGS.IR1)) * s64(9)) / s64(16)) + s64(REGS.OFX));
+      Sx = ((((s64(result) * s64(REGS.IR1)) * s64(9)) / s64(16)) + s64(REGS.OFX));
-        break;
+      break;
 
-      case DisplayAspectRatio::R32_9:
+    case DisplayAspectRatio::R32_9:
-        Sx = ((((s64(result) * s64(REGS.IR1)) * s64(3)) / s64(8)) + s64(REGS.OFX));
+      Sx = ((((s64(result) * s64(REGS.IR1)) * s64(3)) / s64(8)) + s64(REGS.OFX));
-        break;
+      break;
 
-      case DisplayAspectRatio::R8_7:
+    case DisplayAspectRatio::R8_7:
-        Sx = ((((s64(result) * s64(REGS.IR1)) * s64(7)) / s64(6)) + s64(REGS.OFX));
+      Sx = ((((s64(result) * s64(REGS.IR1)) * s64(7)) / s64(6)) + s64(REGS.OFX));
-        break;
+      break;
 
-      case DisplayAspectRatio::R5_4:
+    case DisplayAspectRatio::R5_4:
-        Sx = ((((s64(result) * s64(REGS.IR1)) * s64(16)) / s64(15)) + s64(REGS.OFX));
+      Sx = ((((s64(result) * s64(REGS.IR1)) * s64(16)) / s64(15)) + s64(REGS.OFX));
-        break;
+      break;
 
-      case DisplayAspectRatio::R3_2:
+    case DisplayAspectRatio::R3_2:
-        Sx = ((((s64(result) * s64(REGS.IR1)) * s64(8)) / s64(9)) + s64(REGS.OFX));
+      Sx = ((((s64(result) * s64(REGS.IR1)) * s64(8)) / s64(9)) + s64(REGS.OFX));
-        break;
+      break;
 
-      case DisplayAspectRatio::R2_1:
+    case DisplayAspectRatio::R2_1:
-        Sx = ((((s64(result) * s64(REGS.IR1)) * s64(2)) / s64(3)) + s64(REGS.OFX));
+      Sx = ((((s64(result) * s64(REGS.IR1)) * s64(2)) / s64(3)) + s64(REGS.OFX));
-        break;
+      break;
 
-      case DisplayAspectRatio::R1_1:
+    case DisplayAspectRatio::R1_1:
-        Sx = ((((s64(result) * s64(REGS.IR1)) * s64(7)) / s64(6)) + s64(REGS.OFX));
+      Sx = ((((s64(result) * s64(REGS.IR1)) * s64(7)) / s64(6)) + s64(REGS.OFX));
-        break;
+      break;
 
-      case DisplayAspectRatio::Auto:
+    case DisplayAspectRatio::Custom:
-      case DisplayAspectRatio::R4_3:
+    case DisplayAspectRatio::MatchWindow:
-      case DisplayAspectRatio::PAR1_1:
+      Sx = ((((s64(result) * s64(REGS.IR1)) * s64(s_custom_aspect_ratio_numerator)) /
-      default:
+             s64(s_custom_aspect_ratio_denominator)) +
-        Sx = (s64(result) * s64(REGS.IR1) + s64(REGS.OFX));
+            s64(REGS.OFX));
-        break;
+      break;
-    }
+
-  }
+    case DisplayAspectRatio::Auto:
-  else
+    case DisplayAspectRatio::R4_3:
-  {
+    case DisplayAspectRatio::PAR1_1:
-    Sx = (s64(result) * s64(REGS.IR1) + s64(REGS.OFX));
+    default:
+      Sx = (s64(result) * s64(REGS.IR1) + s64(REGS.OFX));
+      break;
   }
 
   const s64 Sy = s64(result) * s64(REGS.IR2) + s64(REGS.OFY);
@@ -713,70 +770,68 @@ static void RTPS(const s16 V[3], u8 shift, bool lm, bool last)
     const float precise_h_div_sz = float(REGS.H) / precise_z;
     const float fofx = float(REGS.OFX) / float(1 << 16);
     const float fofy = float(REGS.OFY) / float(1 << 16);
-    float precise_x;
+    float precise_x = precise_ir1 * precise_h_div_sz;
-    if (g_settings.gpu_widescreen_hack)
+
+    switch (s_aspect_ratio)
     {
-      precise_x = precise_ir1 * precise_h_div_sz;
+      case DisplayAspectRatio::R16_9:
-      const DisplayAspectRatio ar = g_settings.display_aspect_ratio;
+        precise_x = (precise_x * 3.0f) / 4.0f;
-      switch (ar)
+        break;
-      {
-        case DisplayAspectRatio::R16_9:
-          precise_x = (precise_x * 3.0f) / 4.0f;
-          break;
 
-        case DisplayAspectRatio::R16_10:
+      case DisplayAspectRatio::R16_10:
-          precise_x = (precise_x * 5.0f) / 6.0f;
+        precise_x = (precise_x * 5.0f) / 6.0f;
-          break;
+        break;
 
-        case DisplayAspectRatio::R19_9:
+      case DisplayAspectRatio::R19_9:
-          precise_x = (precise_x * 12.0f) / 19.0f;
+        precise_x = (precise_x * 12.0f) / 19.0f;
-          break;
+        break;
 
-        case DisplayAspectRatio::R20_9:
+      case DisplayAspectRatio::R20_9:
-          precise_x = (precise_x * 3.0f) / 5.0f;
+        precise_x = (precise_x * 3.0f) / 5.0f;
-          break;
+        break;
 
-        case DisplayAspectRatio::R21_9:
+      case DisplayAspectRatio::R21_9:
-          precise_x = (precise_x * 9.0f) / 16.0f;
+        precise_x = (precise_x * 9.0f) / 16.0f;
-          break;
+        break;
 
-        case DisplayAspectRatio::R32_9:
+      case DisplayAspectRatio::R32_9:
-          precise_x = (precise_x * 3.0f) / 8.0f;
+        precise_x = (precise_x * 3.0f) / 8.0f;
-          break;
+        break;
 
-        case DisplayAspectRatio::R8_7:
+      case DisplayAspectRatio::R8_7:
-          precise_x = (precise_x * 7.0f) / 6.0f;
+        precise_x = (precise_x * 7.0f) / 6.0f;
-          break;
+        break;
 
-        case DisplayAspectRatio::R5_4:
+      case DisplayAspectRatio::R5_4:
-          precise_x = (precise_x * 16.0f) / 15.0f;
+        precise_x = (precise_x * 16.0f) / 15.0f;
-          break;
+        break;
 
-        case DisplayAspectRatio::R3_2:
+      case DisplayAspectRatio::R3_2:
-          precise_x = (precise_x * 8.0f) / 9.0f;
+        precise_x = (precise_x * 8.0f) / 9.0f;
-          break;
+        break;
 
-        case DisplayAspectRatio::R2_1:
+      case DisplayAspectRatio::R2_1:
-          precise_x = (precise_x * 2.0f) / 3.0f;
+        precise_x = (precise_x * 2.0f) / 3.0f;
-          break;
+        break;
 
-        case DisplayAspectRatio::R1_1:
+      case DisplayAspectRatio::R1_1:
-          precise_x = (precise_x * 7.0f) / 6.0f;
+        precise_x = (precise_x * 7.0f) / 6.0f;
-          break;
+        break;
 
-        case DisplayAspectRatio::Auto:
+      case DisplayAspectRatio::MatchWindow:
-        case DisplayAspectRatio::R4_3:
+      case DisplayAspectRatio::Custom:
-        case DisplayAspectRatio::PAR1_1:
+        precise_x = precise_x * s_custom_aspect_ratio_f;
-        default:
+        break;
-          break;
+
-      }
+      case DisplayAspectRatio::Auto:
-      precise_x += fofx;
+      case DisplayAspectRatio::R4_3:
-    }
+      case DisplayAspectRatio::PAR1_1:
-    else
+      default:
-    {
+        break;
-      precise_x = fofx + (precise_ir1 * precise_h_div_sz);
     }
 
+    precise_x += fofx;
+
     float precise_y = fofy + (precise_ir2 * precise_h_div_sz);
 
     precise_x = std::clamp<float>(precise_x, -1024.0f, 1023.0f);

src/core/gte.h

@@ -8,6 +8,7 @@ namespace GTE {
 void Initialize();
 void Reset();
 bool DoState(StateWrapper& sw);
+void UpdateAspectRatio();
 
 // control registers are offset by +32
 u32 ReadRegister(u32 index);

src/core/host_interface.cpp

@@ -533,6 +533,8 @@ void HostInterface::SetDefaultSettings(SettingsInterface& si)
   si.SetIntValue("Display", "LineEndOffset", 0);
   si.SetStringValue("Display", "AspectRatio",
                     Settings::GetDisplayAspectRatioName(Settings::DEFAULT_DISPLAY_ASPECT_RATIO));
+  si.SetIntValue("Display", "CustomAspectRatioNumerator", 4);
+  si.GetIntValue("Display", "CustomAspectRatioDenominator", 3);
   si.SetBoolValue("Display", "Force4_3For24Bit", false);
   si.SetBoolValue("Display", "LinearFiltering", true);
   si.SetBoolValue("Display", "IntegerScaling", false);
@@ -803,6 +805,14 @@ void HostInterface::CheckForSettingsChanges(const Settings& old_settings)
       g_gpu->UpdateSettings();
     }
 
+    if (g_settings.display_aspect_ratio != old_settings.display_aspect_ratio ||
+        (g_settings.display_aspect_ratio == DisplayAspectRatio::Custom &&
+         (g_settings.display_aspect_ratio_custom_numerator != old_settings.display_aspect_ratio_custom_numerator ||
+          g_settings.display_aspect_ratio_custom_denominator != old_settings.display_aspect_ratio_custom_denominator)))
+    {
+      GTE::UpdateAspectRatio();
+    }
+
     if (g_settings.gpu_pgxp_enable != old_settings.gpu_pgxp_enable ||
         (g_settings.gpu_pgxp_enable && (g_settings.gpu_pgxp_culling != old_settings.gpu_pgxp_culling ||
                                         g_settings.gpu_pgxp_cpu != old_settings.gpu_pgxp_cpu)))
@@ -899,6 +909,15 @@ void HostInterface::SetUserDirectoryToProgramDirectory()
   m_user_directory = program_directory;
 }
 
+void HostInterface::OnHostDisplayResized()
+{
+  if (System::IsValid())
+  {
+    if (g_settings.display_aspect_ratio == DisplayAspectRatio::MatchWindow)
+      GTE::UpdateAspectRatio();
+  }
+}
+
 std::string HostInterface::GetUserDirectoryRelativePath(const char* format, ...) const
 {
   std::va_list ap;

src/core/host_interface.h

@@ -183,6 +183,9 @@ protected:
   /// Enables "relative" mouse mode, locking the cursor position and returning relative coordinates.
   virtual void SetMouseMode(bool relative, bool hide_cursor);
 
+  /// Call when host display size changes, use with "match display" aspect ratio setting.
+  virtual void OnHostDisplayResized();
+
   /// Sets the user directory to the program directory, i.e. "portable mode".
   void SetUserDirectoryToProgramDirectory();
 

src/core/settings.cpp

@@ -3,6 +3,7 @@
 #include "common/file_system.h"
 #include "common/make_array.h"
 #include "common/string_util.h"
+#include "host_display.h"
 #include "host_interface.h"
 #include <algorithm>
 #include <array>
@@ -222,6 +223,10 @@ void Settings::Load(SettingsInterface& si)
     ParseDisplayAspectRatio(
       si.GetStringValue("Display", "AspectRatio", GetDisplayAspectRatioName(DEFAULT_DISPLAY_ASPECT_RATIO)).c_str())
       .value_or(DEFAULT_DISPLAY_ASPECT_RATIO);
+  display_aspect_ratio_custom_numerator = static_cast<u16>(
+    std::clamp<int>(si.GetIntValue("Display", "CustomAspectRatioNumerator", 4), 1, std::numeric_limits<u16>::max()));
+  display_aspect_ratio_custom_denominator = static_cast<u16>(
+    std::clamp<int>(si.GetIntValue("Display", "CustomAspectRatioDenominator", 3), 1, std::numeric_limits<u16>::max()));
   display_force_4_3_for_24bit = si.GetBoolValue("Display", "Force4_3For24Bit", false);
   display_active_start_offset = static_cast<s16>(si.GetIntValue("Display", "ActiveStartOffset", 0));
   display_active_end_offset = static_cast<s16>(si.GetIntValue("Display", "ActiveEndOffset", 0));
@@ -395,6 +400,8 @@ void Settings::Save(SettingsInterface& si) const
   si.SetIntValue("Display", "LineEndOffset", display_line_end_offset);
   si.SetBoolValue("Display", "Force4_3For24Bit", display_force_4_3_for_24bit);
   si.SetStringValue("Display", "AspectRatio", GetDisplayAspectRatioName(display_aspect_ratio));
+  si.SetIntValue("Display", "CustomAspectRatioNumerator", display_aspect_ratio_custom_numerator);
+  si.GetIntValue("Display", "CustomAspectRatioDenominator", display_aspect_ratio_custom_denominator);
   si.SetBoolValue("Display", "LinearFiltering", display_linear_filtering);
   si.SetBoolValue("Display", "IntegerScaling", display_integer_scaling);
   si.SetBoolValue("Display", "Stretch", display_stretch);
@@ -767,12 +774,12 @@ const char* Settings::GetDisplayCropModeDisplayName(DisplayCropMode crop_mode)
   return s_display_crop_mode_display_names[static_cast<int>(crop_mode)];
 }
 
-static std::array<const char*, 14> s_display_aspect_ratio_names = {
+static std::array<const char*, 16> s_display_aspect_ratio_names = {
-  {TRANSLATABLE("DisplayAspectRatio", "Auto (Game Native)"), "4:3", "16:9", "16:10", "19:9", "20:9", "21:9", "32:9",
+  {TRANSLATABLE("DisplayAspectRatio", "Auto (Game Native)"), "Auto (Match Window)", "Custom", "4:3", "16:9", "16:10",
-   "8:7", "5:4", "3:2", "2:1 (VRAM 1:1)", "1:1", "PAR 1:1"}};
+   "19:9", "20:9", "21:9", "32:9", "8:7", "5:4", "3:2", "2:1 (VRAM 1:1)", "1:1", "PAR 1:1"}};
-static constexpr std::array<float, 14> s_display_aspect_ratio_values = {
+static constexpr std::array<float, 16> s_display_aspect_ratio_values = {
-  {-1.0f, 4.0f / 3.0f, 16.0f / 9.0f, 16.0f / 10.0f, 19.0f / 9.0f, 20.0f / 9.0f, 64.0f / 27.0f, 32.0f / 9.0f,
+  {-1.0f, -1.0f, -1.0f, 4.0f / 3.0f, 16.0f / 9.0f, 16.0f / 10.0f, 19.0f / 9.0f, 20.0f / 9.0f, 64.0f / 27.0f,
-   8.0f / 7.0f, 5.0f / 4.0f, 3.0f / 2.0f, 2.0f / 1.0f, 1.0f, -1.0f}};
+   32.0f / 9.0f, 8.0f / 7.0f, 5.0f / 4.0f, 3.0f / 2.0f, 2.0f / 1.0f, 1.0f, -1.0f}};
 
 std::optional<DisplayAspectRatio> Settings::ParseDisplayAspectRatio(const char* str)
 {
@@ -793,9 +800,32 @@ const char* Settings::GetDisplayAspectRatioName(DisplayAspectRatio ar)
   return s_display_aspect_ratio_names[static_cast<int>(ar)];
 }
 
-float Settings::GetDisplayAspectRatioValue(DisplayAspectRatio ar)
+float Settings::GetDisplayAspectRatioValue() const
 {
-  return s_display_aspect_ratio_values[static_cast<int>(ar)];
+  switch (display_aspect_ratio)
+  {
+    case DisplayAspectRatio::MatchWindow:
+    {
+      const HostDisplay* display = g_host_interface->GetDisplay();
+      if (!display)
+        return s_display_aspect_ratio_values[static_cast<int>(DEFAULT_DISPLAY_ASPECT_RATIO)];
+
+      const u32 width = display->GetWindowWidth();
+      const u32 height = display->GetWindowHeight() - display->GetDisplayTopMargin();
+      return static_cast<float>(width) / static_cast<float>(height);
+    }
+
+    case DisplayAspectRatio::Custom:
+    {
+      return static_cast<float>(display_aspect_ratio_custom_numerator) /
+             static_cast<float>(display_aspect_ratio_custom_denominator);
+    }
+
+    default:
+    {
+      return s_display_aspect_ratio_values[static_cast<int>(display_aspect_ratio)];
+    }
+  }
 }
 
 static std::array<const char*, 3> s_audio_backend_names = {{

src/core/settings.h

@@ -127,6 +127,8 @@ struct Settings
   bool gpu_pgxp_depth_buffer = false;
   DisplayCropMode display_crop_mode = DisplayCropMode::None;
   DisplayAspectRatio display_aspect_ratio = DisplayAspectRatio::Auto;
+  u16 display_aspect_ratio_custom_numerator = 0;
+  u16 display_aspect_ratio_custom_denominator = 0;
   s16 display_active_start_offset = 0;
   s16 display_active_end_offset = 0;
   s8 display_line_start_offset = 0;
@@ -256,6 +258,8 @@ struct Settings
     return audio_output_muted ? 0 : (fast_forwarding ? audio_fast_forward_volume : audio_output_volume);
   }
 
+  float GetDisplayAspectRatioValue() const;
+
   bool HasAnyPerGameMemoryCards() const;
 
   static void CPUOverclockPercentToFraction(u32 percent, u32* numerator, u32* denominator);
@@ -316,7 +320,6 @@ struct Settings
 
   static std::optional<DisplayAspectRatio> ParseDisplayAspectRatio(const char* str);
   static const char* GetDisplayAspectRatioName(DisplayAspectRatio ar);
-  static float GetDisplayAspectRatioValue(DisplayAspectRatio ar);
 
   static std::optional<AudioBackend> ParseAudioBackend(const char* str);
   static const char* GetAudioBackendName(AudioBackend backend);

src/core/types.h

@@ -94,6 +94,8 @@ enum class DisplayCropMode : u8
 enum class DisplayAspectRatio : u8
 {
   Auto,
+  MatchWindow,
+  Custom,
   R4_3,
   R16_9,
   R16_10,

src/duckstation-qt/displaysettingswidget.cpp

@@ -25,6 +25,10 @@ DisplaySettingsWidget::DisplaySettingsWidget(QtHostInterface* host_interface, QW
   SettingWidgetBinder::BindWidgetToEnumSetting(m_host_interface, m_ui.displayAspectRatio, "Display", "AspectRatio",
                                                &Settings::ParseDisplayAspectRatio, &Settings::GetDisplayAspectRatioName,
                                                Settings::DEFAULT_DISPLAY_ASPECT_RATIO);
+  SettingWidgetBinder::BindWidgetToIntSetting(m_host_interface, m_ui.customAspectRatioNumerator, "Display",
+                                              "CustomAspectRatioNumerator", 1);
+  SettingWidgetBinder::BindWidgetToIntSetting(m_host_interface, m_ui.customAspectRatioDenominator, "Display",
+                                              "CustomAspectRatioDenominator", 1);
   SettingWidgetBinder::BindWidgetToEnumSetting(m_host_interface, m_ui.displayCropMode, "Display", "CropMode",
                                                &Settings::ParseDisplayCropMode, &Settings::GetDisplayCropModeName,
                                                Settings::DEFAULT_DISPLAY_CROP_MODE);
@@ -59,10 +63,13 @@ DisplaySettingsWidget::DisplaySettingsWidget(QtHostInterface* host_interface, QW
           &DisplaySettingsWidget::onGPUAdapterIndexChanged);
   connect(m_ui.fullscreenMode, QOverload<int>::of(&QComboBox::currentIndexChanged), this,
           &DisplaySettingsWidget::onGPUFullscreenModeIndexChanged);
+  connect(m_ui.displayAspectRatio, QOverload<int>::of(&QComboBox::currentIndexChanged), this,
+          &DisplaySettingsWidget::onAspectRatioChanged);
   connect(m_ui.displayIntegerScaling, &QCheckBox::stateChanged, this,
           &DisplaySettingsWidget::onIntegerFilteringChanged);
   populateGPUAdaptersAndResolutions();
   onIntegerFilteringChanged();
+  onAspectRatioChanged();
 
   dialog->registerWidgetHelp(
     m_ui.renderer, tr("Renderer"),
@@ -283,3 +290,13 @@ void DisplaySettingsWidget::onIntegerFilteringChanged()
   m_ui.displayLinearFiltering->setEnabled(!m_ui.displayIntegerScaling->isChecked());
   m_ui.displayStretch->setEnabled(!m_ui.displayIntegerScaling->isChecked());
 }
+
+void DisplaySettingsWidget::onAspectRatioChanged()
+{
+  const bool is_custom =
+    static_cast<DisplayAspectRatio>(m_ui.displayAspectRatio->currentIndex()) == DisplayAspectRatio::Custom;
+
+  m_ui.customAspectRatioNumerator->setVisible(is_custom);
+  m_ui.customAspectRatioDenominator->setVisible(is_custom);
+  m_ui.customAspectRatioSeparator->setVisible(is_custom);
+}

src/duckstation-qt/displaysettingswidget.h

@@ -21,6 +21,7 @@ private Q_SLOTS:
   void onGPUAdapterIndexChanged();
   void onGPUFullscreenModeIndexChanged();
   void onIntegerFilteringChanged();
+  void onAspectRatioChanged();
 
 private:
   void setupAdditionalUi();

src/duckstation-qt/displaysettingswidget.ui

@@ -111,7 +111,38 @@
        </widget>
       </item>
       <item row="0" column="1">
-       <widget class="QComboBox" name="displayAspectRatio"/>
+       <layout class="QHBoxLayout" name="horizontalLayout" stretch="1,0,0,0">
+        <item>
+         <widget class="QComboBox" name="displayAspectRatio"/>
+        </item>
+        <item>
+         <widget class="QSpinBox" name="customAspectRatioNumerator">
+          <property name="minimum">
+           <number>1</number>
+          </property>
+          <property name="maximum">
+           <number>9999</number>
+          </property>
+         </widget>
+        </item>
+        <item>
+         <widget class="QLabel" name="customAspectRatioSeparator">
+          <property name="text">
+           <string>:</string>
+          </property>
+         </widget>
+        </item>
+        <item>
+         <widget class="QSpinBox" name="customAspectRatioDenominator">
+          <property name="minimum">
+           <number>1</number>
+          </property>
+          <property name="maximum">
+           <number>9999</number>
+          </property>
+         </widget>
+        </item>
+       </layout>
       </item>
       <item row="1" column="0">
        <widget class="QLabel" name="label_3">

src/frontend-common/common_host_interface.cpp

@@ -575,6 +575,8 @@ void CommonHostInterface::OnHostDisplayResized()
   const u32 new_height = m_display ? m_display->GetWindowHeight() : 0;
   const float new_scale = m_display ? m_display->GetWindowScale() : 1.0f;
 
+  HostInterface::OnHostDisplayResized();
+
   ImGui::GetIO().DisplaySize.x = static_cast<float>(new_width);
   ImGui::GetIO().DisplaySize.y = static_cast<float>(new_height);
 

src/frontend-common/common_host_interface.h

@@ -412,13 +412,13 @@ protected:
   void UpdateSpeedLimiterState();
 
   void RecreateSystem() override;
+  void OnHostDisplayResized() override;
 
   void ApplyGameSettings(bool display_osd_messages);
   void ApplyControllerCompatibilitySettings(u64 controller_mask, bool display_osd_messages);
 
   bool CreateHostDisplayResources();
   void ReleaseHostDisplayResources();
-  void OnHostDisplayResized();
 
   virtual void DrawImGuiWindows();