Fix game crashing when no displays are connected

Author: Susko3

osu.Framework/Platform/SDL2/SDL2Window_Windowing.cs

@@ -27,7 +27,7 @@ private void setupWindowing(FrameworkConfigManager config)
                 ScheduleCommand(() => SDL_SetHint(SDL_HINT_VIDEO_MINIMIZE_ON_FOCUS_LOSS, e.NewValue ? "1" : "0"));
             }, true);
 
-            fetchDisplays();
+            fetchDisplays(generateFakeDisplayIfEmpty: true);
 
             DisplaysChanged += _ => CurrentDisplayBindable.Default = PrimaryDisplay;
             CurrentDisplayBindable.Default = PrimaryDisplay;
@@ -292,6 +292,8 @@ public WindowState WindowState
         // ReSharper disable once UnusedParameter.Local
         private void handleDisplayEvent(SDL_DisplayEvent evtDisplay) => fetchDisplays();
 
+        private static bool fetchDisplayModes => RuntimeInfo.IsDesktop;
+
         /// <summary>
         /// Updates <see cref="Displays"/> with the latest display information reported by SDL.
         /// </summary>
@@ -300,10 +302,36 @@ public WindowState WindowState
         /// <see cref="currentDisplay"/> /
         /// <see cref="CurrentDisplayBindable"/>.
         /// </remarks>
-        private void fetchDisplays()
+        private void fetchDisplays(bool generateFakeDisplayIfEmpty = false)
         {
-            Displays = getSDLDisplays();
-            DisplaysChanged?.Invoke(Displays);
+            var newDisplays = getSDLDisplays();
+
+            if (generateFakeDisplayIfEmpty && newDisplays.Length == 0)
+            {
+                Logger.Log("Got zero displays from SDL during startup. Generating a fake display so we have a valid one to prevent crashes.");
+
+                newDisplays =
+                [
+                    new Display(0,
+                        "Fake osu!framework display",
+                        new Rectangle(0, 0, 1920, 1080),
+                        new Rectangle(0, 0, 1920, 1080),
+                        fetchDisplayModes ? [new DisplayMode("SDL_PIXELFORMAT_XRGB8888", new Size(1920, 1080), 32, 60f, 0)] : [])
+                ];
+            }
+
+            if (newDisplays.Length > 0)
+            {
+                Displays = newDisplays;
+                DisplaysChanged?.Invoke(newDisplays);
+            }
+            else
+            {
+                // keep Displays stale if zero displays are currently detected
+                Logger.Log("Got zero displays from SDL, ignoring.");
+            }
+
+            Debug.Assert(Displays.Length > 0);
         }
 
         /// <summary>
@@ -328,7 +356,7 @@ private static ImmutableArray<Display> getSDLDisplays()
         {
             int numDisplays = SDL_GetNumVideoDisplays();
 
-            if (numDisplays <= 0)
+            if (numDisplays < 0)
                 throw new InvalidOperationException($"Failed to get number of SDL displays. Return code: {numDisplays}. SDL Error: {SDL_GetError()}");
 
             var builder = ImmutableArray.CreateBuilder<Display>(numDisplays);
@@ -363,7 +391,7 @@ private static bool tryGetDisplayFromSDL(int displayIndex, [NotNullWhen(true)] o
 
             DisplayMode[] displayModes = Array.Empty<DisplayMode>();
 
-            if (RuntimeInfo.IsDesktop)
+            if (fetchDisplayModes)
             {
                 int numModes = SDL_GetNumDisplayModes(displayIndex);
 

osu.Framework/Platform/SDL3/SDL3Window_Windowing.cs

@@ -28,7 +28,7 @@ private unsafe void setupWindowing(FrameworkConfigManager config)
                 ScheduleCommand(() => SDL_SetHint(SDL_HINT_VIDEO_MINIMIZE_ON_FOCUS_LOSS, e.NewValue ? "1"u8 : "0"u8).LogErrorIfFailed());
             }, true);
 
-            fetchDisplays();
+            fetchDisplays(generateFakeDisplayIfEmpty: true);
 
             DisplaysChanged += _ => CurrentDisplayBindable.Default = PrimaryDisplay;
             CurrentDisplayBindable.Default = PrimaryDisplay;
@@ -296,6 +296,8 @@ public WindowState WindowState
         // ReSharper disable once UnusedParameter.Local
         private void handleDisplayEvent(SDL_DisplayEvent evtDisplay) => fetchDisplays();
 
+        private static bool fetchDisplayModes => RuntimeInfo.IsDesktop;
+
         /// <summary>
         /// Updates <see cref="Displays"/> with the latest display information reported by SDL.
         /// </summary>
@@ -304,10 +306,36 @@ public WindowState WindowState
         /// <see cref="currentDisplay"/> /
         /// <see cref="CurrentDisplayBindable"/>.
         /// </remarks>
-        private void fetchDisplays()
+        private void fetchDisplays(bool generateFakeDisplayIfEmpty = false)
         {
-            Displays = getSDLDisplays();
-            DisplaysChanged?.Invoke(Displays);
+            var newDisplays = getSDLDisplays();
+
+            if (generateFakeDisplayIfEmpty && newDisplays.Length == 0)
+            {
+                Logger.Log("Got zero displays from SDL during startup. Generating a fake display so we have a valid one to prevent crashes.");
+
+                newDisplays =
+                [
+                    new Display(0,
+                        "Fake osu!framework display",
+                        new Rectangle(0, 0, 1920, 1080),
+                        new Rectangle(0, 0, 1920, 1080),
+                        fetchDisplayModes ? [new DisplayMode("SDL_PIXELFORMAT_XRGB8888", new Size(1920, 1080), 32, 60f, 0)] : [])
+                ];
+            }
+
+            if (newDisplays.Length > 0)
+            {
+                Displays = newDisplays;
+                DisplaysChanged?.Invoke(newDisplays);
+            }
+            else
+            {
+                // keep Displays stale if zero displays are currently detected
+                Logger.Log("Got zero displays from SDL, ignoring.");
+            }
+
+            Debug.Assert(Displays.Length > 0);
         }
 
         /// <summary>
@@ -371,7 +399,7 @@ private static unsafe bool tryGetDisplayFromSDL(int displayIndex, SDL_DisplayID
 
             DisplayMode[] displayModes = Array.Empty<DisplayMode>();
 
-            if (RuntimeInfo.IsDesktop)
+            if (fetchDisplayModes)
             {
                 using var modes = SDL_GetFullscreenDisplayModes(displayID);