Attempt to fix Linux headless Test run with SDL

.github/workflows/tests.yml

@@ -38,7 +38,7 @@ jobs:
         dotnet msbuild Source/Tools/Flax.Build.Tests/Flax.Build.Tests.csproj /m /t:Restore,Build /p:Configuration=Debug /p:Platform=AnyCPU /nologo
     - name: Test
       run: |
-        ${GITHUB_WORKSPACE}/Binaries/Editor/Linux/Development/FlaxTests
+        ${GITHUB_WORKSPACE}/Binaries/Editor/Linux/Development/FlaxTests -headless
         dotnet test -f net8.0 Binaries/Tests/Flax.Build.Tests.dll
         cp Binaries/Editor/Linux/Development/FlaxEngine.CSharp.dll Binaries/Tests
         cp Binaries/Editor/Linux/Development/FlaxEngine.CSharp.runtimeconfig.json Binaries/Tests
@@ -73,7 +73,7 @@ jobs:
       shell: pwsh
       run: |
         $ErrorActionPreference = "Stop"
-        .\Binaries\Editor\Win64\Development\FlaxTests.exe
+        .\Binaries\Editor\Win64\Development\FlaxTests.exe -headless
         if(!$?) { Write-Host "Tests failed with exit code $LastExitCode" -ForegroundColor Red; Exit $LastExitCode }
         dotnet test -f net8.0 Binaries\Tests\Flax.Build.Tests.dll
         xcopy /y Binaries\Editor\Win64\Development\FlaxEngine.CSharp.dll Binaries\Tests

Source/Editor/Editor.cs

@@ -407,7 +407,6 @@ namespace FlaxEditor
 
             // Close splash and show main window
             CloseSplashScreen();
-            Assert.IsNotNull(Windows.MainWindow);
             if (!IsHeadlessMode)
             {
                 Windows.MainWindow.Show();

Source/Editor/Modules/UIModule.cs

@@ -481,6 +481,8 @@ namespace FlaxEditor.Modules
         /// <inheritdoc />
         public override void OnInit()
         {
+            if (Editor.IsHeadlessMode)
+                return;
             Editor.Windows.MainWindowClosing += OnMainWindowClosing;
             var mainWindow = Editor.Windows.MainWindow.GUI;
 

Source/Editor/Modules/WindowsModule.cs

@@ -758,36 +758,39 @@ namespace FlaxEditor.Modules
 
             _windowsLayoutPath = StringUtils.CombinePaths(Globals.ProjectCacheFolder, "WindowsLayout.xml");
 
-            // Create main window
-            var settings = CreateWindowSettings.Default;
-            settings.Title = "Flax Editor";
-            settings.Size = Platform.DesktopSize * 0.75f;
-            settings.MinimumSize = new Float2(200, 150);
-            settings.StartPosition = WindowStartPosition.CenterScreen;
-            settings.ShowAfterFirstPaint = true;
-            
-            if (Utilities.Utils.UseCustomWindowDecorations(isMainWindow: true))
+            if (!Editor.IsHeadlessMode)
             {
-                settings.HasBorder = false;
+                // Create main window
+                var settings = CreateWindowSettings.Default;
+                settings.Title = "Flax Editor";
+                settings.Size = Platform.DesktopSize * 0.75f;
+                settings.MinimumSize = new Float2(200, 150);
+                settings.StartPosition = WindowStartPosition.CenterScreen;
+                settings.ShowAfterFirstPaint = true;
+
+                if (Utilities.Utils.UseCustomWindowDecorations(isMainWindow: true))
+                {
+                    settings.HasBorder = false;
 #if PLATFORM_WINDOWS && !PLATFORM_SDL
-                // Skip OS sizing frame and implement it using LeftButtonHit
-                settings.HasSizingFrame = false;
+                    // Skip OS sizing frame and implement it using LeftButtonHit
+                    settings.HasSizingFrame = false;
 #endif
-            }
+                }
 #if PLATFORM_LINUX && !PLATFORM_SDL
-            settings.HasBorder = false;
+                settings.HasBorder = false;
 #endif
-            MainWindow = Platform.CreateWindow(ref settings);
-            if (MainWindow == null)
-            {
-                Editor.LogError("Failed to create editor main window!");
-                return;
-            }
-            UpdateWindowTitle();
+                MainWindow = Platform.CreateWindow(ref settings);
+                if (MainWindow == null)
+                {
+                    Editor.LogError("Failed to create editor main window!");
+                    return;
+                }
+                UpdateWindowTitle();
 
-            // Link for main window events
-            MainWindow.Closing += MainWindow_OnClosing;
-            MainWindow.Closed += MainWindow_OnClosed;
+                // Link for main window events
+                MainWindow.Closing += MainWindow_OnClosing;
+                MainWindow.Closed += MainWindow_OnClosed;
+            }
 
             // Create default editor windows
             ContentWin = new ContentWindow(Editor);

Source/Engine/Platform/SDL/SDLPlatform.cpp

@@ -23,10 +23,6 @@
 #include <SDL3/SDL_system.h>
 #include <SDL3/SDL_version.h>
 
-#if PLATFORM_LINUX
-#include "Engine/Engine/CommandLine.h"
-#endif
-
 #define DefaultDPI 96
 
 namespace SDLImpl
@@ -106,10 +102,16 @@ bool SDLPlatform::Init()
     SDL_SetHint(SDL_HINT_VIDEO_ALLOW_SCREENSAVER, "1"); // Allow screensaver in Editor when idle
 #endif
 
+    SDL_InitFlags initFlags = SDL_INIT_VIDEO | SDL_INIT_GAMEPAD;
+#if PLATFORM_HAS_HEADLESS_MODE
+    if (CommandLine::Options.Headless.GetValue())
+        initFlags &= ~SDL_INIT_VIDEO;
+#endif
+
     //if (InitInternal())
     //    return true;
 
-    if (!SDL_InitSubSystem(SDL_INIT_VIDEO | SDL_INIT_GAMEPAD))
+    if (!SDL_InitSubSystem(initFlags))
         Platform::Fatal(String::Format(TEXT("Failed to initialize SDL: {0}."), String(SDL_GetError())));
 
 #if PLATFORM_LINUX || PLATFORM_WEB