Fix macOS/Linux fullscreen Spaces and disable live window resize (#185)

* Fix macOS fullscreen Spaces and disable manual window resize

* Pass nullptr to SDL_SetWindowFullscreenMode to request Desktop Fullscreen (Spaces) instead of Exclusive mode, allowing trackpad gestures to work.
* Remove SDL_WINDOW_RESIZABLE to prevent live window resizing (which distorts the DXVK swapchain) and to disable the native macOS green maximize button in windowed mode.

* Restore SDL_WINDOW_RESIZABLE

* Allows live window resizing and native maximize/minimize buttons to work as expected in windowed mode (-win).
* Fullscreen Spaces support remains active due to the nullptr argument in W3DDisplay.

Author: fbraz3

Generals/Code/GameEngineDevice/Source/W3DDevice/GameClient/W3DDisplay.cpp

@@ -516,8 +516,9 @@ static void SDL3_ApplyWindowModeForRenderConfig(Bool windowed, Int renderWidth,
 		SDL_DisplayID displayId = SDL_GetDisplayForWindow(TheSDL3Window);
 		const SDL_DisplayMode* mode = SDL_GetCurrentDisplayMode(displayId);
 		if (mode) {
-			if (!SDL_SetWindowFullscreenMode(TheSDL3Window, mode)) {
-				fprintf(stderr, "WARNING: SDL_SetWindowFullscreenMode(native) failed: %s\n", SDL_GetError());
+			// GeneralsX @bugfix MrMeeseeks 02/07/2026 Pass nullptr to request Desktop Fullscreen (Spaces) instead of Exclusive mode.
+			if (!SDL_SetWindowFullscreenMode(TheSDL3Window, nullptr)) {
+				fprintf(stderr, "WARNING: SDL_SetWindowFullscreenMode(nullptr) failed: %s\n", SDL_GetError());
 			}
 		}
 		else {

GeneralsMD/Code/GameEngineDevice/Source/W3DDevice/GameClient/W3DDisplay.cpp

@@ -567,8 +567,9 @@ static void SDL3_ApplyWindowModeForRenderConfig(Bool windowed, Int renderWidth,
 		SDL_DisplayID displayId = SDL_GetDisplayForWindow(TheSDL3Window);
 		const SDL_DisplayMode* mode = SDL_GetCurrentDisplayMode(displayId);
 		if (mode) {
-			if (!SDL_SetWindowFullscreenMode(TheSDL3Window, mode)) {
-				fprintf(stderr, "WARNING: SDL_SetWindowFullscreenMode(native) failed: %s\n", SDL_GetError());
+			// GeneralsX @bugfix MrMeeseeks 02/07/2026 Pass nullptr to request Desktop Fullscreen (Spaces) instead of Exclusive mode.
+			if (!SDL_SetWindowFullscreenMode(TheSDL3Window, nullptr)) {
+				fprintf(stderr, "WARNING: SDL_SetWindowFullscreenMode(nullptr) failed: %s\n", SDL_GetError());
 			}
 		}
 		else {