Implemented mouse relative mode for iOS 14.1 and newer

src/video/uikit/SDL_uikitevents.h

@@ -31,6 +31,7 @@ extern void SDL_QuitGCKeyboard(void);
 
 extern void SDL_InitGCMouse(void);
 extern SDL_bool SDL_HasGCMouse(void);
+extern SDL_bool SDL_GCMouseRelativeMode(void);
 extern void SDL_QuitGCMouse(void);
 
 #endif /* SDL_uikitevents_h_ */

src/video/uikit/SDL_uikitevents.m

@@ -182,10 +182,22 @@ void SDL_QuitGCKeyboard(void)
 static int mice_connected = 0;
 static id mouse_connect_observer = nil;
 static id mouse_disconnect_observer = nil;
+static bool mouse_relative_mode = SDL_FALSE;
+
+static void UpdateMouseGrab()
+{
+    SDL_VideoDevice *_this = SDL_GetVideoDevice();
+    SDL_Window *window;
+
+    for (window = _this->windows; window != NULL; window = window->next) {
+        SDL_UpdateWindowGrab(window);
+    }
+}
 
 static int SetGCMouseRelativeMode(SDL_bool enabled)
 {
-    /* We'll always send relative motion and we can't warp, so nothing to do here */
+	mouse_relative_mode = enabled;
+    UpdateMouseGrab();
     return 0;
 }
 
@@ -230,6 +242,8 @@ static void OnGCMouseConnected(GCMouse *mouse) API_AVAILABLE(macos(11.0), ios(14
     mouse.handlerQueue = queue;
 
     ++mice_connected;
+
+    UpdateMouseGrab();
 }
 
 static void OnGCMouseDisconnected(GCMouse *mouse) API_AVAILABLE(macos(11.0), ios(14.0), tvos(14.0))
@@ -245,6 +259,8 @@ static void OnGCMouseDisconnected(GCMouse *mouse) API_AVAILABLE(macos(11.0), ios
     for (GCControllerButtonInput *button in mouse.mouseInput.auxiliaryButtons) {
         button.pressedChangedHandler = nil;
     }
+
+    UpdateMouseGrab();
 }
 
 void SDL_InitGCMouse(void)
@@ -284,6 +300,11 @@ SDL_bool SDL_HasGCMouse(void)
     return (mice_connected > 0);
 }
 
+SDL_bool SDL_GCMouseRelativeMode(void)
+{
+    return mouse_relative_mode;
+}
+
 void SDL_QuitGCMouse(void)
 {
     @autoreleasepool {
@@ -320,6 +341,11 @@ SDL_bool SDL_HasGCMouse(void)
     return SDL_FALSE;
 }
 
+SDL_bool SDL_GCMouseRelativeMode(void)
+{
+    return SDL_FALSE;
+}
+
 void SDL_QuitGCMouse(void)
 {
 }

src/video/uikit/SDL_uikitvideo.m

@@ -93,6 +93,7 @@ UIKit_CreateDevice(int devindex)
         device->RaiseWindow = UIKit_RaiseWindow;
         device->SetWindowBordered = UIKit_SetWindowBordered;
         device->SetWindowFullscreen = UIKit_SetWindowFullscreen;
+        device->SetWindowMouseGrab = UIKit_SetWindowMouseGrab;
         device->DestroyWindow = UIKit_DestroyWindow;
         device->GetWindowWMInfo = UIKit_GetWindowWMInfo;
         device->GetDisplayUsableBounds = UIKit_GetDisplayUsableBounds;

src/video/uikit/SDL_uikitviewcontroller.m

@@ -27,8 +27,9 @@
 #include "../SDL_sysvideo.h"
 #include "../../events/SDL_events_c.h"
 
-#import "SDL_uikitviewcontroller.h"
-#import "SDL_uikitmessagebox.h"
+#include "SDL_uikitviewcontroller.h"
+#include "SDL_uikitmessagebox.h"
+#include "SDL_uikitevents.h"
 #include "SDL_uikitvideo.h"
 #include "SDL_uikitmodes.h"
 #include "SDL_uikitwindow.h"
@@ -246,7 +247,20 @@ SDL_HideHomeIndicatorHintChanged(void *userdata, const char *name, const char *o
         return UIRectEdgeNone;
     }
 }
-#endif
+
+- (BOOL)prefersPointerLocked
+{
+    SDL_VideoDevice *_this = SDL_GetVideoDevice();
+    
+    if (SDL_HasGCMouse() &&
+        (SDL_GCMouseRelativeMode() || _this->grabbed_window == window)) {
+        return YES;
+    } else {
+        return NO;
+    }
+}
+
+#endif /* !TARGET_OS_TV */
 
 /*
  ---- Keyboard related functionality below this line ----

src/video/uikit/SDL_uikitwindow.h

@@ -33,6 +33,7 @@ extern void UIKit_HideWindow(_THIS, SDL_Window * window);
 extern void UIKit_RaiseWindow(_THIS, SDL_Window * window);
 extern void UIKit_SetWindowBordered(_THIS, SDL_Window * window, SDL_bool bordered);
 extern void UIKit_SetWindowFullscreen(_THIS, SDL_Window * window, SDL_VideoDisplay * display, SDL_bool fullscreen);
+extern void UIKit_SetWindowMouseGrab(_THIS, SDL_Window * window, SDL_bool grabbed);
 extern void UIKit_DestroyWindow(_THIS, SDL_Window * window);
 extern SDL_bool UIKit_GetWindowWMInfo(_THIS, SDL_Window * window,
                                       struct SDL_SysWMinfo * info);

src/video/uikit/SDL_uikitwindow.m

@@ -320,6 +320,20 @@ UIKit_SetWindowFullscreen(_THIS, SDL_Window * window, SDL_VideoDisplay * display
     }
 }
 
+void
+UIKit_SetWindowMouseGrab(_THIS, SDL_Window * window, SDL_bool grabbed)
+{
+#if !TARGET_OS_TV
+    @autoreleasepool {
+        SDL_WindowData *data = (__bridge SDL_WindowData *) window->driverdata;
+        SDL_uikitviewcontroller *viewcontroller = data.viewcontroller;
+        if (@available(iOS 14.0, *)) {
+            [viewcontroller setNeedsUpdateOfPrefersPointerLocked];
+        }
+    }
+#endif /* !TARGET_OS_TV */
+}
+
 void
 UIKit_DestroyWindow(_THIS, SDL_Window * window)
 {