Revert "Add a basic mouse grab mode when running on macOS"

This reverts commit 587eb48.

main_sdl.m

@@ -20,12 +20,6 @@
 */
 
 #include <Cocoa/Cocoa.h>
-#include <SDL.h>
-
-@interface DPPCResponder : NSResponder
-@end
-
-static DPPCResponder *dppcResponder;
 
 /** @file SDL-specific main function additions for macOS hosts. */
 
@@ -43,55 +37,4 @@ void remap_appkit_menu_shortcuts(void) {
             }
         }
     }
-
-    // Add a "Grab Mouse" commamand to the Window menu.
-    NSMenuItem *windowMenuItem = [[NSApp mainMenu] itemWithTitle:@"Window"];
-    if (windowMenuItem) {
-        NSMenu *windowMenu = [windowMenuItem submenu];
-        if (windowMenu) {
-            NSMenuItem *grabMouseMenuItem = [[NSMenuItem alloc] initWithTitle:@"Grab Mouse"
-                                                                        action:@selector(grabMouse:)
-                                                                 keyEquivalent:@"g"];
-            [grabMouseMenuItem setKeyEquivalentModifierMask:NSEventModifierFlagControl];
-            [windowMenu addItem:grabMouseMenuItem];
-        }
-    }
-
-    // Insert a responder in the chain to handle the command (SDL does not
-    // expose its NSAppDelegate implementation so we can't subclass it).
-    dppcResponder = [DPPCResponder new];
-    [dppcResponder setNextResponder:[NSApp nextResponder]];
-    [NSApp setNextResponder:dppcResponder];
-}
-
-@implementation DPPCResponder
-
-- (BOOL)validateMenuItem:(NSMenuItem *)menuItem {
-    if ([menuItem action] == @selector(grabMouse:)) {
-        [menuItem setState:SDL_GetRelativeMouseMode() ? NSControlStateValueOn : NSControlStateValueOff];
-        return YES;
-    }
-    return [super validateMenuItem:menuItem];
-}
-
-- (void)grabMouse:(id)sender {
-    NSWindow *mainWindow = NSApp.mainWindow;
-    if (mainWindow) {
-        // If we're about to grab the mouse, move the mouse to the middle of the
-        // window so that SDL knows that this window is what we want coordinates
-        // to be relative to.
-        if (!SDL_GetRelativeMouseMode()) {
-            NSRect frame = mainWindow.frame;
-            NSPoint center = NSMakePoint(frame.size.width/2, frame.size.height/2);
-            center = [mainWindow convertPointToScreen:center];
-            CGWarpMouseCursorPosition(center);
-            mainWindow.subtitle = @"Mouse grabbed";
-        } else {
-            mainWindow.subtitle = @"";
-        }
-    }
-
-    SDL_SetRelativeMouseMode(!SDL_GetRelativeMouseMode());
 }
-
-@end