Can drag webview to move window in cococa?
1. 问题
如果cococa程序，在一个==没有titlebar==的window里只有一个webview，是否能够==拖曳这个webview来拖动整个window==呢？当然，直接拖是不行的，webview会先接受这个拖曳drag事件。
对于window中除webview以外的其他控件，其实可以直接重载NSWindow的mouseDown和mouseDragged方法来实现要的效果，但是webview不行，它需要另外重载NSWindow的sendEvent来实现mouse事件的额外操作。
另外，需要注意的是没有titlebar的window，相当于[self.window setStyleMask:(NSBorderlessWindowMask)].对于使用NSBorderlessWindowMask这个’Window Style Masks’时，需要额外实现canBecomeKeyWindow or canBecomeMainWindow返回YES，从而让这
个window成为当前主窗口。Apple官方文档对此的说明如下：
The window displays none of the usual peripheral elements. Useful only for display or caching purposes. A window that uses NSBorderlessWindowMask can’t become key or main, unless you implement canBecomeKeyWindow or canBecomeMainWindow to return YES. Note that you can set a window’s or panel’s style mask to NSBorderlessWindowMask in Interface Builder by deselecting Title Bar in the Appearance section of the Attributes inspector.
2. 代码
将现有window设置成下面这个BorderlessWindow即可。
.h文件：
#import <Cocoa/Cocoa.h>
@interface BorderlessWindow : NSWindow
@end.m文件
#import "BorderlessWindow.h"
@interface BorderlessWindow()
@property (assign) NSPoint initialLocation;
@end
@implementation BorderlessWindow
- (BOOL)canBecomeKeyWindow
{
return YES;
}
- (BOOL)canBecomeMainWindow
{
return YES;
}
- (void)sendEvent:(NSEvent *)theEvent
{
if ([theEvent type] == NSLeftMouseDown)
{
[self mouseDown:theEvent];
}
else if ([theEvent type] == NSLeftMouseDragged)
{
[self mouseDragged:theEvent];
}
[super sendEvent:theEvent];
}
- (void)mouseDown:(NSEvent *)theEvent
{
self.initialLocation = [theEvent locationInWindow];
}
- (void)mouseDragged:(NSEvent *)theEvent
{
NSPoint currentLocation;
NSPoint newOrigin;
NSRect screenFrame = [[NSScreen mainScreen] frame];
NSRect windowFrame = [self frame];
currentLocation = [NSEvent mouseLocation];
newOrigin.x = currentLocation.x - self.initialLocation.x;
newOrigin.y = currentLocation.y - self.initialLocation.y;
// Don't let window get dragged up under the menu bar
if( (newOrigin.y+windowFrame.size.height) > (screenFrame.origin.y+screenFrame.size.height) ){
newOrigin.y=screenFrame.origin.y + (screenFrame.size.height-windowFrame.size.height);
}
//go ahead and move the window to the new location
[self setFrameOrigin:newOrigin];
}