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Sometimes you want your application to keep one of it’s windows always-on-top. A chat application like Adium for example, allows you to keep your conversation window always-on-top so you can follow the conversation whilst still using other applications. In the TellyBox application I wrote, this functionality is also very useful, as you can watch tv whilst still working in other applications.

So the basic implementation was fairly simple. You just use the windowDidResignMain notification, and then re-set the window level a more fitting one. Below I have also wrapped around a preference setting:

- (void)windowDidResignMain:(NSNotification *)notification
{
  // It's always nicer if the user has a choice
  if ([[NSUserDefaults standardUserDefaults] boolForKey:@"DefaultAlwaysOnTop"] == YES) {
    [[self window] setLevel:NSFloatingWindowLevel];
  } else {
    [[self window] setLevel:NSNormalWindowLevel];
  }
}

My TellyBox application allows you to go fullscreen via the existing Flash application embedded in a webkit view. Using just the basic implementation meant that when going into fullscreen mode the frame of the original window remained in view. To fix this I added this extra bit of code, which gets used via the firing of another useful notification windowDidBecomeMain :

- (void)windowDidBecomeMain:(NSNotification *)notification
{
  [[self window] setLevel:NSNormalWindowLevel];
}

which sets the window level back to it’s default value of 0 when it becomes the main window i.e when you select it.

I hope this little snippet helps people trying to achieve the same effect in their apps.

Tags: cocoa, development, OSX

This entry was posted at 4:39 pm on Saturday, April 11th, 2009. You can follow any responses to this post through the RSS 2.0 feed. Both comments and pings are currently closed.