On 4 Sep 2011, at 10:39, Quincey Morris wrote:
> On Sep 4, 2011, at 00:40 , Antonio Nunes wrote:
>
>> I have a control that needs to be highlighted when the font panel is
>> visible. This turns out not to be an easy task. I can't find any
>> notifications that will be triggered whenever the font panel is shown or is
>> hidden.
>
> Why can't you use '[[NSFontPanel sharedFontPanel] isVisible]' (possibly
> checking first with '[NSFontPanel sharedFontPanelExists]' so that you don't
> unnecessarily create it)?
Well, that sent me into a direction that I'm happy with:
User KVO to observe changes to the "visible" property of the font panel.
====
1. When my control gets created it sets itself up as an observer for the
NSWindowDidUpdateNotification for only the font panel object:
…
[[NSNotificationCenter defaultCenter] addObserver:self
selector:@selector(windowDidUpdate:) name:NSWindowDidUpdateNotification
object:[NSFontPanel sharedFontPanel]];
…
2. When the font panel gets shown for the first time the selector is called,
and we set ourselves up as an observer for the "visible" property. We also stop
observing the
NSWindowDidUpdateNotification, since we no longer need it.
- (void)startObservingFontPanelVisibility
{
[[NSFontPanel sharedFontPanel] addObserver:self
forKeyPath:@"visible"
options:NSKeyValueObservingOptionNew
context:nil];
}
- (void)windowDidUpdate:(NSNotification *)notification
{
[self startObservingFontPanelVisibility];
[[NSNotificationCenter defaultCenter] removeObserver:self
name:NSWindowDidUpdateNotification
object:[NSFontPanel
sharedFontPanel]];
}
3. When the visibility of the font panel changes, we now get called and can
change the highlight of the control:
- (void)observeValueForKeyPath:(NSString *)keyPath ofObject:(id)object
change:(NSDictionary *)change context:(void *)context
{
[self setSelected:[[NSFontPanel sharedFontPanel] isVisible]
forSegment:2];
}
====
The only aspect that I'd like to improve is that the font panel gets created
when the first document gets created, even though the user may never actually
use it. I'd like to avoid creating the font panel unnecessarily but a
satisfactory method to do that hasn't yet occurred to me. I could do something
like observe the NSWindowDidUpdateNotification without narrowing it down to the
font panel object and then:
if ([NSFontPanel sharedFontPanelExists] && notification.object ==
[NSFontPanel sharedFontPanel]) {
[self startObservingFontPanelVisibility];
[[NSNotificationCenter defaultCenter] removeObserver:self
name:NSWindowDidUpdateNotification
object:[NSFontPanel sharedFontPanel]];
}
but that would entail that the method is called constantly when any of the
app's windows is updated (until the font panel gets shown for the first time,
if at all), which I think is a worse solution that what I did instead.
-António
-----------------------------------------
Forgiveness is not an occasional act;
it is a permanent attitude.
--Martin Luther King, Jr
-----------------------------------------
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