Implemented Checkbox.SetChecked() on Mac OS X and updated the README.

README.md

@@ -5,8 +5,9 @@ Woah, lots of attention! Thanks!
 ## Updates
 
 - **26 June 2014**
-	- Controls in Windows can now be spaced apart more naturally. Call `w.SetSpaced(true)` to opt in. **Whether this will remain opt-in or whether the name will change is still unknown at this point.**
+-- Controls in Windows can now be spaced apart more naturally. Call `w.SetSpaced(true)` to opt in. **Whether this will remain opt-in or whether the name will change is still unknown at this point.**
-	- There's a new function `Layout()` which provides high-level layout creation. The function was written by [boppreh](https://github.com/boppreh) and details can be found [here](https://github.com/andlabs/ui/pull/19). **Whether this function will stay in the main package or be moved to a subpackage is still unknown.**
+-- There's a new function `Layout()` which provides high-level layout creation. The function was written by [boppreh](https://github.com/boppreh) and details can be found [here](https://github.com/andlabs/ui/pull/19). **Whether this function will stay in the main package or be moved to a subpackage is still unknown.**
+-- There is now `Checkbox.SetChecked()` to set the check state of a Checkbox programmatically.
 
 - **25 June 2014**<br>Labels by default now align themselves relative to the control they are next to. There is a new function `NewStandaloneLabel()` which returns a label whose text is aligned to the top-left corner of the alloted space regardless.
 

objc_darwin.h

@@ -123,6 +123,7 @@ extern void windowSetContentSize(id, intptr_t, intptr_t);
 extern void setProgress(id, intptr_t);
 extern void setAreaSize(id, intptr_t, intptr_t);
 extern void center(id);
+extern void setCheckboxChecked(id, BOOL);
 
 /* combobox_darwin.m */
 extern id makeCombobox(BOOL);

sysdata_darwin.go

@@ -422,3 +422,13 @@ func (s *sysData) center() {
 	}
 	<-ret
 }
+
+func (s *sysData) setChecked(checked bool) {
+	ret := make(chan struct{})
+	defer close(ret)
+	uitask <- func() {
+		C.setCheckboxChecked(s.id, toBOOL(checked))
+		ret <- struct{}{}
+	}
+	<-ret
+}

sysdata_darwin.m

@@ -228,3 +228,13 @@ void center(id w)
 {
 	[toNSWindow(w) center];
 }
+
+void setCheckboxChecked(id checkbox, BOOL check)
+{
+	// -[NSButton setState:] takes a NSInteger but the state constants are NSCellStateValue which is NSUInteger (despite NSMixedState being -1); let's play it safe here
+	if (check) {
+		[toNSButton(checkbox) setState:NSOnState];
+		return;
+	}
+	[toNSButton(checkbox) setState:NSOffState];
+}