Implemented uiTab on Mac OS X. It still doesn't quite work yet; switching from one tab and back doesn't show that tab's controls...

new/tab_darwin.m

@@ -0,0 +1,65 @@
+// 12 april 2015
+#import "uipriv_darwin.h"
+
+// TODO very margins against extra space around the tab
+
+@interface uiNSTabView : NSTabView
+@property uiControl *uiC;
+@end
+
+@implementation uiNSTabView
+
+- (void)viewDidMoveToSuperview
+{
+	if (uiDarwinControlFreeWhenAppropriate(self.uiC, [self superview]))
+		self.uiC = NULL;
+	[super viewDidMoveToSuperview];
+}
+
+@end
+
+// the default new control implementation uses -sizeToFit, which we don't have with NSTabView
+// fortunately, we do have -minimumSize
+static void preferredSize(uiControl *c, uiSizing *d, intmax_t *width, intmax_t *height)
+{
+	uiNSTabView *tv;
+	NSSize s;
+
+	tv = (uiNSTabView *) uiControlHandle(c);
+	s = [tv minimumSize];
+	*width = (intmax_t) (s.width);
+	*height = (intmax_t) (s.height);
+}
+
+uiControl *uiNewTab(void)
+{
+	uiControl *c;
+	uiNSTabView *t;
+
+	c = uiDarwinNewControl([uiNSTabView class], NO, NO);
+	c->preferredSize = preferredSize;
+	t = (uiNSTabView *) uiControlHandle(c);
+	t.uiC = c;
+
+	// also good for NSTabView (same selector and everything)
+	setStandardControlFont((NSControl *) t);
+
+	return c;
+}
+
+void uiTabAddPage(uiControl *c, const char *name, uiControl *child)
+{
+	uiNSTabView *tv;
+	uiContainer *container;
+	NSTabViewItem *i;
+
+	container = [[uiContainer alloc] initWithFrame:NSZeroRect];
+	container.uiChild = child;
+	uiControlSetParent(container.uiChild, (uintptr_t) container);
+
+	i = [[NSTabViewItem alloc] initWithIdentifier:nil];
+	[i setLabel:toNSString(name)];
+	[i setView:container];
+	tv = (uiNSTabView *) uiControlHandle(c);
+	[tv addTabViewItem:i];
+}