Wrote Control.preferredSize() (including Tab.preferredSize()) on Mac OS X.

redo/containerctrls_darwin.go

@@ -19,6 +19,7 @@ func newTab() Tab {
 	t := new(tab)
 	id := C.newTab(unsafe.Pointer(t))
 	t.controlbase = newControl(id)
+	t.fpreferredSize = t.tabpreferredSize
 	return t
 }
 
@@ -32,7 +33,12 @@ func (t *tab) Append(name string, control Control) {
 	s.child.setParent(&controlParent{tabview})
 }
 
-// no need to override Control.allocate() as only prepared the tabbed control; its children will be reallocated when that one is resized
+func (t *tab) tabpreferredSize(d *sizing) (width, height int) {
+	s := C.tabPrefSize(t.id)
+	return int(s.width), int(s.height)
+}
+
+// no need to override Control.commitResize() as only prepared the tabbed control; its children will be reallocated when that one is resized
 
 //export tabResized
 func tabResized(data unsafe.Pointer, width C.intptr_t, height C.intptr_t) {

redo/control_darwin.go

@@ -30,8 +30,8 @@ func newControl(id C.id) *controlbase {
 	}
 	c.fallocate = baseallocate(c)
 	c.fpreferredSize = func(d *sizing) (int, int) {
-		// TODO
-		return 64, 32
+		s := C.controlPrefSize(c.id)
+		return int(s.width), int(s.height)
 	}
 	c.fcommitResize = func(a *allocation, d *sizing) {
 //TODO

redo/objc_darwin.h

@@ -81,6 +81,7 @@ struct xalignment {
 	intptr_t baseline;
 };
 extern struct xsize controlPrefSize(id);
+extern struct xsize tabPrefSize(id);
 extern struct xsize areaPrefSize(id);
 extern struct xalignment alignmentInfo(id, struct xrect);
 

redo/xsizing_darwin.m

@@ -4,6 +4,7 @@
 #import <Cocoa/Cocoa.h>
 
 #define toNSControl(x) ((NSControl *) (x))
+#define toNSTabView(x) ((NSTabView *) (x))
 #define toNSScrollView(x) ((NSScrollView *) (x))
 #define toNSView(x) ((NSView *) (x))
 
@@ -24,6 +25,19 @@ struct xsize controlPrefSize(id control)
 	return s;
 }
 
+struct xsize tabPrefSize(id control)
+{
+	NSTabView *tv;
+	NSSize s;
+	struct xsize t;
+
+	tv = toNSTabView(control);
+	s = [tv minimumSize];
+	t.width = (intptr_t) s.width;
+	t.height = (intptr_t) s.height;
+	return t;
+}
+
 // TODO use this, possibly update to not need scrollview
 /*
 struct xsize areaPrefSize(id scrollview)