Decided to split control removal from parent into its own method removeParent() rather than automatically doing it in setParent().

new/newcontrol_darwin.m

@@ -13,6 +13,7 @@ struct uiSingleViewControl {
 
 #define S(c) ((uiSingleViewControl *) (c))
 
+// TODO this will need to change if we want to provide removal
 static void singleDestroy(uiControl *c)
 {
 	[S(c)->view removeFromSuperview];
@@ -26,18 +27,25 @@ static uintptr_t singleHandle(uiControl *c)
 static void singleSetParent(uiControl *c, uintptr_t parent)
 {
 	uiSingleViewControl *s = S(c);
-	uintptr_t oldparent;
 	NSView *parentView;
 
-	oldparent = s->parent;
 	s->parent = parent;
 	parentView = (NSView *) (s->parent);
-	// TODO will this change parents?
 	[parentView addSubview:s->immediate];
-	updateParent(oldparent);
 	updateParent(s->parent);
 }
 
+static void singleRemoveParent(uiControl *c)
+{
+	uiSingleViewControl *s = S(c);
+	uintptr_t oldparent;
+
+	oldparent = s->parent;
+	s->parent = 0;
+	[s->immediate removeFromSuperview];
+	updateParent(oldparent);
+}
+
 // also good for NSBox and NSProgressIndicator
 static uiSize singlePreferredSize(uiControl *c, uiSizing *d)
 {
@@ -92,6 +100,7 @@ uiControl *uiDarwinNewControl(Class class, BOOL inScrollView, BOOL scrollViewHas
 	c->control.destroy = singleDestroy;
 	c->control.handle = singleHandle;
 	c->control.setParent = singleSetParent;
+	c->control.removeParent = singleRemoveParent;
 	c->control.preferredSize = singlePreferredSize;
 	c->control.resize = singleResize;
 

new/newcontrol_unix.c

@@ -25,17 +25,23 @@ static uintptr_t singleHandle(uiControl *c)
 }
 
 static void singleSetParent(uiControl *c, uintptr_t parent)
+{
+	uiSingleWidgetControl *s = S(c);
+
+	s->parent = parent;
+	gtk_container_add(GTK_CONTAINER(s->parent), s->immediate);
+	updateParent(s->parent);
+}
+
+static void singleRemoveParent(uiControl *c)
 {
 	uiSingleWidgetControl *s = S(c);
 	uintptr_t oldparent;
 
 	oldparent = s->parent;
-	s->parent = parent;
-	if (oldparent != 0)
-		gtk_container_remove(GTK_CONTAINER(oldparent), s->immediate);
-	gtk_container_add(GTK_CONTAINER(s->parent), s->immediate);
+	s->parent = 0;
+	gtk_container_remove(GTK_CONTAINER(oldparent), s->immediate);
 	updateParent(oldparent);
-	updateParent(s->parent);
 }
 
 static uiSize singlePreferredSize(uiControl *c, uiSizing *d)
@@ -101,7 +107,7 @@ uiControl *uiUnixNewControl(GType type, gboolean inScrolledWindow, gboolean scro
 	// with this:
 	// - end user call works (shoudn't be in any container)
 	// - call in uiContainer works (both refs freed)
-	// this also ensures singleSetParent() works properly when changing parents
+	// this also ensures singleRemoveParent() works properly
 	g_object_ref_sink(c->immediate);
 	// and let's free the uiSingleWidgetControl with it
 	g_signal_connect(c->immediate, "destroy", G_CALLBACK(onDestroy), c);
@@ -109,6 +115,7 @@ uiControl *uiUnixNewControl(GType type, gboolean inScrolledWindow, gboolean scro
 	c->control.destroy = singleDestroy;
 	c->control.handle = singleHandle;
 	c->control.setParent = singleSetParent;
+	c->control.removeParent = singleRemoveParent;
 	c->control.preferredSize = singlePreferredSize;
 	c->control.resize = singleResize;
 

new/newcontrol_windows.c

@@ -30,16 +30,25 @@ static uintptr_t singleHandle(uiControl *c)
 }
 
 static void singleSetParent(uiControl *c, uintptr_t parent)
+{
+	uiSingleHWNDControl *s = S(c);
+
+	s->parent = parent;
+	if (SetParent(s->hwnd, (HWND) (s->parent)) == NULL)
+		logLastError("error setting control parent in singleSetParent()");
+	updateParent(s->parent);
+}
+
+static void singleRemoveParent(uiControl *c)
 {
 	uiSingleHWNDControl *s = S(c);
 	uintptr_t oldparent;
 
 	oldparent = s->parent;
-	s->parent = parent;
-	if (SetParent(s->hwnd, (HWND) (s->parent)) == NULL)
-		logLastError("error changing control parent in singleSetParent()");
+	s->parent = 0;
+	if (SetParent(s->hwnd, initialParent) == NULL)
+		logLastError("error removing control parent in singleSetParent()");
 	updateParent(oldparent);
-	updateParent(s->parent);
 }
 
 static uiSize singlePreferredSize(uiControl *c, uiSizing *d)
@@ -102,6 +111,7 @@ uiControl *uiWindowsNewControl(uiWindowsNewControlParams *p)
 	c->control.destroy = singleDestroy;
 	c->control.handle = singleHandle;
 	c->control.setParent = singleSetParent;
+	c->control.removeParent = singleRemoveParent;
 	c->control.preferredSize = singlePreferredSize;
 	c->control.resize = singleResize;
 

new/stack.c

@@ -41,16 +41,26 @@ static void stackSetParent(uiControl *c, uintptr_t parent)
 {
 	stack *s = S(c);
 	uintmax_t i;
-	uintptr_t oldparent;
 
-	oldparent = s->parent;
 	s->parent = parent;
 	for (i = 0; i < S(c)->len; i++)
 		(*(s->controls[i]->setParent))(s->controls[i], s->parent);
-	updateParent(oldparent);
 	updateParent(s->parent);
 }
 
+static void stackRemoveParent(uiControl *c)
+{
+	stack *s = S(c);
+	uintmax_t i;
+	uintptr_t oldparent;
+
+	oldparent = s->parent;
+	s->parent = 0;
+	for (i = 0; i < S(c)->len; i++)
+		(*(s->controls[i]->removeParent))(s->controls[i]);
+	updateParent(oldparent);
+}
+
 static uiSize stackPreferredSize(uiControl *c, uiSizing *d)
 {
 	stack *s = S(c);
@@ -197,6 +207,7 @@ uiControl *uiNewHorizontalStack(void)
 	s->control.destroy = stackDestroy;
 	s->control.handle = stackHandle;
 	s->control.setParent = stackSetParent;
+	s->control.removeParent = stackRemoveParent;
 	s->control.preferredSize = stackPreferredSize;
 	s->control.resize = stackResize;
 

new/uipriv.h

@@ -24,6 +24,7 @@ struct uiControl {
 	void (*destroy)(uiControl *);
 	uintptr_t (*handle)(uiControl *);
 	void (*setParent)(uiControl *, uintptr_t);
+	void (*removeParent)(uiControl *);
 	uiSize (*preferredSize)(uiControl *, uiSizing *);
 	void (*resize)(uiControl *, intmax_t, intmax_t, intmax_t, intmax_t, uiSizing *);
 };