Added a separate system for handling children of controls on GTK+. (I was thinking of doing this on OS X first, but this is probably simpler than saving the expand/align states for uiGroup and uiTab, so I'm doing the GTK+ backend first.) Not actually used yet, just written.

redo/unix/GNUmakeinc.mk

@@ -5,6 +5,7 @@ osCFILES = \
 	unix/box.c \
 	unix/button.c \
 	unix/checkbox.c \
+	unix/child.c \
 	unix/combobox.c \
 	unix/control.c \
 	unix/datetimepicker.c \

redo/unix/child.c

@@ -0,0 +1,120 @@
+// 28 august 2015
+#include "uipriv_unix.h"
+
+// This file contains helpers for managing child controls.
+
+struct child {
+	uiControl *c;
+	GtkWidget *widget;
+
+	gboolean oldhexpand;
+	GtkAlign oldhalign;
+	gboolean oldvexpand;
+	GtkAlign oldvalign;
+
+	// Some children can be boxed; that is, they can have an optionally-margined box around them.
+	// uiGroup, uiTab, and uiWindow all do this.
+	GtkWidget *box;
+
+	// If the child is not boxed, this is its parent.
+	// If the child is boxed, this is the box.
+	GtkContainer *parent;
+
+	// This flag is for users of these functions.
+	// For uiBox, this is "spaced".
+	// For uiTab, this is "margined". (uiGroup and uiWindow have to maintain their margined state themselves, since the margined state is independent of whether there is a child for those two.)
+	int flag;
+};
+
+struct child *newChild(uiControl *child, uiControl *parent, GtkContainer *parentContainer)
+{
+	struct child *c;
+
+	if (child == NULL)
+		return NULL;
+
+	c = uiNew(struct child);
+	c->c = child;
+	c->widget = GTK_WIDGET(uiControlHandle(c->c));
+
+	c->oldhexpand = gtk_widget_get_hexpand(c->widget);
+	c->oldhalign = gtk_widget_get_halign(c->widget);
+	c->oldvexpand = gtk_widget_get_vexpand(c->widget);
+	c->oldvalign = gtk_widget_get_valign(c->widget);
+
+	uiControlSetParent(c->c, parent);
+	gtk_container_add(parentContainer, c->widget);
+	c->parent = parentContainer;
+
+	return c;
+}
+
+struct child *newChildWithBox(uiControl *child, uiControl *parent, GtkContainer *parentContainer, int margined)
+{
+	struct child *c;
+	GtkWidget *box;
+
+	if (child == NULL)
+		return NULL;
+	box = gtk_box_new(GTK_ORIENTATION_HORIZONTAL, 0);
+	c = newChild(child, parent, GTK_CONTAINER(box));
+	c->box = box;
+	gtk_container_add(parentContainer, c->box);
+	childSetMargined(c, margined);
+	return c;
+}
+
+void childRemove(struct child *c)
+{
+	gtk_container_remove(c->parent, c->widget);
+	uiControlSetParent(c->c, NULL);
+
+	gtk_widget_set_hexpand(c->widget, c->oldhexpand);
+	gtk_widget_set_halign(c->widget, c->oldhalign);
+	gtk_widget_set_vexpand(c->widget, c->oldvexpand);
+	gtk_widget_set_valign(c->widget, c->oldvalign);
+
+	if (c->box != NULL)
+		gtk_widget_destroy(c->box);
+
+	uiFree(c);
+}
+
+void childDestroy(struct child *c)
+{
+	uiControl *child;
+
+	child = c->c;
+	childRemove(c);
+	uiControlDestroy(child);
+}
+
+GtkWidget *childWidget(struct child *c)
+{
+	return c->widget;
+}
+
+void childUpdateState(struct child *c)
+{
+	controlUpdateState(c->c);
+}
+
+int childFlag(struct child *c)
+{
+	return c->flag;
+}
+
+void childSetFlag(struct child *c, int flag)
+{
+	c->flag = flag;
+}
+
+GtkWidget *childBox(struct child *c)
+{
+	return c->box;
+}
+
+void childSetMargined(struct child *c, int margined)
+{
+	setMargined(GTK_CONTAINER(c->box), margined);
+}

redo/unix/uipriv_unix.h

@@ -25,5 +25,17 @@ extern void uninitAlloc(void);
 // util.c
 extern void setMargined(GtkContainer *, int);
 
+// child.c
+extern struct child *newChild(uiControl *child, uiControl *parent, GtkContainer *parentContainer);
+extern struct child *newChildWithBox(uiControl *child, uiControl *parent, GtkContainer *parentContainer, int margined);
+extern void childRemove(struct child *c);
+extern void childDestroy(struct child *c);
+extern GtkWidget *childWidget(struct child *c);
+extern void childUpdateState(struct child *c);
+extern int childFlag(struct child *c);
+extern void childSetFlag(struct child *c, int flag);
+extern GtkWidget *childBox(struct child *c);
+extern void childSetMargined(struct child *c, int margined);
+
 // TODO
 #define uiControlQueueResize(...)