diff --git a/area.go b/area.go
index 3c7ff07..211dea1 100644
--- a/area.go
+++ b/area.go
@@ -336,20 +336,29 @@ func (a *Area) make(window *sysData) error {
 	return nil
 }
 
-func (a *Area) setRect(x int, y int, width int, height int, rr *[]resizerequest) {
-	*rr = append(*rr, resizerequest{
-		sysData: a.sysData,
+func (a *Area) allocate(x int, y int, width int, height int, d *sysSizeData) []*allocation {
+	return []*allocation{&allocation{
 		x:       x,
 		y:       y,
 		width:   width,
 		height:  height,
-	})
+		this:		a,
+	}}
 }
 
-func (a *Area) preferredSize() (width int, height int, yoff int) {
-	return a.sysData.preferredSize()
+func (a *Area) preferredSize(d *sysSizeData) (width int, height int) {
+	return a.sysData.preferredSize(d)
 }
 
+func (a *Area) commitResize(a *allocation, d *sysSizeData) {
+	a.sysData.preferredSize(a, d)
+}
+
+func (a *Area) getAuxResizeInfo(d *sysSizeData) {
+	a.sysData.getAuxResizeInfo(d)
+}
+
+
 // internal function, but shared by all system implementations: &img.Pix[0] is not necessarily the first pixel in the image
 func pixelDataPos(img *image.RGBA) int {
 	return img.PixOffset(img.Rect.Min.X, img.Rect.Min.Y)
diff --git a/button.go b/button.go
index 56d9c67..1a352dd 100644
--- a/button.go
+++ b/button.go
@@ -65,16 +65,24 @@ func (b *Button) make(window *sysData) error {
 	return nil
 }
 
-func (b *Button) setRect(x int, y int, width int, height int, rr *[]resizerequest) {
-	*rr = append(*rr, resizerequest{
-		sysData: b.sysData,
+func (b *Button) allocate(x int, y int, width int, height int, d *sysSizeData) []*allocation {
+	return []*allocation{&allocation{
 		x:       x,
 		y:       y,
 		width:   width,
 		height:  height,
-	})
+		this:		b,
+	}}
 }
 
-func (b *Button) preferredSize() (width int, height int, yoff int) {
-	return b.sysData.preferredSize()
+func (b *Button) preferredSize(d *sysSizeData) (width int, height int) {
+	return b.sysData.preferredSize(d)
+}
+
+func (b *Button) commitResize(a *allocation, d *sysSizeData) {
+	b.sysData.preferredSize(a, d)
+}
+
+func (b *Button) getAuxResizeInfo(d *sysSizeData) {
+	b.sysData.getAuxResizeInfo(d)
 }
diff --git a/checkbox.go b/checkbox.go
index 71c2b77..1f2ea58 100644
--- a/checkbox.go
+++ b/checkbox.go
@@ -70,16 +70,24 @@ func (c *Checkbox) make(window *sysData) error {
 	return nil
 }
 
-func (c *Checkbox) setRect(x int, y int, width int, height int, rr *[]resizerequest) {
-	*rr = append(*rr, resizerequest{
-		sysData: c.sysData,
+func (c *Checkbox) allocate(x int, y int, width int, height int, d *sysSizeData) []*allocation {
+	return []*allocation{&allocation{
 		x:       x,
 		y:       y,
 		width:   width,
 		height:  height,
-	})
+		this:		c,
+	}}
 }
 
-func (c *Checkbox) preferredSize() (width int, height int, yoff int) {
-	return c.sysData.preferredSize()
+func (c *Checkbox) preferredSize(d *sysSizeData) (width int, height int) {
+	return c.sysData.preferredSize(d)
+}
+
+func (c *Checkbox) commitResize(a *allocation, d *sysSizeData) {
+	c.sysData.preferredSize(a, d)
+}
+
+func (c *Checkbox) getAuxResizeInfo(d *sysSizeData) {
+	c.sysData.getAuxResizeInfo(d)
 }
diff --git a/combobox.go b/combobox.go
index 5fa391f..9298f87 100644
--- a/combobox.go
+++ b/combobox.go
@@ -147,16 +147,24 @@ func (c *Combobox) make(window *sysData) (err error) {
 	return nil
 }
 
-func (c *Combobox) setRect(x int, y int, width int, height int, rr *[]resizerequest) {
-	*rr = append(*rr, resizerequest{
-		sysData: c.sysData,
+func (c *Combobox) allocate(x int, y int, width int, height int, d *sysSizeData) []*allocation {
+	return []*allocation{&allocation{
 		x:       x,
 		y:       y,
 		width:   width,
 		height:  height,
-	})
+		this:		c,
+	}}
 }
 
-func (c *Combobox) preferredSize() (width int, height int, yoff int) {
-	return c.sysData.preferredSize()
+func (c *Combobox) preferredSize(d *sysSizeData) (width int, height int) {
+	return c.sysData.preferredSize(d)
+}
+
+func (c *Combobox) commitResize(a *allocation, d *sysSizeData) {
+	c.sysData.preferredSize(a, d)
+}
+
+func (c *Combobox) getAuxResizeInfo(d *sysSizeData) {
+	c.sysData.getAuxResizeInfo(d)
 }
diff --git a/label.go b/label.go
index 509c980..6d9ed3b 100644
--- a/label.go
+++ b/label.go
@@ -74,16 +74,24 @@ func (l *Label) make(window *sysData) error {
 	return nil
 }
 
-func (l *Label) setRect(x int, y int, width int, height int, rr *[]resizerequest) {
-	*rr = append(*rr, resizerequest{
-		sysData: l.sysData,
+func (l *Label) allocate(x int, y int, width int, height int, d *sysSizeData) []*allocation {
+	return []*allocation{&allocation{
 		x:       x,
 		y:       y,
 		width:   width,
 		height:  height,
-	})
+		this:		l,
+	}}
 }
 
-func (l *Label) preferredSize() (width int, height int, yoff int) {
-	return l.sysData.preferredSize()
+func (l *Label) preferredSize(d *sysSizeData) (width int, height int) {
+	return l.sysData.preferredSize(d)
+}
+
+func (l *Label) commitResize(a *allocation, d *sysSizeData) {
+	l.sysData.preferredSize(a, d)
+}
+
+func (l *Label) getAuxResizeInfo(d *sysSizeData) {
+	l.sysData.getAuxResizeInfo(d)
 }
diff --git a/lineedit.go b/lineedit.go
index 26fbaa1..3e71db1 100644
--- a/lineedit.go
+++ b/lineedit.go
@@ -68,16 +68,24 @@ func (l *LineEdit) make(window *sysData) error {
 	return nil
 }
 
-func (l *LineEdit) setRect(x int, y int, width int, height int, rr *[]resizerequest) {
-	*rr = append(*rr, resizerequest{
-		sysData: l.sysData,
+func (l *LineEdit) allocate(x int, y int, width int, height int, d *sysSizeData) []*allocation {
+	return []*allocation{&allocation{
 		x:       x,
 		y:       y,
 		width:   width,
 		height:  height,
-	})
+		this:		l,
+	}}
 }
 
-func (l *LineEdit) preferredSize() (width int, height int, yoff int) {
-	return l.sysData.preferredSize()
+func (l *LineEdit) preferredSize(d *sysSizeData) (width int, height int) {
+	return l.sysData.preferredSize(d)
+}
+
+func (l *LineEdit) commitResize(a *allocation, d *sysSizeData) {
+	l.sysData.preferredSize(a, d)
+}
+
+func (l *LineEdit) getAuxResizeInfo(d *sysSizeData) {
+	l.sysData.getAuxResizeInfo(d)
 }
diff --git a/listbox.go b/listbox.go
index dc4cb70..cd7aab1 100644
--- a/listbox.go
+++ b/listbox.go
@@ -150,16 +150,24 @@ func (l *Listbox) make(window *sysData) (err error) {
 	return nil
 }
 
-func (l *Listbox) setRect(x int, y int, width int, height int, rr *[]resizerequest) {
-	*rr = append(*rr, resizerequest{
-		sysData: l.sysData,
+func (l *Listbox) allocate(x int, y int, width int, height int, d *sysSizeData) []*allocation {
+	return []*allocation{&allocation{
 		x:       x,
 		y:       y,
 		width:   width,
 		height:  height,
-	})
+		this:		l,
+	}}
 }
 
-func (l *Listbox) preferredSize() (width int, height int, yoff int) {
-	return l.sysData.preferredSize()
+func (l *Listbox) preferredSize(d *sysSizeData) (width int, height int) {
+	return l.sysData.preferredSize(d)
+}
+
+func (l *Listbox) commitResize(a *allocation, d *sysSizeData) {
+	l.sysData.preferredSize(a, d)
+}
+
+func (l *Listbox) getAuxResizeInfo(d *sysSizeData) {
+	l.sysData.getAuxResizeInfo(d)
 }
diff --git a/progressbar.go b/progressbar.go
index 212620d..c2cd289 100644
--- a/progressbar.go
+++ b/progressbar.go
@@ -56,16 +56,24 @@ func (p *ProgressBar) make(window *sysData) error {
 	return nil
 }
 
-func (p *ProgressBar) setRect(x int, y int, width int, height int, rr *[]resizerequest) {
-	*rr = append(*rr, resizerequest{
-		sysData: p.sysData,
+func (p *ProgressBar) allocate(x int, y int, width int, height int, d *sysSizeData) []*allocation {
+	return []*allocation{&allocation{
 		x:       x,
 		y:       y,
 		width:   width,
 		height:  height,
-	})
+		this:		p,
+	}}
 }
 
-func (p *ProgressBar) preferredSize() (width int, height int, yoff int) {
-	return p.sysData.preferredSize()
+func (p *ProgressBar) preferredSize(d *sysSizeData) (width int, height int) {
+	return p.sysData.preferredSize(d)
+}
+
+func (p *ProgressBar) commitResize(a *allocation, d *sysSizeData) {
+	p.sysData.preferredSize(a, d)
+}
+
+func (p *ProgressBar) getAuxResizeInfo(d *sysSizeData) {
+	p.sysData.getAuxResizeInfo(d)
 }