Devirtualize BLayout::InvalidateLayout(), add a protected hook BLayout::DoLayout(). This will allow for much better control over the propagation of layout invalidations, and therefore cleaner, more optimal code.

headers/os/interface/CardLayout.h

@@ -28,13 +28,12 @@ public:
 	virtual	void				GetHeightForWidth(float width, float* min,
 									float* max, float* preferred);
 
-	virtual	void				InvalidateLayout(bool children = false);
-
 	virtual status_t			Archive(BMessage* into, bool deep = true) const;
 	virtual status_t			AllUnarchived(const BMessage* from);
 	static	BArchivable*		Instantiate(BMessage* from);
 
 protected:
+	virtual	void				LayoutInvalidated(bool children = false);
 	virtual	void				DoLayout();
 	virtual	bool				ItemAdded(BLayoutItem* item, int32 atIndex);
 	virtual	void				ItemRemoved(BLayoutItem* item, int32 fromIndex);

headers/os/interface/Layout.h

@@ -48,7 +48,7 @@ public:
 
 	// Layouting related methods
 
-	virtual	void				InvalidateLayout(bool children = false);
+			void				InvalidateLayout(bool children = false);
 			void				Relayout(bool immediate = false);
 			void				RequireLayout();
 			bool				IsValid();
@@ -73,6 +73,7 @@ protected:
 	// BLayout hook methods
 	virtual	bool				ItemAdded(BLayoutItem* item, int32 atIndex);
 	virtual	void				ItemRemoved(BLayoutItem* item, int32 fromIndex);
+	virtual	void				LayoutInvalidated(bool children);
 	virtual	void				DoLayout() = 0;
 	virtual	void				OwnerChanged(BView* was);
 

headers/os/interface/TwoDimensionalLayout.h

@@ -38,8 +38,6 @@ public:
 
 	virtual	void				SetFrame(BRect frame);
 
-	virtual	void				InvalidateLayout(bool children = false);
-
 	virtual status_t			Archive(BMessage* into, bool deep = true) const;
 	virtual status_t			AllArchived(BMessage* into) const;
 	virtual	status_t			AllUnarchived(const BMessage* from);
@@ -58,6 +56,7 @@ protected:
 				int32	height;
 			};
 
+	virtual	void				LayoutInvalidated(bool children = false);
 	virtual	void				DoLayout();
 
 			BSize				AddInsets(BSize size);

src/kits/interface/CardLayout.cpp

@@ -174,10 +174,8 @@ BCardLayout::GetHeightForWidth(float width, float* min, float* max,
 
 
 void
-BCardLayout::InvalidateLayout(bool children)
+BCardLayout::LayoutInvalidated(bool children)
 {
-	BLayout::InvalidateLayout(children);
-
 	fMinMaxValid = false;
 }
 

src/kits/interface/Layout.cpp

@@ -303,6 +303,7 @@ BLayout::InvalidateLayout(bool children)
 		return;
 
 	fState |= B_LAYOUT_NECESSARY;
+	LayoutInvalidated(children);
 
 	if (children) {
 		for (int32 i = CountItems() - 1; i >= 0; i--)
@@ -522,6 +523,12 @@ BLayout::ItemRemoved(BLayoutItem* item, int32 fromIndex)
 }
 
 
+void
+BLayout::LayoutInvalidated(bool children)
+{
+}
+
+
 void
 BLayout::OwnerChanged(BView* was)
 {

src/kits/interface/SplitLayout.cpp

@@ -546,9 +546,21 @@ BSplitLayout::GetHeightForWidth(float width, float* min, float* max,
 
 
 void
-BSplitLayout::InvalidateLayout(bool children)
+BSplitLayout::LayoutInvalidated(bool children)
 {
-	_InvalidateLayout(true, children);
+	delete fHorizontalLayouter;
+	delete fVerticalLayouter;
+	delete fHorizontalLayoutInfo;
+	delete fVerticalLayoutInfo;
+
+	fHorizontalLayouter = NULL;
+	fVerticalLayouter = NULL;
+	fHorizontalLayoutInfo = NULL;
+	fVerticalLayoutInfo = NULL;
+
+	_InvalidateCachedHeightForWidth();
+
+	fLayoutValid = false;
 }
 
 
@@ -820,28 +832,6 @@ BSplitLayout::ItemRemoved(BLayoutItem* item, int32 atIndex)
 }
 
 
-void
-BSplitLayout::_InvalidateLayout(bool invalidateView, bool children)
-{
-	if (invalidateView)
-		BAbstractLayout::InvalidateLayout(children);
-
-	delete fHorizontalLayouter;
-	delete fVerticalLayouter;
-	delete fHorizontalLayoutInfo;
-	delete fVerticalLayoutInfo;
-
-	fHorizontalLayouter = NULL;
-	fVerticalLayouter = NULL;
-	fHorizontalLayoutInfo = NULL;
-	fVerticalLayoutInfo = NULL;
-
-	_InvalidateCachedHeightForWidth();
-
-	fLayoutValid = false;
-}
-
-
 void
 BSplitLayout::_InvalidateCachedHeightForWidth()
 {

src/kits/interface/SplitLayout.h

@@ -75,8 +75,7 @@ public:
 	virtual	void				GetHeightForWidth(float width, float* min,
 									float* max, float* preferred);
 
-	virtual	void				InvalidateLayout(bool children = false);
+	virtual	void				LayoutInvalidated(bool children);
-
 	virtual	void				DoLayout();
 
 	// interface for BSplitView

src/kits/interface/TwoDimensionalLayout.cpp

@@ -407,14 +407,6 @@ BTwoDimensionalLayout::SetFrame(BRect frame)
 }
 
 
-void
-BTwoDimensionalLayout::InvalidateLayout(bool children)
-{
-	BLayout::InvalidateLayout(children);
-	fLocalLayouter->InvalidateLayout();
-}
-
-
 status_t
 BTwoDimensionalLayout::Archive(BMessage* into, bool deep) const
 {
@@ -464,6 +456,13 @@ BTwoDimensionalLayout::AllUnarchived(const BMessage* from)
 }
 
 
+void
+BTwoDimensionalLayout::LayoutInvalidated(bool children)
+{
+	fLocalLayouter->InvalidateLayout();
+}
+
+
 void
 BTwoDimensionalLayout::DoLayout()
 {