This is it. Update code is ready. At leat I think so. Testing is next. Uh, didn't thought this could be this easy. :-)

git-svn-id: file:///srv/svn/repos/haiku/trunk/current@8320 a95241bf-73f2-0310-859d-f6bbb57e9c96

src/servers/app/server/Layer.cpp

@@ -77,6 +77,7 @@ Layer::Layer(BRect frame, const char *name, int32 token, uint32 resize,
 	clipToPicture	= NULL;
 	
 	// NOW all regions (fVisible, fFullVisible, fFull) are empty
+	fClipReg		= &fVisible;
 	STRACE(("Layer(%s) successfuly created\n", GetName()));
 }
 
@@ -509,8 +510,14 @@ void Layer::RequestDraw(const BRegion &reg, Layer *startFrom)
 			// Update one.
 			BRegion common(lay->fFullVisible);
 			common.IntersectWith(&reg);
-			if (common.CountRects() > 0)
+			if (common.CountRects() > 0){
+				// lock/unlock if we are a winborder
+				if (lay->fClassID == AS_WINBORDER_CLASS)
+					lay->Window()->Lock();
 				lay->RequestDraw(reg, NULL);
+				if (lay->fClassID == AS_WINBORDER_CLASS)
+					lay->Window()->Unlock();
+			}
 		}
 	}
 }
@@ -533,6 +540,21 @@ r.PrintToStream();
 	// empty HOOK function.
 }
 
+void Layer::UpdateStart()
+{
+	// durring update we are not allowed to draw outside the update region.
+	// why should we? we only need that region redrawn!
+	fInUpdate = true;
+	fClipReg = &fUpdateReg;
+}
+
+void Layer::UpdateEnd()
+{
+	// the usual case. Drawing is permited in the whole visible area.
+	fInUpdate = false;
+	fClipReg = &fVisible;
+	fUpdateReg.MakeEmpty();
+}
 
 void Layer::Show(bool invalidate)
 {

src/servers/app/server/Layer.h

@@ -114,9 +114,10 @@ public:
 	void SetAsTopLayer(bool option) { fIsTopLayer = option; }
 	bool IsTopLayer() const { return fIsTopLayer; }
 
-	void UpdateStart() { fInUpdate = true; }
+	void UpdateStart();
-	void UpdateEnd() { fInUpdate = false; }
+	void UpdateEnd();
 	bool InUpdate() const { return fInUpdate; }
+	BRegion* ClippingRegion() const { return fClipReg; }
 
 protected:
 	friend class RootLayer;
@@ -140,6 +141,7 @@ protected:
 	BRegion	fFullVisible;
 	BRegion	fFull;
 	BRegion	fUpdateReg;
+	BRegion *fClipReg;
 	
 	BRegion *clipToPicture;
 	bool clipToPictureInverse;

src/servers/app/server/ServerWindow.cpp

@@ -1455,6 +1455,16 @@ void ServerWindow::DispatchMessage(int32 code)
 
 			break;
 		}
+		case AS_BEGIN_UPDATE:
+		{
+			cl->UpdateStart();
+			break;
+		}
+		case AS_END_UPDATE:
+		{
+			cl->UpdateEnd();
+			break;
+		}
 
 		// ********** END: BView Messages ***********