An invalidated BView does not draw to a BBitmap

[axeld]

When you have the following construct, nothing will ever be drawn to the bitmap:

	BBitmap* bitmap = new BBitmap(frame, B_RGBA32, true);
	BView* view = new BView(bitmap->Bounds(), NULL, 0, B_WILL_DRAW);
	bitmap->AddChild(view);

	if (view->LockLooper()) {
		view->Invalidate();
		view->SetHighColor(225, 225, 225, 128);
		view->FillRect(view->Bounds());

		view->UnlockLooper();
	}

If you remove the Invalidate(), the drawing operation is performed as expected. Needless to say, the code above worked fine under BeOS.

[Jim906]

Reproduces bug

[Jim906]

I think the problem relates to the fact that BBitmap::fWindow cannot receive messages because it is an offscreen BWindow, which means Run is never called.

BView::Invalidate sends an AS_VIEW_INVALIDATE_RECT message to the OffscreenWindow that corresponds to fWindow. The OffscreenWindow, in response, sends back an _UPDATE_ message. Since fWindow can't receive messages, it does not make the expected reply (AS_BEGIN_UPDATE) to the OffscreenWindow. This leaves the OffscreenWindow in a state where fUpdateRequested is true and fInUpdate is false. In this state, Window::GetEffectiveDrawingRegion will decide that the invalidated area can't be drawn to.

This situation can be avoided if OffscreenWindow's base member Window::fUpdatesEnabled is false, because then Window::_SendUpdateMessage won't send the _UPDATE_ message and won't set fUpdateRequested to true. Suggested patch: ​https://review.haiku-os.org/c/haiku/+/5967.

[pulkomandy]

Fixed in hrev56677.

[kim1963]

Replying to pulkomandy:

Fixed in hrev56677.

Should this be considered for beta4?