Please describe the problem:
An additional rectangular selection which made the window to scroll is not shown 
before scrolling the window again.

Steps to reproduce:
1. Open a document.
2. Set the window size or the zoom so the image doesn't fit in the window.
3. Scroll to the top of the document.
4. Draw one rectangular selection (without making the window to scroll).
5. Draw an additional rectangular selection (adding up to the previously 
selected zone). While drawing, drag the mouse to the bottom of the window to 
make the window scroll.
6. After releasing the mouse button (after drawing the second selection), the 
dashed rectangle indicating the additionally selected zone doesn't appear until 
you scroll the window.


Actual results:


Expected results:
The additional rectangle selection should be shown immediately after releasing 
the mouse button.

Does this happen every time?
I tested it a few times, and it seemed not to happen if the selected areas are 
rather small. I'm not sure of this, maybe it happens always anyway.

Other information: