Carbon: scrollbar in wrong position

[David Reitter]

This occurs reproducibly right after visiting a file (in a new  
buffer, i.e. find-file-other-frame) - see the first screenshot. At  
the same time, the slider occurs in the right position up on the  
scrollbar. The situation persists until the relevant portion of the  
window is redrawn.  (The build is using toolkit scrollbars.)
It looks like as if the slider was drawn at a wrong position and  
drawn again later on.

Both problems (the one above and the one below) also occur after I  
start out with the buffer loaded and with rather plain frame  
parameters (fixed with Monaco font) and switch to Lucida14.
It also occurs when switching back to Monaco, and the frame is  
redrawn with the larger width.

It also occurs reliably when I resize the frame in fundamental-mode.

My build settings are:

-DUSE_TOOLKIT_SCROLL_BARS -DUSE_TRANSPARENCY -DUSE_ATSUI  -DSYNC_INPUT

Various fontsets are loaded.

I haven't been able to determine which configuration makes the bug  
appear. I'm happy to try out things, but I'd need some ideas about  
where to start!

Btw, where in the code is the horizontal position of the slider defined?
I would like to move it to the right boundary where it is in all my  
other applications.

N.B., the height of the frame is not an exact multiple of the line  
height, even when resizing the frame (see second screenshot). This  
might be considered a separate bug, if it is a bug and not intended -  
I don't know if this has to do with the strange slider position.