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Re: GUI 'bugs'

From: Nicola Pero
Subject: Re: GUI 'bugs'
Date: Tue, 16 Jan 2001 12:16:53 +0000 (GMT)

> - when scrolling text, textviews often provide 'muesli look' 
> for their text content (the text is messed up)...;-)

I'm pleased to report that - as part of the undergoing work on NSText* -
after fixing deleting and cursor movements - I have fixed a bug in text
view scrolling - which I hope can solve these problems.

It took me `only' seven hours to figure it out. :-)

The problem was that resizing was leaving - in particular conditions - the
_bounds and the _boundsMatrix of the text view in an inconsistent state.  
_bounds were actually scaled (while they shouldn't have) - while
_boundsMatrix was still unscaled.

When the clipview tried then to mark the rectangle represented by its
_bounds as needing redrawn in the document view's coordinate system, it
tried to convert its _bounds into the document view's coordinate system.  
(the document view is the text view).  The conversion was done
incorrectly, because of the inconsistency between _boundsMatrix and the
real _bounds.  As a result, the wrong document visible rect was produced.  
This was further intersected with the document view _bounds, which would
leave a tiny rectangle - sometimes even of 0 size and often mostly outside
the visible area - to be marked as needing redrawing.  As a consequence,
the area which really needed being redrawn was not marked as such, and the
screen representation was messed up.

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