bug#11484: 23.4; Scrolling leaves traces of old text behind

[Jan Djärv]

Hello.

21 okt 2012 kl. 21:56 skrev Eli Zaretskii <eliz@gnu.org>:

>> From: Jan Djärv <jan.h.d@swipnet.se>
>> Date: Sun, 21 Oct 2012 21:07:11 +0200
>> Cc: 11484-done@debbugs.gnu.org
>> 
>> The current solution is to turn off LCD-smoothing.  A better
>> solution would be to draw the whole line every time.
> 
> What do you mean by "redrawing the whole line", and how would that be
> different from what was redrawn in the recipe for this bug?

In the file helix.pqr, there are columns of A:s followed by space.  When 
scrolling fast (or sometimes just going to the end of the buffer), the A:s are 
replaced with Y:s.  But the spacees following the A:s are not redrawn.  I 
assume the display engine correctly assumes that from a character view they 
have not changed and need not be redrawn.  But that extra pixel in A:s lower 
right corner is in the box for the space.  Redrawing the whole line in this 
case would also redraw the space.

That isn't a very good solution now that I think about it, as it would require 
a redraw of the whole line just to draw the cursor.  A more efficient way would 
be to include the previous unchanged character and the following unchanged 
character when redrawing a block of changed characters.

So redrawing the cursor for example would involve redrawing three characters.

        Jan D.