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List:       kde-devel
Subject:    Re: HTMLW
From:       Johannes Sixt <Johannes.Sixt () telecom ! at>
Date:       1998-01-12 21:52:26
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>>>> Hi!
>>>> I think there is a bug in the htmlwidget. If you scroll in KFM, KMail or
>>>> Krn using the arrow-keys or the arrows of the scrollbars, there is a bug
>>>> in the redraw. The new lines arenīt fully drawn.

Hey, people, cool down on this topic! This is a typical scrolling problem under
X, which is asynchronous.

When you scroll fast, the following can happen:

server: sends MouseMove event 1
server: sends MouseMove event 2 (remember, we're scrolling FAST)
client: sends scroll-up request (e.g. 10 pixels) for MouseMove 1
server: sends GraphicsExposure 1 for bottom 10 pixels.
client: sends scroll-up request (e.g. for another 10 pixels) for MouseMove 2.
server: sends GraphicsExposure 2 for bottom 10 pixels.
client: paints bottom 10 pixels for GraphicsExposure 1.
client: paints bottom 10 pixels for GraphicsExposure 2.

You see, that the bottom 10 pixels get drawn twice, whereas a range of 10 pixels
above these don't get drawn at all.

The solution for must be tricky, I guess, difficult at least. I don't have an
idea, though. Perhaps it's necessary to track the event timestamps and move
pending expose events with the scroll requests.

Regards,
-- Hannes

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