[Lazarus] TMemo flicker

[José Mejuto]

El 01/05/2013 12:16, Jürgen Hestermann escribió:

> Yes, if the *programmer* does multiple things to a GUI component. But
> here it was only a single assignment which should not require
> Begin/EndUpdate but this assignment seems to cause multiple things
> internally which make it flicker .
>

Hello,

Before looking inside the LCL code the effect could be explained as 
TMemo text property is completly erased and rewritten each time 
something change in the text, so when the last line is changed, 
internally the whole content is erased and replaced by the new one. When 
the OS component receives the new text it seems to send some messages to 
itself to adjust scrollbars (which begin/end update will block), the 
first one remove scrollbars, the next one fill the text, as the text is 
larger than visible part scrollbar goes to the bottom (this will not 
happend with begin/end update).

The strange thing is that this behavior should produce high CPU usage 
but not a up/down one line effect, so something is wrong either in LCL 
or in the Memo Windows control.

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