https://bugs.documentfoundation.org/show_bug.cgi?id=142585

--- Comment #8 from Adalbert Hanßen <[email protected]> ---
Created attachment 179857
  --> https://bugs.documentfoundation.org/attachment.cgi?id=179857&action=edit
An example which shows the bug (the text in it describes another bug)

For sometime now I've noticed that large parts of my LibreOffice Writer window
occasionally flicker. I first noticed this with very large files. However, I
had also an example of a one page document (but then the flickering frequency
seems to be less than with large files).

The flickering occurs when there is at least the Navigator or Style window open
next to the actual text box. When flickering happens, it happens more often
that keystrokes arrive out of sequence in the editor window. To avoid this, I
have to type very slowly. 

I have indicators on the taskbar that constantly show me the CPU and memory
usage. They show me that both are not the cause of the problem.

When composing an example for #148755 the flickering became extremely bad when
I wrote the last example in it. After I inserted the last image into the table,
it became catastrophic. I could hardly continue writing. Then after patiently
adding more and more text, it got much better. But the flickering is still
there.

The concurrency of the processes in LibreOffice might be insufficiently
organized. Can this problem be improved by waiting to update the screen items
for Styles, Navigator and the items in the Toolbox that control paragraph
format, font size, and other formatting properties and the search box at the
bottom until a writing pause of more than 1/10 of a second has passed? Could
the contents of these screen areas just be calculated for now and not rolled
out continuously? Another possibility would be to provide an order for updating
the concurrent screen pieces: Always those of the categories first, then lower
its priority behind that of the other pieces until those are finished. Of
course, the text edit window should always be served immediately. I would even
consider it acceptable if the areas other than the actual text edit window
would update only during writing pauses, e.g. one or even two seconds after the
last keystroke! The actual background work - e.g. searching, which position in
the heading hierarchy is currently affected etc., can be done continuously in
the background and discarded if necessary, if "dramatic changes" have happened
in the editor window, like insert, PageUp, PageDown change of style sheet or at
all more than a certain number of keystrokes since the last update of the
concurrent screen areas. (For GUI programmers my explanations may sound a bit
amateurish: In the second half of the 1980s I solved a similar problem in an
8086 controlled device this way – that one ran completely without operating
system - ).

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