How to redraw only when form resize is complete?
lazarus / 31-LCL

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Windsurfer · 2015-03-10 12:24

I have a form that contains a graphic, which is created from up to
10,000 thousand data points. I have tuned the code (LCL) to run very
quickly, and I am very happy with the speed in Windows and Linux.

My problem is that when the form is resized, the panels and buttons in
the form do not change very smoothly. Is there a way to suppress the
repaints until the form resize is complete?

i7 processor, Linux Mint 17, 1.4RC2, qt and GTK2.

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Martin_fr · 2015-03-10 13:50

Well I don't know. Maybe you can track the mouse down/up, and set
flag, and in your paint code do a check (the point event will happen,
no matter what)

But I suggest a different approach.

Paint your data to a bitmap, then onpaint only (stretch) draw the
image.

If stretch was needed, then Application.QueueAsyncCall. Or ONIdle Or
ontimer.
There you can redraw your data.
** EXCEPT ** do not draw all at once. Draw small bits, that take
little time. And then set another Application.QueueAsyncCall and
continue (or restart if further resize occurred)

Or repaint in a thread. check regularly, if the current paint, still
fits the size.

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Eugene Loza · 2015-03-10 14:45

Looks something similar to this:
http://stackoverflow.com/questions/1454190/how-can-i-make-my-form-
resize-more-smoothly
and, maybe with this note:
http://forum.lazarus.freepascal.org/index.php?topic=23487.0

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Windsurfer · 2015-03-10 23:00

Thanks for the ideas. I'll post back after some tests.