Flickering with TScrollbox

[simsee]

I have a similar problem to the one described in the following video:

https://www.youtube.com/watch?v=jo7FUPy5SEU

In my case I have a form containing a scrollbox. The form caption shows the current coordinates of the mouse pointer. If the scrollbars are visible, the edge of the scrollnox flickers. If I set the BorderStyle to bsNone, the problem does not occur. Can anything be done to avoid this problem? Thank you.

[KodeZwerg]

Can anything be done to avoid this problem?

Yes.

Thank you.

You are welcome.


Ps. for better help you should provide a test project that shows your problem.

[simsee]

Thanks for the support. The problem arises under Windows o.s. (Lazarus 2.2.6 - FPC 3.2.2 x86_64-win64-win32/win64) . See attached project to reproduce.

[dsiders]

Thanks for the support. The problem arises under Windows o.s. (Lazarus 2.2.6 - FPC 3.2.2 x86_64-win64-win32/win64) . See attached project to reproduce.

The flicker is the border for the control being redrawn. Set the BorderStyle for the TScrollBox to bsNone and the problem is gone.

[simsee]

As I wrote in my initial post, I already know this solution. I would like to know if there are alternatives to eliminating the border.

[jamie]

Turn off the border as stated and drop the scrollbox inside a Tpanel, the Panel has border control that is actually better and it does not flicker like that.

 Just do a CUT of your current scrollbox and Paste inside the Panel, Set the Align=Client for the scrollbox. etc.

[KodeZwerg]

In attachment is a possible fix/solution.

Flickering with my way = zero.

[jamie]

I never use a scrollbox alone anyways. THe border is never on.

[KodeZwerg]

Since topic is not marked as solved, I like to ask what is still wrong / not working?

I would like to know if there are alternatives to eliminating the border.

I showed you an alternate way how everything can stay like it is and you still can manipulate the Caption in whatever way.
Eliminating the Border/Redraw would cause more troubles, it is better to let OS mechanic do its things normally.

[simsee]

Sorry for the delay, I've been busy at work. Both proposed solutions solve the problem, which I believe does not occur with other widgetsets under Linux (Qt, GTK). I haven't tried it, but I report what I read in the comments of the YouTube video I linked. Thanks for the support.

[Martin_fr]

It should be reported: https://gitlab.com/freepascal.org/lazarus/lazarus/-/issues

[Martin_fr]

It may be the scrollbars AutoScroll property.

Disabling that (and just setting the scrollbars) => seems fine

[Martin_fr]

Please test with https://gitlab.com/freepascal.org/lazarus/lazarus/-/commit/4891f1f0e1aebe5903daeff49bd6360b34e09eea

[Martin_fr]

There is still an issue though.

Timer with interval=10

Code: Pascal  [Select][+][-]

1. procedure TForm1.Timer1Timer(Sender: TObject);
2. begin
3.   Invalidate;
4. end;

And it still flickers.

https://gitlab.com/freepascal.org/lazarus/lazarus/-/issues/40548

[simsee]

It seems to me that with the version of Lazarus 3.0 - FPC 3.2.2 x86_64-win64-win32/win64, the fickering problem I reported has been resolved. I am grateful to those who can confirm this on other platforms as well.

Thanks to the development team.