Dear all,
I encountered a flickering problem when using a statusbar under winxp (lazarus v0.9.27 r17839 i386-win32-win32/win64 fpc 2.2.2) Using a code similar to the following:

i:= 0;
while condition do
begin
  readln(f, str);
  label1.Caption:= Format('Number: %d', [i]);
  statusbar1.Panels[0].Text:= Format('Number: %d', [i]);
  Inc(i);
end;

The text in the status bar panel flickers a lot while the same text in the label does not flicker.
On Linux Ubuntu also the statusbar works fine.
Another issue, but I am not sure because I made just some few tests, it seems that writing on the statusbar is a little slower than writing on a label.
Regards,
Andrea

any suggestions?

Andrea Mauri ha scritto:

Andrea Mauri wrote

any suggestions?

Does TStatusBar have a DoubleBuffer property (I cannot test here at this place: no Lazarus available)

Bart

Yes, but the flickering remains both with DoubleBuffered:= True and
DoubleBuffered:= False.
The only difference is that using DoubleBuffered:= True the statusbar
seems to be repainted faster.
Andrea

Bart ha scritto:

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But why, same monitor, same application, labels do not flicker while statusbar flickers?
Andrea

Mattias G?rtner ha scritto:

But why, same monitor, same application, labels do not flicker while statusbar flickers?

If statusbar text and properties do not change and it still flickers when it is repainted, then there is a bug in the double buffering. Please create a bug report.

Mattias

Mattias Gaertner ha scritto:

As I wrote in my first e-mail in this thread the statusbar flickers when the text changes.
This is what I wrote in my first e-mail:

"
Dear all,
I encountered a flickering problem when using a statusbar under winxp (lazarus v0.9.27 r17839 i386-win32-win32/win64 fpc 2.2.2) Using a code similar to the following:

i:= 0;
while condition do
begin
  readln(f, str);
  label1.Caption:= Format('Number: %d', [i]);
  statusbar1.Panels[0].Text:= Format('Number: %d', [i]);
  Inc(i);
end;

The text in the status bar panel flickers a lot while the same text in the label does not flicker.
On Linux Ubuntu also the statusbar works fine.
Another issue, but I am not sure because I made just some few tests, it seems that writing on the statusbar is a little slower than writing on a label.
"

So the text changes (not all the text, 'Number: ' string is fixed) in the statusbar, no other properties change. I encounter this problem only on windows. Labels work properly. Confirm that I have to create a bug report.
Thanks,
Andrea

i:= 0;
while condition do
begin
 readln(f, str);
 label1.Caption:= Format('Number: %d', [i]);
 statusbar1.Panels[0].Text:= Format('Number: %d', [i]);
 Inc(i);
end;

If condition stays true, then statusbar will flicker continuously... (being updated continuously)

you don't have an "exit" condition here (like "while not EOF(F) do")

Maybe this will help?

Also, just for information:
Which OS are you on, which version of that OS and which SVN version (or Lazarus release version)?

Regards,
-Reenen

The code I wrote in the e-mail is just a sample!
Anyway, create a new project, drop a label, a statusbar and a button on the form. Create a panel on the statusbar.
On buttonclick drop the following code:

procedure TForm1.Button1Click(Sender: TObject);
var
i: integer;
begin
i:= 0;
while i < 10000 do
begin
//  Application.ProcessMessages;
  label1.Caption:= Format('Number: %d', [i]);
  statusbar1.Panels[0].Text:= Format('Number: %d', [i]);
  Inc(i);
end;

Clicking on the button the text in the statusbar panel start to be updated, and it flickers. The text in the caption is updated only at the end of the while do cycle.
If I uncomment the line Application.ProcessMessages both texts in label and in statusbar panel are updated during the while do cycle. The text in the label does not flicker while the text in the statusbar panel flickers.
I tested it on WinXP with lazarus v0.9.27 r17856 i386-win32-win32/win64 and fpc 2.2.2
The same code works on Linux with lazarus svn and fpc 2.2.2 (statusbar and label do not flicker).
I hope that I well explained the problem.
Best regards,
Andrea

Reenen Laurie ha scritto:

Great. There you have the bug. The statusbar should not update, just like the label.

If I uncomment the line Application.ProcessMessages both texts in label and in statusbar panel are updated during the while do cycle. The text in the label does not flicker while the text in the statusbar panel flickers.

It probably flickers because of above bug.

Yes, although I'm not a win32 intf developer. Please create a bug report with the above example.

Mattias

Bug report created.
Andrae

Mattias Gaertner ha scritto:

As far as I know, in Delphi the statusbar updates immediatly, contrary to a label.

Michael.

Michael Van Canneyt wrote

As far as I know, in Delphi the statusbar updates immediatly, contrary to a label.

There is a bug in VCL that causes statusbars flicker. It can be fixed by something like not passing WM_ERASEBKGND to DefWindowProc ("something like" is because it was a long time ago, and I cannot remember exactly). All common controls are doublebuffered natively by Windows, so they shouldn't flicker even without doublebuffering in LCL.

Regards,
Sergei

I saw that the bug (ID 0012816) related to this thread has been closed. But I still encounter the same problem as described in my first e-mail. The statusbar panel still flickers.
Andrea

Sergei Gorelkin ha scritto: