[solved] Confused using PrintWindow
lazarus / 39-Graphics

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Cliff48 · 2015-06-27 20:59

Ok tearing the last of my hair out as I keep trying many things to
make something work.  I have a popup menu that:
Code: [Select]procedure TForm1.MenuItem2Click(Sender: TObject);   
begin
  bmp := Tbitmap.Create;
.
.  A bunch of code to manipulate image in a TBitmap
. (content changes each time here). It gets content
. from a DC that was filled via PrintWindow
.
  bmp.Canvas.Changed;
  Image1.Picture.Assign(bmp);
  bmp.Free;
end;


This works perfectly and I can click the menuItem  many times in quick
succession and its fine 9 out of 10 times, or 10 out of ten if not
clicking too quickly.

So I added another menu item:

Code: [Select]procedure TForm1.MenuItem3Click(Sender: TObject);
begin
        // simulating 5 clicks of popup Item2
  for i := 1 to 5 do begin
    Delay(2000);
    MenuItem2Click(self);
  end;
end;

It doesn't matter what I set the delay to, I basically only get the
titlebar from the window I tried to access.  Even the first itteration
(i=1) does this, which leads me to believe its not directly a
PrintWindow issue.

I have also tested by running the program directly (not in IDE) and
get the same results.  Any suggestions greatly appreciated.

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rvk · 2015-06-27 21:21

Quote from: Cliff48 on June 27, 2015, 10:59:24 pmSo I added another
menu item:

Code: [Select]procedure TForm1.MenuItem3Click(Sender: TObject);
begin
        // simulating 5 clicks of popup Item2
  for i := 1 to 5 do begin
    Delay(2000);
    MenuItem2Click(self);
  end;
end;

It doesn't matter what I set the delay to, I basically only get the
titlebar from the window I tried to access.  Even the first itteration
(i=1) does this, which leads me to believe its not directly a
PrintWindow issue.
If you're using this in a loop, like your test menu-item, you'll need
to add a ProcessMessages in there or the application has no way to
update your screen.

So:
Code: [Select]procedure TForm1.MenuItem3Click(Sender: TObject);
begin
        // simulating 5 clicks of popup Item2
  for i := 1 to 5 do begin
    Delay(2000);
    MenuItem2Click(self);
    Application.ProcessMessages;
  end;
end;

Quote from: Cliff48 on June 27, 2015, 10:59:24 pmThis works perfectly
and I can click the menuItem  many times in quick succession and its
fine 9 out of 10 times, or 10 out of ten if not clicking too quickly.
What is actually the problem? What happens 1 time out of those 10??

If it's not updating the image you could add the ProcessMessages in
the MenuItem2Click.

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Cliff48 · 2015-06-27 21:28

Thank you rvk, that fixed it.  Now I am really kicking myself... I
knew that!!!! Why does the brain go looking for ridiculous solutions
instead of ones already in the armoury?

Thanks so much!!

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BitBangerUSA · 2015-06-27 21:58

QuoteWhy does the brain go looking for ridiculous solutions
because, IMO, one of the hardest things to learn in trouble-shooting
is how to recognize when you're going down the wrong path.
i've no doubt you 'knew that' - and that everyone has done the same at
least once.
techies need persistence - as long as it doesn't result in the classic
'doing the same thing over and over and expecting different results'
scenario.