TScrollingWinControl missmatch?
lazarus / 7-LCL

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wotanica · 2010-09-18 21:42

Looking over the Lazarus code i spotted this:

Code: [Select]function TScrollingWinControl.HasVisibleScrollbars:
boolean;
begin
  Result := (VertScrollBar <> nil) and VertScrollBar.Visible and
            (HorzScrollBar <> nil) and HorzScrollBar.Visible;
end;

Shouldent that be OR? E.g:

Code: [Select]function TScrollingWinControl.HasVisibleScrollbars:
boolean;
Begin
  if not (csDestroying in componentstate) then
  Begin
    result:=( assigned(vertscrollbar)
    and vertscrollbar.visible )
    or
    ( assigned(horzscrollbar)
    and horzscrollbar.visible );
  end else
  result:=False;
end;

There may be a horizontal scrollbar visible, but that would be ignored
if the vertical scrollbar is not assigned/visible. I realize that both
objects (scrollbars) are created in the constructor, but if the
vertical scrollbar is invisible, the horizontal state will be
eliminated from the boolean expression?

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Marc · 2010-09-19 15:22

The plural form of HasVisibleScrollbars, imply that both must be there
But indeed it doesn't make sense to me. Nowhere in the LCL this
function is used, so I don't know what it is supposed to do. I'll ask
others.

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wotanica · 2010-09-19 20:39

Yes, i figured it had to mean both since it was plural. But since both
objects are created in the constructor explicitly - the assigned()
checks will always return true unless the component is being destroyed
(hence i figured checking for csDestroying would be better). But both
horizontal and vertical scrollbars may not be visible, either one can
be visible or invisible depending on the content.

In delphi this one is used to determine if there are any scrollbars
visible during loading, assignment etc. I seem to remember that it's
particularly called when cleaning up a view (f.ex in an imageviewer,
this would be called to check if the scrollbars needs to be reseted
prior to loading etc.)

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Marc · 2010-09-20 15:49

I looked in my delphi and I couldn't find it, so I thought it was a
laz only. Where is it implemented ?