[Lazarus] TPairSplitter, Callback when splitter moved

[Jürgen Hestermann]

Am 2013-08-24 22:58, schrieb Mattias Gaertner:
> On Fri, 23 Aug 2013 13:50:16 +0200
> Jürgen Hestermann <juergen.hestermann at gmx.de> wrote:
>
>> I can ensure that the ratio between upper and lower panel is a certain ratio by adding an OnResize method like this:
>> PairSplitter1.Position := Round(PairSplitter1.Height*SplitterRatio);
>> with SplitterRatio beeing something between 0 and 1 (I used 0.5 to make both (nearly) the same size).
>>
>> But if the user now changes the ratio manually I need to update SplitterRatio.
>> What event is driven when the splitter is moved manually so that I can recalculate SplitterRatio?
> When the splitter is moved the size of the first side is changed. So,
> you could use Sides[0].OnResize.
>
Well, unfortunately it's not that easy.

The panel sizes are changed too when the whole form size changes.
That's what I wanted it to do.
In this case the new ratio should *not* be recalculated, just the opposite:
It should resize the 2 controls according to the original ratio.

So the same ratio between both sides should exist even after resizing except
when resizing is caused by moving the splitter in which case a new ratio should be calculated.
But OnResize is called in all cases and I can't distinguish between the user
having moved the splitter or the form has changed (and I reapply the old ratio).

But I found a solution by saving the old height (or width) of the TPairSplitter component:

-------------------------------------------------------------------------------------
var SplitterHeightOld : LongInt;

procedure TForm1.PairSplitter1Resize(Sender : TObject);
begin
PairSplitter1.Position := Round(PairSplitter1.Height*SplitterRatio);
SplitterHeightOld        := PairSplitter1.Height;
end;


procedure TForm1.PairSplitterSide1Resize(Sender : TObject);
begin
if SplitterHeightOld=PairSplitter1.Height then
    SplitterRatio := PairSplitter1.Position/PairSplitter1.Height;
end;
-------------------------------------------------------------------------------------

How would I do this when using TSplitter instead of TPairSplitter?
It seems I need yet another panel that contains the splitter and the 2 other controls
so that I can distinguish between size change caused by change of window size or
by moving the splitter.

In general, I am astonished that this kind of proportial resizing is not implemented and the default in TPairSplitter.
I would think that nearly everybody wants this behaviour when two controls should share the same space.
Why should one of the controls *not* grow when the windows is enlarged (or shrink when it is made smaller)?
At least an event for the splitter move would be needed.
Or even 2 properties "ProportialSizing" (with TRUE as default) and "SizingRatio" (with 0.5 as default).

But too bad if TPaisSplitter will be removed at all.
Why is it still there if it should be removed since so many years?
I thought that internally it is built with TSplitter anyway,
so why is it a problem on certain WidgetSets?