Lazarus: How to Focus on TPanel
lazarus / 31-LCL

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staratel20 · 2016-03-11 19:04

Hi.

After read some forums create that simple code, that not work:

Code: Pascal  [Select][+][-]window.onload = function(){var x1 =
document.getElementById("main_content_section"); if (x1) { var x =
document.getElementsByClassName("geshi");for (var i = 0; i procedure
TForm1.FormCreate(Sender: TObject);var  b :boolean;begin 
Panel1.TabStop:=True;  b:=Panel1.CanFocus;  // b=true in debugger 
Panel1.SetFocus;        // here raising errorend;
Is this behaviour correct?

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howardpc · 2016-03-11 22:54

You can set a panel's TabStop property in its containing form's
OnCreate handler, but OnCreate is is called too early for focusing a
control - the form itself is not active yet, so its controls certainly
cannot be active.
The form's OnActivate (or OnShow) event are the earliest available
moments for setting focus for a contained control.

There's no point calling CanFocus - setting the focus already checks
this for you.

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FTurtle · 2016-03-12 03:02

Code: Pascal  [Select][+][-]window.onload = function(){var x1 =
document.getElementById("main_content_section"); if (x1) { var x =
document.getElementsByClassName("geshi");for (var i = 0; i procedure
TForm1.FormCreate(Sender: TObject);begin  ActiveControl := Panel1;end;

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staratel20 · 2016-03-12 10:47

howardpc: of cause! My fault - create bad isolated example. But when
meet the problem, I was thinking that this code will not work too:

procedure TForm1.FormCreate(Sender: TObject);
begin
  Panel1.TabStop:=true;
end;

procedure TForm1.Button1Click(Sender: TObject);
begin
  Panel1.SetFocus;
end; 

but it works.

Thanks for all answers.

FTurtle: your code was helpful.

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FTurtle · 2016-03-12 11:19

Quote from: staratel20 on March 12, 2016, 11:47:29 amprocedure
TForm1.Button1Click(Sender: TObject);
begin
  Panel1.SetFocus;
end; 

By the way, when experimenting with focus, instead of TButton is
better to use TSpeedButton because it does not take focus and
therefore does not change the situation.

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staratel20 · 2016-03-12 11:39

In form where I need this - all(thanks God) on TSpeedButtons)))

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Windsurfer · 2016-03-12 16:53

Thanks for the TSpeedButton tip.

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SymbolicFrank · 2016-03-17 12:52

The OnActivate and OnShow events are useful, but they can be fired
multiple times.

For a workaround you can use a TTimer:

Code: Pascal  [Select][+][-]window.onload = function(){var x1 =
document.getElementById("main_content_section"); if (x1) { var x =
document.getElementsByClassName("geshi");for (var i = 0; i procedure
TMainForm.StartTimerTimer(Sender: TObject);begin  if not Visible then
Exit;  StartTimer.Enabled := False;  // now do the final
initializationend;

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staratel20 · 2016-03-18 19:40

My problem totally solved. But I'm feel like it's wrong - that
CanFocus return True when actually can't focus on control. If
Panel1<>nil - CanFocus by default must return False. And just created
form must somehow notify childs , that they can take focus. Maybe it's
difficult or I'm wrong, but think it's more correct.