Capturing the tab order of a focused item
lazarus / 31-LCL

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MaxCuriosus · 2020-04-25 11:57

In a form that has a few buttons I would like to determine which one
has the actual focus based on the tab order/index of that button. Is
there some kind of form property that can be used for that?

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lucamar · 2020-04-25 12:33

I don't know exactly what you want to do but you can get the currently
focused control with something like:

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 function
GetFocusedControl(const Root: TControl): TControl;var  i:
Integer;begin  Result := Nil  if Root.ControlCount > 0 then begin   
for i := 0 to Root.ControlCount-1 do      if (Root.Controls[i] is
TWinControl)      and TWinControl(Root.Controls[i].Focused) then
begin        Result := Root.Controls[i];        Break;      end else 
     if Root.Control[i].ControlCount > 0 then begin          Result :=
GetFocusedControl(Root.Control[i]);          if Assigned(Result) then
Break;        end;  end;end;
And to get the tab order:

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 AControl :=
GetFocusedControl(MyForm);if Assigned(AControl) and (AControl is
TWinControl) then  Order := TWincontrol(AControl).TabOrder;  {Or
whatever you want}

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howardpc · 2020-04-25 13:08

Perhaps something like this?
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 unit
uMain; {$mode objfpc}{$H+} interface uses  SysUtils, Forms, Controls,
StdCtrls; type  TForm1 = class(TForm)  published    procedure
FormCreate(Sender: TObject);    procedure IdleEvent(Sender: TObject;
var Done: Boolean);  private const    ButtonCount: Integer = 5; 
private    FButtons: array of TButton;  end; var  Form1:
TForm1; implementation {$R *.lfm} procedure TForm1.FormCreate(Sender:
TObject);var  i: Integer;begin  SetLength(FButtons, ButtonCount);  for
i := 0 to High(FButtons) do    begin      FButtons[i] :=
TButton.Create(Self);      FButtons[i].Caption :=
Format('Button%d',[i+1]);      FButtons[i].Name :=
FButtons[i].Caption;      FButtons[i].Left := 20;      FButtons[i].Top
:= i*30 + 20;      FButtons[i].Parent := Self;    end; 
Application.OnIdle := @IdleEvent;end; procedure
TForm1.IdleEvent(Sender: TObject; var Done: Boolean);const 
priorActiveControl: TWinControl = Nil;begin  case
Assigned(ActiveControl) of    True:  begin             if
(ActiveControl <> priorActiveControl) and (ActiveControl is TButton)
then               begin                 Caption := Format('%s is
active (taborder %d)',[ActiveControl.Name, ActiveControl.TabOrder]); 
              priorActiveControl := ActiveControl;               end; 
         end;    False: Caption := 'There is no control active at
present';  end;  Done := True;end; end.

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MaxCuriosus · 2020-04-26 10:05

lucamar,
with your code the compiler complains a lot with

Error: identifier idents no member "ControlCount"
Error: identifier idents no member "Controls"

In the unit "Controls" under "TControl" I could not find those
identifiers. Is there a minimum version for Lazarus/Pascal? My
configuration is Deb9/Laz2.0.2/FPC3.0.4/x86_64-linux-gtk2.

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lucamar · 2020-04-26 13:52

Quote from: MaxCuriosus on April 26, 2020, 12:05:46 pmwith your code
the compiler complains a lot with
Error: identifier idents no member "ControlCount"
Error: identifier idents no member "Controls"

Yeah, sorry
Actually, those (as well as TabOrder and Focused) are properties of
TWinControl, not of TControl; it should have been:

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 function
GetFocusedControl(const Root: TWinControl): TControl;var  i: Integer; 
Ctrl: TControlbegin  Result := Nil  if Assigned(Root) and
(Root.ControlCount > 0) then begin    for i := 0 to
Root.ControlCount-1 do begin      Ctrl := Root.Controls[i];      if
Ctrl is TWinControl then begin        if TWinControl(Ctrl).Focused
then          Result := Ctrl;        else          if
TWinControl(Ctrl).ControlCount > 0 then            Result :=
GetFocusedControl(Ctrl);        if Assigned(Result) then Break;     
end;    end;  end;end;
And:

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 AControl :=
GetFocusedControl(MyForm);if Assigned(AControl) and (AControl is
TWinControl) then  Order := TWincontrol(AControl).TabOrderelse  Order
:= -1;  {Or whatever you want}

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jamie · 2020-04-26 18:51

Something tells me the order In which the one before and one next is
needed..

How about using the  FORM1.GetTabOrderList(AList) ?

 and from that, you could I guess determine who is who..

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MaxCuriosus · 2020-04-26 19:49

lucamar,
with your latest code the compiler complains at line 15:

Error: Incompatible type for arg no. 1: Got "TControl", expected
"TWinControl"

I think there is an inherent incompatibilty due to the recursive
nature of your algorithm. That may be not trivial to resolve. Could
you try to compile it on your system?

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lucamar · 2020-04-26 20:04

Quote from: MaxCuriosus on April 26, 2020, 09:49:25 pmlucamar,
with your latest code the compiler complains at line 15:

Error: Incompatible type for arg no. 1: Got "TControl", expected
"TWinControl"

I think there is an inherent incompatibilty due to the recursive
nature of your algorithm. That may be not trivial to resolve. Could
you try to compile it on your system?

No incompatibility, just plain human error: I changed the function to
accept a TWinControl so, of course, one can't pass a TControl to it 

Just change those lines to:
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          if
TWinControl(Ctrl).ControlCount > 0 then            Result :=
GetFocusedControl(Ctrl as TWinControl);
By now that code has had so many iterations that it's become plain
ugly, what with all those type-casts. if I were to use it I would
expend a couple minutes making a new, more elegant function.

Edited to add:

Ok, new, tested code:

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 function
GetFocusedControl(const Root: TWinControl): TWinControl;var  i:
Integer;  Ctrl: TWinControl;begin  Result := Nil;  if Assigned(Root)
and (Root.ControlCount > 0) then begin    for i := 0 to
Root.ControlCount-1 do begin      if
Root.Controls[i].InheritsFrom(TWinControl) then        Ctrl :=
Root.Controls[i] as TWinControl;      if Ctrl.Focused then       
Result := Ctrl      else        if Ctrl.ControlCount > 0 then        
Result := GetFocusedControl(Ctrl);      if Assigned(Result) then
Break;    end;  end;end; procedure TForm1.Button1Click(Sender:
TObject);var  AControl: TWinControl;begin  AControl :=
GetFocusedControl(Self);  if Assigned(AControl) then   
ShowMessageFmt('Focusesed control %s (a %s) has TabOrder: %d',       
          [AControl.Name, AControl.ClassName, AControl.TabOrder]) 
else    ShowMessage('No control seems to be focused!?');end;

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MaxCuriosus · 2020-04-26 20:14

lucamar,
OK now that the compiling is successful, I will check how the
recursivity work. Thank you.

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lucamar · 2020-04-26 20:31

Quote from: MaxCuriosus on April 26, 2020, 10:14:44 pmI will check how
the recursivity work. Thank you.
It's actually easy: You first pass a TWinControl to check its Controls
and if it returns a focused one that's that; otherwise, we see if it's
some kind of container and, if so, re-call the function to to check
its controls and if it returns a focused one ...

You get the drift I guess; It basically resembles what we'd do (more
or less) to find a node in a tree.

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MaxCuriosus · 2020-04-26 20:34

howardpc,
thank you for your suggestion. I've adapted your code as below, which
allows me to make the focused button more immediately visible. However
the button font color changes under Linux but not under Windows. Any
idea why?

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.IdleEvent(Sender: TObject; var Done:
Boolean);const  priorActiveControl: TWinControl = Nil;begin  case
Assigned(ActiveControl) of    True:  begin             if
(ActiveControl <> priorActiveControl) and (ActiveControl is TButton)
then               begin//                 Caption := Format('%s is
active (taborder %d)',[ActiveControl.Name, ActiveControl.TabOrder]); 
              if PriorActiveControl<>Nil then                 
 priorActiveControl.Font.Color := clDefault;               
 priorActiveControl := ActiveControl;               
 ActiveControl.Font.Color:=clRed; // and also bold face by default   
                  end;           end; //   False: Caption := 'There is
no control active at present';  end;  Done := True;end;

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jamie · 2020-04-26 22:28

Let me add to the list here

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.Button1Click(Sender: TObject);var  A:TFPlist;begin  A :=
TFPList.Create;  Form1.GetTabOrderList(A);  Caption :=
A.IndexOf(Pointer(ActiveControl)).ToString;  A.Free;end;

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jamie · 2020-04-26 22:42

and this one
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.Button1Click(Sender: TObject);begin  caption :=
Form1.GetControlIndex(ActiveControl).ToString;end;                   
                                  
you see, etherway you can get TabOrder index or Control index...

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howardpc · 2020-04-27 09:46

Quote from: MaxCuriosus on April 26, 2020, 10:34:30 pmhowardpc,
thank you for your suggestion. I've adapted your code as below, which
allows me to make the focused button more immediately visible. However
the button font color changes under Linux but not under Windows. Any
idea why?
I don't use Windows unless forced to, so I do not know.
However, my guess would be that a difference might arise because of
differences between the OS messaging systems.
If so, an

    Application.ProcessMessages
call might make a difference?

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MaxCuriosus · 2020-04-27 21:56

Well gentlemen, there is a lot of new stuff (for me) to digest. If I
don't get an indigestion I will keep you posted.
Thank you all.

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eljo · 2020-04-27 23:16

Sorry if this has already been said but I see a lot redundant code
flying around and I have no desire to read it all, so I'll just ask
have you tried
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  
showmessage(inttotsr(Form1.ActiveControl.TabOrder)); and if yes what
is the problem you stumble upon exactly.

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jamie · 2020-04-28 00:14

I think tab order was a mistake when asked, what they really wanted
was the index of where it lived in the order of controls.

 The TABORDER may not always be the same order of the control in the
controls array.. So if a person needs to know which control is the
next or before in the order of creation that could use many of the
already existing methods...

 I believe this person is writing a RAD system by looking at his post.

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MaxCuriosus · 2020-04-28 22:47

eljo,
what I wanted to achieve has been achieved, see reply #10. Everything
else is for my learning experience. Thank you for your suggestion
anyway.