Forms TScrollBar tutorial

[Freddy1990]

In this tutorial we will learn how to add and use the TScrollBar component in SCAR forms.
We begin with a basic script that shows a form:
program ScrollBarTest;

var
frmDesign: TForm;

procedure InitForm;
begin
frmDesign := CreateForm;
frmDesign.Left := 259;
frmDesign.Top := 132;
frmDesign.Width := 354;
frmDesign.Height := 254;
frmDesign.Caption := 'Menu Testing Form';
frmDesign.Color := clBtnFace;
frmDesign.Font.Color := clWindowText;
frmDesign.Font.Height := -11;
frmDesign.Font.Name := 'MS Sans Serif';
frmDesign.Font.Style := [];
frmDesign.Visible := False;
frmDesign.PixelsPerInch := 96;
end;

procedure SafeInitForm;
var
v: TVariantArray;
begin
SetArrayLength(v, 0);
ThreadSafeCall('InitForm', v);
end;

procedure ShowFormModal;
begin
frmDesign.ShowModal;
end;

procedure SafeShowFormModal;
var
v: TVariantArray;
begin
SetArrayLength(v, 0);
ThreadSafeCall('ShowFormModal', v);
end;

begin
SafeInitForm;
SafeShowFormModal;
end.
http://stuart.existhost.com/freddy/tutimages/menu1.PNG

First to display the scrollbars value we're going to add a label.

So we add the variabledeclaration:
lbl: TLabel;

And we add to the initform procedure:
lbl := TLabel.Create(frmDesign);
lbl.Parent := frmDesign;
lbl.Left := 14;
lbl.Top := 7;
lbl.Width := 95;
lbl.Height := 13;

We don't give the label a text (caption) yet because the scrollbar is going to do that.

This results in the following script:
program ScrollBarTest;

var
frmDesign: TForm;
lbl: TLabel;

procedure InitForm;
begin
frmDesign := CreateForm;
frmDesign.Left := 259;
frmDesign.Top := 132;
frmDesign.Width := 354;
frmDesign.Height := 254;
frmDesign.Caption := 'Scrollbar Testing Form';
frmDesign.Color := clBtnFace;
frmDesign.Font.Color := clWindowText;
frmDesign.Font.Height := -11;
frmDesign.Font.Name := 'MS Sans Serif';
frmDesign.Font.Style := [];
frmDesign.Visible := False;
frmDesign.PixelsPerInch := 96;

lbl := TLabel.Create(frmDesign);
lbl.Parent := frmDesign;
lbl.Left := 14;
lbl.Top := 7;
lbl.Width := 95;
lbl.Height := 13;
end;

procedure SafeInitForm;
var
v: TVariantArray;
begin
setarraylength(v, 0);
ThreadSafeCall('InitForm', v);
end;

procedure ShowFormModal;
begin
frmDesign.ShowModal;
end;

procedure SafeShowFormModal;
var
v: TVariantArray;
begin
setarraylength(v, 0);
ThreadSafeCall('ShowFormModal', v);
end;

begin
SafeInitForm;
SafeShowFormModal;
FreeForm(frmDesign);
end.

Now, first we add the scrollbar to the variabledeclaration:
sb: TScrollBar;

Next we create the scrollbar in our form by adding the following to the initform procedure:
sb := TScrollBar.Create(frmDesign);

Next we add a line to put the scrollbar on our form:
sb.Parent := frmDesign;

Now we define the scrollbars size and position by putting the following in the initform procedure:
sb.Left := 11;
sb.Top := 47;
sb.Width := 300;
sb.Height := 19;

Next we use the Min and Max propertys which will define the scrollbars starting and ending point, the values i use are also default:
sb.Min := 0;
sb.Max := 100;

We also add the position property to the initform peocedure for setting the startingposition, in this case 0 which is also the default position:
sb.Position

To make the label display the position of the scrollbar, we're going to add the folowing procedure:
procedure OnScroll(sender: TObject);
begin
lbl.Caption := 'Scrollbar position: ' + IntToStr(sb.Position);
end;

Finally we add the procedure we just added to the scrollbar's onscroll event in the initform procedure:
sb.OnChange := @OnScroll;

Now we have our final script:
program ScrollBarTest;

var
frmDesign: TForm;
lbl: TLabel;
sb: TScrollBar;

procedure OnScroll(sender: TObject);
begin
lbl.Caption := 'Scrollbar position: ' + IntToStr(sb.Position);
end;

procedure InitForm;
begin
frmDesign := CreateForm;
frmDesign.Left := 259;
frmDesign.Top := 132;
frmDesign.Width := 354;
frmDesign.Height := 254;
frmDesign.Caption := 'Scrollbar Testing Form';
frmDesign.Color := clBtnFace;
frmDesign.Font.Color := clWindowText;
frmDesign.Font.Height := -11;
frmDesign.Font.Name := 'MS Sans Serif';
frmDesign.Font.Style := [];
frmDesign.Visible := False;
frmDesign.PixelsPerInch := 96;

lbl := TLabel.Create(frmDesign);
lbl.Parent := frmDesign;
lbl.Left := 14;
lbl.Top := 7;
lbl.Width := 95;
lbl.Height := 13;

sb := TScrollBar.Create(frmDesign);
sb.Parent := frmDesign;
sb.Left := 11;
sb.Top := 47;
sb.Width := 300;
sb.Height := 19;
sb.Min := 0;
sb.Max := 100;
sb.Position := 0;
sb.OnChange := @OnScroll;
end;

procedure SafeInitForm;
var
v: TVariantArray;
begin
setarraylength(v, 0);
ThreadSafeCall('InitForm', v);
end;

procedure ShowFormModal;
begin
frmDesign.ShowModal;
end;

procedure SafeShowFormModal;
var
v: TVariantArray;
begin
setarraylength(v, 0);
ThreadSafeCall('ShowFormModal', v);
end;

begin
SafeInitForm;
SafeShowFormModal;
FreeForm(frmDesign);
end.
http://stuart.existhost.com/freddy/tutimages/menu6.PNG

Now when we scroll the bar we see the current value show up on the label at the top of the form.

And that concludes this tutorial, have fun.

[Pentti]

Freddy, you are pretty good at forms! :D Your form tutorials are great! :D

[Rick]

So many tuts...so much information.