TScrollBar.Position Property

Indicates the current position of the scroll bar.

Pascal

property Position: Integer;

C++

__property int Position;

Description

Read Position to determine the current position of the thumb tab. This value can be used to determine how to scroll any components controlled by the scroll bar. When the user scrolls the scroll bar, the value of Position changes. Set Position to programmatically move the thumb tab of the scroll bar.

The number of possible positions on the scroll bar is determined by the difference between the Max property and the Min property. If Position has the same value as Min, the thumb tab appears at the far left of a horizontal scroll bar or the top of a vertical scroll bar. If Position has the same value as Max, the thumb tab appears at the far right of a horizontal scroll bar or the bottom of a vertical scroll bar.

C++ Examples:

Copy Code

/*
This example shows how to use a scroll bar to navigate the
pages of a page control.  To run this example, place a
scroll bar and a page control on a form.  Right click the
page control and add 12 pages to it.  Add the following code
to the OnCreate event of the form, the OnChange event of the
page control, and the OnScroll event of the scroll bar.
Note that the LargeChange and SmallChange properties are set
to automatically change the active page by one tab or one
row respectively.  The OnScroll event is used to make the
actual change in the page control, while the OnChange event
of the page control ensures that the scroll bar is kept in
sync with changes made directly to the page control.
*/
void __fastcall TForm1::FormCreate(TObject *Sender)
{
  const TColor colorPalette[12] = {clRed, clGreen, clYellow, clBlue, clWhite, clFuchsia, clTeal, clNavy, clMaroon, clLime, clOlive, clPurple};
  // First, initialize the page control
  PageControl1->TabWidth = PageControl1->ClientWidth/4 - 1;
  PageControl1->ActivePage = PageControl1->Pages[0];
  for (int i = 0; i < PageControl1->PageCount; i++)
    PageControl1->Pages[i]->Brush->Color = colorPalette[i];
  /* set up the scrollbar to reflect
     the structure of the page control */
  ScrollBar1->Max = PageControl1->PageCount - 1;
  ScrollBar1->Min = 0;
  ScrollBar1->SmallChange = 1;
  // set LargeChange to a single row of tabs 
  ScrollBar1->LargeChange = PageControl1->ClientWidth / PageControl1->TabWidth;
}

void __fastcall TForm1::PageControl1Change(TObject *Sender)
{
  ScrollBar1->Position = (dynamic_cast<TPageControl *>(Sender))->ActivePage->PageIndex;
}

void __fastcall TForm1::ScrollBar1Scroll(TObject *Sender,
      TScrollCode ScrollCode, int &ScrollPos)
{
  PageControl1->ActivePage = PageControl1->Pages[ScrollPos];
}

Delphi Examples:

Copy Code

{
This example shows how to use a scroll bar to navigate the
pages of a page control.  To run this example, place a
scroll bar and a page control on a form.  Right click the
page control and add 12 pages to it.  Add the following code
to the OnCreate event of the form, the OnChange event of the
page control, and the OnScroll event of the scroll bar.
Note that the LargeChange and SmallChange properties are set
to automatically change the active page by one tab or one
row respectively.  The OnScroll event is used to make the
actual change in the page control, while the OnChange event
of the page control ensures that the scroll bar is kept in
sync with changes made directly to the page control.
} 
procedure TForm1.FormCreate(Sender: TObject);
var
  i : Integer;
const
  colorpalette: Array[0..11] of TColor = (clRed, clGreen, clYellow, clBlue, clWhite, clFuchsia, clTeal, clNavy, clMaroon, clLime, clOlive, clPurple);
begin
  { First, initialize the page control }
  PageControl1.TabWidth := PageControl1.ClientWidth div 4 - 1;
  PageControl1.ActivePage := PageControl1.Pages[0];
  for i := 0 to PageControl1.PageCount - 1 do
    PageControl1.Pages[i].Brush.Color:= colorPalette[i];
  { set up the scrollbar to reflect the structure of the page control}
  with ScrollBar1 do
  begin
    Max := PageControl1.PageCount - 1;
    Min := 0;
    SmallChange := 1;
    { set LargeChange to a single row of tabs }
    LargeChange := PageControl1.ClientWidth div PageControl1.TabWidth;
  end;
end;

procedure TForm1.PageControl1Change(Sender: TObject);
begin
  with Sender as TPageControl do
    ScrollBar1.Position := ActivePage.PageIndex;
end;

procedure TForm1.ScrollBar1Scroll(Sender: TObject; ScrollCode: TScrollCode;
  var ScrollPos: Integer);
begin
  PageControl1.ActivePage := PageControl1.Pages[ScrollPos];
end;