Question

I just noticed while building a delphi 2010 application that the scrollbar is always the same size when it shows up. The scroller in the middle of the bar is always the same size no matter how much there actually is to scroll. In contrast, most modern applications use scrollbars where the size of the scroller is proportional to the amount available to scroll, so that by looking it is clear how much there is to scroll through. Is there a way to change the scroll properties on my delphi controls, or would that require custom controls?

edit:
The component in this particular instance was a TDBGrid, which scrolled horizontally. I didn’t realize that windows was drawing these scrollbars. Perhaps Warren is correct and the question is unanswerable. Proportional scrollbars may not be ubiquitous on windows but I have yet to find a program on my windows machine that doesn’t use them. Even the delphi 2010 IDE uses them.

Answer 1

This is how I do it in a custom component of mine (a simple text viewer):

procedure TCustomViewer.UpdateScrollInfo;
var
  ScrollInfo: TScrollInfo;
begin
  with ScrollInfo do
  begin
    cbSize := SizeOf(ScrollInfo);
    fMask := SIF_POS or SIF_PAGE or SIF_RANGE or SIF_DISABLENOSCROLL;
    nMin := 0;
    nMax := 1023;
    nPage := PageWidth;
    nPos := FTopLeft.X;
  end;
  SetScrollInfo(Handle, SB_HORZ, ScrollInfo, True);
  with ScrollInfo do
  begin
    nMax := FLines.Count - 1;
    nPage := PageHeight;
    nPos := FTopLeft.Y;
  end;
  SetScrollInfo(Handle, SB_VERT, ScrollInfo, True);
  UpdateCaretPos;
  Update;
end;

IOW, you use a TScrollInfo, fill it up with the values you need to change, including nMax and nPage, and call SetScrollInfo with it, indicating the scroll bar you want to change. I’m sure that most controls with scroll bars control them internally, but if a control doesn’t, you could try SetScrollInfo. It might work for some of them. TScrollInfo and SetScrollInfo are defined in Windows.pas. Here is the MSDN link.