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by Alexander Rublinetsky

Version 1.1 (18K)

Zoomler is a freeware scrollbar-like Delphi native VCL component that can be used for scrolling and zooming any continuous objects: charts, images etc. All its position properties are of Double type - it is convenient for charts, and one can always call Round() if the object has integer coordinates. Zoomler can be horizontal and vertical. It is not a windowed control so it cannot receive focus, thus it has mouse interface only. Zoomler has seven mouse-sensitive areas:

two arrow buttons : for scrolling by 1;
two zooming points (on both sides of the thumb) : for zooming
two areas on either side of the thumb : for one-step scrolling
middle thumb area : for scrolling

Zoomler is inherited from TGraphicControl. It was designed and tested under Delphi 3 but it contains nothing version specific.


DblClkEnable : if TRUE then if double-clicked it is fully zoomed, i.e. Start:=Min; Finish:=Max;
Min, Max : minimum and maximum possible values
Start, Finish : current minimum and maximum position of the thumb. These values are changed by user's mouse activities
Orientation : Horizontal or Vertical -- the way Zoomler draws itself

Other properties are inherited and self-explanatory.


Constructor and destructor.


OnChanged : this event is triggered when user releases the mouse button
OnScrolling, OnZooming : these events are triggered while user is scrolling or zooming.

If the scrolled/zoomed object's painting is not consuming much time it is advised to repaint it in OnScrolling and OnZooming events. But in the case of complicated drawing this will cause poor responsiveness and, possibly, flickering. Then object's Invalidate method have to be called in OnChanged event.


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Last updated on 5/13/99.
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