Graphical Progress Bar for Delphi applications - Partial / Continuous Move

When your application performs a time-consuming operation, you can use a progress bar, the TProgressBar Delphi control, to show how much of the task is completed.

When you do not know how many steps are needed for a progress bar - you might want to display a continuous bar - or a moving graphical object. The UpdateImageProgress takes a reference to a TImage control displaying a picture. By calling the procedure from inside, for example, a timer event (TTimer control), a graphical progress effect is achieved.

The UpdateImageProgress shifts the image to the right - using the boundaries of the image - thus creating a continuous progress bar.

 //"moves" image to the right in "step" steps
 procedure UpdateImageProgress(const img : TImage) ;
 const
   step = 4;
 var
   b : TBitmap;
 begin
   with img.Picture.Bitmap do
   begin
     b := TBitmap.Create;
     try
       b.Width := Width;
       b.Height := Height;
       BitBlt(b.Canvas.Handle, step, 0, Width-step, Height, Canvas.Handle, 0, 0, SRCCOPY) ;
       BitBlt(b.Canvas.Handle, 0, 0, step, Height, Canvas.Handle, Width-step, 0, SRCCOPY) ;
       Assign(b) ;
     finally
       FreeAndNil(b) ;
     end;
   end;
 end;
 

UpdateImageProgress shifts the trailing "step" part of the bitmap to the front, moving the rest along.

Delphi tips navigator:
» Get the Control Under the Mouse in a Delphi application
« Display an Error Message for an OS Error Code using Delphi