DN565745356

Subject: Re: Canvas bbox different in 8.3b1 than 8.2?? - DN [1]

Jan Nijtmans <j.nijtmans@chello.nl> - 28 Dec 1999 - comp.lang.tcl

 Petasis George wrote:
 > Also, my impression is that the canvas object is a little faster now,
 > is that true?

 Yes, it's faster, and for two reasons:

 - All arguments are passed as Tcl_Obj's, which result in less
   string <-> integer conversions.
 - In tkCanvas.c an additional optimization is implemented, which
   calculates the area to be redrawn more agressively. This new
   implementation is especially advantious when the canvas has
   a lot of items outside the visible area.

 Further on, there are two ways of further increasing the speed
 of the canvas, but you need new canvas subcommands for that:
 - Use the new "-state disabled" for items that are insensible to
   the mouse. This saves recalculations when the mouse moves
   over a canvas item.
 - You can now insert and delete individual coordinates in
   the line canvas item. Only those portions of the line
   that change will be redrawn.

 How much faster the new canvas is fully depends on how
 it is used. It could be a little bit slower for canvases
 with only a few items, but no-one will notice that.

 Regards,
 --
 Jan Nijtmans, CMG Arnhem B.V.
 email: j.nijtmans@chello.nl (private)
        jan.nijtmans@cmg.nl  (work)
 url:   http://purl.oclc.org/net/nijtmans/