"Raab, Andreas" wrote:

> Yes - use a cache form for drawing the points directly and pass the entire image to FormCanvas, ala:

> bb _ BitBlt toForm: cacheForm.
> bb combinationRule: Form over.
> bb width: 1; height: 1.
> bb fillColor: Color red.  "Now draw these points offscreen"

    Hey! Thanks a lot to you all...

    Using your code, I speeded everything from ~2000 ms to ~350 ms.

    BUT, I didn't need to use an itermediate cacheForm, I'm just drawing to the
Form I get as argument to #drawOn: (aCanvas form), insted of creating a new one,
and the performance is the same (a little better because I'm not copying from form
to form).
    The major speed gain is in caching the 1 by 1 BitBlt, and then using it to draw in
the canvas.
    Now 99% of the time is consumed in primitives... is there anything else I can do?
Or from here on do I need to improve the algorithm?

    Improved Bye!
    Richie++

PS: Here's my #drawOn:, just in case somebody is interested in it.

drawOn: aCanvas
 | limit elements t1 t2 cacheForm bb |
 self wrapee elementCount < 10 ifTrue: [
  aCanvas line: self bounds origin to: self bounds corner color: Color
blue].
 limit _ self rectangle extent / (self bounds extent).

 t1 _ Time millisecondsToRun: [
  elements _ self wrapee elementsInRectangle: self rectangle limit: limit].


 cacheForm _ aCanvas form. "Form extent: self bounds extent depth:
aCanvas depth."
 bb _ BitBlt toForm: cacheForm.
 bb combinationRule: Form over.
 bb width: 1; height: 1.
 bb fillColor: Color blue.
 "Now draw these points offscreen"

 t2 _ Time millisecondsToRun: [
  elements do: [:each | bb destOrigin: (self toCanvasCoord: each
position); copyBits]].

" aCanvas paintImage: cacheForm at: self bounds origin."
 Transcript
  print: t1; space; print: t2; space;
  show: elements size printString; cr.

And the times shown in Transcript are:

| time to get the points | time to draw the points | number of points |

"without the cacheForm, the 2nd col. was between: 1500 and: 3000 "

38 646 6818    "Direct to aCavnas form"
44 737 6818    "Using a real cacheCanvas"
38 740 6818    "Using a real cacheCanvas"
49 733 6818    "Using a real cacheCanvas"
50 739 6818    "Using a real cacheCanvas"
39 757 6818    "Using a real cacheCanvas"
45 687 6818    "Direct to aCavnas form"

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