[messages] [Developers] Re: [Developers] Re: Roadmap for VASSAL 4

Tim M timothy.mccarron at sbcglobal.net
Tue Mar 29 13:16:13 MST 2011

"uckelman" wrote:
> I was curious to see what could be done with JavaScript as it is now,
> so I worked up two demos over the weekend, one using the HTML5 canvas,
> and one using regular DHTML techniques. I've put the demos here for
> you
> to try:
> http://www.vassalengine.org/~uckelman/js-test.tar.bz2[1]
> http://www.vassalengine.org/~uckelman/js-test.zip[2]
> (Both archives have the same content, download the one you prefer.)
> Once you've unpacked the archive, browse to launch.html, where you'll
> find a link to each of the demos. In each demo, you should be able to
> drag around the pieces. In the elements demo, dragging on the map pans
> it.
> I learned a few things by doing this:
> 1. The canvas demo is unusable for me. It turns out that this has
> nothing to do with the huge map image---it's just as bad when there's
> no map image. What does matter is the size of the canvas. It works
> well
> for me at 1000x1000, but 8000x3000 is 24 times larger. I don't know
> how
> the canvas is implemented in Firefox 3.6.16, but it seems that they're
> not using algorithms which scale up well.
> Also of note here is the fact that every canvas example I was able to
> find on the web assumes that you'll have about 10 objects on your
> canvas, so does collision detection by searching the whole object list
> and testing each one for hits, and also repaints the whole canvas
> every
> time something changes. If you do either of these, instead of using a
> quadtree for collision detection and repainting only changed regions,
> you can't even get a 1000x1000 canvas to work well with 100 objects on
> it.
> 2. The elements demo works well for me. It's also 245 lines of code,
> 41
> of which are just HTML. The reason it's so small is that all I had to
> do
> was write event handlers for some mouse events. The browser is already
> providing all of the collision detection, repainting, drag and drop,
> and image loading. We have thousands of lines of code in VASSAL for
> doing
> essentially the same thing.
> -- 
> J.

So did I.

1. Running the Canvas test doesn't work - "This text is displayed if
your browser does not support HTML5 Canvas." As one would expect if you
are running IE8 or lower which will be at least 60% of the world :)

2. The element test does not work in IE8 either. I can only see the top
left corner of whatever is being displayed  "Axis Air Points". see no
pieces, cannot scroll the map etc..

too many different browser issues to deal with going this approach

[1] http://www.vassalengine.org/~uckelman/js-test.tar.bz2
[2] http://www.vassalengine.org/~uckelman/js-test.zip

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