Use mouse wheel to zoom map in the "Digitize" process

[wuma]

When it is in "Digitize Polygon" or "Digitize LineString" process, there is no way to zoom in the map. Sometimes to digitize a precise shape, it's necessary to zoom in so that the vertex of the polygon could be digitized as precise as possible.

This patch implements it this way:

1. Add a ScaleFeedback method for the digitizers. E.g.

PolygonDigitizer.ScaleFeedback = function(scale, origin)

{

for (var i = 0; i < this.xs.length; ++i) {

var x = this.xs[i]; this.xs[i] = origin.X + (scale * (x - origin.X)); var y = this.ys[i]; this.ys[i] = origin.Y + (scale * (y - origin.Y));

}

this.Feedback(origin.X, origin.Y);

}

2. Modify GotoView function in Ajaxmappane.templ to scale the digitize feedbacks when the view is changed.

function GotoView(x,y,scale,tohistory,moveovimg) {

scale = finscale? GetNearestFiniteScale(scale): NormalizeScale(scale); var zoom; if(zoom = (scale != curScale)) {

HideMapImage(); requestTiles = true;

Update the digitize feedback if (digitizing) {

if (typeof digitizer.ScaleFeedback != "undefined") {

digitizer.ScaleFeedback(curScale / scale, new Point(wheelZoomCursor.X, wheelZoomCursor.Y));

}

}

} else {....

Above change can handle the zoom change. The digitize feedbacks will be changed after the zoom has finished. The reason why we don't provide a "instant" scale feedback (the digitize feedbacks will be updated according to every single mouse wheel change) is because redrawing the digitize feedbacks needs regenerating hundreds of <div> elements which is very CPU consuming.