Loading a custom layer that includes gfx fails under IE7/8

[Patrick Ruzand]

If a custom layer file is created that includes dojox.gfx.canvas, and that layer file is loaded on a browser which doesn't properly support the canvas element, then the following code will cause the layer file evaluation to stop and an Error is raised:

if(typeof dojo.doc.createElement("canvas").getContext("2d").fillText != "function"){
    canvas.Text.extend({
        getTextWidth: function(){
            return 0;
        },
        _renderShape: function(){}
    });
}

Specifically, IE browsers break on the call to getContext. This is problematic primarily because this code will run regardless of whether the browser supports canvas or not

[Patrick Ruzand]

testcase

[Patrick Ruzand]

In [27084]:

fillText API detection code should check canvas is supported by the browser first, fixes #14288

[Patrick Ruzand]

In [27085]:

fillText API detection code should check canvas is supported by the browser first, refs #14288