Investigate reported issues of lag on IE11

[lehni]

https://connect.microsoft.com/IE/feedback/details/836652/ie11-bug-paper-js

[iconexperience]

The big difference between InternetExplorer and Chrome is certainly, that direct in Item.draw() is true in Chrome and false in InternetExplorer. Setting it manually to true in InternetExplorer makes a huge difference.

[iconexperience]

I printed all parameters that are used to determine direct and here are the results:

Chrome / Firefox

opacity 1
param.dontStart undefined
param.clip false
nativeBlend 170
normalBlend false
this._canComposite() true`

InternetExplorer

opacity 1
param.dontStart undefined
param.clip false
nativeBlend false
normalBlend false
this._canComposite() true

As you can see, the only difference is nativeBlend

[iconexperience]

The reason why nativeBlendis false in InternetExplorer is that CanvasRenderingContext2D.globalCompositeOperation does not support blend modes, only composite operations.

[iconexperience]

If you only want to have CandyCrash run faster on InternetExplorer, you should simply remove blendMode: 'screen' in the CandyCrash code, but this way you lose the nice color effect on crashes.

Or you have to find a way to improve non-native blending.

[iconexperience]

I played a little bit more with the parameters and in my opinion the best solution is to set blendMode: 'lighter', which gives a very similar effect to screen and improves performance on InternetExplorer significantly. It then actually runs faster than on Firefox.

[lehni]

Great, thanks for spotting this!