Paper.js: Performance issue with zooming on complex shapes

[jsbroks]

Description/Steps to reproduce

1. Create a path on the sketch (clicking and dragging)
2. Zoom in on shape
3. As you zoom in, frames drop and can potentially crash browser

Link to reproduction test-case

Sketch

Expected result

Smooth transitions well zooming in on complex shapes

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What options do we have for rendering only objects in view? Does anyone have work arounds for this?

[sasensi]

Hi, I can't reproduce the issue, this seems pretty smooth to me (Windows 10/Chrome 72).
What device/browser are you using ?
Can you try to make the reproduction case more obvious by including the shape drawing in the code instead of asking us to draw it ?

[jsbroks]

Test the issue in Windows 10/Ubuntu 18.04 on both FireFox 65.0.1 and Chrome 72.0.3626.121 .

Here is one with an example path once you get to around 0.3 on the scale it starts to freeze up

Edit: Strokes causes the issue to occur earlier, but if you add enough shapes it will persist

[jsbroks]

@sasensi So I figured out what the problem is for my use case, which is probably related to the issue above.

I have many CompoundPath's inside a group and when zooming in it calls the draw function on each Item. This includes the Group class its self... and because the group object does not have the function _canCompose() defined, it defaults to false. This causes the process function to be called which has huge performance implications on large scales.

Is it safe to say we can set the _canComposite() of a group to true?

[sasensi]

@jsbroks, thanks for the clear reproduction example, it makes my browser crash too now.

Based on your investigation, I will try to see if there is something that we can improve to prevent that.