Thank you for the fix!

Thanks for the reply, @avl!

I have a MacBook Pro Retina 13" mid 2014 (model: MGX92). It has only integrated Intel Iris 5100 video, and "About this Mac" tells about 1536 MB of RAM available for it. Other characteristics: CPU Intel Core i5-4308U @ 2.8 GHz (identified by MacCPUID), 8GB RAM, 512 GB SSD.

OS X version: 10.11.1 (15B42)

Hello Everyone,

I'm using Opera on OS X El Capitan 10.11.1 (15B42), and after upgrade to version 33.0.1990.115 (Stable) I faced with strange performance issue, that seems to the rendering acceleration in Opera is not always turns on.

If run Opera with turned on system transparency (the box "Reduce Transparency" on "System Preferences" -> "Accessibility" -> "Display" is unchecked), all websites are rendered very slowly, and when try to scroll a page it brings to rendering lags and freezes and CPU load is grows up to 100%.

But after a set of experiments I discovered that if turn the system transparency off when Opera doesn't running (by checking the box "Reduce Transparency"), start Opera after this, and turn the transparency back on (by un-checking the box "Reduce Transparency") when Opera will running already - the issue is disappears, scrolling works smoothly and does not occurs too much CPU load.

If restart Opera (with keeping the "Reduce Transparency" unchecked) - the issue comes back... I reproduced it several times. Opera 34.0.2036.25 (Stable) also have this problem. The similar problem (CPU load) is mentioned here.

TL;DR we have two situation, and in both of them we running Opera with turned on system transparency:

1. "Reduce Transparency" unchecked -> start Opera -> the perfomance issue is present;
2. "Reduce Transparency" checked -> start Opera -> uncheck "Reduce Transparency" -> the performance issue doesn't appears.

How it could be fixed?

p.s. sorry for my english