Difference between revisions of "Performance Tips"

Revision as of 18:32, 11 February 2017

PowerUI is naturally fast, but there's always a few things you can do to make your UI's go ever faster!

Precompile PowerUI

Performance applies to your development process too. Unless you've got a solid state hard drive, PowerUI can take some 15 seconds to compile. Every time you change any of your C# files. Precompile PowerUI by going to Window > PowerUI > Precompile then just tick the box - that will entirely eliminate this delay for you.

If you change platform, or update Unity, you must precompile it again! That's because things like UNITY_ANDROID matter a lot.

By default, PowerUI only checks the assembly that its own classes are in for tags. If you use custom tags/ properties etc, they should be precompiled with it by putting them in any sub-directory of PowerUI. Alternatively, you can request PowerUI to scan additional assemblies for tags/ properties etc; that's the UI.SearchAssembly method (and you'd do it once during startup).

Boosting Reflow

Reflow is the process that a web user agent goes through to figure out the position of elements on the screen. It's the most expensive thing PowerUI (or any user agent) does so avoiding triggering it will give you some nice savings.

Use paint properties

A range of properties like opacity, color, transform only trigger a paint because they are post processes. Paints are extremely fast.

Limiting reflow scope

Reflow applies to the nearest flow root element. For example, let's say you update the innerHTML of a fixed/absolute/sticky positioned element then only that element will actually reflow. The same applies to any of the nested kids of that positioned element - it'll bubble up the DOM to the nearest flow root, and request to reflow that element. In short, making an element become a flow root is an easy way to massively limit how many elements reflow actually affects.

Set textContent rather than innerHTML

If you know your text contains no HTML then setting to textContent will cause virtually everything to get recycled. Setting innerHTML is fast anyway but textContent does almost nothing.

Disabling Unicode Bidirectionality

If you have no plans to use right-to-left or bidirectional text (like Arabic mixed with English), disable it by deleting PowerUI/Resources/BidirectionalData.bytes. This will give you a small memory saving (about 10kb) and slightly boost text performance.

You can also go further by specifying NoBIDI as a "scripting define symbols" as that will effectively remove all of the code which does the BIDI testing.

Avoid late loading CSS

This is a massive performance drainer - avoid it! Put style as high up your document as you can (e.g. in head). That's because a newly loaded CSS selector must check your entire DOM to see if they match any of the elements already in there. If your DOM is basically empty then this operation is much faster.

Meanwhile, a newly loading element uses a range of indices to very rapidly figure out which selectors actually apply to it.