Retained mode renderers

[taublast]

Hello,

Actually using SkiaSharp for UI construction. Working on optimizing the speed. Noticed that the current SkiaSharp handlers/renderers are recreating/clearing surfaces on every frame. This is neat overall but is a stopper for implementing retained mode rendering, where we could fast-draw only dirty/changed regions over an existing rendering result.

The current implementation of SKGLTextureRenderer, SKSwapChainPanel, SKMetalView, and Blazor SKGLView are all similar in acting in immediate mode:

1. Clear/re-create the entire surface for each new frame
2. Let user redraw everything from scratch
3. Present the result

Would like to attack the creation of retained mode renderers to change this to:

1. Create the surface once/re-create when size/context changed
2. Let user draw on this one surface, so he could re-draw changed regions only, and decide to clear the whole by himself
3. Present the result

Profit:

Faster rendering, especially for UI
Less GPU consumption
Less battery consumption on mobile
Reduce memory bandwidth usage
Closer to classic UI rendering techs, especially Flutter

Would propose to share thoughts and opinions about this.
Is it acceptable to be incorporated inside SkiaSharp?
If yes, should we have separate views for that or add options/props to existing ones?
Unleash hell.

[mattleibow]

This sounds good. I am sure we can all enjoy this.

Whether or not to use separate views, it all depends. If it is just something that a property can do, then no need to add views. But, if for some reason things require many different thibgs we could see what is better.

[taublast]

I see in main repo that skiasharp uses GL renderer for iOS and Metal only on Catalyst, does it?
To know if I need to work on that GL-one too..

[mattleibow]

I think we can just use metal for now. I want to introduce a SKAcceleratedView or something with a backend agnostic implementation.

And try out DirectX on windows without ANGLE.

So yeah, just get things to work in most places, and then we can see. Maybe this is the opportunity to add a new view that is accelerated and agnostic and immediate/retained.

[taublast]

Implemented iOS Metal retained-mode renderer as proof of concept so far, works fine.
Windows GL retained-mode is done too.