Add global shader list support to s2d

[Yanrishatum]

Introduces ability to add global shaders to 2D rendering pipeline.

Rationale: Allows users to add shaders to multiple rendered objects without having to add same shader to all of them, or apply a shader that have to be always present on all 2D objects. This reduces the amount of tedious shader management.
Use-case examples:

• Custom global filtering. In my case bilinear filtering that mimics nearest neighbor but offers reasonably antialiased transition between texels on rotated sprites.
• (From discord) Adding custom pass outputs and shader that outputs to it.
• Shader that is applied to all object children, simplifying the shader management code, as instead of having to add shader to everything in the object tree and tracking that, it's possible to just add shader as global one during root object rendering, and removing it afterwards.

Adds the following API:

• RenderContext.addGlobalShader(shader)
• RenderContext.removeGlobalShader(shader)

A few notes:

• Is there any reason for currentShaders to even exist? It seems fairly redundant, as initShaders only ever called with baseShaderList, and thus it can never be anything other than baseShaderList. Some legacy code leftovers?
• Shaders are added without sort, as they are sorted anyway by Cache.compileRuntimeShader
• It probably would be better to rename baseShaderList to globalShaderList.

[ddmills]

think this needs a null check

Suggested change

	var curShaders = currentShadersTail.next;
	var curShaders = currentShadersTail?.next;

[Yanrishatum]

No, because it's never supposed to be null. Tail points at the last global shader (tail.next points at object-specific shaders), and you should not be able to remove base shader from the global shader list, thus tail is never null.

[ddmills]

🤷 idk i had to change this to make it work locally

[Yanrishatum]

Can you provide an repro sample?

[ncannasse]

Shouldn't we have instead something like push/pop mechanism so we can use it during rendering ?

[Yanrishatum]

Shouldn't we have instead something like push/pop mechanism so we can use it during rendering ?

Elaborate? This is pretty much how it currently behaves. Nothing prevents user from adding shaders mid-rendering and then removing them. Or you mean somehting along the lines push/popGlobalShaderList where user would provide a list of shaders that would replace current list (with exception of base shader) and have them on a stack?