Talk about `renderChildren` again.

One year ago , I created a PR https://github.com/pixijs/pixi.js/pull/3108/ .

I want to add the standalone methods about rendering & updating children. The reason is that user could override them for controlling which sprite/how render the sprite by themself . example:

There is a DisplayObject-Tree:

containerA |_____ spriteA |_____ spriteB |_____ spriteC |_____ subContainerA |_____ … some other sprites else …

Sometimes , I want to decide that render which sprite/how render the sprite by myself, like this :

if ( condition1 ） {
    spriteA.renderWebGL(renderer);
    spriteB.renderWebGL(renderer);
} else if ( condition2 ） {
    spriteB.renderWebGL(renderer);
    spriteC.renderWebGL(renderer);
    spriteA.renderWebGL(renderer);
} else  if ( condition3 ）  {
    spriteC.renderWebGL(renderer);
    subContainerA.renderWebGL(renderer);
} else {
    subContainerA.renderWebGL(renderer);
}

The logic above can’t be solved by children.sort. If we extract the method about rendering children , user could override the renderChildrenWebGL & renderChildrenCanvas, it’s easy. there is another use case for custom remove :

container.renderChildrenWebGL = function(renderer) {
    // In one game loop , the render is the last thing about an entity normally.
    // So we could remove the entity in render function.
    var i = 0,
        len = this.children.length;
    while (i < len) {
        var child = this.children[i];
        if (child._toRemove) {
            len--;
            this.removeChildAt(i, child);
            continue;
        }
        child.renderWebGL(renderer);
        i++;
    }
};

---

If no standalone renderChildren , users have to override renderWebGL , renderCanvas, renderAdvancedWebGL , it’s complex , in especial renderAdvancedWebGL. And if the logic in Container.prototype.renderWebGL/renderAdvancedWebGL changed , users have to re-override them again.

But the logic of renderChildrenWebGL & renderChildrenCanvas is very clear , and they won’t be changed.

One year ago , @englercj refused my PR , the reason is performance . In the past year , I’ve tested many games (more than 20 games , and more than 100 test-cases) , I found this PR is not the hotspot of performance, even never affected performance. (BTW, I found the updateTransformChildren is needless , I and my friends never used it).

In the real game , we could use many sprites , but the count of container is not big at the same time( in one game tick), so the 1 function-call won’t take the performance down.

So I hope you could think the PR again, please, thank you.

[ivanpopelyshev]

@finscn im working on a way to override pixi container methods in a plugin, and your input is significant. Lets close this one, I’ll address it later 😃

[lock[bot]]

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