Remove depthTest setting, improve container sorting, clean up renderer

[obiot]

Summary

• Remove depthTest application setting — GPU depth sorting is incompatible with 2D alpha blending. The "z-buffer" option never worked correctly for 2D sprites (see Enable GPU depth sorting for 2D sprite rendering in WebGL #1370 for full analysis). Depth testing remains available internally for 3D mesh rendering only.
• Improve container sorting — cache comparator function via sortOn getter/setter, simplify comparators by removing legacy null guards
• Clean up renderer — move customShader to base Renderer class so Renderable no longer checks renderer type

Changes

Removed

• DepthTest type and depthTest setting from ApplicationSettings
• depthTest from defaultApplicationSettings
• Depth test toggle from WebGL renderer init (always disabled for 2D)
• Depth buffer clear from clear() (only drawMesh uses it, clears locally)
• depthTest: "z-buffer" from platformer example
• Depth test info from console header

Improved

• Container.sortOn is now a getter/setter that caches the comparator — avoids "_sort" + sortOn.toUpperCase() lookup on each sort
• Sort comparators simplified: _sortZ, _sortReverseZ, _sortX, _sortY — removed null guards, use || short-circuit

Cleaned up

• customShader moved to base Renderer class
• Renderable.preDraw/postDraw no longer checks typeof renderer.gl !== "undefined"
• drawMesh simplified: always restores depth to disabled state (no conditional)

Test plan

• All 2388 tests pass
• New tests for sort comparators (_sortZ, _sortReverseZ, _sortX, _sortY) and sortOn caching
• Platformer example renders correctly
• 3D mesh rendering still works (drawMesh enables/disables depth locally)

🤖 Generated with Claude Code

[Copilot]

Pull request overview

This PR removes the depthTest application setting (WebGL depth sorting for 2D) and simplifies WebGL renderer state handling, while also optimizing Container child sorting by caching the comparator and simplifying comparator implementations.

Changes:

• Remove depthTest from application settings/defaults and WebGL renderer initialization/clearing behavior.
• Optimize Container sorting via cached comparator (sortOn getter/setter) and simplified comparator functions.
• Move customShader to the base Renderer to avoid renderer-type checks in Renderable.

Reviewed changes

Copilot reviewed 11 out of 11 changed files in this pull request and generated 3 comments.

Show a summary per file

File	Description
packages/melonjs/tests/container.spec.js	Adds unit tests for container comparators and sortOn comparator caching.
packages/melonjs/src/video/webgl/webgl_renderer.js	Disables depth testing for 2D by default; updates clear behavior; simplifies depth enable/restore in drawMesh.
packages/melonjs/src/video/renderer.js	Declares customShader on the base renderer.
packages/melonjs/src/renderable/renderable.js	Removes renderer-type guard when setting/resetting customShader.
packages/melonjs/src/renderable/container.js	Introduces cached comparator via sortOn accessor; simplifies sort comparators.
packages/melonjs/src/application/settings.ts	Removes DepthTest type and depthTest from ApplicationSettings.
packages/melonjs/src/application/header.ts	Removes depth test info from the console header.
packages/melonjs/src/application/defaultApplicationSettings.ts	Removes the depthTest default setting.
packages/melonjs/src/application/application.ts	Removes depthTest normalization and related world.autoSort toggling logic.
packages/melonjs/CHANGELOG.md	Documents breaking removal of depthTest and related renderer/container changes.
packages/examples/src/examples/platformer/createGame.ts	Removes depthTest: "z-buffer" from the platformer example.

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[Copilot]

Pull request overview

Copilot reviewed 11 out of 11 changed files in this pull request and generated 5 comments.

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[Copilot]

Pull request overview

Copilot reviewed 14 out of 14 changed files in this pull request and generated 2 comments.

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[Copilot]

Renderable.parentApp now assumes this.ancestor.getRootAncestor() exists whenever this.ancestor is set. This is not always true: Entity assigns this.children[0].ancestor = this (see entity.js), so calling parentApp on an Entity's child renderable will throw at runtime. Please restore a safe guard (e.g., check for getRootAncestor before calling, or walk up .ancestor until reaching a Container/root that has .app).

Suggested change

	this._parentApp = this.ancestor.getRootAncestor().app;
	if (typeof this.ancestor.getRootAncestor === "function") {
	const rootAncestor = this.ancestor.getRootAncestor();
	this._parentApp = rootAncestor && rootAncestor.app;
	} else {
	let ancestor = this.ancestor;
	while (ancestor) {
	if (ancestor.app) {
	this._parentApp = ancestor.app;
	break;
	}
	ancestor = ancestor.ancestor;
	}
	}

[Copilot]

addChild() now always calls createGUID(child.id). Several renderables (e.g. Entity) default id to an empty string, and createGUID() does arithmetic on the index parameter (GUID_index += index), so passing a non-number can coerce GUID_index into a string and break GUID generation. Consider only passing child.id when it is a finite number, otherwise call createGUID() without an argument (or normalize with Number(child.id) and a fallback).

Suggested change

	child.GUID = createGUID(child.id);
	child.GUID = Number.isFinite(child.id)
	? createGUID(child.id)
	: createGUID();