spine-runtimes/spine-ts/spine-webgl/src/PolygonBatcher.ts

/******************************************************************************
 * Spine Runtimes License Agreement
 * Last updated July 28, 2023. Replaces all prior versions.
 *
 * Copyright (c) 2013-2023, Esoteric Software LLC
 *
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 *
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import { BlendMode, Disposable } from "@esotericsoftware/spine-core";
import { GLTexture } from "./GLTexture.js";
import { Mesh, Position2Attribute, ColorAttribute, TexCoordAttribute, Color2Attribute } from "./Mesh.js";
import { Shader } from "./Shader.js";
import { ManagedWebGLRenderingContext } from "./WebGL.js";

const GL_ONE = 1;
const GL_ONE_MINUS_SRC_COLOR = 0x0301;
const GL_SRC_ALPHA = 0x0302;
const GL_ONE_MINUS_SRC_ALPHA = 0x0303;
const GL_ONE_MINUS_DST_ALPHA = 0x0305;
const GL_DST_COLOR = 0x0306;

export class PolygonBatcher implements Disposable {
	public static disableCulling = false;

	private context: ManagedWebGLRenderingContext;
	private drawCalls = 0;
	private static globalDrawCalls = 0;
	isDrawing = false;
	private mesh: Mesh;
	private shader: Shader | null = null;
	private lastTexture: GLTexture | null = null;
	private verticesLength = 0;
	private indicesLength = 0;
	private srcColorBlend: number;
	private srcAlphaBlend: number;
	private dstBlend: number;
	private cullWasEnabled = false;

	constructor (context: ManagedWebGLRenderingContext | WebGLRenderingContext, twoColorTint: boolean = true, maxVertices: number = 10920) {
		if (maxVertices > 10920) throw new Error("Can't have more than 10920 triangles per batch: " + maxVertices);
		this.context = context instanceof ManagedWebGLRenderingContext ? context : new ManagedWebGLRenderingContext(context);
		let attributes = twoColorTint ?
			[new Position2Attribute(), new ColorAttribute(), new TexCoordAttribute(), new Color2Attribute()] :
			[new Position2Attribute(), new ColorAttribute(), new TexCoordAttribute()];
		this.mesh = new Mesh(context, attributes, maxVertices, maxVertices * 3);
		let gl = this.context.gl;
		this.srcColorBlend = gl.SRC_ALPHA;
		this.srcAlphaBlend = gl.ONE;
		this.dstBlend = gl.ONE_MINUS_SRC_ALPHA;
	}

	begin (shader: Shader) {
		if (this.isDrawing) throw new Error("PolygonBatch is already drawing. Call PolygonBatch.end() before calling PolygonBatch.begin()");
		this.drawCalls = 0;
		this.shader = shader;
		this.lastTexture = null;
		this.isDrawing = true;

		let gl = this.context.gl;
		gl.enable(gl.BLEND);
		gl.blendFuncSeparate(this.srcColorBlend, this.dstBlend, this.srcAlphaBlend, this.dstBlend);

		if (PolygonBatcher.disableCulling) {
			this.cullWasEnabled = gl.isEnabled(gl.CULL_FACE);
			if (this.cullWasEnabled) gl.disable(gl.CULL_FACE);
		}
	}

	private static blendModesGL: { srcRgb: number, srcRgbPma: number, dstRgb: number, srcAlpha: number }[] = [
		{ srcRgb: GL_SRC_ALPHA, srcRgbPma: GL_ONE, dstRgb: GL_ONE_MINUS_SRC_ALPHA, srcAlpha: GL_ONE },
		{ srcRgb: GL_SRC_ALPHA, srcRgbPma: GL_ONE, dstRgb: GL_ONE, srcAlpha: GL_ONE },
		{ srcRgb: GL_DST_COLOR, srcRgbPma: GL_DST_COLOR, dstRgb: GL_ONE_MINUS_SRC_ALPHA, srcAlpha: GL_ONE },
		{ srcRgb: GL_ONE, srcRgbPma: GL_ONE, dstRgb: GL_ONE_MINUS_SRC_COLOR, srcAlpha: GL_ONE }
	]

	setBlendMode (blendMode: BlendMode, premultipliedAlpha: boolean) {
		const blendModeGL = PolygonBatcher.blendModesGL[blendMode];
		const srcColorBlend = premultipliedAlpha ? blendModeGL.srcRgbPma : blendModeGL.srcRgb;
		const srcAlphaBlend = blendModeGL.srcAlpha;
		const dstBlend = blendModeGL.dstRgb;

		if (this.srcColorBlend == srcColorBlend && this.srcAlphaBlend == srcAlphaBlend && this.dstBlend == dstBlend) return;
		this.srcColorBlend = srcColorBlend;
		this.srcAlphaBlend = srcAlphaBlend;
		this.dstBlend = dstBlend;
		if (this.isDrawing) {
			this.flush();
		}
		let gl = this.context.gl;
		gl.blendFuncSeparate(srcColorBlend, dstBlend, srcAlphaBlend, dstBlend);
	}

	draw (texture: GLTexture, vertices: ArrayLike<number>, indices: Array<number>) {
		if (texture != this.lastTexture) {
			this.flush();
			this.lastTexture = texture;
		} else if (this.verticesLength + vertices.length > this.mesh.getVertices().length ||
			this.indicesLength + indices.length > this.mesh.getIndices().length) {
			this.flush();
		}

		let indexStart = this.mesh.numVertices();
		this.mesh.getVertices().set(vertices, this.verticesLength);
		this.verticesLength += vertices.length;
		this.mesh.setVerticesLength(this.verticesLength)

		let indicesArray = this.mesh.getIndices();
		for (let i = this.indicesLength, j = 0; j < indices.length; i++, j++)
			indicesArray[i] = indices[j] + indexStart;
		this.indicesLength += indices.length;
		this.mesh.setIndicesLength(this.indicesLength);
	}

	flush () {
		if (this.verticesLength == 0) return;
		if (!this.lastTexture) throw new Error("No texture set.");
		if (!this.shader) throw new Error("No shader set.");
		this.lastTexture.bind();
		this.mesh.draw(this.shader, this.context.gl.TRIANGLES);

		this.verticesLength = 0;
		this.indicesLength = 0;
		this.mesh.setVerticesLength(0);
		this.mesh.setIndicesLength(0);
		this.drawCalls++;
		PolygonBatcher.globalDrawCalls++;
	}

	end () {
		if (!this.isDrawing) throw new Error("PolygonBatch is not drawing. Call PolygonBatch.begin() before calling PolygonBatch.end()");
		if (this.verticesLength > 0 || this.indicesLength > 0) this.flush();
		this.shader = null;
		this.lastTexture = null;
		this.isDrawing = false;

		let gl = this.context.gl;
		gl.disable(gl.BLEND);
		if (PolygonBatcher.disableCulling) {
			if (this.cullWasEnabled) gl.enable(gl.CULL_FACE);
		}
	}

	getDrawCalls () {
		return this.drawCalls;
	}

	static getAndResetGlobalDrawCalls () {
		let result = PolygonBatcher.globalDrawCalls;
		PolygonBatcher.globalDrawCalls = 0;
		return result;
	}

	dispose () {
		this.mesh.dispose();
	}
}