feat(renderer): render image textures

renderer/image-textures.ts

@@ -0,0 +1,173 @@
+import type { Asset } from "@core/asset";
+import type { ScreenRect, WebGlRendererContext } from "./types";
+
+export type ImageTextureRenderer = {
+  render(asset: Asset, rect: ScreenRect): boolean;
+  dispose(): void;
+};
+
+type TextureEntry =
+  | { status: "loading"; image: HTMLImageElement }
+  | { status: "ready"; texture: WebGLTexture }
+  | { status: "error" };
+
+export function createImageTextureRenderer(context: WebGlRendererContext, invalidate: () => void): ImageTextureRenderer {
+  const { gl } = context;
+  const program = createProgram(gl);
+  const positionLocation = gl.getAttribLocation(program, "a_position");
+  const texCoordLocation = gl.getAttribLocation(program, "a_texCoord");
+  const samplerLocation = gl.getUniformLocation(program, "u_image");
+  const positionBuffer = gl.createBuffer();
+  const texCoordBuffer = gl.createBuffer();
+  const textures = new Map<string, TextureEntry>();
+
+  if (!positionBuffer || !texCoordBuffer || !samplerLocation) throw new Error("Failed to create image texture renderer");
+
+  gl.bindBuffer(gl.ARRAY_BUFFER, texCoordBuffer);
+  gl.bufferData(gl.ARRAY_BUFFER, new Float32Array([0, 0, 1, 0, 0, 1, 0, 1, 1, 0, 1, 1]), gl.STATIC_DRAW);
+
+  return {
+    render(asset, rect) {
+      const entry = getTextureEntry(context, textures, asset, invalidate);
+      if (entry.status !== "ready") return false;
+
+      gl.disable(gl.SCISSOR_TEST);
+      gl.enable(gl.BLEND);
+      gl.blendFunc(gl.SRC_ALPHA, gl.ONE_MINUS_SRC_ALPHA);
+      gl.useProgram(program);
+
+      gl.activeTexture(gl.TEXTURE0);
+      gl.bindTexture(gl.TEXTURE_2D, entry.texture);
+      gl.uniform1i(samplerLocation, 0);
+
+      gl.bindBuffer(gl.ARRAY_BUFFER, positionBuffer);
+      gl.bufferData(gl.ARRAY_BUFFER, rectVertices(context.canvas, rect), gl.DYNAMIC_DRAW);
+      gl.enableVertexAttribArray(positionLocation);
+      gl.vertexAttribPointer(positionLocation, 2, gl.FLOAT, false, 0, 0);
+
+      gl.bindBuffer(gl.ARRAY_BUFFER, texCoordBuffer);
+      gl.enableVertexAttribArray(texCoordLocation);
+      gl.vertexAttribPointer(texCoordLocation, 2, gl.FLOAT, false, 0, 0);
+
+      gl.drawArrays(gl.TRIANGLES, 0, 6);
+      gl.disable(gl.BLEND);
+      gl.enable(gl.SCISSOR_TEST);
+      return true;
+    },
+    dispose() {
+      for (const entry of textures.values()) {
+        if (entry.status === "ready") gl.deleteTexture(entry.texture);
+      }
+      gl.deleteBuffer(positionBuffer);
+      gl.deleteBuffer(texCoordBuffer);
+      gl.deleteProgram(program);
+    },
+  };
+}
+
+function getTextureEntry(
+  context: WebGlRendererContext,
+  textures: Map<string, TextureEntry>,
+  asset: Asset,
+  invalidate: () => void,
+): TextureEntry {
+  const cached = textures.get(asset.id);
+  if (cached) return cached;
+
+  const image = new Image();
+  textures.set(asset.id, { status: "loading", image });
+  image.onload = () => {
+    const texture = createTexture(context.gl, image);
+    textures.set(asset.id, { status: "ready", texture });
+    invalidate();
+  };
+  image.onerror = () => {
+    textures.set(asset.id, { status: "error" });
+    invalidate();
+  };
+  image.src = asset.source;
+
+  return { status: "loading", image };
+}
+
+function createTexture(gl: WebGL2RenderingContext, image: HTMLImageElement) {
+  const texture = gl.createTexture();
+  if (!texture) throw new Error("Failed to create image texture");
+
+  gl.bindTexture(gl.TEXTURE_2D, texture);
+  gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_WRAP_S, gl.CLAMP_TO_EDGE);
+  gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_WRAP_T, gl.CLAMP_TO_EDGE);
+  gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_MIN_FILTER, gl.LINEAR);
+  gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_MAG_FILTER, gl.LINEAR);
+  gl.pixelStorei(gl.UNPACK_FLIP_Y_WEBGL, false);
+  gl.texImage2D(gl.TEXTURE_2D, 0, gl.RGBA, gl.RGBA, gl.UNSIGNED_BYTE, image);
+
+  return texture;
+}
+
+function rectVertices(canvas: HTMLCanvasElement, rect: ScreenRect) {
+  const x1 = (rect.x / canvas.width) * 2 - 1;
+  const x2 = ((rect.x + rect.w) / canvas.width) * 2 - 1;
+  const y1 = 1 - (rect.y / canvas.height) * 2;
+  const y2 = 1 - ((rect.y + rect.h) / canvas.height) * 2;
+
+  return new Float32Array([x1, y1, x2, y1, x1, y2, x1, y2, x2, y1, x2, y2]);
+}
+
+function createProgram(gl: WebGL2RenderingContext) {
+  const vertexShader = compileShader(
+    gl,
+    gl.VERTEX_SHADER,
+    `#version 300 es
+    in vec2 a_position;
+    in vec2 a_texCoord;
+    out vec2 v_texCoord;
+    void main() {
+      gl_Position = vec4(a_position, 0.0, 1.0);
+      v_texCoord = a_texCoord;
+    }`,
+  );
+  const fragmentShader = compileShader(
+    gl,
+    gl.FRAGMENT_SHADER,
+    `#version 300 es
+    precision mediump float;
+    uniform sampler2D u_image;
+    in vec2 v_texCoord;
+    out vec4 outColor;
+    void main() {
+      outColor = texture(u_image, v_texCoord);
+    }`,
+  );
+  const program = gl.createProgram();
+  if (!program) throw new Error("Failed to create image shader program");
+
+  gl.attachShader(program, vertexShader);
+  gl.attachShader(program, fragmentShader);
+  gl.linkProgram(program);
+  gl.deleteShader(vertexShader);
+  gl.deleteShader(fragmentShader);
+
+  if (!gl.getProgramParameter(program, gl.LINK_STATUS)) {
+    const message = gl.getProgramInfoLog(program) ?? "Unknown program link error";
+    gl.deleteProgram(program);
+    throw new Error(message);
+  }
+
+  return program;
+}
+
+function compileShader(gl: WebGL2RenderingContext, type: number, source: string) {
+  const shader = gl.createShader(type);
+  if (!shader) throw new Error("Failed to create shader");
+
+  gl.shaderSource(shader, source);
+  gl.compileShader(shader);
+  if (!gl.getShaderParameter(shader, gl.COMPILE_STATUS)) {
+    const message = gl.getShaderInfoLog(shader) ?? "Unknown shader compile error";
+    gl.deleteShader(shader);
+    throw new Error(message);
+  }
+
+  return shader;
+}