western-shooter/src/rendering/framebuffer.ts

export class Framebuffer {
  public readonly framebuffer: WebGLFramebuffer;
  public readonly texture: WebGLTexture;
  public readonly width: number;
  public readonly height: number;

  constructor(gl: WebGL2RenderingContext, width: number, height: number) {
    this.width = width;
    this.height = height;

    // Create texture for the framebuffer
    const texture = gl.createTexture();
    if (!texture) {
      throw new Error('Failed to create framebuffer texture');
    }
    this.texture = texture;

    gl.bindTexture(gl.TEXTURE_2D, texture);
    gl.texImage2D(
      gl.TEXTURE_2D,
      0,
      gl.RGBA,
      width,
      height,
      0,
      gl.RGBA,
      gl.UNSIGNED_BYTE,
      null
    );

    // Nearest-neighbor filtering for pixel-perfect upscaling
    gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_MIN_FILTER, gl.NEAREST);
    gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_MAG_FILTER, gl.NEAREST);
    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);

    // Create framebuffer
    const framebuffer = gl.createFramebuffer();
    if (!framebuffer) {
      throw new Error('Failed to create framebuffer');
    }
    this.framebuffer = framebuffer;

    gl.bindFramebuffer(gl.FRAMEBUFFER, framebuffer);
    gl.framebufferTexture2D(
      gl.FRAMEBUFFER,
      gl.COLOR_ATTACHMENT0,
      gl.TEXTURE_2D,
      texture,
      0
    );

    // Check framebuffer status
    const status = gl.checkFramebufferStatus(gl.FRAMEBUFFER);
    if (status !== gl.FRAMEBUFFER_COMPLETE) {
      throw new Error(`Framebuffer not complete: ${status}`);
    }

    // Unbind
    gl.bindFramebuffer(gl.FRAMEBUFFER, null);
    gl.bindTexture(gl.TEXTURE_2D, null);
  }

  bind(gl: WebGL2RenderingContext): void {
    gl.bindFramebuffer(gl.FRAMEBUFFER, this.framebuffer);
    gl.viewport(0, 0, this.width, this.height);
  }

  unbind(gl: WebGL2RenderingContext): void {
    gl.bindFramebuffer(gl.FRAMEBUFFER, null);
  }
}