protected _set_data(nvertices: number): void {
   const n = nvertices * 4;  // in bytes
   // Set buffer size
   this.vbo_x.set_size(n)
   this.vbo_y.set_size(n)
   this.vbo_a.set_size(n)
   this.vbo_s.set_size(n)
   // Upload data for x and y, apply a baked-in offset for float32 precision (issue #3795)
   // The exact value for the baked_offset does not matter, as long as it brings the data to less extreme values
   const xx = new Float64Array(this.glyph._x)
   const yy = new Float64Array(this.glyph._y)
   for (let i = 0, end = nvertices; i < end; i++) {
      xx[i] += this._baked_offset[0]
      yy[i] += this._baked_offset[1]
   }
   this.vbo_x.set_data(0, new Float32Array(xx))
   this.vbo_y.set_data(0, new Float32Array(yy))
   // Angle if available; circle does not have angle. If we don't set data, angle is default 0 in glsl
   if (this.glyph._angle != null) {
     this.vbo_a.set_data(0, new Float32Array(this.glyph._angle))
   }
   // Radius is special; some markes allow radius in data-coords instead of screen coords
   // @radius tells us that radius is in units, sradius is the pre-calculated screen radius
   if (this.glyph instanceof CircleView && this.glyph._radius != null)
     this.vbo_s.set_data(0, new Float32Array(map(this.glyph.sradius, (s) => s*2)))
   else
     this.vbo_s.set_data(0, new Float32Array(this.glyph._size))
 }

    _set_data() {
      this._bake();

      this.vbo_position.set_size(this.V_position.length*4);
      this.vbo_position.set_data(0, this.V_position);

      this.vbo_tangents.set_size(this.V_tangents.length*4);
      this.vbo_tangents.set_data(0, this.V_tangents);

      this.vbo_angles.set_size(this.V_angles.length*4);
      this.vbo_angles.set_data(0, this.V_angles);

      this.vbo_texcoord.set_size(this.V_texcoord.length*4);
      return this.vbo_texcoord.set_data(0, this.V_texcoord);
    }

  draw(indices: number[], mainGlyph: MarkerView | CircleView, trans: Transform): void {
    // The main glyph has the data, *this* glyph has the visuals.
    const mainGlGlyph = mainGlyph.glglyph
    const {nvertices} = mainGlGlyph

    // Upload data if we must. Only happens for main glyph.
    if (mainGlGlyph.data_changed) {
      if (!(isFinite(trans.dx) && isFinite(trans.dy))) {
        return;  // not sure why, but it happens on init sometimes (#4367)
      }
      mainGlGlyph._baked_offset = [trans.dx, trans.dy];  // float32 precision workaround; used in _set_data() and below
      mainGlGlyph._set_data(nvertices)
      mainGlGlyph.data_changed = false
    } else if (this.glyph instanceof CircleView && this.glyph._radius != null &&
               (this.last_trans == null || trans.sx != this.last_trans.sx || trans.sy != this.last_trans.sy)) {
      // Keep screen radius up-to-date for circle glyph. Only happens when a radius is given
      this.last_trans = trans
      this.vbo_s.set_data(0, new Float32Array(map(this.glyph.sradius, (s) => s*2)))
    }

    // Update visuals if we must. Can happen for all glyphs.
    if (this.visuals_changed) {
      this._set_visuals(nvertices)
      this.visuals_changed = false
    }

    // Handle transformation to device coordinates
    // Note the baked-in offset to avoid float32 precision problems
    const baked_offset = mainGlGlyph._baked_offset
    this.prog.set_uniform('u_pixel_ratio', 'float', [trans.pixel_ratio])
    this.prog.set_uniform('u_canvas_size', 'vec2', [trans.width, trans.height])
    this.prog.set_uniform('u_offset', 'vec2', [trans.dx - baked_offset[0], trans.dy - baked_offset[1]])
    this.prog.set_uniform('u_scale', 'vec2', [trans.sx, trans.sy])

    // Select buffers from main glyph
    // (which may be this glyph but maybe not if this is a (non)selection glyph)
    this.prog.set_attribute('a_x', 'float', mainGlGlyph.vbo_x)
    this.prog.set_attribute('a_y', 'float', mainGlGlyph.vbo_y)
    this.prog.set_attribute('a_size', 'float', mainGlGlyph.vbo_s)
    this.prog.set_attribute('a_angle', 'float', mainGlGlyph.vbo_a)

    // Draw directly or using indices. Do not handle indices if they do not
    // fit in a uint16; WebGL 1.0 does not support uint32.
    if (indices.length == 0)
      return
    else if (indices.length === nvertices)
      this.prog.draw(this.gl.POINTS, [0, nvertices])
    else if (nvertices < 65535) {
      // On IE the marker size is reduced to 1 px when using an index buffer
      // A MS Edge dev on Twitter said on 24-04-2014: "gl_PointSize > 1.0 works
      // in DrawArrays; gl_PointSize > 1.0 in DrawElements is coming soon in the
      // next renderer update.
      const ua = window.navigator.userAgent
      if ((ua.indexOf("MSIE ") + ua.indexOf("Trident/") + ua.indexOf("Edge/")) > 0) {
         logger.warn('WebGL warning: IE is known to produce 1px sprites whith selections.')
       }
      this.index_buffer.set_size(indices.length*2)
      this.index_buffer.set_data(0, new Uint16Array(indices))
      this.prog.draw(this.gl.POINTS, this.index_buffer)
    } else {
      // Work around the limit that the indexbuffer must be uint16. We draw in chunks.
      // First collect indices in chunks
      const chunksize = 64000;  // 65536
      const chunks: number[][] = []
      for (let i = 0, end = Math.ceil(nvertices/chunksize); i < end; i++) {
         chunks.push([])
      }
      for (let i = 0, end = indices.length; i < end; i++) {
        const uint16_index = indices[i] % chunksize
        const chunk = Math.floor(indices[i] / chunksize)
        chunks[chunk].push(uint16_index)
      }
      // Then draw each chunk
      for (let chunk = 0, end = chunks.length; chunk < end; chunk++) {
        const these_indices = new Uint16Array(chunks[chunk])
        const offset = chunk * chunksize * 4
        if (these_indices.length === 0) {
          continue
        }
        this.prog.set_attribute('a_x', 'float', mainGlGlyph.vbo_x, 0, offset)
        this.prog.set_attribute('a_y', 'float', mainGlGlyph.vbo_y, 0, offset)
        this.prog.set_attribute('a_size', 'float', mainGlGlyph.vbo_s, 0, offset)
        this.prog.set_attribute('a_angle', 'float', mainGlGlyph.vbo_a, 0, offset)
        if (this.vbo_linewidth.used) {
          this.prog.set_attribute('a_linewidth', 'float', this.vbo_linewidth, 0, offset)
        }
        if (this.vbo_fg_color.used) {
          this.prog.set_attribute('a_fg_color', 'vec4', this.vbo_fg_color, 0, offset * 4)
        }
        if (this.vbo_bg_color.used) {
          this.prog.set_attribute('a_bg_color', 'vec4', this.vbo_bg_color, 0, offset * 4)
        }
        // The actual drawing
        this.index_buffer.set_size(these_indices.length*2)
        this.index_buffer.set_data(0, these_indices)
        this.prog.draw(this.gl.POINTS, this.index_buffer)
      }
    }
  }