class_docstr: Gather a set of glyphs relative to a given font name and size
  
  This currently stores characters in a `TextureAtlas` object which uses
  a 2D RGB texture to store unsigned 8-bit integer data. In the future this
  could be changed to a ``GL_R8`` texture instead of RGB when OpenGL ES
  3.0+ is standard. Since VisPy tries to stay compatible with OpenGL ES 2.0
  we are using an ``RGB`` texture. Using a single channel texture should
  improve performance by requiring less data to be sent to the GPU and to
  remote backends (jupyter notebook).
  
  Parameters
  ----------
  font : dict
      Dict with entries "face", "size", "bold", "italic".
  renderer : instance of SDFRenderer
      SDF renderer to use.
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docstr: Build and store a glyph corresponding to an individual character
  
  Parameters
  ----------
  char : str
      A single character to be represented.
code: def _load_char(self, char):
      """Build and store a glyph corresponding to an individual character
  
      Parameters
      ----------
      char : str
          A single character to be represented.
      """
      assert isinstance(char, str) and len(char) == 1
      assert char not in self._glyphs
      # load new glyph data from font
      _load_glyph(self._font, char, self._glyphs)
      # put new glyph into the texture
      glyph = self._glyphs[char]
      bitmap = glyph["bitmap"]
  
      # convert to padded array
      data = np.zeros(
          (
              bitmap.shape[0] + 2 * self._spread,
              bitmap.shape[1] + 2 * self._spread,
          ),
          np.uint8,
      )
      data[
          self._spread : -self._spread, self._spread : -self._spread
      ] = bitmap
  
      # Store, while scaling down to proper size
      height = data.shape[0] // self.ratio
      width = data.shape[1] // self.ratio
      region = self._atlas.get_free_region(width + 2, height + 2)
      if region is None:
          raise RuntimeError("Cannot store glyph")
      x, y, w, h = region
      x, y, w, h = x + 1, y + 1, w - 2, h - 2
  
      self._renderer.render_to_texture(
          data, self._atlas, (x, y), (w, h)
      )
      u0 = x / float(self._atlas.shape[1])
      v0 = y / float(self._atlas.shape[0])
      u1 = (x + w) / float(self._atlas.shape[1])
      v1 = (y + h) / float(self._atlas.shape[0])
      texcoords = (u0, v0, u1, v1)
      glyph.update(dict(size=(w, h), texcoords=texcoords))
  
imports: from __future__ import division
  import numpy
  from copy import deepcopy
  import sys
  from ._sdf_gpu import SDFRendererGPU
  from ._sdf_cpu import _calc_distance_field
  from ...gloo import TextureAtlas, IndexBuffer, VertexBuffer
  from ...gloo import context
  from ...gloo.wrappers import _check_valid
  from ...util.fonts import _load_glyph
  from ..transforms import STTransform
  from ...color import ColorArray
  from ..visual import Visual
  from ...io import load_spatial_filters
label_desc: Use image node_id 5 for calling the TextureFont obj's underlying member method code with example usage: obj._load_char(char) without return types