Anaconda Enterprise: Documentation

# Creating Latex Labels

This example shows how to create a custom `LaTexLabel` class that uses a third party Javascript library, KaTex, in order to render LaTex onto the plot.

    """ The LaTex example was derived from: http://matplotlib.org/users/usetex.html
    """

    import numpy as np

    from bokeh.models import Label
    from bokeh.plotting import figure, show

    JS_CODE = """
    import {Label, LabelView} from "models/annotations/label"

    export class LatexLabelView extends LabelView
      render: () ->

        #--- Start of copied section from ``Label.render`` implementation

        ctx = @plot_view.canvas_view.ctx

        # Here because AngleSpec does units tranform and label doesn't support specs
        switch @model.angle_units
          when "rad" then angle = -1 * @model.angle
          when "deg" then angle = -1 * @model.angle * Math.PI/180.0

        if @model.x_units == "data"
          vx = @xscale.compute(@model.x)
        else
          vx = @model.x
        sx = @canvas.vx_to_sx(vx)

        if @model.y_units == "data"
          vy = @yscale.compute(@model.y)
        else
          vy = @model.y
        sy = @canvas.vy_to_sy(vy)

        if @model.panel?
          panel_offset = @_get_panel_offset()
          sx += panel_offset.x
          sy += panel_offset.y

        #--- End of copied section from ``Label.render`` implementation

        # Must render as superpositioned div (not on canvas) so that KaTex
        # css can properly style the text
        @_css_text(ctx, "", sx + @model.x_offset, sy - @model.y_offset, angle)

        # ``katex`` is loaded into the global window at runtime
        # katex.renderToString returns a html ``span`` element
        katex.render(@model.text, @el, {displayMode: true})

    export class LatexLabel extends Label
      type: 'LatexLabel'
      default_view: LatexLabelView
    """

    class LatexLabel(Label):
        """A subclass of the Bokeh built-in `Label` that supports rendering
        LaTex using the KaTex typesetting library.

        Only the render method of LabelView is overloaded to perform the
        text -> latex (via katex) conversion. Note: ``render_mode="canvas``
        isn't supported and certain DOM manipulation happens in the Label
        superclass implementation that requires explicitly setting
        `render_mode='css'`).
        """
        __javascript__ = ["https://cdnjs.cloudflare.com/ajax/libs/KaTeX/0.6.0/katex.min.js"]
        __css__ = ["https://cdnjs.cloudflare.com/ajax/libs/KaTeX/0.6.0/katex.min.css"]
        __implementation__ = JS_CODE

    x = np.arange(0.0, 1.0 + 0.01, 0.01)
    y = np.cos(2*2*np.pi*x) + 2

    p = figure(title="LaTex Demonstration", plot_width=500, plot_height=500)
    p.line(x, y)

    # Note: must set ``render_mode="css"``
    latex = LatexLabel(text="f = \sum_{n=1}^\infty\\frac{-e^{i\pi}}{2^n}!",
                       x=35, y=445, x_units='screen', y_units='screen',
                       render_mode='css', text_font_size='16pt',
                       background_fill_color='#ffffff')

    p.add_layout(latex)

    show(p)