Add MarkupText

[naveen521kk]

Motivation

Add MarkupText which is previously in Community Edition
This would use a Pango specific markup that looks like HTML.

Proposed changes

There are some specific implementation here about <color>
and <gradient>
Pango doesn't support <gradient> or <color> instead it works with color attribute and the gradient isn't supported.
Since SVGMobject doesn't know about parsing colours from SVG image and implementation of <color> and <gradient> is added.

• Add a new class MarkupText

Comments

Most parts of the code were authored by PhilippImhof and copied from Manim Community. I have added him as co-author in that commit

Test

Code:

class TextExample(Scene):
    def construct(self):
        a1 = MarkupText('<span style="italic">italic</span>')
        a2 = MarkupText('<span weight="bold">bold</span>')
        a3 = MarkupText('<span font="Roboto">Roboto Font</span>')
        a4 = MarkupText('<span font="Cursive">Cursive Font</span>')
        a5 = MarkupText('<color col="RED"><span font="Cursive">Red</span></color>')
        a6 = MarkupText('<gradient from="RED" to="BLUE">Gradient</gradient>')
        v = VGroup(a1, a2, a3, a4, a5, a6).arrange_in_grid()
        self.play(FadeIn(v))

Result:

TextExample.mp4

[naveen521kk]

@3b1b does this look good to you?