Changing fonts in "Text" does not work

[kolibril13]

Hi, maybe it is only on my system (Ubuntu 20.04), but using this example:

class Example5Text(Scene):
        def construct(self):
            text = Text('Hello world', font='Source Han Sans').scale(3)
            self.add(text)

should give this result:

(image is taken from 3b1b/manim#680)
However, when I run it on my machine, it only renders the text with the default font.
To distinguish the default font from Source Han Sans, note that the "ll" has no small arc at the bottom in the default font.

[naveen521kk]

Did you install the font Source Han Sans in your computer? Currently, there is no warning for this. You can check whether it is installed using

fc-list

command in Linux.

Possibly fixed by #471 where it uses Pango for rendering where it raises warning if font not found.

[behackl]

I cannot reproduce this either, looks like you might simply be missing the font.

[cobordism]

We should treat this as a bug report: "if the font is not installed, no error message is shown"

[naveen521kk]

We should treat this as a bug report: "if the font is not installed, no error message is shown"

That's why I am doing #471 where Pango warns the user if font not installed.

[leotrs]

We should still add @cobordism 's suggestion to the current Text, while we wait until the Panel text becomes the default

[naveen521kk]

We should still add @cobordism 's suggestion to the current Text, while we wait until the Panel text becomes the default

It's not possible in Cairo toy api and that's why moving to Pango helps. I would say implementing your idea is not that good, pretty much and it requires a lot of work to make it cross platform.
I suggest to wait until we get Pango for this job.

[behackl]

True, the cairo documentation mentions rather explicitly that cairo does not provide a way to check available fonts:

Selects a family and style of font from a simplified description as a family name, slant and weight. Cairo provides no operation to list available family names on the system (this is a “toy”, remember), but the standard CSS2 generic family names, (“serif”, “sans-serif”, “cursive”, “fantasy”, “monospace”), are likely to work as expected

(Source: https://pycairo.readthedocs.io/en/latest/reference/context.html#cairo.Context.select_font_face)

We can still add an explicit warning to the docstring of Text, and otherwise resolve this via #471 until we switch to Pango.

[naveen521kk]

Now this a duplicate of #393

[leotrs]

What I meant is the following:

1. If someone tries to use the current Text to change font (or do anything else that the dummy Cairo package cannot do), we should issue a warning.
2. The PangoText class should issue the correct warnings when fonts aren't installed.

I believe @naveen521kk says that his PR will handle point number 2. But I don't think we are handling point number 1.

[naveen521kk]

The PangoText class should issue the correct warnings when fonts aren't installed.

I didn't do any effort to implement the second one. Simply it itself gives the below error message.

[kolibril13]

Is there anyone how wants to make an example of how to change fonts into the docs?

[cobordism]

What happened to all the text examples?
I see only one example here: https://manimce.readthedocs.io/en/latest/examples/text.html

but my completely unrelated PR which was compiled earlier today, still shows 12 examples https://manimce--483.org.readthedocs.build/en/483/examples/text.html

Were all the text examples removed today? and if so, why?