Add a way for applications to supply custom fonts

[jwiggins]

Closes #555

This works well with the QPainter and AGG backends. It does not work with the Quartz backend. Also, I was not able to test this properly with Wx because the feature isn't supported in the wheel that I installed (perhaps it's a macOS thing?).

[jwiggins]

Perhaps this: QStandardPaths: XDG_RUNTIME_DIR not set, defaulting to '/tmp/runtime-runner' has something to do with the failure?

[jwiggins]

Works just fine on Windows 🎉

[jwiggins]

From the Qt docs:

Adding application fonts on Unix/X11 platforms without fontconfig is currently not supported.

Also, QFontDatabase::addApplicationFont is a static method.

[jwiggins]

macOS + pyqt appears to have crashed when running the OpenGL drawing tests... Sort of an improvement. The tests are passing for the new feature.

[rahulporuri]

I've been trying to experiment with the new add_application_font api but i'm having trouble finding an actual font file i can download and make use of - i'm not sure what the font name in the test font files is which are used in the tests.

Update : I came across the Noto fonts (https://web.archive.org/web/20150411172453if_/http://www.google.com/get/noto/) while browsing the Microsoft Font Typography Vendor page (https://docs.microsoft.com/en-gb/typography/font-list/). I was able to successfully add it in the kiva_explorer using

fontfilepath = "C:\\Users\\rporuri\\Downloads\\NotoSans-hinted\\NotoSans-Regular.ttf"
add_application_font(fontfilepath)
fontfilepath = "C:\\Users\\rporuri\\Downloads\\NotoSerif-hinted\\NotoSerif-Regular.ttf"
add_application_font(fontfilepath)

but then when I tried using the font via gc.set_font(Font('Noto', size=42)), I get nothing. I don't see errors specific to the Noto font and I just see the default font used in the kiva explorer application.

Edit : Noto Sans and Noto Serif are what need to be passed to Font - and the code works now like I expect it to. 🎉

[rahulporuri]

LGTM with a few questions/comments. I tested this in the kiva explorer with a font I downloaded and things worked as expected.

There's one minor user improvement I request. When I downloaded the Font, I downloaded a zip archive which contained 4 font files - one for each style i.e. regular, bold, bold italic and italic. I needed to add each font file separately to be able to use style kwarg to Font correctly. Do you think it makes sense to support passing directories to add_application_font?

We should also update the user documentation - but we can also do that in a separate PR if you prefer that.

[rahulporuri]

I didn't know that sorting a set will return a list - in case anyone was wondering if it'll be a problem that we're returning an empty list above but a sorted set here.

[rahulporuri]

I tried using the kiva explorer on wx (because i wanted to try this PR on wx) and I ran into a few issues across ETS - enthought/pyface#901, enthought/traitsui#1535 and #713.

[rahulporuri]

After fixing issues with the ETS libraries (traitsui and pyface) underneath, I was actually able to get this working with the wx toolkit - and it works perfectly 🎉

[jwiggins]

The macOS test is calling abort() from some PyObjC code...

Fatal Python error: Aborted

Current thread 0x0000000109bbddc0 (most recent call first):
  File "/Users/runner/work/enable/enable/.edm/envs/enable-test-3.6-pyqt/lib/python3.6/site-packages/pyglet/libs/darwin/cocoapy/runtime.py", line 775 in __call__
  File "/Users/runner/work/enable/enable/.edm/envs/enable-test-3.6-pyqt/lib/python3.6/site-packages/pyglet/libs/darwin/cocoapy/runtime.py", line 805 in __call__
  File "/Users/runner/work/enable/enable/.edm/envs/enable-test-3.6-pyqt/lib/python3.6/site-packages/pyglet/window/cocoa/__init__.py", line 314 in dispatch_events
  File "/Users/runner/work/enable/enable/.edm/envs/enable-test-3.6-pyqt/lib/python3.6/site-packages/kiva/tests/test_gl_drawing.py", line 76 in draw_and_check
...

• https://github.com/enthought/enable/blob/master/kiva/tests/test_gl_drawing.py#L76
• https://github.com/pyglet/pyglet/blob/v1.5.15/pyglet/window/cocoa/__init__.py#L314
• https://github.com/pyglet/pyglet/blob/v1.5.15/pyglet/libs/darwin/cocoapy/runtime.py#L769-L805

[jwiggins]

I've disabled the GL drawing test on everything but Linux now. CI is finally happy (and I still hate the GL backend).