feat: parse html markup to rich_text

[hepp3n]

Hey!

This PR adds additional dependency, tl for HTML parsing. It's also provide new module markup with simple parser of HTML tags allowed by https://specifications.freedesktop.org/notification/1.2/markup.html

From my simple testing, cosmic-notifications display correct rich_text and also works with nested tags.

This will display like those:

However I did not test this properly with third party applications like Vivaldi, or Slack which displays HTML in notifications. I just used some website which sends defined body via Zen Browser.

Links are not clickable, just styled text. Also images are skipped for now.

#edit

btw. Notification applet require new changes, I can implement this if this PR seems OK to you.

• Closes Notifications from other browsers like Vivaldi just display information in HTML #33
• Closes fix: Strip and render HTML markup in notification bodies #115

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[jacobgkau]

Testing this with the examples at: https://web-push-book.gauntface.com/demos/notification-examples/

Links & icons before:

Links & icons after:

Both "Title & Body" tests triggered a crash that caused the panel to disappear and restart before. After, those two work:

The only problem I'm seeing is that the hyperlink color is too dark in dark mode. It probably needs to be sourced from the COSMIC theme somehow instead of being hard-coded to that blue color. Can you either set the color more intelligently, or leave it the default text color for now (especially as the links aren't clickable, yet, anyway)?

CC @pop-os/ux-- not sure what the correct color to use for hyperlink text would be. Notifications use the window background color for the background. Would accent color suffice? It looks like we currently use accent color for the links in the View -> About menus in some of our COSMIC apps (although the links in those cases use a tinted version of the container background, rather than the window background, for their background color). We also have an "Interface text hint" setting, but I'm not sure what actually uses that right now.

[mmstick]

Link text color would be accent_text_color.

[maria-komarova]

We also have an "Interface text hint" setting, but I'm not sure what actually uses that right now.

Interface text tint is used as the base color to derive the text color if it was customized by the user. It's black/white by default depending on the mode.

[hepp3n]

Both "Title & Body" tests triggered a crash that caused the panel to disappear and restart before

Hmm, wonder what was the issue here.

[jacobgkau]

The link color's appearing correctly now:

We'll probably want them to be clickable eventually, but this is definitely a net improvement for handling other markup as well as preventing that crash.

[KaKi87]

Hi,

Turns out this fixes notifications as they appear, but the issue remains when opening notification history.

Thanks