Add preview column to Column View

[shiruken1]

Fixes #1601 and gives text preview for "text/*" and "application/sql" mimetypes

[shiruken1]

@jeremypw @alainm23 wutcha'll think? I'd like to pad the Box to the middle of the colpane, but this is my first time coding in Vala (Love it!) and using the Gtk/Gdk libs, which i haven't figured out how to "pad" like in CSS. Open to feedback!

P.S: Oh yeah, and padding between the info_grid items, as well

[shiruken1]

@leonardo-lemos I took it out of draft mode a little too quickly and forgot about text preview. No clue what pattern to follow to pull that off, and I know it's technically out of scope for the issue, but I feel it's in the spirit of mirroring OSX' preview panel, yes?

Thoughts?

[jeremypw]

@shiruken1 I applaud you for having the courage to get to grips with Files code - its not easy! The screenshot looks very promising. I'll take some time to go through the code and get back to you with specific issues. I suspect we will want to have a preference switch to turn this feature on and off. @danirabbit Are you willing to extend Files in this way? I know you have expressed doubts about file previewing before but there seems to be a significant demand for it. I have no objection if implemented well.

[shiruken1]

@shiruken1 I applaud you for having the courage to get to grips with Files code - its not easy! The screenshot looks very promising. I'll take some time to go through the code and get back to you with specific issues. I suspect we will want to have a preference switch to turn this feature on and off. @danirabbit Are you willing to extend Files in this way? I know you have expressed doubts about file previewing before but there seems to be a significant demand for it. I have no objection if implemented well.

Thanks!

Thankfully my C# coding came in handy to get my eyes adjusted (10+ years of Node and Python) but I gotta say the codebase is neat and tidy for the most part, making it easy for me to pattern-match.

I did wanna propose pulling construct_info_panel out of PropertiesWindow and placing it in AbstractPropertiesDialog, so DetailsColumn could piggy-back off of as much as possible to keep the code DRY. Lmk!

[teamcons]

P.S: I don't like the approach, but I'm having to use the timeout to get it to work, since on_slot_selection_changed is the only way in Miller to reliably get the latest selection

Sometimes there is a race between different signals being emitted/handled and an Idle or Timeout is the simplest way to fix it. I'll look to see whether there is a better way in this case.

Vala lock() feature?

[jeremypw]

@teamcons lock() can be useful where the race involves changes to a single property but only works within a class I think (one class cannot lock a property of a different class). In this case using a different design eliminated the race anyway.

[jeremypw]

@shiruken1 Once we are happy with the functionality I'll go through and fix any remaining code-style issues. They don't all show up as lint.

[shiruken1]

@jeremypw sounds great. Let me know if there's anything I can do to help out further. Cheers!

[jeremypw]

Some nit-picking comments/suggestions on code-style.

• Use var when the type is implicit in the assignment
• Whitespace after closing brace of code blocks
• Whitespace after statements only where the focus changes (generally speaking but this is open to interpretation and personal preference)
• Don't make format changes to old code that is not being modified in order to minimise the diff.

[jeremypw]

@shiruken1 Yes, sorry I should have made another PR with that many suggestions I guess. You can batch them up rather than commit separately I think. Looks like I introduced some lint which is a disadvantage of making changes on Github. Just some trailing white space - can you fix that please?

[shiruken1]

No worires! I tried putting everything in commit 9068a04, but GH was still showing your comments as unresolved. Just pushed a cleanup commit to handle trailing white space 🚀

[jeremypw]

Pushing to v7.3.0, which should go out before year end, to give more time for others to review but I am happy to merge something usable even if not perfect and iterate on it as required.

@wpkelso Are you able to re-review?