~sircmpwn/aerc

ref: 0.1.1 aerc/lib/ui d---------
Add Tabs history

Fixes #77: When closing a tab, bring you back to the one you last had focused
ensureScroll on text input frames
Implement scrolling in text input
Show account wizard if no accounts configured
New account wizard, part one
lib/ui/ui: use atomic instead of channel

This makes it so an atomic `invalid` value is used instead of an unbuffered
channel. When many invalidations kick in, a lot of values were sent to the
channel.

(Since OnInvalidate's callback can be run in any goroutine, we need to be
careful about races here.)
Update internal state and draw from the same goroutine

This commit introduces a new Aerc.Tick function that should be called to
refresh the internal state. This in turn makes each AccountView process worker
events.

The UI goroutine repeatedly refreshes the internal state before drawing a new
frame. The reason for this is that many worker messages may need to be
processed for a single frame, and drawing the UI is far slower than refreshing
the internal state. This has been confirmed in my testing (calling Aerc.Tick
only once per frame results in a slower display).

Many synchronization code has been removed. We can now write widgets without
having to care so much about races. The remaining sync users are:

- widgets/spinner: the spinner value is updated from inside an internal
  goroutine
- lib/ui/invalidatable: Invalidate may be called from any goroutine
- lib/ui/grid: same
- lib/ui/ui: an internal goroutine needs read access to UI.exit
- worker/types/worker: Worker.callbacks is used for both worker and UI
  callbacks

The exact goroutine requirements for Drawable have been documented.
Let caller pass in custom headers to compose
Update tab name as subject changes

Also moves truncation to the tab widget
Spec out review message screen
Implement :{next,prev}-field in compose view
Add initial compose widget
Refactor ctx stashing out of exline
Split ex line text handling into dedicated widget
lib/ui: fix UI.Exit race condition

UI.Exit can be accessed from goroutines drawing, goroutines executing
commands and goroutines waiting for events.

    Write at 0x00c0002b2040 by main goroutine:
      main.main.func1()
          /home/simon/src/aerc2/aerc.go:76 +0x33d
      git.sr.ht/~sircmpwn/aerc2/widgets.(*Aerc).BeginExCommand.func1()
          /home/simon/src/aerc2/widgets/aerc.go:245 +0x89
      git.sr.ht/~sircmpwn/aerc2/widgets.(*ExLine).Event()
          /home/simon/src/aerc2/widgets/exline.go:131 +0x442
      git.sr.ht/~sircmpwn/aerc2/widgets.(*Aerc).Event()
          /home/simon/src/aerc2/widgets/aerc.go:116 +0x83c
      git.sr.ht/~sircmpwn/aerc2/widgets.(*Aerc).simulate()
          /home/simon/src/aerc2/widgets/aerc.go:109 +0x12a
      git.sr.ht/~sircmpwn/aerc2/widgets.(*Aerc).Event()
          /home/simon/src/aerc2/widgets/aerc.go:142 +0x722
      git.sr.ht/~sircmpwn/aerc2/lib/ui.(*UI).Tick()
          /home/simon/src/aerc2/lib/ui/ui.go:75 +0x33f
      main.main()
          /home/simon/src/aerc2/aerc.go:94 +0x497

    Previous read at 0x00c0002b2040 by goroutine 19:
      git.sr.ht/~sircmpwn/aerc2/lib/ui.Initialize.func1()
          /home/simon/src/aerc2/lib/ui/ui.go:45 +0x97

    Goroutine 19 (running) created at:
      git.sr.ht/~sircmpwn/aerc2/lib/ui.Initialize()
          /home/simon/src/aerc2/lib/ui/ui.go:44 +0x372
      main.main()
          /home/simon/src/aerc2/aerc.go:87 +0x3a9
lib/ui: fix Grid race condition

This was is more complicated than others. The cells list is accessed by
multiple goroutines:

- Some change the Grid's contents via AddChild/RemoveChild
- Some call Draw
- Some invalidate the grid via Invalidate

Invalidate calls are tricky to handle because they will also invalidate all
child cells. This will inturn trigger the cellInvalidated callback, which needs
to read the list of cells.

For this reason, we use a sync.RWLock which allows multiple concurrent reads.

Below is the race fixed by this commit.

    Read at 0x00c0000bc3d0 by goroutine 7:
      git.sr.ht/~sircmpwn/aerc2/lib/ui.(*Grid).cellInvalidated()
          /home/simon/src/aerc2/lib/ui/grid.go:181 +0x45
      git.sr.ht/~sircmpwn/aerc2/lib/ui.(*Grid).cellInvalidated-fm()
          /home/simon/src/aerc2/lib/ui/grid.go:179 +0x55
      git.sr.ht/~sircmpwn/aerc2/lib/ui.(*Invalidatable).DoInvalidate()
          /home/simon/src/aerc2/lib/ui/invalidatable.go:22 +0x85
      git.sr.ht/~sircmpwn/aerc2/lib/ui.(*Bordered).contentInvalidated-fm()
          /home/simon/src/aerc2/lib/ui/borders.go:39 +0x56
      git.sr.ht/~sircmpwn/aerc2/lib/ui.(*Invalidatable).DoInvalidate()
          /home/simon/src/aerc2/lib/ui/invalidatable.go:22 +0x85
      git.sr.ht/~sircmpwn/aerc2/widgets.NewDirectoryList.func1()
          /home/simon/src/aerc2/widgets/dirlist.go:81 +0x55
      git.sr.ht/~sircmpwn/aerc2/lib/ui.(*Invalidatable).DoInvalidate()
          /home/simon/src/aerc2/lib/ui/invalidatable.go:22 +0x85
      git.sr.ht/~sircmpwn/aerc2/widgets.(*Spinner).Start.func1()
          /home/simon/src/aerc2/widgets/spinner.go:88 +0x82

    Previous write at 0x00c0000bc3d0 by main goroutine:
      [failed to restore the stack]

    Goroutine 7 (running) created at:
      git.sr.ht/~sircmpwn/aerc2/widgets.(*Spinner).Start()
          /home/simon/src/aerc2/widgets/spinner.go:46 +0x98
      git.sr.ht/~sircmpwn/aerc2/widgets.NewDirectoryList()
          /home/simon/src/aerc2/widgets/dirlist.go:37 +0x28b
      git.sr.ht/~sircmpwn/aerc2/widgets.NewAccountView()
          /home/simon/src/aerc2/widgets/account.go:49 +0x5ca
      git.sr.ht/~sircmpwn/aerc2/widgets.NewAerc()
          /home/simon/src/aerc2/widgets/aerc.go:60 +0x807
      main.main()
          /home/simon/src/aerc2/aerc.go:65 +0x33e
lib/ui: fix GridCell.invalid race

This is read/written from different goroutines.

    Write at 0x00c00009c6f0 by goroutine 7:
      git.sr.ht/~sircmpwn/aerc2/lib/ui.(*Grid).cellInvalidated()
          /home/simon/src/aerc2/lib/ui/grid.go:189 +0x122
      git.sr.ht/~sircmpwn/aerc2/lib/ui.(*Grid).cellInvalidated-fm()
          /home/simon/src/aerc2/lib/ui/grid.go:178 +0x55
      git.sr.ht/~sircmpwn/aerc2/lib/ui.(*Invalidatable).DoInvalidate()
          /home/simon/src/aerc2/lib/ui/invalidatable.go:22 +0x85
      git.sr.ht/~sircmpwn/aerc2/lib/ui.(*Bordered).contentInvalidated-fm()
          /home/simon/src/aerc2/lib/ui/borders.go:39 +0x56
      git.sr.ht/~sircmpwn/aerc2/lib/ui.(*Invalidatable).DoInvalidate()
          /home/simon/src/aerc2/lib/ui/invalidatable.go:22 +0x85
      git.sr.ht/~sircmpwn/aerc2/widgets.NewDirectoryList.func1()
          /home/simon/src/aerc2/widgets/dirlist.go:81 +0x55
      git.sr.ht/~sircmpwn/aerc2/lib/ui.(*Invalidatable).DoInvalidate()
          /home/simon/src/aerc2/lib/ui/invalidatable.go:22 +0x85
      git.sr.ht/~sircmpwn/aerc2/widgets.(*Spinner).Start.func1()
          /home/simon/src/aerc2/widgets/spinner.go:88 +0x82

    Previous write at 0x00c00009c6f0 by main goroutine:
      [failed to restore the stack]

    Goroutine 7 (running) created at:
      git.sr.ht/~sircmpwn/aerc2/widgets.(*Spinner).Start()
          /home/simon/src/aerc2/widgets/spinner.go:46 +0x98
      git.sr.ht/~sircmpwn/aerc2/widgets.NewDirectoryList()
          /home/simon/src/aerc2/widgets/dirlist.go:37 +0x28b
      git.sr.ht/~sircmpwn/aerc2/widgets.NewAccountView()
          /home/simon/src/aerc2/widgets/account.go:49 +0x5ca
      git.sr.ht/~sircmpwn/aerc2/widgets.NewAerc()
          /home/simon/src/aerc2/widgets/aerc.go:60 +0x807
      main.main()
          /home/simon/src/aerc2/aerc.go:65 +0x33e
lib/ui: introduce Invalidatable

Many Drawable implementations have their own Invalidate and OnInvalidate
functions, with an unexported onInvalidate field. However OnInvalidate and
Invalidate are usually not called in the same goroutine. This results in a race
on this field, e.g.:

    Read at 0x00c000094748 by goroutine 7:
      git.sr.ht/~sircmpwn/aerc2/widgets.NewDirectoryList.func1()
          /home/simon/src/aerc2/widgets/dirlist.go:85 +0x56
      git.sr.ht/~sircmpwn/aerc2/widgets.(*Spinner).Start.func1()
          /home/simon/src/aerc2/widgets/spinner.go:93 +0x1bb

    Previous write at 0x00c000094748 by main goroutine:
      [failed to restore the stack]

    Goroutine 7 (running) created at:
      git.sr.ht/~sircmpwn/aerc2/widgets.(*Spinner).Start()
          /home/simon/src/aerc2/widgets/spinner.go:46 +0x8f
      git.sr.ht/~sircmpwn/aerc2/widgets.NewDirectoryList()
          /home/simon/src/aerc2/widgets/dirlist.go:37 +0x286
      git.sr.ht/~sircmpwn/aerc2/widgets.NewAccountView()
          /home/simon/src/aerc2/widgets/account.go:50 +0x5ca
      git.sr.ht/~sircmpwn/aerc2/widgets.NewAerc()
          /home/simon/src/aerc2/widgets/aerc.go:60 +0x800
      main.main()
          /home/simon/src/aerc2/aerc.go:65 +0x33e

To fix this, introduce a new type, Invalidatable, which protects the field.
Unfortunately the Drawable must be passed to the callback function in
Invalidate, so we still need to re-implement this in each Invalidatable user.
Add basic message viewer mockup
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