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.

1 files changed, 0 insertions, 19 deletions

diff --git a/lib/msgstore.go b/lib/msgstore.go
index fbffa0a7..827d7cbf 100644
--- a/lib/msgstore.go
+++ b/lib/msgstore.go
@@ -2,7 +2,6 @@ package lib
 
 import (
 	"io"
-	"sync"
 	"time"
 
 	"github.com/emersion/go-imap"
@@ -12,8 +11,6 @@ import (
 
 // Accesses to fields must be guarded by MessageStore.Lock/Unlock
 type MessageStore struct {
-	sync.Mutex
-
 	Deleted  map[uint32]interface{}
 	DirInfo  types.DirectoryInfo
 	Messages map[uint32]*types.MessageInfo
@@ -49,9 +46,6 @@ func NewMessageStore(worker *types.Worker,
 func (store *MessageStore) FetchHeaders(uids []uint32,
 	cb func(*types.MessageInfo)) {
 
-	store.Lock()
-	defer store.Unlock()
-
 	// TODO: this could be optimized by pre-allocating toFetch and trimming it
 	// at the end. In practice we expect to get most messages back in one frame.
 	var toFetch imap.SeqSet
@@ -74,9 +68,6 @@ func (store *MessageStore) FetchHeaders(uids []uint32,
 }
 
 func (store *MessageStore) FetchFull(uids []uint32, cb func(io.Reader)) {
-	store.Lock()
-	defer store.Unlock()
-
 	// TODO: this could be optimized by pre-allocating toFetch and trimming it
 	// at the end. In practice we expect to get most messages back in one frame.
 	var toFetch imap.SeqSet
@@ -134,8 +125,6 @@ func merge(to *types.MessageInfo, from *types.MessageInfo) {
 }
 
 func (store *MessageStore) Update(msg types.WorkerMessage) {
-	store.Lock()
-
 	update := false
 	switch msg := msg.(type) {
 	case *types.DirectoryInfo:
@@ -201,8 +190,6 @@ func (store *MessageStore) Update(msg types.WorkerMessage) {
 		update = true
 	}
 
-	store.Unlock()
-
 	if update {
 		store.update()
 	}
@@ -220,7 +207,6 @@ func (store *MessageStore) update() {
 
 func (store *MessageStore) Delete(uids []uint32,
 	cb func(msg types.WorkerMessage)) {
-	store.Lock()
 
 	var set imap.SeqSet
 	for _, uid := range uids {
@@ -228,8 +214,6 @@ func (store *MessageStore) Delete(uids []uint32,
 		store.Deleted[uid] = nil
 	}
 
-	store.Unlock()
-
 	store.worker.PostAction(&types.DeleteMessages{Uids: set}, cb)
 	store.update()
 }
@@ -249,7 +233,6 @@ func (store *MessageStore) Copy(uids []uint32, dest string,
 
 func (store *MessageStore) Move(uids []uint32, dest string,
 	cb func(msg types.WorkerMessage)) {
-	store.Lock()
 
 	var set imap.SeqSet
 	for _, uid := range uids {
@@ -257,8 +240,6 @@ func (store *MessageStore) Move(uids []uint32, dest string,
 		store.Deleted[uid] = nil
 	}
 
-	store.Unlock()
-
 	store.worker.PostAction(&types.CopyMessages{
 		Destination: dest,
 		Uids:        set,