dirlist: use shorter delay before listing directory contents

1 second is a bit excessive. Use 200ms which should cover most quick
folder changes.

Add an option to make that delay configurable by the users.

References: https://todo.sr.ht/~rjarry/aerc/16
Fixes: cb3090956c ("dirlist: skip unnecessary change-folder action")
Suggested-by: Koni Marti <koni.marti@gmail.com>
Signed-off-by: Robin Jarry <robin@jarry.cc>

config/aerc.conf.in

@@ -74,6 +74,13 @@ pinned-tab-marker='`'
 # Default: %n %>r
 dirlist-format=%n %>r
 
+# Delay after which the messages are actually listed when entering a directory.
+# This avoids loading messages when skipping over folders and makes the UI more
+# responsive. If you do not want that, set it to 0s.
+#
+# Default: 200ms
+dirlist-delay=200ms
+
 # List of space-separated criteria to sort the messages by, see *sort*
 # command in *aerc*(1) for reference. Prefixing a criterion with "-r "
 # reverses that criterion.

config/config.go

@@ -47,6 +47,7 @@ type UIConfig struct {
 	Spinner             string        `ini:"spinner"`
 	SpinnerDelimiter    string        `ini:"spinner-delimiter"`
 	DirListFormat       string        `ini:"dirlist-format"`
+	DirListDelay        time.Duration `ini:"dirlist-delay"`
 	Sort                []string      `delim:" "`
 	NextMessageOnDelete bool          `ini:"next-message-on-delete"`
 	CompletionDelay     time.Duration `ini:"completion-delay"`
@@ -564,6 +565,7 @@ func LoadConfigFromFile(root *string, sharedir string, logger *log.Logger) (*Aer
 			Spinner:             "[..]    , [..]   ,  [..]  ,   [..] ,    [..],   [..] ,  [..]  , [..]   ",
 			SpinnerDelimiter:    ",",
 			DirListFormat:       "%n %>r",
+			DirListDelay:        200 * time.Millisecond,
 			NextMessageOnDelete: true,
 			CompletionDelay:     250 * time.Millisecond,
 			CompletionPopovers:  true,

doc/aerc-config.5.scd

@@ -177,6 +177,14 @@ These options are configured in the *[ui]* section of aerc.conf.
 |  %>X
 :  make format specifier 'X' be right justified
 
+*dirlist-delay*
+	Delay after which the messages are actually listed when entering
+	a directory. This avoids loading messages when skipping over folders
+	and makes the UI more responsive. If you do not want that, set it to
+	0s.
+
+	Default: 200ms
+
 *next-message-on-delete*
 	Moves to next message when the current message is deleted
 

widgets/dirlist.go

@@ -96,7 +96,7 @@ func (dirlist *DirectoryList) Select(name string) {
 
 	go func() {
 		select {
-		case <-time.After(1 * time.Second):
+		case <-time.After(dirlist.aercConf.Ui.DirListDelay):
 			dirlist.worker.PostAction(&types.OpenDirectory{Directory: name},
 				func(msg types.WorkerMessage) {
 					switch msg.(type) {