dirlist: skip unnecessary change-folder action

when traversing the directory list, aerc will fetch the contents for
every directory even though the user might just move on to the next.
This causes an unnecessary delay (and load on the worker) and can be
avoided by skipping the old change-folder action when a newer one
arrives within a predefined time interval.

Signed-off-by: Koni Marti <koni.marti@gmail.com>

1 files changed, 55 insertions, 39 deletions

diff --git a/widgets/dirlist.go b/widgets/dirlist.go
index e6f95e1a..53afc1dd 100644
--- a/widgets/dirlist.go
+++ b/widgets/dirlist.go
@@ -6,6 +6,7 @@ import (
 	"math"
 	"regexp"
 	"sort"
+	"time"
 
 	"github.com/gdamore/tcell/v2"
 	"github.com/mattn/go-runewidth"
@@ -20,27 +21,29 @@ import (
 
 type DirectoryList struct {
 	ui.Invalidatable
-	aercConf  *config.AercConfig
-	acctConf  *config.AccountConfig
-	store     *lib.DirStore
-	dirs      []string
-	logger    *log.Logger
-	selecting string
-	selected  string
-	scroll    int
-	spinner   *Spinner
-	worker    *types.Worker
+	aercConf   *config.AercConfig
+	acctConf   *config.AccountConfig
+	store      *lib.DirStore
+	dirs       []string
+	logger     *log.Logger
+	selecting  string
+	selected   string
+	scroll     int
+	spinner    *Spinner
+	worker     *types.Worker
+	skipSelect chan bool
 }
 
 func NewDirectoryList(conf *config.AercConfig, acctConf *config.AccountConfig,
 	logger *log.Logger, worker *types.Worker) *DirectoryList {
 
 	dirlist := &DirectoryList{
-		aercConf: conf,
-		acctConf: acctConf,
-		logger:   logger,
-		store:    lib.NewDirStore(),
-		worker:   worker,
+		aercConf:   conf,
+		acctConf:   acctConf,
+		logger:     logger,
+		store:      lib.NewDirStore(),
+		worker:     worker,
+		skipSelect: make(chan bool),
 	}
 	uiConf := dirlist.UiConfig()
 	dirlist.spinner = NewSpinner(&uiConf)
@@ -87,32 +90,45 @@ func (dirlist *DirectoryList) UpdateList(done func(dirs []string)) {
 
 func (dirlist *DirectoryList) Select(name string) {
 	dirlist.selecting = name
-	dirlist.worker.PostAction(&types.OpenDirectory{Directory: name},
-		func(msg types.WorkerMessage) {
-			switch msg.(type) {
-			case *types.Error:
-				dirlist.selecting = ""
-			case *types.Done:
-				dirlist.selected = dirlist.selecting
-				dirlist.filterDirsByFoldersConfig()
-				hasSelected := false
-				for _, d := range dirlist.dirs {
-					if d == dirlist.selected {
-						hasSelected = true
-						break
+
+	close(dirlist.skipSelect)
+	dirlist.skipSelect = make(chan bool)
+
+	go func() {
+		select {
+		case <-time.After(1 * time.Second):
+			dirlist.worker.PostAction(&types.OpenDirectory{Directory: name},
+				func(msg types.WorkerMessage) {
+					switch msg.(type) {
+					case *types.Error:
+						dirlist.selecting = ""
+						dirlist.selected = ""
+					case *types.Done:
+						dirlist.selected = dirlist.selecting
+						dirlist.filterDirsByFoldersConfig()
+						hasSelected := false
+						for _, d := range dirlist.dirs {
+							if d == dirlist.selected {
+								hasSelected = true
+								break
+							}
+						}
+						if !hasSelected && dirlist.selected != "" {
+							dirlist.dirs = append(dirlist.dirs, dirlist.selected)
+						}
+						if dirlist.acctConf.EnableFoldersSort {
+							sort.Strings(dirlist.dirs)
+						}
+						dirlist.sortDirsByFoldersSortConfig()
 					}
-				}
-				if !hasSelected && dirlist.selected != "" {
-					dirlist.dirs = append(dirlist.dirs, dirlist.selected)
-				}
-				if dirlist.acctConf.EnableFoldersSort {
-					sort.Strings(dirlist.dirs)
-				}
-				dirlist.sortDirsByFoldersSortConfig()
-			}
+					dirlist.Invalidate()
+				})
 			dirlist.Invalidate()
-		})
-	dirlist.Invalidate()
+		case <-dirlist.skipSelect:
+			dirlist.logger.Println("dirlist: skip", name)
+			return
+		}
+	}()
 }
 
 func (dirlist *DirectoryList) Selected() string {