Implement suspending the app using ctrl-z

Co-authored-by: Stefan Haller <stefan@haller-berlin.de>

go.mod

@@ -37,6 +37,7 @@ require (
 	github.com/xo/terminfo v0.0.0-20210125001918-ca9a967f8778
 	golang.org/x/exp v0.0.0-20240719175910-8a7402abbf56
 	golang.org/x/sync v0.16.0
+	golang.org/x/sys v0.34.0
 	gopkg.in/ozeidan/fuzzy-patricia.v3 v3.0.0
 	gopkg.in/yaml.v3 v3.0.1
 )
@@ -77,7 +78,6 @@ require (
 	github.com/xanzy/ssh-agent v0.3.3 // indirect
 	golang.org/x/crypto v0.37.0 // indirect
 	golang.org/x/net v0.39.0 // indirect
-	golang.org/x/sys v0.34.0 // indirect
 	golang.org/x/term v0.33.0 // indirect
 	golang.org/x/text v0.27.0 // indirect
 	gopkg.in/fsnotify.v1 v1.4.7 // indirect

pkg/config/user_config.go

@@ -390,6 +390,7 @@ type KeybindingConfig struct {
 type KeybindingUniversalConfig struct {
 	Quit                              string   `yaml:"quit"`
 	QuitAlt1                          string   `yaml:"quit-alt1"`
+	SuspendApp                        string   `yaml:"suspendApp"`
 	Return                            string   `yaml:"return"`
 	QuitWithoutChangingDirectory      string   `yaml:"quitWithoutChangingDirectory"`
 	TogglePanel                       string   `yaml:"togglePanel"`
@@ -854,6 +855,7 @@ func GetDefaultConfig() *UserConfig {
 			Universal: KeybindingUniversalConfig{
 				Quit:                              "q",
 				QuitAlt1:                          "<c-c>",
+				SuspendApp:                        "<c-z>",
 				Return:                            "<esc>",
 				QuitWithoutChangingDirectory:      "Q",
 				TogglePanel:                       "<tab>",

pkg/gui/controllers.go

@@ -109,6 +109,7 @@ func (gui *Gui) resetHelpersAndControllers() {
 		AmendHelper:     helpers.NewAmendHelper(helperCommon, gpgHelper),
 		FixupHelper:     helpers.NewFixupHelper(helperCommon),
 		Commits:         commitsHelper,
+		SuspendResume:   helpers.NewSuspendResumeHelper(helperCommon),
 		Snake:           helpers.NewSnakeHelper(helperCommon),
 		Diff:            diffHelper,
 		Repos:           reposHelper,

pkg/gui/controllers/global_controller.go

@@ -123,6 +123,20 @@ func (self *GlobalController) GetKeybindings(opts types.KeybindingsOpts) []*type
 			Modifier: gocui.ModNone,
 			Handler:  self.quitWithoutChangingDirectory,
 		},
+		{
+			Key:         opts.GetKey(opts.Config.Universal.SuspendApp),
+			Modifier:    gocui.ModNone,
+			Handler:     self.c.Helpers().SuspendResume.SuspendApp,
+			Description: self.c.Tr.SuspendApp,
+			GetDisabledReason: func() *types.DisabledReason {
+				if !self.c.Helpers().SuspendResume.CanSuspendApp() {
+					return &types.DisabledReason{
+						Text: self.c.Tr.CannotSuspendApp,
+					}
+				}
+				return nil
+			},
+		},
 		{
 			Key:         opts.GetKey(opts.Config.Universal.ToggleWhitespaceInDiffView),
 			Handler:     self.toggleWhitespace,

pkg/gui/controllers/helpers/helpers.go

@@ -35,6 +35,7 @@ type Helpers struct {
 	AmendHelper    *AmendHelper
 	FixupHelper    *FixupHelper
 	Commits        *CommitsHelper
+	SuspendResume  *SuspendResumeHelper
 	Snake          *SnakeHelper
 	// lives in context package because our contexts need it to render to main
 	Diff              *DiffHelper

pkg/gui/controllers/helpers/signal_handling.go

@@ -0,0 +1,59 @@
+//go:build !windows
+
+package helpers
+
+import (
+	"os"
+	"os/signal"
+	"syscall"
+
+	"github.com/sirupsen/logrus"
+	"golang.org/x/sys/unix"
+)
+
+func canSuspendApp() bool {
+	return true
+}
+
+func sendStopSignal() error {
+	return syscall.Kill(0, syscall.SIGSTOP)
+}
+
+// setForegroundPgrp sets the current process group as the foreground process group
+// for the terminal, allowing the program to read input after resuming from suspension.
+func setForegroundPgrp() error {
+	fd, err := unix.Open("/dev/tty", unix.O_RDWR, 0)
+	if err != nil {
+		return err
+	}
+	defer unix.Close(fd)
+
+	pgid := syscall.Getpgrp()
+
+	return unix.IoctlSetPointerInt(fd, unix.TIOCSPGRP, pgid)
+}
+
+func handleResumeSignal(log *logrus.Entry, onResume func() error) {
+	if err := setForegroundPgrp(); err != nil {
+		log.Warning(err)
+		return
+	}
+
+	if err := onResume(); err != nil {
+		log.Warning(err)
+	}
+}
+
+func installResumeSignalHandler(log *logrus.Entry, onResume func() error) {
+	go func() {
+		sigs := make(chan os.Signal, 1)
+		signal.Notify(sigs, syscall.SIGCONT)
+
+		for sig := range sigs {
+			switch sig {
+			case syscall.SIGCONT:
+				handleResumeSignal(log, onResume)
+			}
+		}
+	}()
+}

pkg/gui/controllers/helpers/signal_handling_windows.go

@@ -0,0 +1,16 @@
+package helpers
+
+import (
+	"github.com/sirupsen/logrus"
+)
+
+func canSuspendApp() bool {
+	return false
+}
+
+func sendStopSignal() error {
+	return nil
+}
+
+func installResumeSignalHandler(log *logrus.Entry, onResume func() error) {
+}

pkg/gui/controllers/helpers/suspend_resume_helper.go

@@ -0,0 +1,31 @@
+package helpers
+
+type SuspendResumeHelper struct {
+	c *HelperCommon
+}
+
+func NewSuspendResumeHelper(c *HelperCommon) *SuspendResumeHelper {
+	return &SuspendResumeHelper{
+		c: c,
+	}
+}
+
+func (s *SuspendResumeHelper) CanSuspendApp() bool {
+	return canSuspendApp()
+}
+
+func (s *SuspendResumeHelper) SuspendApp() error {
+	if !canSuspendApp() {
+		return nil
+	}
+
+	if err := s.c.Suspend(); err != nil {
+		return err
+	}
+
+	return sendStopSignal()
+}
+
+func (s *SuspendResumeHelper) InstallResumeSignalHandler() {
+	installResumeSignalHandler(s.c.Log, s.c.Resume)
+}

pkg/gui/gui.go

@@ -848,6 +848,8 @@ func (gui *Gui) Run(startArgs appTypes.StartArgs) error {
 
 	gui.BackgroundRoutineMgr.startBackgroundRoutines()
 
+	gui.Helpers().SuspendResume.InstallResumeSignalHandler()
+
 	gui.c.Log.Info("starting main loop")
 
 	// setting here so we can use it in layout.go

pkg/gui/gui_common.go

@@ -42,6 +42,14 @@ func (self *guiCommon) RunSubprocess(cmdObj *oscommands.CmdObj) (bool, error) {
 	return self.gui.runSubprocessWithSuspense(cmdObj)
 }
 
+func (self *guiCommon) Suspend() error {
+	return self.gui.suspend()
+}
+
+func (self *guiCommon) Resume() error {
+	return self.gui.resume()
+}
+
 func (self *guiCommon) Context() types.IContextMgr {
 	return self.gui.State.ContextMgr
 }

pkg/gui/types/common.go

@@ -56,6 +56,9 @@ type IGuiCommon interface {
 	RunSubprocess(cmdObj *oscommands.CmdObj) (bool, error)
 	RunSubprocessAndRefresh(*oscommands.CmdObj) error
 
+	Suspend() error
+	Resume() error
+
 	Context() IContextMgr
 	ContextForKey(key ContextKey) Context
 

pkg/i18n/english.go

@@ -382,6 +382,8 @@ type TranslationSet struct {
 	ScrollUp                              string
 	ScrollUpMainWindow                    string
 	ScrollDownMainWindow                  string
+	SuspendApp                            string
+	CannotSuspendApp                      string
 	AmendCommitTitle                      string
 	AmendCommitPrompt                     string
 	AmendCommitWithConflictsMenuPrompt    string
@@ -1456,6 +1458,8 @@ func EnglishTranslationSet() *TranslationSet {
 		ScrollUp:                             "Scroll up",
 		ScrollUpMainWindow:                   "Scroll up main window",
 		ScrollDownMainWindow:                 "Scroll down main window",
+		SuspendApp:                           "Suspend the application",
+		CannotSuspendApp:                     "Suspending the application is not supported on Windows",
 		AmendCommitTitle:                     "Amend commit",
 		AmendCommitPrompt:                    "Are you sure you want to amend this commit with your staged files?",
 		AmendCommitWithConflictsMenuPrompt:   "WARNING: you are about to amend the last finished commit with your resolved conflicts. This is very unlikely to be what you want at this point. More likely, you simply want to continue the rebase instead.\n\nDo you still want to amend the previous commit?",