commands: add :suspend

Add :suspend to suspend the aerc process, returning to shell. Include
documentation and default Ctrl-z keybinding for it.

Changelog-added: New `:suspend` command bound to `<C-z>` by default.
Signed-off-by: Nojus Gudinavičius <nojus.gudinavicius@gmail.com>
Signed-off-by: Robin Jarry <robin@jarry.cc>

5 files changed, 64 insertions, 0 deletions

diff --git a/commands/suspend.go b/commands/suspend.go
new file mode 100644
index 00000000..80d59028
--- /dev/null
+++ b/commands/suspend.go
@@ -0,0 +1,22 @@
+package commands
+
+import "git.sr.ht/~rjarry/aerc/lib/ui"
+
+type Suspend struct{}
+
+func init() {
+	register(Suspend{})
+}
+
+func (Suspend) Aliases() []string {
+	return []string{"suspend"}
+}
+
+func (Suspend) Complete(args []string) []string {
+	return nil
+}
+
+func (Suspend) Execute(args []string) error {
+	ui.QueueSuspend()
+	return nil
+}
diff --git a/config/binds.conf b/config/binds.conf
index 1b0c42c2..c0e28af9 100644
--- a/config/binds.conf
+++ b/config/binds.conf
@@ -9,6 +9,7 @@
 ? = :help keys<Enter>
 <C-c> = :prompt 'Quit?' quit<Enter>
 <C-q> = :prompt 'Quit?' quit<Enter>
+<C-z> = :suspend<Enter>
 
 [messages]
 q = :prompt 'Quit?' quit<Enter>
diff --git a/doc/aerc.1.scd b/doc/aerc.1.scd
index a48735d7..8443302c 100644
--- a/doc/aerc.1.scd
+++ b/doc/aerc.1.scd
@@ -167,6 +167,9 @@ These commands work in any context.
 *:choose* *-o* _<key>_ _<text>_ _<command>_ [*-o* _<key>_ _<text>_ _<command>_]...
 	Prompts the user to choose from various options.
 
+*:suspend*
+	Suspends the aerc process. Some ongoing connections may be terminated.
+
 *:quit* [*-f*]++
 *:exit* [*-f*]
 	Exits aerc. If a task is being performed that should not be interrupted
diff --git a/lib/ui/ui.go b/lib/ui/ui.go
index d2506b48..6a28eb9c 100644
--- a/lib/ui/ui.go
+++ b/lib/ui/ui.go
@@ -1,7 +1,10 @@
 package ui
 
 import (
+	"os"
+	"os/signal"
 	"sync/atomic"
+	"syscall"
 
 	"github.com/gdamore/tcell/v2"
 )
@@ -38,6 +41,8 @@ var state struct {
 	screen  tcell.Screen
 	popover *Popover
 	dirty   uint32 // == 1 if render has been queued in Redraw channel
+	// == 1 if suspend is pending
+	suspending uint32
 }
 
 func Initialize(content DrawableInteractive) error {
@@ -79,6 +84,34 @@ func Exit() {
 	close(Quit)
 }
 
+var SuspendQueue = make(chan bool, 1)
+
+func QueueSuspend() {
+	if atomic.SwapUint32(&state.suspending, 1) != 1 {
+		SuspendQueue <- true
+	}
+}
+
+func Suspend() error {
+	var err error
+	if atomic.SwapUint32(&state.suspending, 0) != 0 {
+		err = state.screen.Suspend()
+		if err == nil {
+			sigcont := make(chan os.Signal, 1)
+			signal.Notify(sigcont, syscall.SIGCONT)
+			err = syscall.Kill(0, syscall.SIGTSTP)
+			if err == nil {
+				<-sigcont
+			}
+			signal.Reset(syscall.SIGCONT)
+			err = state.screen.Resume()
+			state.content.Draw(state.ctx)
+			state.screen.Show()
+		}
+	}
+	return err
+}
+
 func Close() {
 	state.screen.Fini()
 }
diff --git a/main.go b/main.go
index fe3a2e7b..d63c9eef 100644
--- a/main.go
+++ b/main.go
@@ -307,6 +307,11 @@ loop:
 			callback()
 		case <-ui.Redraw:
 			ui.Render()
+		case <-ui.SuspendQueue:
+			err = ui.Suspend()
+			if err != nil {
+				app.PushError(fmt.Sprintf("suspend: %s", err))
+			}
 		case <-ui.Quit:
 			err = app.CloseBackends()
 			if err != nil {