Kill running preview process after 500ms when focus has changed

Close #1383
Close #1384

2 files changed, 24 insertions, 8 deletions

diff --git a/src/util/util_unix.go b/src/util/util_unix.go
index fc63c027..6331275c 100644
--- a/src/util/util_unix.go
+++ b/src/util/util_unix.go
@@ -9,17 +9,26 @@ import (
 )
 
 // ExecCommand executes the given command with $SHELL
-func ExecCommand(command string) *exec.Cmd {
+func ExecCommand(command string, setpgid bool) *exec.Cmd {
 	shell := os.Getenv("SHELL")
 	if len(shell) == 0 {
 		shell = "sh"
 	}
-	return ExecCommandWith(shell, command)
+	return ExecCommandWith(shell, command, setpgid)
 }
 
 // ExecCommandWith executes the given command with the specified shell
-func ExecCommandWith(shell string, command string) *exec.Cmd {
-	return exec.Command(shell, "-c", command)
+func ExecCommandWith(shell string, command string, setpgid bool) *exec.Cmd {
+	cmd := exec.Command(shell, "-c", command)
+	if setpgid {
+		cmd.SysProcAttr = &syscall.SysProcAttr{Setpgid: true}
+	}
+	return cmd
+}
+
+// KillCommand kills the process for the given command
+func KillCommand(cmd *exec.Cmd) error {
+	return syscall.Kill(-cmd.Process.Pid, syscall.SIGKILL)
 }
 
 // IsWindows returns true on Windows
@@ -27,7 +36,7 @@ func IsWindows() bool {
 	return false
 }
 
-// SetNonBlock executes syscall.SetNonblock on file descriptor
+// SetNonblock executes syscall.SetNonblock on file descriptor
 func SetNonblock(file *os.File, nonblock bool) {
 	syscall.SetNonblock(int(file.Fd()), nonblock)
 }
diff --git a/src/util/util_windows.go b/src/util/util_windows.go
index 41a9a5c7..51715cd8 100644
--- a/src/util/util_windows.go
+++ b/src/util/util_windows.go
@@ -10,13 +10,15 @@ import (
 )
 
 // ExecCommand executes the given command with cmd
-func ExecCommand(command string) *exec.Cmd {
+func ExecCommand(command string, setpgid bool) *exec.Cmd {
 	return ExecCommandWith("cmd", command)
 }
 
 // ExecCommandWith executes the given command with cmd. _shell parameter is
 // ignored on Windows.
-func ExecCommandWith(_shell string, command string) *exec.Cmd {
+// FIXME: setpgid is unused. We set it in the Unix implementation so that we
+// can kill preview process with its child processes at once.
+func ExecCommandWith(_shell string, command string, setpgid bool) *exec.Cmd {
 	cmd := exec.Command("cmd")
 	cmd.SysProcAttr = &syscall.SysProcAttr{
 		HideWindow:    false,
@@ -26,12 +28,17 @@ func ExecCommandWith(_shell string, command string) *exec.Cmd {
 	return cmd
 }
 
+// KillCommand kills the process for the given command
+func KillCommand(cmd *exec.Cmd) error {
+	return cmd.Process.Kill()
+}
+
 // IsWindows returns true on Windows
 func IsWindows() bool {
 	return true
 }
 
-// SetNonBlock executes syscall.SetNonblock on file descriptor
+// SetNonblock executes syscall.SetNonblock on file descriptor
 func SetNonblock(file *os.File, nonblock bool) {
 	syscall.SetNonblock(syscall.Handle(file.Fd()), nonblock)
 }