Cleanup pager processes after closing a msgviewer

A pager is spawned every time an email is viewed but not killed off when
quitting the msgviewer, thus leading to process leakage. This patch
fixes this by adding a Close method to the msgview widget, which is
called in the close command.

Signed-off-by: Kevin Kuehler <keur@xcf.berkeley.edu>

commands/msgview/close.go

@@ -25,6 +25,7 @@ func (Close) Execute(aerc *widgets.Aerc, args []string) error {
 		return errors.New("Usage: close")
 	}
 	mv, _ := aerc.SelectedTab().(*widgets.MessageViewer)
+	mv.Close()
 	aerc.RemoveTab(mv)
 	return nil
 }

widgets/msgviewer.go

@@ -284,6 +284,10 @@ func (mv *MessageViewer) NextPart() {
 	mv.Invalidate()
 }
 
+func (mv *MessageViewer) Close() {
+	mv.switcher.Cleanup()
+}
+
 func (ps *PartSwitcher) Invalidate() {
 	ps.DoInvalidate(ps)
 }
@@ -381,6 +385,12 @@ func (ps *PartSwitcher) MouseEvent(localX int, localY int, event tcell.Event) {
 	}
 }
 
+func (ps *PartSwitcher) Cleanup() {
+	for _, partViewer := range ps.parts {
+		partViewer.Cleanup()
+	}
+}
+
 func (mv *MessageViewer) Event(event tcell.Event) bool {
 	return mv.switcher.Event(event)
 }
@@ -593,6 +603,13 @@ func (pv *PartViewer) Draw(ctx *ui.Context) {
 	pv.term.Draw(ctx)
 }
 
+func (pv *PartViewer) Cleanup() {
+	if pv.pager != nil && pv.pager.Process != nil {
+		pv.pager.Process.Kill()
+		pv.pager = nil
+	}
+}
+
 type HeaderView struct {
 	ui.Invalidatable
 	Name  string