viewer: add key passthrough mode

When trying to search in less, keys bound to viewer functions can't be
used as part of the search query, which makes the search useless.

Add a view::passthrough binding mode and a :toggle-key-passthrough
command go toggle in and out of that mode. By default, typing '/' in the
viewer is bound to enabling key passthrough and automatically inserting
'/', to easily enter "less" search mode. When in the passthrough mode,
all bindings are ignored by default. The default binds.conf only defines
a single keybinding in that mode: <Esc> to get back out. $ex is bound to
<C-x> to allow typing colons.

Signed-off-by: Kt Programs <ktprograms@gmail.com>
Acked-by: Robin Jarry <robin@jarry.cc>

commands/msgview/toggle-key-passthrough.go

@@ -0,0 +1,35 @@
+package msgview
+
+import (
+	"errors"
+
+	"git.sr.ht/~rjarry/aerc/widgets"
+)
+
+type ToggleKeyPassthrough struct{}
+
+func init() {
+	register(ToggleKeyPassthrough{})
+}
+
+func (ToggleKeyPassthrough) Aliases() []string {
+	return []string{"toggle-key-passthrough"}
+}
+
+func (ToggleKeyPassthrough) Complete(aerc *widgets.Aerc, args []string) []string {
+	return nil
+}
+
+func (ToggleKeyPassthrough) Execute(aerc *widgets.Aerc, args []string) error {
+	if len(args) != 1 {
+		return errors.New("Usage: toggle-key-passthrough")
+	}
+	mv, _ := aerc.SelectedTab().(*widgets.MessageViewer)
+	keyPassthroughEnabled := mv.ToggleKeyPassthrough()
+	if keyPassthroughEnabled {
+		aerc.SetExtraStatus("[passthrough]")
+	} else {
+		aerc.ClearExtraStatus()
+	}
+	return nil
+}

config/binds.conf

@@ -56,6 +56,7 @@ N = :prev-result<Enter>
 <Esc> = :clear<Enter>
 
 [view]
+/ = :toggle-key-passthrough<Enter>/
 q = :close<Enter>
 | = :pipe<space>
 D = :delete<Enter>
@@ -74,6 +75,11 @@ H = :toggle-headers<Enter>
 J = :next<Enter>
 K = :prev<Enter>
 
+[view::passthrough]
+$noinherit = true
+$ex = <C-x>
+<Esc> = :toggle-key-passthrough<Enter>
+
 [compose]
 # Keybindings used when the embedded terminal is not selected in the compose
 # view

config/config.go

@@ -112,6 +112,7 @@ type BindingConfig struct {
 	ComposeReview          *KeyBindings
 	MessageList            *KeyBindings
 	MessageView            *KeyBindings
+	MessageViewPassthrough *KeyBindings
 	Terminal               *KeyBindings
 }
 
@@ -143,6 +144,7 @@ type ViewerConfig struct {
 	ShowHeaders    bool       `ini:"show-headers"`
 	AlwaysShowMime bool       `ini:"always-show-mime"`
 	HeaderLayout   [][]string `ini:"-"`
+	KeyPassthrough bool       `ini:"-"`
 }
 
 type TriggersConfig struct {
@@ -598,6 +600,7 @@ func LoadConfigFromFile(root *string, logger *log.Logger) (*AercConfig, error) {
 			ComposeReview:          NewKeyBindings(),
 			MessageList:            NewKeyBindings(),
 			MessageView:            NewKeyBindings(),
+			MessageViewPassthrough: NewKeyBindings(),
 			Terminal:               NewKeyBindings(),
 		},
 
@@ -708,6 +711,7 @@ func LoadConfigFromFile(root *string, logger *log.Logger) (*AercConfig, error) {
 		"messages":          &config.Bindings.MessageList,
 		"terminal":          &config.Bindings.Terminal,
 		"view":              &config.Bindings.MessageView,
+		"view::passthrough": &config.Bindings.MessageViewPassthrough,
 		"compose::editor":   &config.Bindings.ComposeEditor,
 		"compose::review":   &config.Bindings.ComposeReview,
 	}

doc/aerc-config.5.scd

@@ -564,6 +564,10 @@ are:
 *[view]*
 	keybindings for the message viewer
 
+*[view::passthrough]*
+	keybindings for the viewer, when in key passthrough mode
+	(toggled with :toggle-key-passthrough)
+
 *[compose]*
 	keybindings for the message composer
 

widgets/aerc.go

@@ -201,7 +201,12 @@ func (aerc *Aerc) getBindings() *config.KeyBindings {
 			return aerc.conf.MergeContextualBinds(aerc.conf.Bindings.Compose, config.BIND_CONTEXT_ACCOUNT, selectedAccountName, "compose")
 		}
 	case *MessageViewer:
+		switch view.Bindings() {
+		case "view::passthrough":
+			return aerc.conf.MergeContextualBinds(aerc.conf.Bindings.MessageViewPassthrough, config.BIND_CONTEXT_ACCOUNT, selectedAccountName, "view::passthrough")
+		default:
 			return aerc.conf.MergeContextualBinds(aerc.conf.Bindings.MessageView, config.BIND_CONTEXT_ACCOUNT, selectedAccountName, "view")
+		}
 	case *Terminal:
 		return aerc.conf.Bindings.Terminal
 	default:

widgets/msgviewer.go

@@ -286,6 +286,11 @@ func (mv *MessageViewer) ToggleHeaders() {
 	switcher.Invalidate()
 }
 
+func (mv *MessageViewer) ToggleKeyPassthrough() bool {
+	mv.conf.Viewer.KeyPassthrough = !mv.conf.Viewer.KeyPassthrough
+	return mv.conf.Viewer.KeyPassthrough
+}
+
 func (mv *MessageViewer) SelectedMessagePart() *PartInfo {
 	switcher := mv.switcher
 	part := switcher.parts[switcher.selected]
@@ -325,6 +330,14 @@ func (mv *MessageViewer) NextPart() {
 	mv.Invalidate()
 }
 
+func (mv *MessageViewer) Bindings() string {
+	if mv.conf.Viewer.KeyPassthrough {
+		return "view::passthrough"
+	} else {
+		return "view"
+	}
+}
+
 func (mv *MessageViewer) Close() error {
 	mv.switcher.Cleanup()
 	return nil