A minibuffer option to set the preferred terminal type

Sometimes the terminal variable TERM does not correctly capture the
capabilities of the running terminal - for example, TERM might report 8
colors whereas the terminal can actually support 256. Termshark has a
config variable, main.term, that can be used to set this variable so
that termshark will use the correct terminal settings. This change
exposes that setting to the minibuffer e.g.

set term screen-256color    # saves as main.term in termshark.toml
set noterm                  # clears the setting

ui/lastline.go

@@ -13,11 +13,14 @@ import (
 	"github.com/gcla/gowid/gwutil"
 	"github.com/gcla/termshark/v2"
 	"github.com/gcla/termshark/v2/widgets/minibuffer"
+	"github.com/gdamore/tcell/terminfo"
+	"github.com/gdamore/tcell/terminfo/dynamic"
 )
 
 //======================================================================
 
 var notEnoughArgumentsErr = fmt.Errorf("Not enough arguments provided")
+var invalidSetCommandErr = fmt.Errorf("Invalid set command")
 
 type minibufferFn func(gowid.IApp, ...string) error
 
@@ -100,9 +103,7 @@ func (s unhelpfulArg) Completions() []string {
 
 //======================================================================
 
-type setArg struct {
-	arg string
-}
+type setArg struct{}
 
 var _ minibuffer.IArg = setArg{}
 
@@ -118,6 +119,8 @@ func (s setArg) Completions() []string {
 		"dark-mode",
 		"disable-shark-fin",
 		"packet-colors",
+		"term",
+		"noterm",
 	}
 }
 
@@ -142,6 +145,15 @@ func parseOnOff(str string) (bool, error) {
 	return false, strconv.ErrSyntax
 }
 
+func validateTerm(term string) error {
+	var err error
+	_, err = terminfo.LookupTerminfo(term)
+	if err != nil {
+		_, _, err = dynamic.LoadTerminfo(term)
+	}
+	return err
+}
+
 type setCommand struct{}
 
 var _ minibuffer.IAction = setCommand{}
@@ -150,7 +162,8 @@ func (d setCommand) Run(app gowid.IApp, args ...string) error {
 	var err error
 	var b bool
 	var i uint64
-	if len(args) == 3 {
+	switch len(args) {
+	case 3:
 		switch args[1] {
 		case "auto-scroll":
 			if b, err = parseOnOff(args[2]); err == nil {
@@ -179,9 +192,26 @@ func (d setCommand) Run(app gowid.IApp, args ...string) error {
 				termshark.SetConf("main.packet-colors", PacketColors)
 				OpenMessage(fmt.Sprintf("Packet colors are now %s", gwutil.If(b, "on", "off").(string)), appView, app)
 			}
+		case "term":
+			if err = validateTerm(args[2]); err == nil {
+				termshark.SetConf("main.term", args[2])
+				app.Run(gowid.RunFunction(func(app gowid.IApp) {
+					OpenMessage(fmt.Sprintf("Terminal type is now %s\n(Requires restart)", args[2]), appView, app)
+				}))
+			}
+		default:
+			err = invalidSetCommandErr
+		}
+	case 2:
+		switch args[1] {
+		case "noterm":
+			termshark.DeleteConf("main.term")
+			app.Run(gowid.RunFunction(func(app gowid.IApp) {
+				OpenMessage("Terminal type is now unset\n(Requires restart)", appView, app)
+			}))
+		default:
+			err = invalidSetCommandErr
 		}
-	} else {
-		err = notEnoughArgumentsErr
 	}
 
 	if err != nil {