Start of base screen refactoring.

A lot of functionality is duplicated across screen implementations,
and adding convenience methods is onerous because one needs to touch
each implementation with what is mostly copy-paste coding.

This represents the start of refactoring to eliminate redundant code
from each implemenation and provide for it in a common layer.

console_win.go

@@ -1,7 +1,7 @@
 //go:build windows
 // +build windows
 
-// Copyright 2022 The TCell Authors
+// Copyright 2023 The TCell Authors
 //
 // Licensed under the Apache License, Version 2.0 (the "License");
 // you may not use file except in compliance with the License.
@@ -175,7 +175,7 @@ var vtCursorStyles = map[CursorStyle]string{
 // with the current process.  The Screen makes use of the Windows Console
 // API to display content and read events.
 func NewConsoleScreen() (Screen, error) {
-	return &cScreen{}, nil
+	return &baseScreen{screenImpl: &cScreen{}}, nil
 }
 
 func (s *cScreen) Init() error {
@@ -894,14 +894,6 @@ func (s *cScreen) mapStyle(style Style) uint16 {
 	return attr
 }
 
-func (s *cScreen) SetCell(x, y int, style Style, ch ...rune) {
-	if len(ch) > 0 {
-		s.SetContent(x, y, ch[0], ch[1:], style)
-	} else {
-		s.SetContent(x, y, ' ', nil, style)
-	}
-}
-
 func (s *cScreen) SetContent(x, y int, primary rune, combining []rune, style Style) {
 	s.Lock()
 	if !s.fini {
@@ -1154,10 +1146,6 @@ func (s *cScreen) resize() {
 	_ = s.PostEvent(NewEventResize(w, h))
 }
 
-func (s *cScreen) Clear() {
-	s.Fill(' ', s.style)
-}
-
 func (s *cScreen) Fill(r rune, style Style) {
 	s.cells.Fill(r, style)
 }

screen.go

@@ -263,7 +263,6 @@ type Screen interface {
 	// Tty returns the underlying Tty. If the screen is not a terminal, the
 	// returned bool will be false
 	Tty() (Tty, bool)
-
 }
 
 // NewScreen returns a default Screen suitable for the user's terminal
@@ -302,3 +301,61 @@ const (
 	CursorStyleBlinkingBar
 	CursorStyleSteadyBar
 )
+
+// screenImpl is a subset of Screen that can be used with baseScreen to formulate
+// a complete implementation of Screen.  See Screen for doc comments about methods.
+type screenImpl interface {
+	Init() error
+	Fini()
+	Fill(rune, Style)
+	GetContent(x, y int) (primary rune, combining []rune, style Style, width int)
+	SetContent(x int, y int, primary rune, combining []rune, style Style)
+	SetStyle(style Style)
+	ShowCursor(x int, y int)
+	HideCursor()
+	SetCursorStyle(CursorStyle)
+	Size() (width, height int)
+	ChannelEvents(ch chan<- Event, quit <-chan struct{})
+	PollEvent() Event
+	HasPendingEvent() bool
+	PostEvent(ev Event) error
+	PostEventWait(ev Event)
+	EnableMouse(...MouseFlags)
+	DisableMouse()
+	EnablePaste()
+	DisablePaste()
+	EnableFocus()
+	DisableFocus()
+	HasMouse() bool
+	Colors() int
+	Show()
+	Sync()
+	CharacterSet() string
+	RegisterRuneFallback(r rune, subst string)
+	UnregisterRuneFallback(r rune)
+	CanDisplay(r rune, checkFallbacks bool) bool
+	Resize(int, int, int, int)
+	HasKey(Key) bool
+	Suspend() error
+	Resume() error
+	Beep() error
+	SetSize(int, int)
+	LockRegion(x, y, width, height int, lock bool)
+	Tty() (Tty, bool)
+}
+
+type baseScreen struct {
+	screenImpl
+}
+
+func (b *baseScreen) SetCell(x int, y int, style Style, ch ...rune) {
+	if len(ch) > 0 {
+		b.SetContent(x, y, ch[0], ch[1:], style)
+	} else {
+		b.SetContent(x, y, ' ', nil, style)
+	}
+}
+
+func (b *baseScreen) Clear() {
+	b.Fill(' ', StyleDefault)
+}

tscreen.go

@@ -94,7 +94,7 @@ func NewTerminfoScreenFromTtyTerminfo(tty Tty, ti *terminfo.Terminfo) (s Screen,
 		t.fallback[k] = v
 	}
 
-	return t, nil
+	return &baseScreen{screenImpl: t}, nil
 }
 
 // NewTerminfoScreenFromTty returns a Screen using a custom Tty implementation.
@@ -595,10 +595,6 @@ func (t *tScreen) SetStyle(style Style) {
 	t.Unlock()
 }
 
-func (t *tScreen) Clear() {
-	t.Fill(' ', t.style)
-}
-
 func (t *tScreen) Fill(r rune, style Style) {
 	t.Lock()
 	if !t.fini {
@@ -622,14 +618,6 @@ func (t *tScreen) GetContent(x, y int) (rune, []rune, Style, int) {
 	return mainc, combc, style, width
 }
 
-func (t *tScreen) SetCell(x, y int, style Style, ch ...rune) {
-	if len(ch) > 0 {
-		t.SetContent(x, y, ch[0], ch[1:], style)
-	} else {
-		t.SetContent(x, y, ' ', nil, style)
-	}
-}
-
 func (t *tScreen) encodeRune(r rune, buf []byte) []byte {
 
 	nb := make([]byte, 6)

wscreen.go

@@ -30,7 +30,7 @@ func NewTerminfoScreen() (Screen, error) {
 	t := &wScreen{}
 	t.fallback = make(map[rune]string)
 
-	return t, nil
+	return &baseScreen{screenImpl: t}, nil
 }
 
 type wScreen struct {
@@ -79,10 +79,6 @@ func (t *wScreen) SetStyle(style Style) {
 	t.Unlock()
 }
 
-func (t *wScreen) Clear() {
-	t.Fill(' ', t.style)
-}
-
 func (t *wScreen) Fill(r rune, style Style) {
 	t.Lock()
 	t.cells.Fill(r, style)
@@ -102,14 +98,6 @@ func (t *wScreen) GetContent(x, y int) (rune, []rune, Style, int) {
 	return mainc, combc, style, width
 }
 
-func (t *wScreen) SetCell(x, y int, style Style, ch ...rune) {
-	if len(ch) > 0 {
-		t.SetContent(x, y, ch[0], ch[1:], style)
-	} else {
-		t.SetContent(x, y, ' ', nil, style)
-	}
-}
-
 // paletteColor gives a more natural palette color actually matching
 // typical XTerm.  We might in the future want to permit styling these
 // via CSS.