fixes #462 Console resizing

This supports both terminfo (Linux, macOS) terminals, and
the legacy Windows console.  Perversely, the "modern" Windows
terminal doesn't support application initiated resizing yet.

_demos/setsize.go

@@ -0,0 +1,101 @@
+//go:build ignore
+// +build ignore
+
+// Copyright 2022 The TCell Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use file except in compliance with the License.
+// You may obtain a copy of the license at
+//
+//    http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package main
+
+import (
+	"fmt"
+	"os"
+
+	"github.com/gdamore/tcell/v2"
+	"github.com/gdamore/tcell/v2/encoding"
+
+	"github.com/mattn/go-runewidth"
+)
+
+func emitStr(s tcell.Screen, x, y int, style tcell.Style, str string) {
+	for _, c := range str {
+		var comb []rune
+		w := runewidth.RuneWidth(c)
+		if w == 0 {
+			comb = []rune{c}
+			c = ' '
+			w = 1
+		}
+		s.SetContent(x, y, c, comb, style)
+		x += w
+	}
+}
+
+func displayDemo(s tcell.Screen) {
+	w, h := s.Size()
+	s.Clear()
+	style := tcell.StyleDefault.Foreground(tcell.ColorCadetBlue.TrueColor()).Background(tcell.ColorWhite)
+	sizeStr := fmt.Sprintf("%d x %d", w, h)
+	helpStr := "Use cursors to resize, ESC to exit."
+	emitStr(s, (w-len(sizeStr))/2, h/2, style, sizeStr)
+	emitStr(s, (w-len(helpStr))/2, h/2+1, tcell.StyleDefault, helpStr)
+	s.Show()
+}
+
+// This program just prints "Hello, World!".  Press ESC to exit.
+func main() {
+	encoding.Register()
+
+	s, e := tcell.NewScreen()
+	if e != nil {
+		fmt.Fprintf(os.Stderr, "%v\n", e)
+		os.Exit(1)
+	}
+	if e := s.Init(); e != nil {
+		fmt.Fprintf(os.Stderr, "%v\n", e)
+		os.Exit(1)
+	}
+
+	defStyle := tcell.StyleDefault.
+		Background(tcell.ColorBlack).
+		Foreground(tcell.ColorWhite)
+	s.SetStyle(defStyle)
+
+	displayDemo(s)
+
+	for {
+		switch ev := s.PollEvent().(type) {
+		case *tcell.EventResize:
+			s.Sync()
+			displayDemo(s)
+		case *tcell.EventKey:
+			switch ev.Key() {
+			case tcell.KeyEscape:
+				s.Fini()
+				os.Exit(0)
+			case tcell.KeyRight:
+				w, h := s.Size()
+				s.SetSize(w+1, h)
+			case tcell.KeyLeft:
+				w, h := s.Size()
+				s.SetSize(w-1, h)
+			case tcell.KeyUp:
+				w, h := s.Size()
+				s.SetSize(w, h-1)
+			case tcell.KeyDown:
+				w, h := s.Size()
+				s.SetSize(w, h+1)
+			}
+		}
+	}
+}