better handling of random encodings

gui.go

@@ -147,10 +147,6 @@ type Gui struct {
 	// match any known sequence, ESC means KeyEsc.
 	InputEsc bool
 
-	// If ASCII is true then use ASCII instead of unicode to draw the
-	// interface. Using ASCII is more portable.
-	ASCII bool
-
 	// SupportOverlaps is true when we allow for view edges to overlap with other
 	// view edges
 	SupportOverlaps bool
@@ -754,9 +750,7 @@ func (g *Gui) clear(fg, bg Attribute) (int, int) {
 // drawFrameEdges draws the horizontal and vertical edges of a view.
 func (g *Gui) drawFrameEdges(v *View, fgColor, bgColor Attribute) error {
 	runeH, runeV := '─', '│'
-	if g.ASCII {
-		runeH, runeV = '-', '|'
-	} else if len(v.FrameRunes) >= 2 {
+	if len(v.FrameRunes) >= 2 {
 		runeH, runeV = v.FrameRunes[0], v.FrameRunes[1]
 	}
 
@@ -882,9 +876,6 @@ func (g *Gui) drawFrameCorners(v *View, fgColor, bgColor Attribute) error {
 		runeBL = corner(v, TOP|RIGHT)
 		runeBR = corner(v, TOP|LEFT)
 	}
-	if g.ASCII {
-		runeTL, runeTR, runeBL, runeBR = '+', '+', '+', '+'
-	}
 
 	corners := []struct {
 		x, y int

tcell_driver.go

@@ -8,6 +8,7 @@ import (
 	"time"
 
 	"github.com/gdamore/tcell/v2"
+	"github.com/mattn/go-runewidth"
 )
 
 // We probably don't want this being a global variable for YOLO for now
@@ -20,19 +21,50 @@ type oldStyle struct {
 	outputMode OutputMode
 }
 
+var runeReplacements = map[rune]string{
+	'┌': "+",
+	'┐': "+",
+	'└': "+",
+	'┘': "+",
+	'─': "-",
+
+	// using a hyphen here actually looks weird.
+	// We see these characters when in portrait mode
+	'╶': " ",
+	'╴': " ",
+
+	'├': "+",
+	'│': "|",
+	'▼': "v",
+	'►': ">",
+	'▲': "^",
+	'◄': "<",
+}
+
 // tcellInit initializes tcell screen for use.
 func (g *Gui) tcellInit() error {
+	runewidth.DefaultCondition.EastAsianWidth = false
+	tcell.SetEncodingFallback(tcell.EncodingFallbackASCII)
+
 	if s, e := tcell.NewScreen(); e != nil {
 		return e
 	} else if e = s.Init(); e != nil {
 		return e
 	} else {
+		registerRuneFallbacks(s)
+
 		g.screen = s
 		Screen = s
 		return nil
 	}
 }
 
+func registerRuneFallbacks(s tcell.Screen) {
+	for before, after := range runeReplacements {
+		s.RegisterRuneFallback(before, after)
+	}
+}
+
 // tcellInitSimulation initializes tcell screen for use.
 func (g *Gui) tcellInitSimulation() error {
 	s := tcell.NewSimulationScreen("")