Add truecolor support for Windows, if available (#2156)

- Update to latest tcell which has 24 bit Windows support
- light renderer under Windows defaults to Dark256, if possible
- Respect TCELL_TRUECOLOR
- Remove tcell 1.3 references

src/tui/light.go

@@ -3,7 +3,6 @@ package tui
 import (
 	"fmt"
 	"os"
-	"os/exec"
 	"regexp"
 	"strconv"
 	"strings"
@@ -126,17 +125,6 @@ func NewLightRenderer(theme *ColorTheme, forceBlack bool, mouse bool, tabstop in
 	return &r
 }
 
-func (r *LightRenderer) defaultTheme() *ColorTheme {
-	if strings.Contains(os.Getenv("TERM"), "256") {
-		return Dark256
-	}
-	colors, err := exec.Command("tput", "colors").Output()
-	if err == nil && atoi(strings.TrimSpace(string(colors)), 16) > 16 {
-		return Dark256
-	}
-	return Default16
-}
-
 func repeat(r rune, times int) string {
 	if times > 0 {
 		return strings.Repeat(string(r), times)

src/tui/light_unix.go

@@ -5,6 +5,8 @@ package tui
 import (
 	"fmt"
 	"os"
+	"os/exec"
+	"strings"
 	"syscall"
 
 	"github.com/junegunn/fzf/src/util"
@@ -15,6 +17,17 @@ func IsLightRendererSupported() bool {
 	return true
 }
 
+func (r *LightRenderer) defaultTheme() *ColorTheme {
+	if strings.Contains(os.Getenv("TERM"), "256") {
+		return Dark256
+	}
+	colors, err := exec.Command("tput", "colors").Output()
+	if err == nil && atoi(strings.TrimSpace(string(colors)), 16) > 16 {
+		return Dark256
+	}
+	return Default16
+}
+
 func (r *LightRenderer) fd() int {
 	return int(r.ttyin.Fd())
 }

src/tui/light_windows.go

@@ -34,6 +34,14 @@ func IsLightRendererSupported() bool {
 	return canSetVt100
 }
 
+func (r *LightRenderer) defaultTheme() *ColorTheme {
+	// the getenv check is borrowed from here: https://github.com/gdamore/tcell/commit/0c473b86d82f68226a142e96cc5a34c5a29b3690#diff-b008fcd5e6934bf31bc3d33bf49f47d8R178:
+	if !IsLightRendererSupported() || os.Getenv("ConEmuPID") != "" || os.Getenv("TCELL_TRUECOLOR") == "disable" {
+		return Default16
+	}
+	return Dark256
+}
+
 func (r *LightRenderer) initPlatform() error {
 	//outHandle := windows.Stdout
 	outHandle, _ := syscall.Open("CONOUT$", syscall.O_RDWR, 0)