v0.2.0 16 colors, default colors, /dev/tty, bracketed paste, themed form controls

internal/env/env.go

@@ -0,0 +1,46 @@
+// Package env reads what the environment says about a terminal's colors,
+// for terminal and inline alike
+package env
+
+import (
+	"os"
+	"strings"
+)
+
+// Colors reports how many colors the environment says the terminal shows:
+// 16 on a text console, which wins over COLORTERM since profiles export it
+// everywhere; 1<<24 when the terminal announces true color; else 256
+func Colors() int {
+	switch {
+	case textConsole(os.Getenv("TERM")):
+		return 16
+	case trueColor():
+		return 1 << 24
+	}
+	return 256
+}
+
+// textConsole reports a TERM limited to 16 colors: the Linux VT, FreeBSD
+// syscons, VT100-class terminals (vt and a digit, not vte) and *-16color
+func textConsole(term string) bool {
+	return term == "linux" || term == "ansi" || strings.HasPrefix(term, "cons25") ||
+		len(term) > 2 && term[:2] == "vt" && term[2] >= '0' && term[2] <= '9' ||
+		strings.HasSuffix(term, "-16color")
+}
+
+// trueColorVars are set by emulators that draw 24-bit color
+var trueColorVars = []string{"KITTY_WINDOW_ID", "KONSOLE_VERSION", "ITERM_SESSION_ID",
+	"ALACRITTY_WINDOW_ID", "ALACRITTY_LOG", "WEZTERM_PANE", "WT_SESSION", "WT_PROFILE_ID"}
+
+func trueColor() bool {
+	if ct := os.Getenv("COLORTERM"); ct == "truecolor" || ct == "24bit" {
+		return true
+	}
+	for _, v := range trueColorVars {
+		if os.Getenv(v) != "" {
+			return true
+		}
+	}
+	term := os.Getenv("TERM")
+	return strings.Contains(term, "truecolor") || strings.Contains(term, "24bit") || strings.Contains(term, "direct")
+}