feat(ansi): XTWINOPS and WindowOp functions (#323)

This implements the XTWINOPS and WindowOp functions that allow
manipulating the terminal window. Using `ansi.WindowOp` with
`ReportWindowSizeWinOp`, we can query the terminal for the pixel size of
the window. This is useful for rendering images in the terminal and
calculate the cell size based on how many pixels and cells are available.

See https://invisible-island.net/xterm/ctlseqs/ctlseqs.html#h4-Functions-using-CSI-_-ordered-by-the-final-character-lparen-s-rparen:CSI-Ps;Ps;Ps-t.1EB0

ansi/winop.go

@@ -0,0 +1,47 @@
+package ansi
+
+import (
+	"strconv"
+	"strings"
+)
+
+const (
+	// ResizeWindowWinOp is a window operation that resizes the terminal
+	// window.
+	ResizeWindowWinOp = 4
+
+	// ReportWindowSizeWinOp is a window operation that reports the size of the
+	// terminal window in pixels.
+	ReportWindowSizeWinOp = 14
+)
+
+// WindowOp (XTWINOPS) is a sequence that manipulates the terminal window.
+//
+//	CSI Ps ; Ps ; Ps t
+//
+// Ps is a semicolon-separated list of parameters.
+// See https://invisible-island.net/xterm/ctlseqs/ctlseqs.html#h4-Functions-using-CSI-_-ordered-by-the-final-character-lparen-s-rparen:CSI-Ps;Ps;Ps-t.1EB0
+func WindowOp(p int, ps ...int) string {
+	if p <= 0 {
+		return ""
+	}
+
+	if len(ps) == 0 {
+		return "\x1b[" + strconv.Itoa(p) + "t"
+	}
+
+	params := make([]string, 0, len(ps)+1)
+	params = append(params, strconv.Itoa(p))
+	for _, p := range ps {
+		if p >= 0 {
+			params = append(params, strconv.Itoa(p))
+		}
+	}
+
+	return "\x1b[" + strings.Join(params, ";") + "t"
+}
+
+// XTWINOPS is an alias for [WindowOp].
+func XTWINOPS(p int, ps ...int) string {
+	return WindowOp(p, ps...)
+}