Detect the terminal size with a syscall.

This will only work on Linux.

1 files changed, 23 insertions, 5 deletions

diff --git a/mandelbrot.go b/mandelbrot.go
index 482850a..686625b 100644
--- a/mandelbrot.go
+++ b/mandelbrot.go
@@ -2,8 +2,23 @@ package main
 
 import (
 	"fmt"
+	"os"
+	"syscall"
+	"unsafe"
 )
 
+func terminalSize() (cols int, lines int, err error) {
+	const tiocgwinsz uintptr = 21523
+
+	ts := new(struct {
+		wsRow, wsCol, wsXPixel, wsYPixel uint16
+	})
+	if _, _, err := syscall.Syscall(syscall.SYS_IOCTL, 1, tiocgwinsz, uintptr(unsafe.Pointer(ts))); err != 0 {
+		return 0, 0, err
+	}
+	return int(ts.wsCol), int(ts.wsRow), nil
+}
+
 func mandelbrot(x0, y0 float64) int {
 	var x, y, x2, y2 float64
 	for i := 0; i < 1000; i++ {
@@ -24,13 +39,16 @@ func main() {
 		xRange = 2.47
 		yMin   = -1.12
 		yRange = 2.24
+	)
 
-		width  = 80
-		height = 25
+	width, height, err := terminalSize()
+	if err != nil {
+		fmt.Fprintln(os.Stderr, err)
+		os.Exit(1)
+	}
 
-		xStep = xRange / float64(width)
-		yStep = yRange / float64(height)
-	)
+	xStep := xRange / float64(width)
+	yStep := yRange / float64(height)
 
 	y := yMin
 	for i := 0; i < height; i++ {