world: reorganize and start the magic

1 files changed, 33 insertions, 0 deletions

diff --git a/world/tty-commands.scm b/world/tty-commands.scm
new file mode 100644
index 0000000..90d896e
--- /dev/null
+++ b/world/tty-commands.scm
@@ -0,0 +1,33 @@
+;; https://invisible-island.net/xterm/ctlseqs/ctlseqs.html
+
+;; Clear the screen better:
+;; https://invisible-island.net/xterm/ctlseqs/ctlseqs.html#h2-The-Alternate-Screen-Buffer
+
+(define csi-lead "\x1b[")
+
+(define (str-csi . args)
+  (apply string-append csi-lead args))
+
+(define (csi-command! . args)
+  (write-string (apply str-csi args))
+  (flush-output-port))
+
+; These are xterm things, but they are widely adopted
+(define (enable-alternate-buffer!)
+  (csi-command! "?1049h"))
+(define (disable-alternate-buffer!)
+  (csi-command! "?1049l"))
+
+(define (erase-screen!) (csi-command! "2J"))
+
+(define (move-cursor! x y)
+  "Also valid with CSI<L>;<C>f being <L> and <C> line number and column
+  number respectively. In ttys, cursor starts at 1,1"
+  (csi-command! (number->string (+ y 1)) ";" (number->string (+ 1 x)) "H"))
+
+(define (ui-initialize!)
+  (enable-alternate-buffer!)
+  (move-cursor! 0 0))
+
+(define (ui-deinitialize!)
+  (disable-alternate-buffer!))