tty: enable writing to tty and add smcup in example

Signed-off-by: Tim Culverhouse <tim@timculverhouse.com>

examples/main.zig

@@ -19,6 +19,8 @@ pub fn main() !void {
     try vx.start();
     defer vx.stop();
 
+    try vx.enterAltScreen();
+
     outer: while (true) {
         const event = vx.nextEvent();
         log.debug("event: {}\r\n", .{event});

src/Tty.zig

@@ -167,6 +167,13 @@ pub fn run(
     }
 }
 
+/// write to the tty
+//
+// TODO: buffer the writes
+pub fn write(self: *Tty, bytes: []const u8) !usize {
+    return os.write(self.fd, bytes);
+}
+
 /// makeRaw enters the raw state for the terminal.
 pub fn makeRaw(fd: os.fd_t) !os.termios {
     const state = try os.tcgetattr(fd);
@@ -218,6 +225,7 @@ fn ior(inout: u32, group: usize, num: usize, len: usize) usize {
     return (inout | ((len & IOCPARM_MASK) << 16) | ((group) << 8) | (num));
 }
 
+/// The size of the terminal screen
 pub const Winsize = struct {
     rows: usize,
     cols: usize,

src/vaxis.zig

@@ -1,6 +1,7 @@
 const std = @import("std");
 
-const queue = @import("queue.zig");
+const Queue = @import("queue.zig").Queue;
+const ctlseqs = @import("ctlseqs.zig");
 const Tty = @import("Tty.zig");
 const Key = @import("Key.zig");
 const Screen = @import("Screen.zig");
@@ -27,18 +28,21 @@ pub fn Vaxis(comptime T: type) type {
         /// the event queue for Vaxis
         //
         // TODO: is 512 ok?
-        queue: queue.Queue(T, 512),
+        queue: Queue(T, 512),
 
         tty: ?Tty,
 
         screen: Screen,
 
+        alt_screen: bool,
+
         /// Initialize Vaxis with runtime options
         pub fn init(_: Options) !Self {
             return Self{
                 .queue = .{},
                 .tty = null,
                 .screen = Screen.init(),
+                .alt_screen = false,
             };
         }
 
@@ -49,6 +53,9 @@ pub fn Vaxis(comptime T: type) type {
         pub fn deinit(self: *Self, alloc: ?std.mem.Allocator) void {
             if (self.tty) |_| {
                 var tty = &self.tty.?;
+                if (self.alt_screen) {
+                    _ = tty.write(ctlseqs.rmcup) catch {};
+                }
                 tty.deinit();
             }
             if (alloc) |a| self.screen.deinit(a);
@@ -98,6 +105,24 @@ pub fn Vaxis(comptime T: type) type {
                 .screen = &self.screen,
             };
         }
+
+        pub fn enterAltScreen(self: *Self) !void {
+            if (self.tty) |_| {
+                var tty = &self.tty.?;
+                _ = try tty.write(ctlseqs.smcup);
+                self.alt_screen = true;
+            }
+        }
+
+        pub fn exitaltScreen(self: *Self) !void {
+            if (self.tty) |_| {
+                if (!self.alt_screen) return;
+
+                var tty = &self.tty.?;
+                _ = try tty.write(ctlseqs.rmcup);
+                self.alt_screen = false;
+            }
+        }
     };
 }