respect application cursor keys for arrow (DECCKM)

This fixes the arrow keys in htop.

src/Window.zig

@@ -980,6 +980,29 @@ fn keyCallback(
                     win.io_thread.wakeup.send() catch {};
                 },
 
+                .cursor_key => |ck| {
+                    // We send a different sequence depending on if we're
+                    // in cursor keys mode. We're in "normal" mode if cursor
+                    // keys mdoe is NOT set.
+                    const normal = normal: {
+                        win.renderer_state.mutex.lock();
+                        defer win.renderer_state.mutex.unlock();
+                        break :normal !win.io.terminal.modes.cursor_keys;
+                    };
+
+                    if (normal) {
+                        _ = win.io_thread.mailbox.push(.{
+                            .write_stable = ck.normal,
+                        }, .{ .forever = {} });
+                    } else {
+                        _ = win.io_thread.mailbox.push(.{
+                            .write_stable = ck.application,
+                        }, .{ .forever = {} });
+                    }
+
+                    win.io_thread.wakeup.send() catch {};
+                },
+
                 .copy_to_clipboard => {
                     // We can read from the renderer state without holding
                     // the lock because only we will write to this field.

src/config.zig

@@ -190,12 +190,31 @@ pub const Config = struct {
             .{ .paste_from_clipboard = {} },
         );
 
-        try result.keybind.set.put(alloc, .{ .key = .up }, .{ .csi = "A" });
-        try result.keybind.set.put(alloc, .{ .key = .down }, .{ .csi = "B" });
-        try result.keybind.set.put(alloc, .{ .key = .right }, .{ .csi = "C" });
-        try result.keybind.set.put(alloc, .{ .key = .left }, .{ .csi = "D" });
-        try result.keybind.set.put(alloc, .{ .key = .home }, .{ .csi = "H" });
-        try result.keybind.set.put(alloc, .{ .key = .end }, .{ .csi = "F" });
+        try result.keybind.set.put(alloc, .{ .key = .up }, .{ .cursor_key = .{
+            .normal = "\x1b[A",
+            .application = "\x1bOA",
+        } });
+        try result.keybind.set.put(alloc, .{ .key = .down }, .{ .cursor_key = .{
+            .normal = "\x1b[B",
+            .application = "\x1bOB",
+        } });
+        try result.keybind.set.put(alloc, .{ .key = .right }, .{ .cursor_key = .{
+            .normal = "\x1b[C",
+            .application = "\x1bOC",
+        } });
+        try result.keybind.set.put(alloc, .{ .key = .left }, .{ .cursor_key = .{
+            .normal = "\x1b[D",
+            .application = "\x1bOD",
+        } });
+        try result.keybind.set.put(alloc, .{ .key = .home }, .{ .cursor_key = .{
+            .normal = "\x1b[H",
+            .application = "\x1bOH",
+        } });
+        try result.keybind.set.put(alloc, .{ .key = .end }, .{ .cursor_key = .{
+            .normal = "\x1b[F",
+            .application = "\x1bOF",
+        } });
+
         try result.keybind.set.put(alloc, .{ .key = .page_up }, .{ .csi = "5~" });
         try result.keybind.set.put(alloc, .{ .key = .page_down }, .{ .csi = "6~" });
 

src/input/Binding.zig

@@ -15,6 +15,7 @@ action: Action,
 
 pub const Error = error{
     InvalidFormat,
+    InvalidAction,
 };
 
 /// Parse the format "ctrl+a=csi:A" into a binding. The format is
@@ -101,6 +102,9 @@ pub fn parse(input: []const u8) !Binding {
                         break :action @unionInit(Action, field.name, param);
                     },
 
+                    // Cursor keys can't be set currently
+                    Action.CursorKey => return Error.InvalidAction,
+
                     else => unreachable,
                 }
             }
@@ -127,6 +131,10 @@ pub const Action = union(enum) {
     /// without the CSI header ("ESC ]" or "\x1b]").
     csi: []const u8,
 
+    /// Send data to the pty depending on whether cursor key mode is
+    /// enabled ("application") or disabled ("normal").
+    cursor_key: CursorKey,
+
     /// Copy and paste.
     copy_to_clipboard: void,
     paste_from_clipboard: void,
@@ -152,6 +160,11 @@ pub const Action = union(enum) {
 
     /// Quit ghostty
     quit: void,
+
+    pub const CursorKey = struct {
+        normal: []const u8,
+        application: []const u8,
+    };
 };
 
 /// Trigger is the associated key state that can trigger an action.

src/terminal/Terminal.zig

@@ -72,6 +72,7 @@ previous_char: ?u21 = null,
 modes: packed struct {
     const Self = @This();
 
+    cursor_keys: bool = false, // 1
     reverse_colors: bool = false, // 5,
     origin: bool = false, // 6
     autowrap: bool = true, // 7

src/terminal/ansi.zig

@@ -42,6 +42,17 @@ pub const RenditionAspect = enum(u16) {
 /// values correspond to the `?`-prefixed modes, since those are the ones
 /// of primary interest. The enum value is the mode value.
 pub const Mode = enum(u16) {
+    /// This control function selects the sequences the arrow keys send.
+    /// You can use the four arrow keys to move the cursor through the current
+    /// page or to send special application commands.
+    ///
+    /// If the DECCKM function is set, then the arrow keys send application
+    /// sequences to the host.
+    ///
+    /// If the DECCKM function is reset, then the arrow keys send ANSI cursor
+    /// sequences to the host.
+    cursor_keys = 1,
+
     /// Change terminal wide between 80 and 132 column mode. When set
     /// (with ?40 set), resizes terminal to 132 columns and keeps it that
     /// wide. When unset, resizes to 80 columns.

src/termio/Exec.zig

@@ -627,6 +627,10 @@ const StreamHandler = struct {
 
     pub fn setMode(self: *StreamHandler, mode: terminal.Mode, enabled: bool) !void {
         switch (mode) {
+            .cursor_keys => {
+                self.terminal.modes.cursor_keys = enabled;
+            },
+
             .reverse_colors => {
                 self.terminal.modes.reverse_colors = enabled;