libghostty: add option to set default cursor style

Adds an option to `libghostty-vt` to configure the default cursor style
that should be displayed when an app sends a DECSCUSR reset sequence
(`CSI 0 q`).

include/ghostty/vt/terminal.h

@@ -232,6 +232,26 @@ typedef enum GHOSTTY_ENUM_TYPED {
   GHOSTTY_TERMINAL_SCREEN_MAX_VALUE = GHOSTTY_ENUM_MAX_VALUE,
 } GhosttyTerminalScreen;
 
+/**
+ * Visual style of the terminal cursor.
+ *
+ * @ingroup terminal
+ */
+typedef enum GHOSTTY_ENUM_TYPED {
+  /** Bar cursor (DECSCUSR 5, 6). */
+  GHOSTTY_TERMINAL_CURSOR_STYLE_BAR = 0,
+
+  /** Block cursor (DECSCUSR 1, 2). */
+  GHOSTTY_TERMINAL_CURSOR_STYLE_BLOCK = 1,
+
+  /** Underline cursor (DECSCUSR 3, 4). */
+  GHOSTTY_TERMINAL_CURSOR_STYLE_UNDERLINE = 2,
+
+  /** Hollow block cursor. */
+  GHOSTTY_TERMINAL_CURSOR_STYLE_BLOCK_HOLLOW = 3,
+  GHOSTTY_TERMINAL_CURSOR_STYLE_MAX_VALUE = GHOSTTY_ENUM_MAX_VALUE,
+} GhosttyTerminalCursorStyle;
+
 /**
  * Scrollbar state for the terminal viewport.
  *
@@ -608,6 +628,15 @@ typedef enum GHOSTTY_ENUM_TYPED {
    * Input type: GhosttySelection*
    */
   GHOSTTY_TERMINAL_OPT_SELECTION = 21,
+
+  /**
+   * Set the default cursor style used by DECSCUSR reset (CSI 0 q).
+   *
+   * A NULL value pointer resets to the built-in default block cursor.
+   *
+   * Input type: GhosttyTerminalCursorStyle*
+   */
+  GHOSTTY_TERMINAL_OPT_DEFAULT_CURSOR_STYLE = 22,
   GHOSTTY_TERMINAL_OPT_MAX_VALUE = GHOSTTY_ENUM_MAX_VALUE,
 } GhosttyTerminalOption;
 

src/terminal/c/terminal.zig

@@ -5,6 +5,7 @@ const lib = @import("../lib.zig");
 const CAllocator = lib.alloc.Allocator;
 pub const ZigTerminal = @import("../Terminal.zig");
 const Stream = @import("../stream_terminal.zig").Stream;
+const Screen = @import("../Screen.zig");
 const ScreenSet = @import("../ScreenSet.zig");
 const PageList = @import("../PageList.zig");
 const apc = @import("../apc.zig");
@@ -326,6 +327,7 @@ pub const Option = enum(c_int) {
     apc_max_bytes = 19,
     apc_max_bytes_kitty = 20,
     selection = 21,
+    default_cursor_style = 22,
 
     /// Input type expected for setting the option.
     pub fn InType(comptime self: Option) type {
@@ -349,6 +351,7 @@ pub const Option = enum(c_int) {
             => ?*const bool,
             .apc_max_bytes, .apc_max_bytes_kitty => ?*const usize,
             .selection => ?*const selection_c.CSelection,
+            .default_cursor_style => ?*const TerminalCursorStyle,
         };
     }
 };
@@ -464,10 +467,36 @@ fn setTyped(
                 wrapper.terminal.screens.active.clearSelection();
             }
         },
+        .default_cursor_style => {
+            const style = (if (value) |ptr| ptr.* else TerminalCursorStyle.block).toZig() orelse return .invalid_value;
+            wrapper.stream.handler.default_cursor_style = style;
+            if (wrapper.stream.handler.default_cursor) {
+                wrapper.terminal.screens.active.cursor.cursor_style = style;
+            }
+        },
     }
     return .success;
 }
 
+/// C: GhosttyTerminalCursorStyle
+pub const TerminalCursorStyle = enum(c_int) {
+    bar = 0,
+    block = 1,
+    underline = 2,
+    block_hollow = 3,
+    _,
+
+    fn toZig(self: TerminalCursorStyle) ?Screen.CursorStyle {
+        return switch (self) {
+            .bar => .bar,
+            .block => .block,
+            .underline => .underline,
+            .block_hollow => .block_hollow,
+            _ => null,
+        };
+    }
+};
+
 /// C: GhosttyDeviceAttributes
 pub const DeviceAttributes = Effects.CDeviceAttributes;
 

src/terminal/stream_terminal.zig

@@ -43,6 +43,10 @@ pub const Handler = struct {
     /// the kitty graphics protocol.
     apc_handler: apc.Handler = .{},
 
+    /// Default cursor style used by DECSCUSR reset (CSI 0 q).
+    default_cursor: bool = true,
+    default_cursor_style: Screen.CursorStyle = .block,
+
     pub const Effects = struct {
         /// Called when the terminal needs to write data back to the pty,
         /// e.g. in response to a DECRQM query. The data is only valid
@@ -152,12 +156,18 @@ pub const Handler = struct {
                 self.terminal.screens.active.cursor.x + 1,
             ),
             .cursor_style => {
+                self.default_cursor = false;
+
                 const blink = switch (value) {
                     .default, .steady_block, .steady_bar, .steady_underline => false,
                     .blinking_block, .blinking_bar, .blinking_underline => true,
                 };
                 const style: Screen.CursorStyle = switch (value) {
-                    .default, .blinking_block, .steady_block => .block,
+                    .default => style: {
+                        self.default_cursor = true;
+                        break :style self.default_cursor_style;
+                    },
+                    .blinking_block, .steady_block => .block,
                     .blinking_bar, .steady_bar => .bar,
                     .blinking_underline, .steady_underline => .underline,
                 };
@@ -228,7 +238,11 @@ pub const Handler = struct {
             },
             .active_status_display => self.terminal.status_display = value,
             .decaln => try self.terminal.decaln(),
-            .full_reset => self.terminal.fullReset(),
+            .full_reset => {
+                self.terminal.fullReset();
+                self.default_cursor = true;
+                self.terminal.screens.active.cursor.cursor_style = self.default_cursor_style;
+            },
             .start_hyperlink => try self.terminal.screens.active.startHyperlink(value.uri, value.id),
             .end_hyperlink => self.terminal.screens.active.endHyperlink(),
             .semantic_prompt => try self.terminal.semanticPrompt(value),