Add cursor visibility controls

Add cross-platform cursor visibility operations so console users can
hide the cursor while redrawing without platform-specific code.

Author: nobu

ext/io/console/console.c

@@ -1410,6 +1410,54 @@ console_cursor_pos(VALUE io)
 #endif
 }
 
+static VALUE
+console_cursor_visibility(VALUE io, int visible)
+{
+#ifdef _WIN32
+    HANDLE h = (HANDLE)rb_w32_get_osfhandle(GetWriteFD(io));
+    CONSOLE_CURSOR_INFO info;
+
+    if (!GetConsoleCursorInfo(h, &info)) {
+	rb_syserr_fail(LAST_ERROR, 0);
+    }
+    info.bVisible = visible;
+    if (!SetConsoleCursorInfo(h, &info)) {
+	rb_syserr_fail(LAST_ERROR, 0);
+    }
+#else
+    rb_io_write(io, rb_str_new_cstr(visible ? CSI "?25h" : CSI "?25l"));
+#endif
+    return io;
+}
+
+/*
+ * call-seq:
+ *   io.hide_cursor             -> io
+ *
+ * Hides the cursor.
+ *
+ * You must require 'io/console' to use this method.
+ */
+static VALUE
+console_hide_cursor(VALUE io)
+{
+    return console_cursor_visibility(io, 0);
+}
+
+/*
+ * call-seq:
+ *   io.show_cursor             -> io
+ *
+ * Shows the cursor.
+ *
+ * You must require 'io/console' to use this method.
+ */
+static VALUE
+console_show_cursor(VALUE io)
+{
+    return console_cursor_visibility(io, 1);
+}
+
 /*
  * call-seq:
  *   io.goto(line, column)      -> io
@@ -2201,6 +2249,8 @@ InitVM_console(void)
     rb_define_method(rb_cIO, "goto", console_goto, 2);
     rb_define_method(rb_cIO, "cursor", console_cursor_pos, 0);
     rb_define_method(rb_cIO, "cursor=", console_cursor_set, 1);
+    rb_define_method(rb_cIO, "hide_cursor", console_hide_cursor, 0);
+    rb_define_method(rb_cIO, "show_cursor", console_show_cursor, 0);
     rb_define_method(rb_cIO, "cursor_up", console_cursor_up, 1);
     rb_define_method(rb_cIO, "cursor_down", console_cursor_down, 1);
     rb_define_method(rb_cIO, "cursor_left", console_cursor_left, 1);

test/io/console/test_io_console.rb

@@ -444,6 +444,16 @@ def test_cursor_position
     end
   end
 
+  def test_cursor_visibility
+    run_pty(<<~'RUBY') do |r, _, _|
+      con = IO.console
+      abort unless con.hide_cursor.equal?(con)
+      abort unless con.show_cursor.equal?(con)
+    RUBY
+      assert_equal("\e[?25l\e[?25h", r.read(12))
+    end
+  end unless RbConfig::CONFIG["host_os"] =~ /mswin|mingw/
+
   def assert_ctrl(expect, cc, r, w)
     sleep 0.1
     w.print cc
@@ -700,6 +710,36 @@ def test_pressed_invalid
 
 RbConfig::CONFIG["host_os"] =~ /mswin|mingw/ and defined?(IO.console) and IO.console and \
 TestIO_Console.class_eval do
+  def test_cursor_visibility
+    require "fiddle/import"
+
+    kernel32 = Module.new do
+      extend Fiddle::Importer
+      dlload "kernel32.dll"
+      extern "void *CreateFileW(void *, long, long, void *, long, long, void *)"
+      extern "int CloseHandle(void *)"
+      extern "int GetConsoleCursorInfo(void *, void *)"
+    end
+    File.open("CONOUT$", "r+") do |output|
+      info = [0, 0].pack("L<L<")
+      path = "CONOUT$\0".encode("UTF-16LE")
+      handle = kernel32.CreateFileW(path, -0x40000000, 3, nil, 3, 0, nil)
+      assert_not_equal(0, kernel32.GetConsoleCursorInfo(handle, info))
+      size, visible = info.unpack("L<L<")
+      begin
+        assert_same(output, output.hide_cursor)
+        assert_not_equal(0, kernel32.GetConsoleCursorInfo(handle, info))
+        assert_equal([size, 0], info.unpack("L<L<"))
+        assert_same(output, output.show_cursor)
+        assert_not_equal(0, kernel32.GetConsoleCursorInfo(handle, info))
+        assert_equal([size, 1], info.unpack("L<L<"))
+      ensure
+        visible == 0 ? output.hide_cursor : output.show_cursor
+        kernel32.CloseHandle(handle)
+      end
+    end
+  end
+
   def test_console_input_events
     require "fiddle"