added special Q-Register ":" for accessing dot

* We cannot call it "." since that introduces a local register
  and we don't want to add an unnecessary syntactic exception.
* Allows the idiom [: ... ]: to temporarily move around.
  Also, you can now write ^E\: without having to store dot in a register first.
* In the future we might add an ^E register as well for byte offsets.
  However, there are much fewer useful applications.
* Of course, you can now also write nU: instead of nJ, Q: instead of "." and
  n%: instead of "nC.". However it's all not really useful.

4 files changed, 55 insertions, 0 deletions

diff --git a/src/core-commands.c b/src/core-commands.c
index c3ec3dd..60e7bcc 100644
--- a/src/core-commands.c
+++ b/src/core-commands.c
@@ -123,6 +123,8 @@ teco_state_start_comma(teco_machine_main_t *ctx, GError **error)
  * \(lq.\(rq pushes onto the stack, the current
  * position (also called <dot>) of the currently
  * selected buffer or Q-Register.
+ *
+ * <dot> is also available in Q-Register \(lq:\(rq.
  */
 static void
 teco_state_start_dot(teco_machine_main_t *ctx, GError **error)
diff --git a/src/main.c b/src/main.c
index 40191b4..e93a3de 100644
--- a/src/main.c
+++ b/src/main.c
@@ -399,6 +399,8 @@ main(int argc, char **argv)
 	teco_qreg_table_insert(&teco_qreg_table_globals, teco_qreg_plain_new("_", 1));
 	/* replacement string register */
 	teco_qreg_table_insert(&teco_qreg_table_globals, teco_qreg_plain_new("-", 1));
+	/* current document's dot (":") */
+	teco_qreg_table_insert(&teco_qreg_table_globals, teco_qreg_dot_new());
 	/* current buffer name and number ("*") */
 	teco_qreg_table_insert(&teco_qreg_table_globals, teco_qreg_bufferinfo_new());
 	/* current working directory ("$") */
diff --git a/src/qreg.c b/src/qreg.c
index 1ce727f..061b685 100644
--- a/src/qreg.c
+++ b/src/qreg.c
@@ -398,6 +398,56 @@ teco_qreg_plain_new(const gchar *name, gsize len)
 	return teco_qreg_new(&vtable, name, len);
 }
 
+/* see also teco_state_start_jump() */
+static gboolean
+teco_qreg_dot_set_integer(teco_qreg_t *qreg, teco_int_t value, GError **error)
+{
+	gssize pos = teco_interface_glyphs2bytes(value);
+	if (pos < 0) {
+		g_set_error_literal(error, TECO_ERROR, TECO_ERROR_MOVE,
+		                    "Attempt to move pointer off page when setting Q-Register \":\"");
+		return FALSE;
+	}
+
+	teco_interface_ssm(SCI_GOTOPOS, pos, 0);
+	return TRUE;
+}
+
+static gboolean
+teco_qreg_dot_undo_set_integer(teco_qreg_t *qreg, GError **error)
+{
+	if (teco_current_doc_must_undo())
+		undo__teco_interface_ssm(SCI_GOTOPOS,
+		                         teco_interface_ssm(SCI_GETCURRENTPOS, 0, 0), 0);
+	return TRUE;
+}
+
+/* see also teco_state_start_dot() */
+static gboolean
+teco_qreg_dot_get_integer(teco_qreg_t *qreg, teco_int_t *ret, GError **error)
+{
+	sptr_t pos = teco_interface_ssm(SCI_GETCURRENTPOS, 0, 0);
+	*ret = teco_interface_bytes2glyphs(pos);
+	return TRUE;
+}
+
+/** @static @memberof teco_qreg_t */
+teco_qreg_t *
+teco_qreg_dot_new(void)
+{
+	static teco_qreg_vtable_t vtable = TECO_INIT_QREG(
+		.set_integer = teco_qreg_dot_set_integer,
+		.undo_set_integer = teco_qreg_dot_undo_set_integer,
+		.get_integer = teco_qreg_dot_get_integer
+	);
+
+	/*
+	 * If we wanted to use ".", we'd have to either make this a local register
+	 * or add ".." as special syntax equivalent to [.].
+	 */
+	return teco_qreg_new(&vtable, ":", 1);
+}
+
 static gboolean
 teco_qreg_radix_set_integer(teco_qreg_t *qreg, teco_int_t value, GError **error)
 {
diff --git a/src/qreg.h b/src/qreg.h
index 4a7c15c..a29b6ed 100644
--- a/src/qreg.h
+++ b/src/qreg.h
@@ -112,6 +112,7 @@ struct teco_qreg_t {
 };
 
 teco_qreg_t *teco_qreg_plain_new(const gchar *name, gsize len);
+teco_qreg_t *teco_qreg_dot_new(void);
 teco_qreg_t *teco_qreg_bufferinfo_new(void);
 teco_qreg_t *teco_qreg_workingdir_new(void);
 teco_qreg_t *teco_qreg_clipboard_new(const gchar *name);