implemented ^Y/^S commands for receiving pattern match/insertion ranges and lengths (refs #27)

* Allows storing pattern matches into Q-Registers (^YXq).
* You can also refer to subpatterns marked by ^E[...] by passing a number > 0.
  This is equivalent to \0-9 references in many programming languages.
* It's especially useful for supporting TECO's equivalent of structural regular expressions.
  This will be done with additional macros.
* You can also simply back up to the beginning of an insertion or search.
  So I...$^SC leaves dot at the beginning of the insertion.
  S...$^SC leaves dot before the found pattern.
  This has been previously requested by users.
* Perhaps there should be ^Y string building characters as well to backreference
  in search-replacement commands (TODO).
  This means that the search commands would have to store the matched text itself
  in teco_range_t structures since FR deletes the matched text before
  processing the replacement string.
  It could also be made into a FR/FS-specific construct,
  so we don't fetch the substrings unnecessarily.
* This differs from DEC TECO in always returning the same range even after dot movements,
  since we are storing start/end byte positions instead of only the length.
  Also DEC TECO does not support fetching subpattern ranges.

1 files changed, 5 insertions, 0 deletions

diff --git a/src/qreg-commands.c b/src/qreg-commands.c
index 89618da..9f22de9 100644
--- a/src/qreg-commands.c
+++ b/src/qreg-commands.c
@@ -299,6 +299,7 @@ teco_state_queryqreg_got_register(teco_machine_main_t *ctx, teco_qreg_t *qreg,
 
 /*$ Q Qq query
  * Qq -> n -- Query Q-Register existence, its integer or string characters
+ * -Qq -> -n
  * <position>Qq -> character
  * :Qq -> -1 | size
  *
@@ -533,6 +534,10 @@ teco_state_getqregstring_got_register(teco_machine_main_t *ctx, teco_qreg_t *qre
 	if (!qreg->vtable->get_string(qreg, &str.data, &str.len, NULL, error))
 		return NULL;
 
+	teco_undo_gsize(teco_ranges[0].from) = teco_interface_ssm(SCI_GETCURRENTPOS, 0, 0);
+	teco_undo_gsize(teco_ranges[0].to) = teco_ranges[0].from + str.len;
+	teco_undo_guint(teco_ranges_count) = 1;
+
 	if (str.len > 0) {
 		teco_interface_ssm(SCI_BEGINUNDOACTION, 0, 0);
 		teco_interface_ssm(SCI_ADDTEXT, str.len, (sptr_t)str.data);