vis: take symbolic keys into account when evaluating key prefixes

Previously `ci<` would have no immediate effect because in operator
pending mode `i<` was wrongly treated as a powwible prefix of `i<Tab>`.

Fix #624

1 files changed, 32 insertions, 6 deletions

diff --git a/vis.c b/vis.c
index b1b9002..edf3f0c 100644
--- a/vis.c
+++ b/vis.c
@@ -1113,6 +1113,26 @@ bool vis_keys_utf8(Vis *vis, const char *keys, char utf8[static UTFmax+1]) {
 	return true;
 }
 
+typedef struct {
+	Vis *vis;
+	size_t len;         // length of the prefix
+	int count;          // how many bindings can complete this prefix
+	bool angle_bracket; // does the prefix end with '<'
+} PrefixCompletion;
+
+static bool isprefix(const char *key, void *value, void *data) {
+	PrefixCompletion *completion = data;
+	if (!completion->angle_bracket) {
+		completion->count++;
+	} else {
+		const char *start = key + completion->len;
+		const char *end = vis_keys_next(completion->vis, start);
+		if (end && start + 1 == end)
+			completion->count++;
+	}
+	return completion->count == 1;
+}
+
 static void vis_keys_process(Vis *vis, size_t pos) {
 	Buffer *buf = &vis->input_queue;
 	char *keys = buf->data + pos, *start = keys, *cur = keys, *end = keys, *binding_end = keys;;
@@ -1143,12 +1163,18 @@ static void vis_keys_process(Vis *vis, size_t pos) {
 					binding = match;
 					binding_end = end;
 				}
-				/* "<" is never treated as a prefix because it
-				 * is used to denote special key symbols */
-				if (strcmp(start, "<")) {
-					prefix = (!match && map_contains(mode->bindings, start)) ||
-					         (match && !map_leaf(mode->bindings, start));
-				}
+
+				const Map *pmap = map_prefix(mode->bindings, start);
+				PrefixCompletion completions = {
+					.vis = vis,
+					.len = cur - start,
+					.count = 0,
+					.angle_bracket = !strcmp(cur, "<"),
+				};
+				map_iterate(pmap, isprefix, &completions);
+
+				prefix = (!match && completions.count > 0) ||
+				         ( match && completions.count > 1);
 			}
 		}