feat(selector): handle repeated key until release

in horizontal mode, Left key highlights the previous candidate,
and fall back to navigator when already at the first candidate.
when Left is held down, do not fall back until the next key press.

src/rime/gear/selector.cc

@@ -118,8 +118,14 @@ inline static bool is_linear_layout(Context* ctx) {
 }
 
 ProcessResult Selector::ProcessKeyEvent(const KeyEvent& key_event) {
-  if (key_event.release() || key_event.alt())
+  if (key_event.release()) {
+    last_key_ = 0;
+    key_repeat_ = 0;
     return kNoop;
+  }
+  if (key_event.alt() || key_event.super())
+    return kNoop;
+
   Context* ctx = engine_->context();
   if (ctx->composition().empty())
     return kNoop;
@@ -133,11 +139,18 @@ ProcessResult Selector::ProcessKeyEvent(const KeyEvent& key_event) {
     is_linear_layout(ctx) ? Linear : Stacked;
   auto result = KeyBindingProcessor::ProcessKeyEvent(
     key_event, ctx, text_orientation | candidate_list_layout);
+
+  int ch = key_event.keycode();
   if (result != kNoop) {
+    if (last_key_ == ch) {
+      ++key_repeat_;
+    } else {
+      last_key_ = ch;
+      key_repeat_ = 1;
+    }
     return result;
   }
 
-  int ch = key_event.keycode();
   int index = -1;
   const string& select_keys(engine_->schema()->select_keys());
   if (!select_keys.empty() &&
@@ -210,8 +223,9 @@ bool Selector::PreviousCandidate(Context* ctx) {
     return false;
   int index = comp.back().selected_index;
   if (index <= 0) {
-    // in case of linear layout, fall back to navigator
-    return !is_linear_layout(ctx);
+    // in case of linear layout, fall back to navigator;
+    // repeated key press should be handled by the same processor.
+    return !is_linear_layout(ctx) || key_repeat_ > 0;
   }
   comp.back().selected_index = index - 1;
   comp.back().tags.insert("paging");
@@ -256,7 +270,6 @@ bool Selector::End(Context* ctx) {
   return Home(ctx);
 }
 
-
 bool Selector::SelectCandidateAt(Context* ctx, int index) {
   Composition& comp = ctx->composition();
   if (comp.empty())

src/rime/gear/selector.h

@@ -37,6 +37,10 @@ class Selector : public Processor, public KeyBindingProcessor<Selector, 4> {
   Handler End;
 
   bool SelectCandidateAt(Context* ctx, int index);
+
+ private:
+  int last_key_ = 0;
+  int key_repeat_ = 0;
 };
 
 }  // namespace rime