Add optional emoji extension pack

Fixes #33

Adds an installable emoji content/input extension, a generic candidate-picker IME backend, and registry support for small content supplement fonts.

modules/ui_shared/include/ui/localization.h

@@ -28,6 +28,7 @@ struct ImeInfo
     const char* display_name = nullptr;
     const char* backend = nullptr;
     const char* layout = nullptr;
+    std::size_t candidate_count = 0;
     bool builtin = true;
 };
 
@@ -46,6 +47,8 @@ const lv_font_t* locale_preview_font(const char* locale_id, const lv_font_t* asc
 bool ensure_content_font_for_text(const char* text);
 std::size_t ime_count();
 const ImeInfo* ime_at(std::size_t index);
+std::size_t ime_candidate_count(const char* ime_id);
+const char* ime_candidate_at(const char* ime_id, std::size_t index);
 std::size_t enabled_ime_count();
 bool ime_enabled(const char* ime_id);
 bool set_ime_enabled(const char* ime_id, bool enabled, bool persist = true);

modules/ui_shared/include/ui/widgets/ime/ime_widget.h

@@ -62,6 +62,7 @@ class ImeWidget
     bool commit_candidate(int candidate_index);
     bool pinyin_mode() const;
     bool direct_keyboard_mode() const;
+    bool candidate_picker_mode() const;
 
     static void on_toggle_clicked(lv_event_t* e);
     static void on_touch_key_event(lv_event_t* e);
@@ -85,6 +86,8 @@ class ImeWidget
     std::string committed_text_;
     bool touch_keyboard_enabled_ = false;
     int candidate_window_start_ = 0;
+    int script_input_index_ = 0;
+    int candidate_picker_index_ = 0;
 };
 
 } // namespace widgets