LibGUI: Add an optional "automatic" autocomplete feature to TextEditor

This aims to be a "smart" autocomplete that tries to present the user
with useful suggestions without being in the way (too much).
Here is its current configuration:
- Show suggestions 800ms after something is inserted in the editor
- if something else is inserted in that period, reset it back to 800ms
  to allow the user to type uninterrupted
- cancel any shown autocomplete (and the timer) on external changes
  (paste, cut, etc)

3 files changed, 75 insertions, 12 deletions

diff --git a/Libraries/LibGUI/AutocompleteProvider.cpp b/Libraries/LibGUI/AutocompleteProvider.cpp
index 9ca6b14372..b2d6266ff2 100644
--- a/Libraries/LibGUI/AutocompleteProvider.cpp
+++ b/Libraries/LibGUI/AutocompleteProvider.cpp
@@ -92,6 +92,8 @@ public:
     }
     virtual void update() override {};
 
+    void set_suggestions(Vector<AutocompleteProvider::Entry>&& suggestions) { m_suggestions = move(suggestions); }
+
 private:
     Vector<AutocompleteProvider::Entry> m_suggestions;
 };
@@ -111,16 +113,21 @@ AutocompleteBox::AutocompleteBox(TextEditor& editor)
 
 void AutocompleteBox::update_suggestions(Vector<AutocompleteProvider::Entry>&& suggestions)
 {
-    if (suggestions.is_empty())
-        return;
-
     bool has_suggestions = !suggestions.is_empty();
-    m_suggestion_view->set_model(adopt(*new AutocompleteSuggestionModel(move(suggestions))));
+    if (m_suggestion_view->model()) {
+        auto& model = *static_cast<AutocompleteSuggestionModel*>(m_suggestion_view->model());
+        model.set_suggestions(move(suggestions));
+    } else {
+        m_suggestion_view->set_model(adopt(*new AutocompleteSuggestionModel(move(suggestions))));
+        m_suggestion_view->update();
+        if (has_suggestions)
+            m_suggestion_view->set_cursor(m_suggestion_view->model()->index(0), GUI::AbstractView::SelectionUpdate::Set);
+    }
 
+    m_suggestion_view->model()->update();
+    m_suggestion_view->update();
     if (!has_suggestions)
-        m_suggestion_view->selection().clear();
-    else
-        m_suggestion_view->selection().set(m_suggestion_view->model()->index(0));
+        close();
 }
 
 bool AutocompleteBox::is_visible() const
@@ -130,7 +137,12 @@ bool AutocompleteBox::is_visible() const
 
 void AutocompleteBox::show(Gfx::IntPoint suggstion_box_location)
 {
+    if (!m_suggestion_view->model() || m_suggestion_view->model()->row_count() == 0)
+        return;
+
     m_popup_window->move_to(suggstion_box_location);
+    if (!is_visible())
+        m_suggestion_view->move_cursor(GUI::AbstractView::CursorMovement::Home, GUI::AbstractTableView::SelectionUpdate::Set);
     m_popup_window->show();
 }
 
diff --git a/Libraries/LibGUI/TextEditor.cpp b/Libraries/LibGUI/TextEditor.cpp
index 1a5feede4d..114800f800 100644
--- a/Libraries/LibGUI/TextEditor.cpp
+++ b/Libraries/LibGUI/TextEditor.cpp
@@ -713,6 +713,7 @@ void TextEditor::sort_selected_lines()
 
 void TextEditor::keydown_event(KeyEvent& event)
 {
+    TemporaryChange change { m_should_keep_autocomplete_box, true };
     if (m_autocomplete_box && m_autocomplete_box->is_visible() && (event.key() == KeyCode::Key_Return || event.key() == KeyCode::Key_Tab)) {
         m_autocomplete_box->apply_suggestion();
         m_autocomplete_box->close();
@@ -979,6 +980,8 @@ void TextEditor::keydown_event(KeyEvent& event)
     if (event.key() == KeyCode::Key_Backspace) {
         if (!is_editable())
             return;
+        if (m_autocomplete_box)
+            m_autocomplete_box->close();
         if (has_selection()) {
             delete_selection();
             did_update_selection();
@@ -1017,6 +1020,8 @@ void TextEditor::keydown_event(KeyEvent& event)
     if (event.modifiers() == Mod_Shift && event.key() == KeyCode::Key_Delete) {
         if (!is_editable())
             return;
+        if (m_autocomplete_box)
+            m_autocomplete_box->close();
         delete_current_line();
         return;
     }
@@ -1024,17 +1029,15 @@ void TextEditor::keydown_event(KeyEvent& event)
     if (event.key() == KeyCode::Key_Delete) {
         if (!is_editable())
             return;
+        if (m_autocomplete_box)
+            m_autocomplete_box->close();
         do_delete();
         return;
     }
 
     if (!event.shift() && !event.alt() && event.ctrl() && event.key() == KeyCode::Key_Space) {
         if (m_autocomplete_provider) {
-            m_autocomplete_provider->provide_completions([&](auto completions) {
-                m_autocomplete_box->update_suggestions(move(completions));
-                auto position = content_rect_for_position(cursor()).bottom_right().translated(screen_relative_rect().top_left().translated(ruler_width(), 0).translated(10, 5));
-                m_autocomplete_box->show(position);
-            });
+            try_show_autocomplete();
             update_autocomplete.disarm();
             return;
         }
@@ -1044,6 +1047,8 @@ void TextEditor::keydown_event(KeyEvent& event)
         StringBuilder sb;
         sb.append_code_point(event.code_point());
 
+        if (should_autocomplete_automatically())
+            m_autocomplete_timer->start();
         insert_at_cursor_or_replace_selection(sb.to_string());
         return;
     }
@@ -1428,6 +1433,19 @@ void TextEditor::undefer_reflow()
     }
 }
 
+void TextEditor::try_show_autocomplete()
+{
+    if (m_autocomplete_provider) {
+        m_autocomplete_provider->provide_completions([&](auto completions) {
+            auto has_completions = !completions.is_empty();
+            m_autocomplete_box->update_suggestions(move(completions));
+            auto position = content_rect_for_position(cursor()).bottom_right().translated(screen_relative_rect().top_left().translated(ruler_width(), 0).translated(10, 5));
+            if (has_completions)
+                m_autocomplete_box->show(position);
+        });
+    }
+}
+
 void TextEditor::enter_event(Core::Event&)
 {
     m_automatic_selection_scroll_timer->stop();
@@ -1437,6 +1455,10 @@ void TextEditor::leave_event(Core::Event&)
 {
     if (m_in_drag_select)
         m_automatic_selection_scroll_timer->start();
+    if (m_autocomplete_timer)
+        m_autocomplete_timer->stop();
+    if (m_autocomplete_box)
+        m_autocomplete_box->close();
 }
 
 void TextEditor::did_change()
@@ -1445,6 +1467,10 @@ void TextEditor::did_change()
     recompute_all_visual_lines();
     m_undo_action->set_enabled(can_undo());
     m_redo_action->set_enabled(can_redo());
+    if (m_autocomplete_box && !m_should_keep_autocomplete_box) {
+        m_autocomplete_timer->stop();
+        m_autocomplete_box->close();
+    }
     if (!m_has_pending_change_notification) {
         m_has_pending_change_notification = true;
         deferred_invoke([this](auto&) {
@@ -1848,4 +1874,19 @@ void TextEditor::set_visualize_trailing_whitespace(bool enabled)
     update();
 }
 
+void TextEditor::set_should_autocomplete_automatically(bool value)
+{
+    if (value == should_autocomplete_automatically())
+        return;
+
+    if (value) {
+        ASSERT(m_autocomplete_provider);
+        m_autocomplete_timer = Core::Timer::create_single_shot(m_automatic_autocomplete_delay_ms, [this] { try_show_autocomplete(); });
+        return;
+    }
+
+    remove_child(*m_autocomplete_timer);
+    m_autocomplete_timer = nullptr;
+}
+
 }
diff --git a/Libraries/LibGUI/TextEditor.h b/Libraries/LibGUI/TextEditor.h
index f5b8b2284c..7a0dcb0456 100644
--- a/Libraries/LibGUI/TextEditor.h
+++ b/Libraries/LibGUI/TextEditor.h
@@ -30,6 +30,7 @@
 #include <AK/NonnullOwnPtrVector.h>
 #include <AK/NonnullRefPtrVector.h>
 #include <LibCore/ElapsedTimer.h>
+#include <LibCore/Timer.h>
 #include <LibGUI/Forward.h>
 #include <LibGUI/ScrollableWidget.h>
 #include <LibGUI/TextDocument.h>
@@ -163,6 +164,9 @@ public:
     const AutocompleteProvider* autocomplete_provider() const;
     void set_autocomplete_provider(OwnPtr<AutocompleteProvider>&&);
 
+    bool should_autocomplete_automatically() const { return m_autocomplete_timer; }
+    void set_should_autocomplete_automatically(bool);
+
     bool is_in_drag_select() const { return m_in_drag_select; }
 
 protected:
@@ -212,6 +216,8 @@ private:
     void defer_reflow();
     void undefer_reflow();
 
+    void try_show_autocomplete();
+
     int icon_size() const { return 16; }
     int icon_padding() const { return 2; }
 
@@ -323,8 +329,12 @@ private:
     OwnPtr<SyntaxHighlighter> m_highlighter;
     OwnPtr<AutocompleteProvider> m_autocomplete_provider;
     OwnPtr<AutocompleteBox> m_autocomplete_box;
+    bool m_should_keep_autocomplete_box { false };
+    size_t m_automatic_autocomplete_delay_ms { 800 };
 
     RefPtr<Core::Timer> m_automatic_selection_scroll_timer;
+    RefPtr<Core::Timer> m_autocomplete_timer;
+
     Gfx::IntPoint m_last_mousemove_position;
 
     RefPtr<Gfx::Bitmap> m_icon;