LibGUI: Make AbstractView accept drags (and delegate to model)

Libraries/LibGUI/AbstractView.cpp

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2018-2020, Andreas Kling <kling@serenityos.org>
+ * Copyright (c) 2018-2021, Andreas Kling <kling@serenityos.org>
  * All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
@@ -74,6 +74,7 @@ void AbstractView::model_did_update(unsigned int flags)
         m_edit_index = {};
         m_hovered_index = {};
         m_cursor_index = {};
+        m_drop_candidate_index = {};
         clear_selection();
     } else {
         // FIXME: These may no longer point to whatever they did before,
@@ -86,6 +87,8 @@ void AbstractView::model_did_update(unsigned int flags)
             m_hovered_index = {};
         if (!model()->is_valid(m_cursor_index))
             m_cursor_index = {};
+        if (!model()->is_valid(m_drop_candidate_index))
+            m_drop_candidate_index = {};
         selection().remove_matching([this](auto& index) { return !model()->is_valid(index); });
     }
 }
@@ -720,4 +723,43 @@ void AbstractView::focusin_event(FocusEvent& event)
     }
 }
 
+void AbstractView::drag_enter_event(DragEvent& event)
+{
+    if (!model())
+        return;
+    // NOTE: Right now, AbstractView always accepts drags since we won't get "drag move" events
+    //       unless we accept the "drag enter" event.
+    //       We might be able to reduce event traffic by communicating the set of drag-accepting
+    //       rects in this widget to the windowing system somehow.
+    event.accept();
+    dbgln("accepting drag of {}", event.mime_types().first());
+}
+
+void AbstractView::drag_move_event(DragEvent& event)
+{
+    if (!model())
+        return;
+    auto index = index_at_event_position(event.position());
+    ModelIndex new_drop_candidate_index;
+    if (index.is_valid()) {
+        bool acceptable = model()->accepts_drag(index, event.mime_types());
+        if (acceptable)
+            new_drop_candidate_index = index;
+    }
+    if (m_drop_candidate_index != new_drop_candidate_index) {
+        m_drop_candidate_index = new_drop_candidate_index;
+        update();
+    }
+    if (m_drop_candidate_index.is_valid())
+        event.accept();
+}
+
+void AbstractView::drag_leave_event(Event&)
+{
+    if (m_drop_candidate_index.is_valid()) {
+        m_drop_candidate_index = {};
+        update();
+    }
+}
+
 }

Libraries/LibGUI/AbstractView.h

@@ -153,6 +153,9 @@ protected:
     virtual void mouseup_event(MouseEvent&) override;
     virtual void doubleclick_event(MouseEvent&) override;
     virtual void context_menu_event(ContextMenuEvent&) override;
+    virtual void drag_enter_event(DragEvent&) override;
+    virtual void drag_move_event(DragEvent&) override;
+    virtual void drag_leave_event(Event&) override;
     virtual void drop_event(DropEvent&) override;
     virtual void leave_event(Core::Event&) override;
     virtual void hide_event(HideEvent&) override;
@@ -180,6 +183,8 @@ protected:
     void do_search(String&&);
     bool is_highlighting_searching(const ModelIndex&) const;
 
+    ModelIndex drop_candidate_index() const { return m_drop_candidate_index; }
+
     bool m_editable { false };
     bool m_searchable { true };
     ModelIndex m_edit_index;
@@ -202,6 +207,7 @@ private:
     String m_searching;
     RefPtr<Core::Timer> m_searching_timer;
     ModelIndex m_cursor_index;
+    ModelIndex m_drop_candidate_index;
     SelectionBehavior m_selection_behavior { SelectionBehavior::SelectItems };
     SelectionMode m_selection_mode { SelectionMode::SingleSelection };
     unsigned m_edit_triggers { EditTrigger::DoubleClicked | EditTrigger::EditKeyPressed };

Libraries/LibGUI/IconView.cpp

@@ -265,22 +265,6 @@ void IconView::mouseup_event(MouseEvent& event)
     AbstractView::mouseup_event(event);
 }
 
-void IconView::drag_move_event(DragEvent& event)
-{
-    auto index = index_at_event_position(event.position());
-    ModelIndex new_drop_candidate_index;
-    if (index.is_valid()) {
-        bool acceptable = model()->accepts_drag(index, event.mime_types());
-        if (acceptable)
-            new_drop_candidate_index = index;
-    }
-    if (m_drop_candidate_index != new_drop_candidate_index) {
-        m_drop_candidate_index = new_drop_candidate_index;
-        update();
-    }
-    event.accept();
-}
-
 bool IconView::update_rubber_banding(const Gfx::IntPoint& position)
 {
     auto adjusted_position = to_content_position(position);
@@ -577,7 +561,7 @@ void IconView::paint_event(PaintEvent& event)
             draw_item_text(painter, item_data.index, item_data.selected, item_data.text_rect, item_data.text, font, Gfx::TextAlignment::Center, Gfx::TextElision::Right);
         }
 
-        if (item_data.index == m_drop_candidate_index) {
+        if (item_data.index == drop_candidate_index()) {
             // FIXME: This visualization is not great, as it's also possible to drop things on the text label..
             painter.draw_rect(item_data.icon_rect.inflated(8, 8), palette().selection(), true);
         }

Libraries/LibGUI/IconView.h

@@ -71,7 +71,6 @@ private:
     virtual void mousedown_event(MouseEvent&) override;
     virtual void mousemove_event(MouseEvent&) override;
     virtual void mouseup_event(MouseEvent&) override;
-    virtual void drag_move_event(DragEvent&) override;
     virtual void did_change_hovered_index(const ModelIndex& old_index, const ModelIndex& new_index) override;
     virtual void did_change_cursor_index(const ModelIndex& old_index, const ModelIndex& new_index) override;
 
@@ -165,8 +164,6 @@ private:
     Gfx::IntPoint m_rubber_band_origin;
     Gfx::IntPoint m_rubber_band_current;
 
-    ModelIndex m_drop_candidate_index;
-
     FlowDirection m_flow_direction { FlowDirection::LeftToRight };
 
     mutable Vector<ItemData> m_item_data_cache;