LibGUI: Track selection starting index in AbstractView (#6515)

Modifying the selection while holding the shift button and selecting
with the mouse or the arrow keys no longer results in broken selections.

Fixes #6279.

2 files changed, 21 insertions, 13 deletions

diff --git a/Userland/Libraries/LibGUI/AbstractView.cpp b/Userland/Libraries/LibGUI/AbstractView.cpp
index 48a4c480bf..9dbda5c75a 100644
--- a/Userland/Libraries/LibGUI/AbstractView.cpp
+++ b/Userland/Libraries/LibGUI/AbstractView.cpp
@@ -91,6 +91,7 @@ void AbstractView::model_did_update(unsigned int flags)
             m_drop_candidate_index = {};
         selection().remove_matching([this](auto& index) { return !model()->is_valid(index); });
     }
+    m_selection_start_index = {};
 }
 
 void AbstractView::clear_selection()
@@ -103,6 +104,11 @@ void AbstractView::set_selection(const ModelIndex& new_index)
     m_selection.set(new_index);
 }
 
+void AbstractView::set_selection_start_index(const ModelIndex& new_index)
+{
+    m_selection_start_index = new_index;
+}
+
 void AbstractView::add_selection(const ModelIndex& new_index)
 {
     m_selection.add(new_index);
@@ -341,9 +347,10 @@ void AbstractView::mouseup_event(MouseEvent& event)
         // in mousedown_event(), because we could be seeing a start of a drag.
         // Since we're here, it was not that; so fix up the selection now.
         auto index = index_at_event_position(event.position());
-        if (index.is_valid())
+        if (index.is_valid()) {
             set_selection(index);
-        else
+            set_selection_start_index(index);
+        } else
             clear_selection();
         m_might_drag = false;
         update();
@@ -450,20 +457,21 @@ void AbstractView::set_cursor(ModelIndex index, SelectionUpdate selection_update
         selection_update = SelectionUpdate::Set;
 
     if (model()->is_valid(index)) {
-        if (selection_update == SelectionUpdate::Set)
+        if (selection_update == SelectionUpdate::Set) {
             set_selection(index);
-        else if (selection_update == SelectionUpdate::Ctrl)
+            set_selection_start_index(index);
+        } else if (selection_update == SelectionUpdate::Ctrl) {
             toggle_selection(index);
-        else if (selection_update == SelectionUpdate::ClearIfNotSelected) {
+        } else if (selection_update == SelectionUpdate::ClearIfNotSelected) {
             if (!m_selection.contains(index))
                 clear_selection();
         } else if (selection_update == SelectionUpdate::Shift) {
-            // Toggle all from cursor to new index.
-            auto min_row = min(cursor_index().row(), index.row());
-            auto max_row = max(cursor_index().row(), index.row());
-            auto min_column = min(cursor_index().column(), index.column());
-            auto max_column = max(cursor_index().column(), index.column());
+            auto min_row = min(selection_start_index().row(), index.row());
+            auto max_row = max(selection_start_index().row(), index.row());
+            auto min_column = min(selection_start_index().column(), index.column());
+            auto max_column = max(selection_start_index().column(), index.column());
 
+            clear_selection();
             for (auto row = min_row; row <= max_row; ++row) {
                 for (auto column = min_column; column <= max_column; ++column) {
                     auto new_index = model()->index(row, column);
@@ -471,9 +479,6 @@ void AbstractView::set_cursor(ModelIndex index, SelectionUpdate selection_update
                         toggle_selection(new_index);
                 }
             }
-
-            // Finally toggle the cursor index again to make it go back to its current state.
-            toggle_selection(cursor_index());
         }
 
         // FIXME: Support the other SelectionUpdate types
diff --git a/Userland/Libraries/LibGUI/AbstractView.h b/Userland/Libraries/LibGUI/AbstractView.h
index 15018ab301..10cf80d086 100644
--- a/Userland/Libraries/LibGUI/AbstractView.h
+++ b/Userland/Libraries/LibGUI/AbstractView.h
@@ -136,6 +136,7 @@ public:
     virtual void scroll_into_view(const ModelIndex&, [[maybe_unused]] bool scroll_horizontally = true, [[maybe_unused]] bool scroll_vertically = true) { }
 
     const ModelIndex& cursor_index() const { return m_cursor_index; }
+    const ModelIndex& selection_start_index() const { return m_selection_start_index; }
     void set_cursor(ModelIndex, SelectionUpdate, bool scroll_cursor_into_view = true);
 
     bool is_tab_key_navigation_enabled() const { return m_tab_key_navigation_enabled; }
@@ -163,6 +164,7 @@ protected:
 
     virtual void clear_selection();
     virtual void set_selection(const ModelIndex&);
+    virtual void set_selection_start_index(const ModelIndex&);
     virtual void add_selection(const ModelIndex&);
     virtual void remove_selection(const ModelIndex&);
     virtual void toggle_selection(const ModelIndex&);
@@ -206,6 +208,7 @@ protected:
 private:
     RefPtr<Model> m_model;
     ModelSelection m_selection;
+    ModelIndex m_selection_start_index;
     String m_searching;
     RefPtr<Core::Timer> m_searching_timer;
     ModelIndex m_cursor_index;