Bring Mac wxDataViewCtrl::GetItemRect() in sync with other ports

Return empty rectangle if the item is not currently visible, for
whatever reason, and use physical coordinates for the rectangle origin.

This makes the unit test for GetItemRect() pass under macOS too.

src/osx/cocoa/dataview.mm

@@ -2295,8 +2295,33 @@ wxDataViewItem wxCocoaDataViewControl::GetTopItem() const
 
 wxRect wxCocoaDataViewControl::GetRectangle(const wxDataViewItem& item, const wxDataViewColumn *columnPtr)
 {
-    return wxFromNSRect([m_osxView superview],[m_OutlineView frameOfCellAtColumn:GetColumnPosition(columnPtr)
+    NSView* const parent = [m_osxView superview];
+
+    wxRect r = wxFromNSRect(parent, [m_OutlineView frameOfCellAtColumn:GetColumnPosition(columnPtr)
             row:[m_OutlineView rowForItem:[m_DataSource getDataViewItemFromBuffer:item]]]);
+
+    // For hidden items, i.e. items not shown because their parent is
+    // collapsed, the native method returns rectangles with negative width, but
+    // we're supposed to just return an empty rectangle in this case. To be on
+    // the safe side, also check for the height as well, even if it seems to be
+    // always 0 in this case.
+    if ( r.width < 0 || r.height < 0 )
+        return wxRect();
+
+    // Also adjust the vertical coordinates to use physical window coordinates
+    // instead of the logical ones returned by frameOfCellAtColumn:row:
+    NSScrollView* const scrollView = [m_OutlineView enclosingScrollView];
+    const wxRect
+        visible = wxFromNSRect(parent, scrollView.contentView.visibleRect);
+
+    // We are also supposed to return empty rectangle if the item is not
+    // visible because it is scrolled out of view.
+    if ( r.GetBottom() < visible.GetTop() || r.GetTop() > visible.GetBottom() )
+        return wxRect();
+
+    r.y -= visible.y;
+
+    return r;
 }
 
 bool wxCocoaDataViewControl::IsExpanded(const wxDataViewItem& item) const