QQuickTableView: check if we need to rebuild when syncing with syncView

Since different tables can have different sized
models, it can also happen, as the views are being flicked
around, that some views temporarily end up with no
visible rows and columns in the viewport. When that
happens, we continually check if the columns should
become visible again, and if so, schedule a rebuild.

Change-Id: Ic84e47fd5d7968c1f1408eb122e38fa841e7aec7
Reviewed-by: Mitch Curtis <mitch.curtis@qt.io>

1 files changed, 17 insertions, 5 deletions

diff --git a/src/quick/items/qquicktableview.cpp b/src/quick/items/qquicktableview.cpp
index ae1daccb39..e169ac4aec 100644
--- a/src/quick/items/qquicktableview.cpp
+++ b/src/quick/items/qquicktableview.cpp
@@ -2025,13 +2025,11 @@ void QQuickTableViewPrivate::syncWithPendingChanges()
     Q_Q(QQuickTableView);
     viewportRect = QRectF(q->contentX(), q->contentY(), q->width(), q->height());
 
-    // Sync rebuild options first, in case we schedule a rebuild from one of the
-    // other sync calls above. If so, we need to start a new rebuild from the top.
-    syncRebuildOptions();
-
     syncModel();
     syncDelegate();
     syncSyncView();
+
+    syncRebuildOptions();
 }
 
 void QQuickTableViewPrivate::syncRebuildOptions()
@@ -2121,7 +2119,6 @@ void QQuickTableViewPrivate::syncSyncView()
 
             assignedSyncView->d_func()->syncChildren.append(q);
             scheduledRebuildOptions |= RebuildOption::ViewportOnly;
-            q->polish();
         }
 
         syncView = assignedSyncView;
@@ -2134,6 +2131,21 @@ void QQuickTableViewPrivate::syncSyncView()
         q->setColumnSpacing(syncView->columnSpacing());
     if (syncVertically)
         q->setRowSpacing(syncView->rowSpacing());
+
+    if (syncView && loadedItems.isEmpty() && !tableSize.isEmpty()) {
+        // When we have a syncView, we can sometimes temporarily end up with no loaded items.
+        // This can happen if the syncView has a model with more rows or columns than us, in
+        // which case the viewport can end up in a place where we have no rows or columns to
+        // show. In that case, check now if the viewport has been flicked back again, and
+        // that we can rebuild the table with a visible top-left cell.
+        const auto syncView_d = syncView->d_func();
+        if (!syncView_d->loadedItems.isEmpty()) {
+            if (syncHorizontally && syncView_d->leftColumn() <= tableSize.width() - 1)
+                scheduledRebuildOptions |= QQuickTableViewPrivate::RebuildOption::ViewportOnly;
+            else if (syncVertically && syncView_d->topRow() <= tableSize.height() - 1)
+                scheduledRebuildOptions |= QQuickTableViewPrivate::RebuildOption::ViewportOnly;
+        }
+    }
 }
 
 void QQuickTableViewPrivate::connectToModel()