QQuickTableView: forceLayout() should work, even when no items are loaded

As it stood, we would return early from forceLayout if no items
were loaded. This made sense, since when no items are
loaded, there would be no items to lay out.

But after we changed the logic so that an application can
show or hide rows and columns by returning an empty size
from the size providers, we now always need to do a layout
to check if some rows or columns should become visible.

Fixes: QTBUG-92076
Change-Id: I2a07bf8e62cfeebcbe36c01aa92eca3ed8227cd3
Reviewed-by: Mitch Curtis <mitch.curtis@qt.io>
Reviewed-by: Shawn Rutledge <shawn.rutledge@qt.io>
(cherry picked from commit 9ba9336ec4515d157a1207fad1dcd2de311527ac)
Reviewed-by: Qt Cherry-pick Bot <cherrypick_bot@qt-project.org>

2 files changed, 42 insertions, 3 deletions

diff --git a/src/quick/items/qquicktableview.cpp b/src/quick/items/qquicktableview.cpp
index 1b71bd5a53..47c9d76318 100644
--- a/src/quick/items/qquicktableview.cpp
+++ b/src/quick/items/qquicktableview.cpp
@@ -1074,6 +1074,15 @@ void QQuickTableViewPrivate::shiftLoadedTableRect(const QPointF newPosition)
 
 QQuickTableViewPrivate::RebuildOptions QQuickTableViewPrivate::checkForVisibilityChanges()
 {
+    // This function will check if there are any visibility changes among
+    // the _already loaded_ rows and columns. Note that there can be rows
+    // and columns to the bottom or right that was not loaded, but should
+    // now become visible (in case there is free space around the table).
+    if (loadedItems.isEmpty()) {
+        // Report no changes
+        return RebuildOption::None;
+    }
+
     // Go through all columns from first to last, find the columns that used
     // to be hidden and not loaded, and check if they should become visible
     // (and vice versa). If there is a change, we need to rebuild.
@@ -1118,9 +1127,6 @@ QQuickTableViewPrivate::RebuildOptions QQuickTableViewPrivate::checkForVisibilit
 
 void QQuickTableViewPrivate::forceLayout()
 {
-    if (loadedItems.isEmpty())
-        return;
-
     clearEdgeSizeCache();
     RebuildOptions rebuildOptions = RebuildOption::None;
 
diff --git a/tests/auto/quick/qquicktableview/tst_qquicktableview.cpp b/tests/auto/quick/qquicktableview/tst_qquicktableview.cpp
index 2bd7c38a11..8a85575cca 100644
--- a/tests/auto/quick/qquicktableview/tst_qquicktableview.cpp
+++ b/tests/auto/quick/qquicktableview/tst_qquicktableview.cpp
@@ -121,6 +121,7 @@ private slots:
     void checkForceLayoutFunction();
     void checkForceLayoutEndUpDoingALayout();
     void checkForceLayoutDuringModelChange();
+    void checkForceLayoutWhenAllItemsAreHidden();
     void checkContentWidthAndHeight();
     void checkPageFlicking();
     void checkExplicitContentWidthAndHeight();
@@ -635,6 +636,38 @@ void tst_QQuickTableView::checkForceLayoutDuringModelChange()
     QCOMPARE(tableView->rows(), initialRowCount + 1);
 }
 
+void tst_QQuickTableView::checkForceLayoutWhenAllItemsAreHidden()
+{
+    // Check that you can have a TableView where all columns are
+    // initially hidden, and then show some columns and call
+    // forceLayout(). This should make the columns become visible.
+    LOAD_TABLEVIEW("forcelayout.qml");
+
+    // Tell all columns to be hidden
+    const char *propertyName = "columnWidths";
+    view->rootObject()->setProperty(propertyName, 0);
+
+    const int rows = 3;
+    const int columns = 3;
+    auto model = TestModelAsVariant(rows, columns);
+    tableView->setModel(model);
+
+    WAIT_UNTIL_POLISHED;
+
+    // Check that the we have no items loaded
+    QCOMPARE(tableViewPrivate->loadedColumns.count(), 0);
+    QCOMPARE(tableViewPrivate->loadedRows.count(), 0);
+    QCOMPARE(tableViewPrivate->loadedItems.count(), 0);
+
+    // Tell all columns to be visible
+    view->rootObject()->setProperty(propertyName, 10);
+    tableView->forceLayout();
+
+    QCOMPARE(tableViewPrivate->loadedRows.count(), rows);
+    QCOMPARE(tableViewPrivate->loadedColumns.count(), columns);
+    QCOMPARE(tableViewPrivate->loadedItems.count(), rows * columns);
+}
+
 void tst_QQuickTableView::checkContentWidthAndHeight()
 {
     // Check that contentWidth/Height reports the correct size of the