TableView: ensure we update content size upon model changes

For tables of non-trivial sizes, we usually don't know what the
content size will be unless we load all rows and columns, which
we simply cannot do. Because of this, we have up till now chosen
a strategy where we normally just calculate a predicted content
size up-front, when we table is built, and afterwards just stick
to that prediction.

This strategy works for big tables that fills more than one size
of the viewport, and if the number of rows and column in the model
stays around the same. But for tables that start off smaller than
the viewport, and later expands to grow out of it, it simply fails.
And the failure is such that the tableview can get stuck, with no
way way for the user to flick around to see the rest of the contents.

An example is TreeView that might only show the root node at
start-up, but as you start to expand the tree, it will quickly add
more rows than what fits inside the viewport. And in that case, the
contentHeight will be totally off, and in turn, make the scrollbar
be based on wrong values, and sometimes not work at all (e.g if
it has the flag Flickable::StopAtBounds).

This patch will change the implementation so that we recalculate
the content size whenever it should logially change. That is, if
e.g the model add or remove rows and columns, or if you change
spacing. This still doesn't mean that contentWidth/Height reports
the correct size of the table, but at least it will be a better
guestimate for smaller tables, and at the same time, work
together with Flickable and ScrollBars.

Fixes: QTBUG-87680
Change-Id: Ie2d2e7c1f1519dc7a5d5269a6d25e34cf441b3fe
Reviewed-by: Shawn Rutledge <shawn.rutledge@qt.io>
(cherry picked from commit dac2c8aec4917742aed6e311cf542dc37da60809)

1 files changed, 86 insertions, 10 deletions

diff --git a/tests/auto/quick/qquicktableview/tst_qquicktableview.cpp b/tests/auto/quick/qquicktableview/tst_qquicktableview.cpp
index b876ead301..6339e5a59d 100644
--- a/tests/auto/quick/qquicktableview/tst_qquicktableview.cpp
+++ b/tests/auto/quick/qquicktableview/tst_qquicktableview.cpp
@@ -178,6 +178,8 @@ private slots:
     void delegateWithRequiredProperties();
     void checkThatFetchMoreIsCalledWhenScrolledToTheEndOfTable();
     void replaceModel();
+    void checkContentSize_data();
+    void checkContentSize();
 };
 
 tst_QQuickTableView::tst_QQuickTableView()
@@ -590,6 +592,12 @@ void tst_QQuickTableView::checkForceLayoutEndUpDoingALayout()
 
     for (auto fxItem : tableViewPrivate->loadedItems)
         QCOMPARE(fxItem->item->height(), newDelegateSize);
+
+    // Check that the content height has been updated as well
+    const qreal rowSpacing = tableView->rowSpacing();
+    const qreal colSpacing = tableView->columnSpacing();
+    QCOMPARE(tableView->contentWidth(), (10 * (newDelegateSize + colSpacing)) - colSpacing);
+    QCOMPARE(tableView->contentHeight(), (9 * (newDelegateSize + rowSpacing)) - rowSpacing);
 }
 
 void tst_QQuickTableView::checkForceLayoutDuringModelChange()
@@ -1295,10 +1303,10 @@ void tst_QQuickTableView::checkSpacingValues()
     tableView->polish();
     WAIT_UNTIL_POLISHED;
 
-    const qreal expectedInitialContentWidth = columnCount * (delegateWidth + tableView->columnSpacing()) - tableView->columnSpacing();
-    const qreal expectedInitialContentHeight = rowCount * (delegateHeight + tableView->rowSpacing()) - tableView->rowSpacing();
-    QCOMPARE(tableView->contentWidth(), expectedInitialContentWidth);
-    QCOMPARE(tableView->contentHeight(), expectedInitialContentHeight);
+    qreal expectedContentWidth = columnCount * (delegateWidth + tableView->columnSpacing()) - tableView->columnSpacing();
+    qreal expectedContentHeight = rowCount * (delegateHeight + tableView->rowSpacing()) - tableView->rowSpacing();
+    QCOMPARE(tableView->contentWidth(), expectedContentWidth);
+    QCOMPARE(tableView->contentHeight(), expectedContentHeight);
 
     // Valid spacing assignment
     tableView->setRowSpacing(42);
@@ -1309,12 +1317,10 @@ void tst_QQuickTableView::checkSpacingValues()
     tableView->polish();
     WAIT_UNTIL_POLISHED;
 
-    // Even after changing spacing, TableView will keep the initial guesstimated content size. The
-    // reason is that deciding the content size based on the currently visible row/columns/spacing
-    // will almost always be at a little bit wrong at best. So instead of pretending that TableView
-    // knows what the size of the full table is, it sticks with the first guesstimate.
-    QCOMPARE(tableView->contentWidth(), expectedInitialContentWidth);
-    QCOMPARE(tableView->contentHeight(), expectedInitialContentHeight);
+    expectedContentWidth = columnCount * (delegateWidth + tableView->columnSpacing()) - tableView->columnSpacing();
+    expectedContentHeight = rowCount * (delegateHeight + tableView->rowSpacing()) - tableView->rowSpacing();
+    QCOMPARE(tableView->contentWidth(), expectedContentWidth);
+    QCOMPARE(tableView->contentHeight(), expectedContentHeight);
 
     // Negative spacing is allowed, and can be used to eliminate double edges
     // in the grid if the delegate is a rectangle with a border.
@@ -2775,6 +2781,76 @@ void tst_QQuickTableView::replaceModel()
     QCOMPARE(tableView->contentHeight(), 0);
 }
 
+void tst_QQuickTableView::checkContentSize_data()
+{
+    QTest::addColumn<int>("rowCount");
+    QTest::addColumn<int>("colCount");
+
+    QTest::newRow("4x4") << 4 << 4;
+    QTest::newRow("100x100") << 100 << 100;
+    QTest::newRow("0x0") << 0 << 0;
+}
+
+void tst_QQuickTableView::checkContentSize()
+{
+    QFETCH(int, rowCount);
+    QFETCH(int, colCount);
+
+    // Check that the content size is initially correct, and that
+    // it updates when we change e.g the model or spacing (QTBUG-87680)
+    LOAD_TABLEVIEW("plaintableview.qml");
+
+    TestModel model(rowCount, colCount);
+    tableView->setModel(QVariant::fromValue(&model));
+    tableView->setRowSpacing(1);
+    tableView->setColumnSpacing(2);
+
+    WAIT_UNTIL_POLISHED;
+
+    const qreal delegateWidth = 100;
+    const qreal delegateHeight = 50;
+    qreal colSpacing = tableView->columnSpacing();
+    qreal rowSpacing = tableView->rowSpacing();
+
+    // Check that content size has the exepected initial values
+    QCOMPARE(tableView->contentWidth(), colCount == 0 ? 0 : (colCount * (delegateWidth + colSpacing)) - colSpacing);
+    QCOMPARE(tableView->contentHeight(), rowCount == 0 ? 0 : (rowCount * (delegateHeight + rowSpacing)) - rowSpacing);
+
+    // Set no spacing
+    rowSpacing = 0;
+    colSpacing = 0;
+    tableView->setRowSpacing(rowSpacing);
+    tableView->setColumnSpacing(colSpacing);
+    WAIT_UNTIL_POLISHED;
+    QCOMPARE(tableView->contentWidth(), colCount * delegateWidth);
+    QCOMPARE(tableView->contentHeight(), rowCount * delegateHeight);
+
+    // Set typical spacing values
+    rowSpacing = 2;
+    colSpacing = 3;
+    tableView->setRowSpacing(rowSpacing);
+    tableView->setColumnSpacing(colSpacing);
+    WAIT_UNTIL_POLISHED;
+    QCOMPARE(tableView->contentWidth(), colCount == 0 ? 0 : (colCount * (delegateWidth + colSpacing)) - colSpacing);
+    QCOMPARE(tableView->contentHeight(), rowCount == 0 ? 0 : (rowCount * (delegateHeight + rowSpacing)) - rowSpacing);
+
+    // Add a row and a column
+    model.insertRow(0);
+    model.insertColumn(0);
+    rowCount = model.rowCount();
+    colCount = model.columnCount();
+    WAIT_UNTIL_POLISHED;
+    QCOMPARE(tableView->contentWidth(), (colCount * (delegateWidth + colSpacing)) - colSpacing);
+    QCOMPARE(tableView->contentHeight(), (rowCount * (delegateHeight + rowSpacing)) - rowSpacing);
+
+    // Remove a row (this should also make affect contentWidth if rowCount becomes 0)
+    model.removeRow(0);
+    rowCount = model.rowCount();
+    WAIT_UNTIL_POLISHED;
+    QCOMPARE(tableView->contentWidth(), rowCount == 0 ? 0 : (colCount * (delegateWidth + colSpacing)) - colSpacing);
+    QCOMPARE(tableView->contentHeight(), rowCount == 0 ? 0 : (rowCount * (delegateHeight + rowSpacing)) - rowSpacing);
+}
+
 QTEST_MAIN(tst_QQuickTableView)
 
 #include "tst_qquicktableview.moc"