QQuickTableView: change how we calculate content size

The current calculations where a bit off. Change it to be
precise, and add an auto test to verify the contentWidth/Height
ends up correct as the flickable is flicked towards the end of
the table.

Change-Id: I784a1bba2ea8fddd09cee8ecda7e2089c8b5c74f
Reviewed-by: Mitch Curtis <mitch.curtis@qt.io>

3 files changed, 180 insertions, 17 deletions

diff --git a/src/quick/items/qquicktableview.cpp b/src/quick/items/qquicktableview.cpp
index e93544c37a..23f6e79049 100644
--- a/src/quick/items/qquicktableview.cpp
+++ b/src/quick/items/qquicktableview.cpp
@@ -174,14 +174,14 @@ void QQuickTableViewPrivate::updateContentWidth()
     if (currentRightColumn > contentSizeBenchMarkPoint.x()) {
         contentSizeBenchMarkPoint.setX(currentRightColumn);
 
-        qreal currentWidth = loadedTableOuterRect.right();
-        qreal averageCellSize = currentWidth / (currentRightColumn + 1);
-        qreal averageSize = averageCellSize + cellSpacing.width();
-        qreal estimatedWith = (tableSize.width() * averageSize) - cellSpacing.width();
+        const qreal spacing = currentRightColumn * cellSpacing.width();
+        const qreal margins = tableMargins.left() + tableMargins.right();
+        qreal currentWidth = loadedTableOuterRect.right() - tableMargins.left();
+        const qreal averageCellWidth = (currentWidth - spacing) / (currentRightColumn + 1);
+        qreal estimatedWidth = (tableSize.width() * (averageCellWidth + cellSpacing.width())) - cellSpacing.width();
 
-        // loadedTableOuterRect has already been adjusted for left margin
-        currentWidth += tableMargins.right();
-        estimatedWith += tableMargins.right();
+        currentWidth += margins;
+        estimatedWidth += margins;
 
         if (currentRightColumn >= tableSize.width() - 1) {
             // We are at the last column, and can set the exact width
@@ -189,12 +189,12 @@ void QQuickTableViewPrivate::updateContentWidth()
                 q->setContentWidth(currentWidth);
         } else if (currentWidth >= q->implicitWidth()) {
             // We are at the estimated width, but there are still more columns
-            q->setContentWidth(estimatedWith);
+            q->setContentWidth(estimatedWidth);
         } else {
             // Only set a new width if the new estimate is substantially different
-            qreal diff = 1 - (estimatedWith / q->implicitWidth());
+            qreal diff = 1 - (estimatedWidth / q->implicitWidth());
             if (qAbs(diff) > thresholdBeforeAdjust)
-                q->setContentWidth(estimatedWith);
+                q->setContentWidth(estimatedWidth);
         }
     }
 }
@@ -209,14 +209,14 @@ void QQuickTableViewPrivate::updateContentHeight()
     if (currentBottomRow > contentSizeBenchMarkPoint.y()) {
         contentSizeBenchMarkPoint.setY(currentBottomRow);
 
-        qreal currentHeight = loadedTableOuterRect.bottom();
-        qreal averageCellSize = currentHeight / (currentBottomRow + 1);
-        qreal averageSize = averageCellSize + cellSpacing.height();
-        qreal estimatedHeight = (tableSize.height() * averageSize) - cellSpacing.height();
+        const qreal spacing = currentBottomRow * cellSpacing.height();
+        const qreal margins = tableMargins.top() + tableMargins.bottom();
+        qreal currentHeight = loadedTableOuterRect.bottom() - tableMargins.top();
+        const qreal averageCellHeight = (currentHeight - spacing) / (currentBottomRow + 1);
+        qreal estimatedHeight = (tableSize.height() * (averageCellHeight + cellSpacing.height())) - cellSpacing.height();
 
-        // loadedTableOuterRect has already been adjusted for top margin
-        currentHeight += tableMargins.bottom();
-        estimatedHeight += tableMargins.bottom();
+        currentHeight += margins;
+        estimatedHeight += margins;
 
         if (currentBottomRow >= tableSize.height() - 1) {
             // We are at the last row, and can set the exact height
diff --git a/tests/auto/quick/qquicktableview/data/contentwidthheight.qml b/tests/auto/quick/qquicktableview/data/contentwidthheight.qml
new file mode 100644
index 0000000000..2c9d64c20e
--- /dev/null
+++ b/tests/auto/quick/qquicktableview/data/contentwidthheight.qml
@@ -0,0 +1,82 @@
+/****************************************************************************
+**
+** Copyright (C) 2018 The Qt Company Ltd.
+** Contact: https://www.qt.io/licensing/
+**
+** This file is part of the QtQuick module of the Qt Toolkit.
+**
+** $QT_BEGIN_LICENSE:LGPL$
+** Commercial License Usage
+** Licensees holding valid commercial Qt licenses may use this file in
+** accordance with the commercial license agreement provided with the
+** Software or, alternatively, in accordance with the terms contained in
+** a written agreement between you and The Qt Company. For licensing terms
+** and conditions see https://www.qt.io/terms-conditions. For further
+** information use the contact form at https://www.qt.io/contact-us.
+**
+** GNU Lesser General Public License Usage
+** Alternatively, this file may be used under the terms of the GNU Lesser
+** General Public License version 3 as published by the Free Software
+** Foundation and appearing in the file LICENSE.LGPL3 included in the
+** packaging of this file. Please review the following information to
+** ensure the GNU Lesser General Public License version 3 requirements
+** will be met: https://www.gnu.org/licenses/lgpl-3.0.html.
+**
+** GNU General Public License Usage
+** Alternatively, this file may be used under the terms of the GNU
+** General Public License version 2.0 or (at your option) the GNU General
+** Public license version 3 or any later version approved by the KDE Free
+** Qt Foundation. The licenses are as published by the Free Software
+** Foundation and appearing in the file LICENSE.GPL2 and LICENSE.GPL3
+** included in the packaging of this file. Please review the following
+** information to ensure the GNU General Public License requirements will
+** be met: https://www.gnu.org/licenses/gpl-2.0.html and
+** https://www.gnu.org/licenses/gpl-3.0.html.
+**
+** $QT_END_LICENSE$
+**
+****************************************************************************/
+
+import QtQuick 2.12
+import QtQuick.Window 2.3
+import Qt.labs.tableview 1.0
+
+Item {
+    width: 640
+    height: 450
+
+    property alias tableView: tableView
+    property Component delegate: tableViewDelegate
+
+    TableView {
+        id: tableView
+        width: 500
+        height: 500
+        anchors.margins: 1
+        clip: true
+        delegate: tableViewDelegate
+        cacheBuffer: 0
+        columnSpacing: 1
+        rowSpacing: 1
+        leftMargin: 10
+        rightMargin: 10
+        topMargin: 10
+        bottomMargin: 10
+        columnWidthProvider: function(column) { return column < 20 ? 100 : 200 }
+        rowHeightProvider: function(row) { return row < 20 ? 100 : 200 }
+    }
+
+    Component {
+        id: tableViewDelegate
+        Rectangle {
+            objectName: "tableViewDelegate"
+            color: "lightgray"
+            border.width: 1
+            Text {
+                anchors.centerIn: parent
+                text: column
+            }
+        }
+    }
+
+}
diff --git a/tests/auto/quick/qquicktableview/tst_qquicktableview.cpp b/tests/auto/quick/qquicktableview/tst_qquicktableview.cpp
index 7418189ee1..94d3a356fe 100644
--- a/tests/auto/quick/qquicktableview/tst_qquicktableview.cpp
+++ b/tests/auto/quick/qquicktableview/tst_qquicktableview.cpp
@@ -95,6 +95,7 @@ private slots:
     void checkRowHeightProvider();
     void checkRowHeightProviderInvalidReturnValues();
     void checkRowHeightProviderNotCallable();
+    void checkContentWidthAndHeight();
     void noDelegate();
     void countDelegateItems_data();
     void countDelegateItems();
@@ -400,6 +401,86 @@ void tst_QQuickTableView::checkRowHeightProviderNotCallable()
         QCOMPARE(fxItem->item->height(), kDefaultRowHeight);
 }
 
+void tst_QQuickTableView::checkContentWidthAndHeight()
+{
+    // Check that contentWidth/Height reports the correct size of the the
+    // table, based on knowledge of the rows and columns that has been loaded.
+    LOAD_TABLEVIEW("contentwidthheight.qml");
+
+    // Vertical and horizontal properties should be mirrored, so we only have
+    // to do the calculations once, and use them for both axis, below.
+    QCOMPARE(tableView->width(), tableView->height());
+    QCOMPARE(tableView->rowSpacing(), tableView->columnSpacing());
+    QCOMPARE(tableView->leftMargin(), tableView->rightMargin());
+    QCOMPARE(tableView->topMargin(), tableView->bottomMargin());
+
+    const int tableSize = 100;
+    const int cellSizeSmall = 100;
+    const int cellSizeLarge = 200;
+    const int spacing = 1;
+    const int margin = 10;
+    const int smallCellCount = 20;
+    const int largeCellCount = tableSize - smallCellCount;
+    const qreal spacingAndMargins = ((tableSize - 1) * spacing) + (margin * 2);
+    auto model = TestModelAsVariant(tableSize, tableSize);
+
+    tableView->setModel(model);
+
+    WAIT_UNTIL_POLISHED;
+
+    const qreal expectedSizeInit = (tableSize * cellSizeSmall) + ((tableSize - 1) * spacing) + (margin * 2);
+    QCOMPARE(tableView->contentWidth(), expectedSizeInit);
+    QCOMPARE(tableView->contentHeight(), expectedSizeInit);
+
+    // Flick in 5 more rows and columns, but not so far that we start loading in
+    // the ones that are bigger. Loading in more rows and columns of the same
+    // size as the initial ones should not change the first prediction.
+    qreal flickTo = ((cellSizeSmall + spacing) * 5) + margin;
+    tableView->setContentX(flickTo);
+    tableView->setContentY(flickTo);
+
+    QCOMPARE(tableView->contentWidth(), expectedSizeInit);
+    QCOMPARE(tableView->contentHeight(), expectedSizeInit);
+
+    // Flick to row and column 20 (smallCellCount), since there the row and
+    // column sizes increases with 100. Check that TableView then adjusts
+    // contentWidth and contentHeight accordingly.
+    flickTo = ((cellSizeSmall + spacing) * smallCellCount) + margin - spacing;
+    tableView->setContentX(flickTo);
+    tableView->setContentY(flickTo);
+
+    const int largeSizeCellCountInView = qCeil(tableView->width() / cellSizeLarge);
+    const int bottomRow = smallCellCount + largeSizeCellCountInView - 1;
+    QCOMPARE(tableViewPrivate->loadedTable.right(), bottomRow);
+
+    const qreal firstHalfLength = smallCellCount * cellSizeSmall;
+    const qreal secondHalfOneScreenLength = largeSizeCellCountInView * cellSizeLarge;
+    const qreal lengthAfterFlick = firstHalfLength + secondHalfOneScreenLength;
+    const qreal averageCellSize = lengthAfterFlick / (smallCellCount + largeSizeCellCountInView);
+    const qreal expectedSizeHalf = (tableSize * averageCellSize) + spacingAndMargins;
+
+    QCOMPARE(tableView->contentWidth(), expectedSizeHalf);
+    QCOMPARE(tableView->contentHeight(), expectedSizeHalf);
+
+    // Flick to the end (row/column 100, and overshoot a bit), and
+    // check that we then end up with the exact content width/height.
+    const qreal secondHalfLength = largeCellCount * cellSizeLarge;
+    const qreal expectedFullSize = (firstHalfLength + secondHalfLength) + spacingAndMargins;
+    tableView->setContentX(expectedFullSize);
+    tableView->setContentY(expectedFullSize);
+
+    QCOMPARE(tableView->contentWidth(), expectedFullSize);
+    QCOMPARE(tableView->contentHeight(), expectedFullSize);
+
+    // Flick back to start. Since we know the actual table
+    // size, contentWidth/Height shouldn't change.
+    tableView->setContentX(0);
+    tableView->setContentY(0);
+
+    QCOMPARE(tableView->contentWidth(), expectedFullSize);
+    QCOMPARE(tableView->contentHeight(), expectedFullSize);
+}
+
 void tst_QQuickTableView::noDelegate()
 {
     // Check that you can skip setting a delegate without