Fix possibly corrupted log clusters when using custom tab stops

The calculateTabWidth() can trigger shaping of the item, which can
cause the layout data to be reallocated, so we need to update the
local pointers to it, like we do when we explicitly invoke the
shaper.

[ChangeLog][Text] Fixed problems with text layout when using custom
tab stops.

Task-number: QTBUG-43126
Change-Id: Ifaeeeb4bfb1a55e6638b12b444f53d2679d3d1e6
Reviewed-by: Konstantin Ritt <ritt.ks@gmail.com>

2 files changed, 39 insertions, 0 deletions

diff --git a/src/gui/text/qtextlayout.cpp b/src/gui/text/qtextlayout.cpp
index 733bb57928..52d2ba0d54 100644
--- a/src/gui/text/qtextlayout.cpp
+++ b/src/gui/text/qtextlayout.cpp
@@ -1776,6 +1776,11 @@ void QTextLine::layout_helper(int maxGlyphs)
 
             QFixed x = line.x + line.textWidth + lbh.tmpData.textWidth + lbh.spaceData.textWidth;
             QFixed tabWidth = eng->calculateTabWidth(item, x);
+            attributes = eng->attributes();
+            if (!attributes)
+                return;
+            lbh.logClusters = eng->layoutData->logClustersPtr;
+            lbh.glyphs = eng->shapedGlyphs(&current);
 
             lbh.spaceData.textWidth += tabWidth;
             lbh.spaceData.length++;
diff --git a/tests/auto/gui/text/qtextlayout/tst_qtextlayout.cpp b/tests/auto/gui/text/qtextlayout/tst_qtextlayout.cpp
index a9a358711b..4b2970cd17 100644
--- a/tests/auto/gui/text/qtextlayout/tst_qtextlayout.cpp
+++ b/tests/auto/gui/text/qtextlayout/tst_qtextlayout.cpp
@@ -116,6 +116,7 @@ private slots:
     void boundingRectForSetLineWidth();
     void glyphLessItems();
     void justifyTrailingSpaces();
+    void layoutWithCustomTabStops();
 
     // QTextLine stuff
     void setNumColumnsWrapAtWordBoundaryOrAnywhere();
@@ -2050,5 +2051,38 @@ void tst_QTextLayout::nbsp()
     layout.endLayout();
 }
 
+void tst_QTextLayout::layoutWithCustomTabStops()
+{
+    QScopedPointer<QTextLayout> textLayout(new QTextLayout);
+    QList<QTextOption::Tab> tabStops;
+
+    const int tabWidth = 18;
+    const int maxTabPos = 2500;
+    for (int tabPos = tabWidth; tabPos < maxTabPos; tabPos += tabWidth)
+        tabStops << QTextOption::Tab(tabPos, QTextOption::LeftTab);
+
+    QTextOption textOption;
+    textOption.setTabs(tabStops);
+    textLayout->setTextOption(textOption);
+
+    textLayout->setText(QStringLiteral("\ta aa aa aa aa aa aa"));
+
+    textLayout->beginLayout();
+    textLayout->createLine();
+    textLayout->endLayout();
+
+    qreal shortWidth = textLayout->maximumWidth();
+
+    textLayout->setText(QStringLiteral("\ta aa aa aa aa aa aa aa aa aa aa aa aa a"));
+
+    textLayout->beginLayout();
+    textLayout->createLine();
+    textLayout->endLayout();
+
+    qreal longWidth = textLayout->maximumWidth();
+
+    QVERIFY(longWidth > shortWidth);
+}
+
 QTEST_MAIN(tst_QTextLayout)
 #include "tst_qtextlayout.moc"