Fix possible crash in QTextDocument

With trailing spaces in some cases, we would not get the
"no justification at end of paragraph" special case, and continue
in the code, getting the unexpected case where line_length becomes
< 0 which would lead to memory corruption because we were writing
outside our buffers. I added an assert to catch this type of bug
earlier, and I added the trailing spaces to the test for the end
of the paragraph.

The test case added is one example which would crash.

Task-number: QTBUG-27354
Change-Id: Id720a6fa55dbc709ce04dd5321e55687bf960d75
Reviewed-by: Lars Knoll <lars.knoll@digia.com>

1 files changed, 25 insertions, 0 deletions

diff --git a/tests/auto/gui/text/qtextdocument/tst_qtextdocument.cpp b/tests/auto/gui/text/qtextdocument/tst_qtextdocument.cpp
index cf3265d446..966102033c 100644
--- a/tests/auto/gui/text/qtextdocument/tst_qtextdocument.cpp
+++ b/tests/auto/gui/text/qtextdocument/tst_qtextdocument.cpp
@@ -184,6 +184,8 @@ private slots:
 
     void htmlExportImportBlockCount();
 
+    void QTBUG27354_spaceAndSoftSpace();
+
 private:
     void backgroundImage_checkExpectedHtml(const QTextDocument &doc);
 
@@ -2900,5 +2902,28 @@ void tst_QTextDocument::htmlExportImportBlockCount()
     QCOMPARE(document.blockCount(), 5);
 }
 
+void tst_QTextDocument::QTBUG27354_spaceAndSoftSpace()
+{
+    QTextDocument document;
+    {
+        QTextCursor cursor(&document);
+        QTextBlockFormat blockFormat;
+        blockFormat.setAlignment(Qt::AlignJustify);
+        cursor.mergeBlockFormat(blockFormat);
+        cursor.insertText("ac");
+        cursor.insertBlock();
+        cursor.insertText(" ");
+        cursor.insertText(QChar(0x2028));
+    }
+
+    // Trigger justification of text
+    QImage image(1000, 1000, QImage::Format_ARGB32);
+    image.fill(0);
+    {
+        QPainter p(&image);
+        document.drawContents(&p, image.rect());
+    }
+}
+
 QTEST_MAIN(tst_QTextDocument)
 #include "tst_qtextdocument.moc"