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Client: Don't crash with long window titles using UTF-16 characters

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Previously, we set the max length in QString character length, which means
UTF-16 characters (of potentially three bytes) counts as one character. The max
limit of libwayland, however, is in bytes (and the string itself is converted
to UTF-8).

Fix it by dividing the character limit by three because in the worst case each
UTF-16 character will use three bytes when UTF-8 encoded.

Fixes: QTBUG-78478
Change-Id: Idf4721894e0fe6f3cd92bdc6ada7b0ea4199ea63
Reviewed-by: Paul Olav Tvete <paul.tvete@qt.io>
This commit is contained in:
Johan Klokkhammer Helsing 2019-09-18 08:56:57 +02:00 committed by Johan Helsing
parent 7dfa3f9d50
commit 7c4b2334a3
2 changed files with 15 additions and 2 deletions
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6
src/plugins/platforms/wayland/qwaylandwindow.cpp
View File

@ -298,8 +298,10 @@ void QWaylandWindow::setWindowTitle(const QString &title)
const QString formatted = formatWindowTitle(title, separator); const QString formatted = formatWindowTitle(title, separator);
const int libwaylandMaxBufferSize = 4096; const int libwaylandMaxBufferSize = 4096;
// Some parts of the buffer is used for metadata, so subtract 100 to be on the safe side // Some parts of the buffer is used for metadata, so subtract 100 to be on the safe side.
const int maxLength = libwaylandMaxBufferSize - 100; // Also, QString is in utf-16, which means that in the worst case each character will be
// three bytes when converted to utf-8 (which is what libwayland uses), so divide by three.
const int maxLength = libwaylandMaxBufferSize / 3 - 100;
auto truncated = QStringRef(&formatted).left(maxLength); auto truncated = QStringRef(&formatted).left(maxLength);
if (truncated.length() < formatted.length()) { if (truncated.length() < formatted.length()) {

11
tests/auto/wayland/client/tst_client.cpp
View File

@ -178,6 +178,7 @@ private slots:
void hiddenPopupParent(); void hiddenPopupParent();
void glWindow(); void glWindow();
void longWindowTitle(); void longWindowTitle();
void longWindowTitleWithUtf16Characters();
private: private:
MockCompositor *compositor = nullptr; MockCompositor *compositor = nullptr;
@ -494,6 +495,16 @@ void tst_WaylandClient::longWindowTitle()
QTRY_VERIFY(compositor->surface()); QTRY_VERIFY(compositor->surface());
} }
void tst_WaylandClient::longWindowTitleWithUtf16Characters()
{
QWindow window;
QString absurdlyLongTitle = QString("三").repeated(10000);
Q_ASSERT(absurdlyLongTitle.length() == 10000); // just making sure the test isn't broken
window.setTitle(absurdlyLongTitle);
window.show();
QTRY_VERIFY(compositor->surface());
}
int main(int argc, char **argv) int main(int argc, char **argv)
{ {
setenv("XDG_RUNTIME_DIR", ".", 1); setenv("XDG_RUNTIME_DIR", ".", 1);