QPixmap::load: ensure QBitmap stays a QBitmap even on failure

... and avoid detach()ing potentially large data for just
preserving the QPlatformPixmap::pixelType().

A QBitmap differs from a QPixmap (its base class, urgh)
by always having a data != nullptr and a Bitmap pixel
type, yet load() was unconditionally setting 'data' to
nullptr on failure, turning a QBitmap into a non-QBitmap.

Fix by move-assigning a null QBitmap instead of resetting
'data'.

Add some tests.

Change-Id: Ida58b3b24d96472a5f9d0f18f81cc763edcf3c16
Reviewed-by: Anton Kudryavtsev <a.kudryavtsev@netris.ru>
Reviewed-by: Edward Welbourne <edward.welbourne@qt.io>
Reviewed-by: Ulf Hermann <ulf.hermann@qt.io>

1 files changed, 27 insertions, 0 deletions

diff --git a/tests/auto/gui/image/qpixmap/tst_qpixmap.cpp b/tests/auto/gui/image/qpixmap/tst_qpixmap.cpp
index 4ffe357d09..286f00c111 100644
--- a/tests/auto/gui/image/qpixmap/tst_qpixmap.cpp
+++ b/tests/auto/gui/image/qpixmap/tst_qpixmap.cpp
@@ -1508,6 +1508,33 @@ void tst_QPixmap::loadAsBitmapOrPixmap()
     QVERIFY(!bitmap.isNull());
     QCOMPARE(bitmap.depth(), 1);
     QVERIFY(bitmap.isQBitmap());
+
+    // check that a QBitmap stays a QBitmap even when loading fails:
+    ok = bitmap.load(QString());
+    QVERIFY(!ok);
+    QVERIFY(bitmap.isNull());
+    QVERIFY(bitmap.isQBitmap());
+
+    ok = bitmap.load("does not exist");
+    QVERIFY(!ok);
+    QVERIFY(bitmap.isNull());
+    QVERIFY(bitmap.isQBitmap());
+
+    ok = bitmap.load("does not exist.png");
+    QVERIFY(!ok);
+    QVERIFY(bitmap.isNull());
+    QVERIFY(bitmap.isQBitmap());
+
+    QTemporaryFile garbage;
+    QVERIFY(garbage.open());
+    const QString garbagePath = garbage.fileName();
+    garbage.write(reinterpret_cast<const char *>(&garbage), sizeof garbage);
+    garbage.close();
+
+    ok = bitmap.load(garbagePath);
+    QVERIFY(!ok);
+    QVERIFY(bitmap.isNull());
+    QVERIFY(bitmap.isQBitmap());
 }
 
 void tst_QPixmap::toImageDeepCopy()