Fix Text with ElideRight not being rendered when reparented

Consider the following example:

    Item {
        width: 100
        height: 30

        Text {
            width: parent ? parent.width : 0
            height: parent ? parent.height : 0
            elide: Text.ElideRight
            text: "wot"
        }
    }

When setting the Text item's parent to null, its explicit width and
height are set to 0. When restoring its parent (the Item), its
explicit width and height are set to 100 and 30 again, but the text
itself is still not rendered.

The cause can be seen here:

    if (!(widthChanged || widthMaximum) && !d->isLineLaidOutConnected()) {
        // only height has changed
        if (newGeometry.height() > oldGeometry.height()) {
            if (!d->heightExceeded) // Height is adequate and growing.
                goto geomChangeDone;

heightExceeded was false, because 30 > 12 (or whatever the implicit
height happened to be), so the text was not laid out again, even though
it went from having an explicit height of 0 to an explicit height of
30.

Fix the issue by only executing the goto if the old explicit height
wasn't 0.

Task-number: QTBUG-60328
Task-number: QTBUG-67145
Change-Id: I7f4d2f95bc95c850133ba91ac2d1a02c7ee159b6
Reviewed-by: Eskil Abrahamsen Blomfeldt <eskil.abrahamsen-blomfeldt@qt.io>

2 files changed, 54 insertions, 0 deletions

diff --git a/tests/auto/quick/qquicktext/data/elideParentChanged.qml b/tests/auto/quick/qquicktext/data/elideParentChanged.qml
new file mode 100644
index 0000000000..f605cf58f1
--- /dev/null
+++ b/tests/auto/quick/qquicktext/data/elideParentChanged.qml
@@ -0,0 +1,13 @@
+import QtQuick 2.0
+
+Item {
+    width: 100
+    height: 30
+
+    Text {
+        width: parent ? parent.width : 0
+        height: parent ? parent.height : 0
+        elide: Text.ElideRight
+        text: "wot"
+    }
+}
diff --git a/tests/auto/quick/qquicktext/tst_qquicktext.cpp b/tests/auto/quick/qquicktext/tst_qquicktext.cpp
index 609a84ce82..89d2590c03 100644
--- a/tests/auto/quick/qquicktext/tst_qquicktext.cpp
+++ b/tests/auto/quick/qquicktext/tst_qquicktext.cpp
@@ -38,6 +38,7 @@
 #include <QFontMetrics>
 #include <qmath.h>
 #include <QtQuick/QQuickView>
+#include <QtQuick/qquickitemgrabresult.h>
 #include <private/qguiapplication_p.h>
 #include <limits.h>
 #include <QtGui/QMouseEvent>
@@ -64,6 +65,7 @@ private slots:
     void width();
     void wrap();
     void elide();
+    void elideParentChanged();
     void multilineElide_data();
     void multilineElide();
     void implicitElide_data();
@@ -554,6 +556,45 @@ void tst_qquicktext::elide()
     }
 }
 
+// QTBUG-60328
+// Tests that text with elide set is rendered after
+// having its parent cleared and then set again.
+void tst_qquicktext::elideParentChanged()
+{
+    QQuickView window;
+    window.setSource(testFileUrl("elideParentChanged.qml"));
+    QTRY_COMPARE(window.status(), QQuickView::Ready);
+
+    window.show();
+    QVERIFY(QTest::qWaitForWindowExposed(&window));
+
+    QQuickItem *root = window.rootObject();
+    QVERIFY(root);
+    QCOMPARE(root->childItems().size(), 1);
+
+    // Store a snapshot of the scene so that we can compare it later.
+    QSharedPointer<QQuickItemGrabResult> grabResult = root->grabToImage();
+    QTRY_VERIFY(!grabResult->image().isNull());
+    const QImage expectedItemImageGrab(grabResult->image());
+
+    // Clear the text's parent. It shouldn't render anything.
+    QQuickItem *text = root->childItems().first();
+    text->setParentItem(nullptr);
+    QCOMPARE(text->width(), 0.0);
+    QCOMPARE(text->height(), 0.0);
+
+    // Set the parent back to what it was. The text should
+    // be rendered identically to how it was before.
+    text->setParentItem(root);
+    QCOMPARE(text->width(), 100.0);
+    QCOMPARE(text->height(), 30.0);
+
+    grabResult = root->grabToImage();
+    QTRY_VERIFY(!grabResult->image().isNull());
+    const QImage actualItemImageGrab(grabResult->image());
+    QCOMPARE(actualItemImageGrab, expectedItemImageGrab);
+}
+
 void tst_qquicktext::multilineElide_data()
 {
     QTest::addColumn<QQuickText::TextFormat>("format");