Fix incorrectly aligned text whose size depends on its implicit size

The if statement in QQuickTextPrivate::setupTextLayout() was missing
an OR clause for the case where the line width is neither greater
nor less than the old width/natural width, but has actually changed.
If that sounds confusing, it's because it is. Basically, the outer
layouting loop in that function needs to run twice for this scenario,
so that's what this patch makes it do.

Change-Id: I13777667eb13506d50f05e9766785a1c2c46125c
Task-number: QTBUG-50738
Task-number: QTBUG-50740
Reviewed-by: Liang Qi <liang.qi@qt.io>

3 files changed, 75 insertions, 2 deletions

diff --git a/src/quick/items/qquicktext.cpp b/src/quick/items/qquicktext.cpp
index 044e6ce8c1..ee5965676c 100644
--- a/src/quick/items/qquicktext.cpp
+++ b/src/quick/items/qquicktext.cpp
@@ -882,11 +882,11 @@ QRectF QQuickTextPrivate::setupTextLayout(qreal *const baseline)
 
             // If the width of the item has changed and it's possible the result of wrapping,
             // eliding, scaling has changed, or the text is not left aligned do another layout.
-            if ((lineWidth < qMin(oldWidth, naturalWidth) || (widthExceeded && lineWidth > oldWidth))
+            if ((!qFuzzyCompare(lineWidth, oldWidth) || (widthExceeded && lineWidth > oldWidth))
                     && (singlelineElide || multilineElide || canWrap || horizontalFit
                         || q->effectiveHAlign() != QQuickText::AlignLeft)) {
                 widthChanged = true;
-                widthExceeded = false;
+                widthExceeded = lineWidth >= qMin(oldWidth, naturalWidth);
                 heightExceeded = false;
                 continue;
             }
diff --git a/tests/auto/quick/qquicktext/data/hAlignWidthDependsOnImplicitWidth.qml b/tests/auto/quick/qquicktext/data/hAlignWidthDependsOnImplicitWidth.qml
new file mode 100644
index 0000000000..4358a58f57
--- /dev/null
+++ b/tests/auto/quick/qquicktext/data/hAlignWidthDependsOnImplicitWidth.qml
@@ -0,0 +1,25 @@
+import QtQuick 2.6
+
+Item {
+    width: 200
+    height: 200
+
+    property alias text: label.text
+    property alias horizontalAlignment: label.horizontalAlignment
+    property alias elide: label.elide
+    property int extraWidth: 0
+
+    Rectangle {
+        border.color: "red"
+        x: 100
+        width: label.implicitWidth + extraWidth
+        height: label.implicitHeight
+
+        Text {
+            id: label
+            anchors.fill: parent
+            text: 'press me'
+            horizontalAlignment: Text.AlignHCenter
+        }
+    }
+}
diff --git a/tests/auto/quick/qquicktext/tst_qquicktext.cpp b/tests/auto/quick/qquicktext/tst_qquicktext.cpp
index 7db9078a7b..bdff985027 100644
--- a/tests/auto/quick/qquicktext/tst_qquicktext.cpp
+++ b/tests/auto/quick/qquicktext/tst_qquicktext.cpp
@@ -151,6 +151,9 @@ private slots:
 
     void padding();
 
+    void hAlignWidthDependsOnImplicitWidth_data();
+    void hAlignWidthDependsOnImplicitWidth();
+
 private:
     QStringList standard;
     QStringList richText;
@@ -4170,6 +4173,51 @@ void tst_qquicktext::padding()
     delete root;
 }
 
+void tst_qquicktext::hAlignWidthDependsOnImplicitWidth_data()
+{
+    QTest::addColumn<QQuickText::HAlignment>("horizontalAlignment");
+    QTest::addColumn<QQuickText::TextElideMode>("elide");
+    QTest::addColumn<int>("extraWidth");
+
+    QTest::newRow("AlignHCenter, ElideNone, 0 extraWidth") << QQuickText::AlignHCenter << QQuickText::ElideNone << 0;
+    QTest::newRow("AlignRight, ElideNone, 0 extraWidth") << QQuickText::AlignRight << QQuickText::ElideNone << 0;
+    QTest::newRow("AlignHCenter, ElideRight, 0 extraWidth") << QQuickText::AlignHCenter << QQuickText::ElideRight << 0;
+    QTest::newRow("AlignRight, ElideRight, 0 extraWidth") << QQuickText::AlignRight << QQuickText::ElideRight << 0;
+    QTest::newRow("AlignHCenter, ElideNone, 20 extraWidth") << QQuickText::AlignHCenter << QQuickText::ElideNone << 20;
+    QTest::newRow("AlignRight, ElideNone, 20 extraWidth") << QQuickText::AlignRight << QQuickText::ElideNone << 20;
+    QTest::newRow("AlignHCenter, ElideRight, 20 extraWidth") << QQuickText::AlignHCenter << QQuickText::ElideRight << 20;
+    QTest::newRow("AlignRight, ElideRight, 20 extraWidth") << QQuickText::AlignRight << QQuickText::ElideRight << 20;
+}
+
+void tst_qquicktext::hAlignWidthDependsOnImplicitWidth()
+{
+    QFETCH(QQuickText::HAlignment, horizontalAlignment);
+    QFETCH(QQuickText::TextElideMode, elide);
+    QFETCH(int, extraWidth);
+
+    QScopedPointer<QQuickView> window(new QQuickView);
+    window->setSource(testFileUrl("hAlignWidthDependsOnImplicitWidth.qml"));
+    QTRY_COMPARE(window->status(), QQuickView::Ready);
+
+    window->show();
+    QVERIFY(QTest::qWaitForWindowExposed(window.data()));
+
+    QQuickItem *rect = window->rootObject();
+    QVERIFY(rect);
+
+    QVERIFY(rect->setProperty("horizontalAlignment", horizontalAlignment));
+    QVERIFY(rect->setProperty("elide", elide));
+    QVERIFY(rect->setProperty("extraWidth", extraWidth));
+
+    QImage image = window->grabWindow();
+    const int rectX = 100 * window->screen()->devicePixelRatio();
+    QCOMPARE(numberOfNonWhitePixels(0, rectX - 1, image), 0);
+
+    QVERIFY(rect->setProperty("text", "this is mis-aligned"));
+    image = window->grabWindow();
+    QCOMPARE(numberOfNonWhitePixels(0, rectX - 1, image), 0);
+}
+
 QTEST_MAIN(tst_qquicktext)
 
 #include "tst_qquicktext.moc"