Text: don't fall back to full-width layout if availableWidth == 0

If Text.width == Text.rightPadding, there is no space to render any
text; but in that case, QQuickTextPrivate::availableWidth() returns 0:
it's incorrect to fall back to layout.maximumWidth() and allow rendering
the whole line. Prior to 6ec2693d4a3c95ca9ff0c349d3c587a7f1402c05
we were checking width() here, so let's do that again.

Fixes: QTBUG-83413
Change-Id: I3ee3b49406577c3aa005a3ca3606308ff0a21d8d
Reviewed-by: Oliver Eftevaag <oliver.eftevaag@qt.io>
(cherry picked from commit 406ff6b53d02b8db4231e473982fe593fb1e48c6)
Reviewed-by: Shawn Rutledge <shawn.rutledge@qt.io>

3 files changed, 85 insertions, 0 deletions

diff --git a/tests/auto/quick/qquicktext/data/padding.qml b/tests/auto/quick/qquicktext/data/padding.qml
index ab0a37d041..f830af0e40 100644
--- a/tests/auto/quick/qquicktext/data/padding.qml
+++ b/tests/auto/quick/qquicktext/data/padding.qml
@@ -9,4 +9,30 @@ Text {
     leftPadding: 30
     rightPadding: 40
     bottomPadding: 50
+
+    Rectangle {
+        width: parent.leftPadding
+        height: parent.height
+        color: "#6600FF00"
+    }
+
+    Rectangle {
+        width: parent.width
+        height: parent.topPadding
+        color: "#66888800"
+    }
+
+    Rectangle {
+        x: parent.width - parent.rightPadding
+        width: parent.rightPadding
+        height: parent.height
+        color: "#6600FFFF"
+    }
+
+    Rectangle {
+        y: parent.height - parent.bottomPadding
+        width: parent.width
+        height: parent.bottomPadding
+        color: "#66880088"
+    }
 }
diff --git a/tests/auto/quick/qquicktext/data/paddingInLoader.qml b/tests/auto/quick/qquicktext/data/paddingInLoader.qml
new file mode 100644
index 0000000000..6ef7c25a9b
--- /dev/null
+++ b/tests/auto/quick/qquicktext/data/paddingInLoader.qml
@@ -0,0 +1,14 @@
+import QtQuick 2.12
+
+Item {
+    width: 30
+    height: 30
+    Loader {
+        anchors.fill: parent
+        sourceComponent: Text {
+            rightPadding: 30
+            text: "Some text"
+            elide: Text.ElideRight
+        }
+    }
+}
diff --git a/tests/auto/quick/qquicktext/tst_qquicktext.cpp b/tests/auto/quick/qquicktext/tst_qquicktext.cpp
index fe3f696dfa..ff191bbc7f 100644
--- a/tests/auto/quick/qquicktext/tst_qquicktext.cpp
+++ b/tests/auto/quick/qquicktext/tst_qquicktext.cpp
@@ -55,6 +55,8 @@ QT_BEGIN_NAMESPACE
 extern void qt_setQtEnableTestFont(bool value);
 QT_END_NAMESPACE
 
+Q_LOGGING_CATEGORY(lcTests, "qt.quick.tests")
+
 class tst_qquicktext : public QQmlDataTest
 {
     Q_OBJECT
@@ -153,6 +155,7 @@ private slots:
     void growFromZeroWidth();
 
     void padding();
+    void paddingInLoader();
 
     void hintingPreference();
 
@@ -4342,6 +4345,20 @@ void tst_qquicktext::padding()
     obj->setElideMode(QQuickText::ElideRight);
     QCOMPARE(obj->implicitWidth(), cw + obj->leftPadding() + obj->rightPadding());
     QCOMPARE(obj->implicitHeight(), ch + obj->topPadding() + obj->bottomPadding());
+
+    obj->setLeftPadding(0);
+    QCOMPARE(obj->implicitWidth(), cw + obj->leftPadding() + obj->rightPadding());
+
+    obj->setWidth(cw);
+    obj->setRightPadding(cw);
+    QCOMPARE(obj->contentWidth(), 0);
+
+    for (int incr = 1; incr < 50 && qFuzzyIsNull(obj->contentWidth()); ++incr)
+        obj->setWidth(cw + incr);
+    QVERIFY(obj->contentWidth() > 0);
+    qCDebug(lcTests) << "increasing Text width from" << cw << "to" << obj->width()
+                     << "rendered a character: contentWidth now" << obj->contentWidth();
+
     obj->setElideMode(QQuickText::ElideNone);
     obj->resetWidth();
 
@@ -4386,6 +4403,34 @@ void tst_qquicktext::padding()
     delete root;
 }
 
+void tst_qquicktext::paddingInLoader() // QTBUG-83413
+{
+    QQuickView view(testFileUrl("paddingInLoader.qml"));
+    view.show();
+    view.requestActivate();
+    QVERIFY(QTest::qWaitForWindowExposed(&view));
+    QQuickText *qtext = view.rootObject()->findChild<QQuickText*>();
+    QVERIFY(qtext);
+    QQuickTextPrivate *textPrivate = QQuickTextPrivate::get(qtext);
+    QVERIFY(textPrivate);
+    QCOMPARE(qtext->contentWidth(), 0); // does not render text, because width == rightPadding
+    QCOMPARE(textPrivate->availableWidth(), 0);
+
+    qtext->setLeftPadding(qtext->width());
+    qtext->setRightPadding(0);
+    QCOMPARE(qtext->contentWidth(), 0); // does not render text, because width == leftPadding
+    QCOMPARE(textPrivate->availableWidth(), 0);
+
+    qtext->setRightPadding(qtext->width());
+    QCOMPARE(qtext->contentWidth(), 0); // does not render text: available space is negative
+    QCOMPARE(textPrivate->availableWidth(), -qtext->width());
+
+    qtext->setLeftPadding(2);
+    qtext->setRightPadding(2);
+    QVERIFY(qtext->contentWidth() > 0); // finally space is available to render text
+    QCOMPARE(textPrivate->availableWidth(), qtext->width() - 4);
+}
+
 void tst_qquicktext::hintingPreference()
 {
     {