Fix calculation of text margin if line edit contains side widgets

The previous implementation leads to infinite chain of showing/hidden
line edit under circumstances described in QTBUG-54676. We basically got
the situation when size hint were calculated differently depending on
the line edit visibility state. In this case toolbar layout have to
show/hide extension button and line edit a lot of times and can never
leave this "loop" (please note, that the chain is much more complicated
in reality):
Resize toolbar -> Set layout geometry -> Size is OK to display line edit
-> Set layout geometry -> Hide extension button -> Set layout geometry
(wrong size is calculated here, so "run out of space") -> Hide line edit
-> Set layout geometry -> Show extension button -> Set layout geometry -
> Size is OK to display line edit ... And we're in the "loop"

Clear button is hidden if there is no text in a line edit.
In the previous implementation, the button was always visible, only
opacity was changing in order to "hide" the button. It resulted to
incorrect size hints (regular and minimum).
In the current implementation the button is really hidden/shown, and
size hints calculated correctly.
Also updated unit test for line edit.

Remove code duplication in functions for calculation text margin

Fixes: QTBUG-54676
Change-Id: I4549c9ea98e10b750ba855a07037f6392276358b
Reviewed-by: Shawn Rutledge <shawn.rutledge@qt.io>

2 files changed, 81 insertions, 1 deletions

diff --git a/tests/auto/widgets/widgets/qlineedit/tst_qlineedit.cpp b/tests/auto/widgets/widgets/qlineedit/tst_qlineedit.cpp
index 448e2030bc..95799905de 100644
--- a/tests/auto/widgets/widgets/qlineedit/tst_qlineedit.cpp
+++ b/tests/auto/widgets/widgets/qlineedit/tst_qlineedit.cpp
@@ -4451,10 +4451,11 @@ void tst_QLineEdit::clearButtonVisibleAfterSettingText_QTBUG_45518()
     QTRY_VERIFY(clearButton->opacity() > 0);
     QTRY_COMPARE(clearButton->cursor().shape(), Qt::ArrowCursor);
 
-    QTest::mouseClick(clearButton, Qt::LeftButton, 0, clearButton->rect().center());
+    QTest::mouseClick(clearButton, Qt::LeftButton, nullptr, clearButton->rect().center());
     QTRY_COMPARE(edit.text(), QString());
 
     QTRY_COMPARE(clearButton->opacity(), qreal(0));
+    QVERIFY(clearButton->isHidden());
     QTRY_COMPARE(clearButton->cursor().shape(), clearButton->parentWidget()->cursor().shape());
 
     edit.setClearButtonEnabled(false);
diff --git a/tests/auto/widgets/widgets/qtoolbar/tst_qtoolbar.cpp b/tests/auto/widgets/widgets/qtoolbar/tst_qtoolbar.cpp
index 301801ed2e..d6c165642e 100644
--- a/tests/auto/widgets/widgets/qtoolbar/tst_qtoolbar.cpp
+++ b/tests/auto/widgets/widgets/qtoolbar/tst_qtoolbar.cpp
@@ -42,6 +42,7 @@
 #include <qlineedit.h>
 #include <qkeysequence.h>
 #include <qmenu.h>
+#include <qlabel.h>
 #include <private/qtoolbarextension_p.h>
 
 QT_FORWARD_DECLARE_CLASS(QAction)
@@ -80,6 +81,8 @@ private slots:
 
     void task191727_layout();
     void task197996_visibility();
+
+    void extraCpuConsumption(); // QTBUG-54676
 };
 
 
@@ -1098,5 +1101,81 @@ void tst_QToolBar::task197996_visibility()
     QTRY_VERIFY(toolBar->widgetForAction(pAction)->isVisible());
 }
 
+class ShowHideEventCounter : public QObject
+{
+public:
+    using QObject::QObject;
+
+    bool eventFilter(QObject *watched, QEvent *event) override
+    {
+        if (qobject_cast<QLineEdit*>(watched) && !event->spontaneous()) {
+            if (event->type() == QEvent::Show)
+                ++m_showEventsCount;
+
+            if (event->type() == QEvent::Hide)
+                ++m_hideEventsCount;
+        }
+
+        return QObject::eventFilter(watched, event);
+    }
+
+    uint showEventsCount() const { return m_showEventsCount; }
+    uint hideEventsCount() const { return m_hideEventsCount; }
+
+private:
+    uint m_showEventsCount = 0;
+    uint m_hideEventsCount = 0;
+};
+
+void tst_QToolBar::extraCpuConsumption()
+{
+    QMainWindow mainWindow;
+
+    auto tb = new QToolBar(&mainWindow);
+    tb->setMovable(false);
+
+    auto extensions = tb->findChildren<QToolBarExtension *>();
+    QVERIFY(!extensions.isEmpty());
+
+    auto extensionButton = extensions.at(0);
+    QVERIFY(extensionButton);
+
+    tb->addWidget(new QLabel("Lorem ipsum dolor sit amet"));
+
+    auto le = new QLineEdit;
+    le->setClearButtonEnabled(true);
+    le->setText("Lorem ipsum");
+    tb->addWidget(le);
+
+    mainWindow.addToolBar(tb);
+    mainWindow.show();
+    QVERIFY(QTest::qWaitForWindowActive(&mainWindow));
+
+    auto eventCounter = new ShowHideEventCounter(&mainWindow);
+    le->installEventFilter(eventCounter);
+
+    auto defaultSize = mainWindow.size();
+
+    // Line edit should be hidden now and extension button should be displayed
+    for (double p = 0.7; extensionButton->isHidden() || qFuzzyCompare(p, 0.); p -= 0.01) {
+        mainWindow.resize(int(defaultSize.width() * p), defaultSize.height());
+    }
+    QVERIFY(!extensionButton->isHidden());
+
+    // Line edit should be visible, but smaller
+    for (double p = 0.75; !extensionButton->isHidden() || qFuzzyCompare(p, 1.); p += 0.01) {
+        mainWindow.resize(int(defaultSize.width() * p), defaultSize.height());
+    }
+    QVERIFY(extensionButton->isHidden());
+
+    // Dispatch all pending events
+    qApp->sendPostedEvents();
+    qApp->processEvents();
+
+    QCOMPARE(eventCounter->showEventsCount(), eventCounter->hideEventsCount());
+    QCOMPARE(eventCounter->showEventsCount(), uint(1));
+    QCOMPARE(eventCounter->hideEventsCount(), uint(1));
+}
+
 QTEST_MAIN(tst_QToolBar)
 #include "tst_qtoolbar.moc"