QTest: add QDeadlineTimer qWaitFor() overload

For Forever timers, don't check the remaining time.

Merge src_corelib_kernel_qtestsupport_core_snippet.cpp and
src_corelib_kernel_qtestsupport_core.cpp.

[ChangeLog][QtCore][QTest] Added QDeadlineTimer qWaitFor() overload.

Change-Id: I74c3f362b77206426136a418e656465e43f45b09
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>

src/corelib/kernel/qtestsupport_core.cpp

@@ -54,18 +54,31 @@ void QTest::qSleep(std::chrono::milliseconds msecs)
 
 /*! \fn template <typename Functor> bool QTest::qWaitFor(Functor predicate, int timeout)
 
+    \since 5.10
+    \overload
+
     Waits for \a timeout milliseconds or until the \a predicate returns true.
 
-    Returns \c true if the \a predicate returned true at any point, otherwise returns \c false.
+    This is equivalent to calling:
+    \code
+    qWaitFor(predicate, QDeadlineTimer(timeout));
+    \endcode
+*/
+
+/*! \fn template <typename Functor> bool QTest::qWaitFor(Functor predicate, QDeadlineTimer deadline)
+    \since 6.7
+
+    Waits until \a deadline has expired, or until \a predicate returns true, whichever
+    happens first.
+
+    Returns \c true if \a predicate returned true at any point, otherwise returns \c false.
 
     Example:
 
-    \snippet code/src_corelib_kernel_qtestsupport_core_snippet.cpp 0
+    \snippet code/src_corelib_kernel_qtestsupport_core.cpp 2
 
     The code above will wait for the object to become ready, for a
     maximum of three seconds.
-
-    \since 5.10
 */
 
 /*!

src/corelib/kernel/qtestsupport_core.h

@@ -16,7 +16,8 @@ Q_CORE_EXPORT void qSleep(int ms);
 Q_CORE_EXPORT void qSleep(std::chrono::milliseconds msecs);
 
 template <typename Functor>
-[[nodiscard]] static bool qWaitFor(Functor predicate, int timeout = 5000)
+[[nodiscard]] static bool
+qWaitFor(Functor predicate, QDeadlineTimer deadline = QDeadlineTimer(std::chrono::seconds{5}))
 {
     // We should not spin the event loop in case the predicate is already true,
     // otherwise we might send new events that invalidate the predicate.
@@ -27,9 +28,9 @@ template <typename Functor>
     // timeout like 1ms, so we we can't use a simple while-loop here based on
     // the deadline timer not having timed out. Use do-while instead.
 
-    int remaining = timeout;
-    QDeadlineTimer deadline(remaining, Qt::PreciseTimer);
+    using namespace std::chrono;
 
+    auto remaining = 0ms;
     do {
         // We explicitly do not pass the remaining time to processEvents, as
         // that would keep spinning processEvents for the whole duration if
@@ -43,15 +44,27 @@ template <typename Functor>
         if (predicate())
             return true;
 
-        remaining = int(deadline.remainingTime());
-        if (remaining > 0)
-            qSleep(qMin(10, remaining));
-        remaining = int(deadline.remainingTime());
-    } while (remaining > 0);
+        if (deadline.isForever()) { // No point checking remaining time
+            qSleep(10ms);
+            continue;
+        }
+
+        remaining = ceil<milliseconds>(deadline.remainingTimeAsDuration());
+        if (remaining == 0ms)
+            break;
+
+        qSleep(std::min(10ms, remaining));
+    } while (!deadline.hasExpired());
 
     return predicate(); // Last chance
 }
 
+template <typename Functor>
+[[nodiscard]] static bool qWaitFor(Functor predicate, int timeout)
+{
+    return qWaitFor(predicate, QDeadlineTimer(timeout));
+}
+
 Q_CORE_EXPORT void qWait(int ms);
 
 Q_CORE_EXPORT void qWait(std::chrono::milliseconds msecs);

src/testlib/doc/snippets/code/src_corelib_kernel_qtestsupport_core.cpp

@@ -7,6 +7,7 @@ class MyObject
 {
     public:
         int isReady();
+        bool startup();
 };
 
 // dummy function
@@ -25,3 +26,15 @@ int MyObject::isReady()
 //! [1]
 return 1;
 }
+
+static bool startup()
+{
+//! [2]
+    MyObject obj;
+    obj.startup();
+    using namespace std::chrono_literals;
+    const bool result = QTest::qWaitFor([&obj]() { return obj.isReady(); },
+                                        QDeadlineTimer(3s));
+//! [2]
+    return result;
+}

src/testlib/doc/snippets/code/src_corelib_kernel_qtestsupport_core_snippet.cpp

@@ -1,10 +0,0 @@
-// Copyright (C) 2020 The Qt Company Ltd.
-// SPDX-License-Identifier: LicenseRef-Qt-Commercial OR BSD-3-Clause
-
-//! [0]
-    MyObject obj;
-    obj.startup();
-    QTest::qWaitFor([&]() {
-        return obj.isReady();
-    }, 3000);
-//! [0]