QtWidgets: use Q_UNLIKELY for every qWarning() (1)

If, after checking a condition, we issue a qWarning(),
by definition that check is unlikely to be true.

Tell the compiler so it can move the error handling
code out of the normal code path to increase the
effective icache size.

This change contains the changes to the util/,
dialogs/ and widgets/ subdirs.

Moved conditional code around where possible so that
we could always use Q_UNLIKELY, instead of having to
revert to Q_LIKELY here and there.

In QSystemTrayIcon::setVisible(), as a drive-by, I
swapped the evaluation order of an &&-expression
(newly wrapped in Q_UNLIKELY) to be more readable
and more efficient (cheaper check first) at the same
time.

Change-Id: I3564c5a5deacba49d67d3989fb0b53e680c57fcb
Reviewed-by: Olivier Goffart (Woboq GmbH) <ogoffart@woboq.com>

1 files changed, 10 insertions, 10 deletions

diff --git a/src/widgets/widgets/qmdiarea.cpp b/src/widgets/widgets/qmdiarea.cpp
index 1864b42a80..55ae866358 100644
--- a/src/widgets/widgets/qmdiarea.cpp
+++ b/src/widgets/widgets/qmdiarea.cpp
@@ -179,7 +179,7 @@ using namespace QMdi;
 // Asserts in debug mode, gives warning otherwise.
 static bool sanityCheck(const QMdiSubWindow * const child, const char *where)
 {
-    if (!child) {
+    if (Q_UNLIKELY(!child)) {
         const char error[] = "null pointer";
         Q_ASSERT_X(false, where, error);
         qWarning("%s:%s", where, error);
@@ -190,13 +190,13 @@ static bool sanityCheck(const QMdiSubWindow * const child, const char *where)
 
 static bool sanityCheck(const QList<QWidget *> &widgets, const int index, const char *where)
 {
-    if (index < 0 || index >= widgets.size()) {
+    if (Q_UNLIKELY(index < 0 || index >= widgets.size())) {
         const char error[] = "index out of range";
         Q_ASSERT_X(false, where, error);
         qWarning("%s:%s", where, error);
         return false;
     }
-    if (!widgets.at(index)) {
+    if (Q_UNLIKELY(!widgets.at(index))) {
         const char error[] = "null pointer";
         Q_ASSERT_X(false, where, error);
         qWarning("%s:%s", where, error);
@@ -1831,12 +1831,12 @@ void QMdiArea::setActiveSubWindow(QMdiSubWindow *window)
         return;
     }
 
-    if (d->childWindows.isEmpty()) {
+    if (Q_UNLIKELY(d->childWindows.isEmpty())) {
         qWarning("QMdiArea::setActiveSubWindow: workspace is empty");
         return;
     }
 
-    if (d->childWindows.indexOf(window) == -1) {
+    if (Q_UNLIKELY(d->childWindows.indexOf(window) == -1)) {
         qWarning("QMdiArea::setActiveSubWindow: window is not inside workspace");
         return;
     }
@@ -1960,7 +1960,7 @@ void QMdiArea::activatePreviousSubWindow()
 */
 QMdiSubWindow *QMdiArea::addSubWindow(QWidget *widget, Qt::WindowFlags windowFlags)
 {
-    if (!widget) {
+    if (Q_UNLIKELY(!widget)) {
         qWarning("QMdiArea::addSubWindow: null pointer to widget");
         return 0;
     }
@@ -1972,7 +1972,7 @@ QMdiSubWindow *QMdiArea::addSubWindow(QWidget *widget, Qt::WindowFlags windowFla
 
     // Widget is already a QMdiSubWindow
     if (child) {
-        if (d->childWindows.indexOf(child) != -1) {
+        if (Q_UNLIKELY(d->childWindows.indexOf(child) != -1)) {
             qWarning("QMdiArea::addSubWindow: window is already added");
             return child;
         }
@@ -2003,7 +2003,7 @@ QMdiSubWindow *QMdiArea::addSubWindow(QWidget *widget, Qt::WindowFlags windowFla
 */
 void QMdiArea::removeSubWindow(QWidget *widget)
 {
-    if (!widget) {
+    if (Q_UNLIKELY(!widget)) {
         qWarning("QMdiArea::removeSubWindow: null pointer to widget");
         return;
     }
@@ -2014,7 +2014,7 @@ void QMdiArea::removeSubWindow(QWidget *widget)
 
     if (QMdiSubWindow *child = qobject_cast<QMdiSubWindow *>(widget)) {
         int index = d->childWindows.indexOf(child);
-        if (index == -1) {
+        if (Q_UNLIKELY(index == -1)) {
             qWarning("QMdiArea::removeSubWindow: window is not inside workspace");
             return;
         }
@@ -2038,7 +2038,7 @@ void QMdiArea::removeSubWindow(QWidget *widget)
         }
     }
 
-    if (!found)
+    if (Q_UNLIKELY(!found))
         qWarning("QMdiArea::removeSubWindow: widget is not child of any window inside QMdiArea");
 }