Removing item or adding item in QGraphicsScene always updates input method hints when focuseditem has ItemAcceptsInputMethod

PRECONDITIONS:
1. set of items (A) in qgraphicsscene
2. focused to an item (b) that has QGraphicsItem::ItemAcceptsInputMethod

STEPS LEADING TO PROBLEM:
1. remove the set of items (A) from scene

EXPECTED OUTCOME:
No extensive input method hint updates

ACTUAL OUTCOME:
For each item removed, input method hint state is updated, even though the
state doesn't change and focused item does not change.

Creates performance problems when input method plugin updates the hints via IPC.

Testcase shows a bit of performance problem with standard Linux without any input method plugins.
On my computer non-focus case (benchmark) is 1s and focus case (bug demo) is ~1.5s.

To run benchmark testcase:
./qt-im-scene

To run testcase demonstrating the problem:
./qt-im-scene 1

Might be fixable with patch similar to:

diff --git a/src/gui/kernel/qwidget.cpp b/src/gui/kernel/qwidget.cpp
index fd9deb5..b85b4e9 100644
— a/src/gui/kernel/qwidget.cpp
+++ b/src/gui/kernel/qwidget.cpp
@@ -9325,6 +9325,9 @@ void QWidget::setInputMethodHints(Qt::InputMethodHints
hints)
{
#ifndef QT_NO_IM
Q_D(QWidget);
+ if (d->imHints == hints)
+ return;
+
d->imHints = hints;
// Optimization to update input context only it has already been created.
if (d->ic || qApp->d_func()->inputContext) {

For internal bug tracking, please see:
https://projects.maemo.org/bugzilla/show_bug.cgi?id=265172