tdf#143135 Qt break recursive IM QueryCursorRect

To reproduce the Impress crash, you need an IM, e.g. fcitx / ibus.
This is triggered by having an active input, like double-clicking
one of a presentations text fields, then leaving the window and
switching back to it.

This results in a stack exhaustion in a few seconds. The backtrace
is basically:

QWidget::setFocus
QtFrame::ToTop
sd::Window::GrabFocus
ImplHandleExtTextInputPos
QtWidget::inputMethodQuery
QInputMethod::cursorRectangle
QWidget::setFocus
QApplication::setActiveWindow
QtInstance::DoYield
main

I scratched my head over the longer backtrace for while, but there
seems to be no good way to prevent this from LO's POV. The only
alternative from the Qt VCL plugin is QtFrame::ToTop. That code
is less ugly (no mutable or cached result), but QtWidget::
inputMethodQuery is earlier in the backtrace.

Change-Id: Ief3a8e44bca295cc676e75050d52d70a1da98a88
Reviewed-on: https://gerrit.libreoffice.org/c/core/+/132643
Tested-by: Jenkins
Reviewed-by: Michael Weghorn <m.weghorn@posteo.de>
Reviewed-by: Jan-Marek Glogowski <glogow@fbihome.de>
(cherry picked from commit e81385277c091dabb1f6542a94229d7dcc77289b)
Reviewed-on: https://gerrit.libreoffice.org/c/core/+/132612

3 files changed, 19 insertions, 7 deletions

diff --git a/vcl/inc/qt5/QtWidget.hxx b/vcl/inc/qt5/QtWidget.hxx
index 801cd290ff88..e2a22d3c9f18 100644
--- a/vcl/inc/qt5/QtWidget.hxx
+++ b/vcl/inc/qt5/QtWidget.hxx
@@ -19,6 +19,7 @@
 
 #pragma once
 
+#include <QtCore/QRect>
 #include <QtWidgets/QWidget>
 #include <rtl/ustring.hxx>
 
@@ -36,6 +37,8 @@ class QtWidget : public QWidget
 
     QtFrame& m_rFrame;
     bool m_bNonEmptyIMPreeditSeen;
+    mutable bool m_bInInputMethodQueryCursorRectangle;
+    mutable QRect m_aImCursorRectangle;
     int m_nDeltaX;
     int m_nDeltaY;
 
diff --git a/vcl/qt5/QtFrame.cxx b/vcl/qt5/QtFrame.cxx
index ad9c03d0bfa1..bcd95494dabd 100644
--- a/vcl/qt5/QtFrame.cxx
+++ b/vcl/qt5/QtFrame.cxx
@@ -795,8 +795,9 @@ void QtFrame::ToTop(SalFrameToTop nFlags)
         pWidget->activateWindow();
     else if ((nFlags & SalFrameToTop::GrabFocus) || (nFlags & SalFrameToTop::GrabFocusOnly))
     {
-        pWidget->activateWindow();
-        pWidget->setFocus();
+        if (!(nFlags & SalFrameToTop::GrabFocusOnly))
+            pWidget->activateWindow();
+        pWidget->setFocus(Qt::OtherFocusReason);
     }
 }
 
diff --git a/vcl/qt5/QtWidget.cxx b/vcl/qt5/QtWidget.cxx
index 86431a3488b1..ab8bf2dc0017 100644
--- a/vcl/qt5/QtWidget.cxx
+++ b/vcl/qt5/QtWidget.cxx
@@ -623,6 +623,7 @@ QtWidget::QtWidget(QtFrame& rFrame, Qt::WindowFlags f)
     : QWidget(Q_NULLPTR, f)
     , m_rFrame(rFrame)
     , m_bNonEmptyIMPreeditSeen(false)
+    , m_bInInputMethodQueryCursorRectangle(false)
     , m_nDeltaX(0)
     , m_nDeltaY(0)
 {
@@ -796,11 +797,18 @@ QVariant QtWidget::inputMethodQuery(Qt::InputMethodQuery property) const
         }
         case Qt::ImCursorRectangle:
         {
-            const qreal fRatio = m_rFrame.devicePixelRatioF();
-            SalExtTextInputPosEvent aPosEvent;
-            m_rFrame.CallCallback(SalEvent::ExtTextInputPos, &aPosEvent);
-            return QVariant(QRect(aPosEvent.mnX / fRatio, aPosEvent.mnY / fRatio,
-                                  aPosEvent.mnWidth / fRatio, aPosEvent.mnHeight / fRatio));
+            if (!m_bInInputMethodQueryCursorRectangle)
+            {
+                m_bInInputMethodQueryCursorRectangle = true;
+                SalExtTextInputPosEvent aPosEvent;
+                m_rFrame.CallCallback(SalEvent::ExtTextInputPos, &aPosEvent);
+                const qreal fRatio = m_rFrame.devicePixelRatioF();
+                m_aImCursorRectangle.setRect(aPosEvent.mnX / fRatio, aPosEvent.mnY / fRatio,
+                                             aPosEvent.mnWidth / fRatio,
+                                             aPosEvent.mnHeight / fRatio);
+                m_bInInputMethodQueryCursorRectangle = false;
+            }
+            return QVariant(m_aImCursorRectangle);
         }
         case Qt::ImAnchorPosition:
         {