From d5b054afabc07b528b3e545a00bdc19194c47f98 Mon Sep 17 00:00:00 2001
From: Jan-Marek Glogowski <glogow@fbihome.de>
Date: Wed, 6 Apr 2022 18:59:10 +0200
Subject: [PATCH] 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)
---
 vcl/inc/qt5/Qt5Widget.hxx |  3 +++
 vcl/qt5/Qt5Frame.cxx      |  5 +++--
 vcl/qt5/Qt5Widget.cxx     | 18 +++++++++++++-----
 3 files changed, 19 insertions(+), 7 deletions(-)

diff --git a/vcl/inc/qt5/Qt5Widget.hxx b/vcl/inc/qt5/Qt5Widget.hxx
index 7bf7ead6ae9a..cfdabc4abe01 100644
--- a/vcl/inc/qt5/Qt5Widget.hxx
+++ b/vcl/inc/qt5/Qt5Widget.hxx
@@ -19,6 +19,7 @@
 
 #pragma once
 
+#include <QtCore/QRect>
 #include <QtWidgets/QWidget>
 #include <rtl/ustring.hxx>
 
@@ -36,6 +37,8 @@ class Qt5Widget : public QWidget
 
     Qt5Frame& m_rFrame;
     bool m_bNonEmptyIMPreeditSeen;
+    mutable bool m_bInInputMethodQueryCursorRectangle;
+    mutable QRect m_aImCursorRectangle;
     int m_nDeltaX;
     int m_nDeltaY;
 
diff --git a/vcl/qt5/Qt5Frame.cxx b/vcl/qt5/Qt5Frame.cxx
index 322f293828cd..36c2e6a580d3 100644
--- a/vcl/qt5/Qt5Frame.cxx
+++ b/vcl/qt5/Qt5Frame.cxx
@@ -771,8 +771,9 @@ void Qt5Frame::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/Qt5Widget.cxx b/vcl/qt5/Qt5Widget.cxx
index 02bc22ee3d44..f23646ae781a 100644
--- a/vcl/qt5/Qt5Widget.cxx
+++ b/vcl/qt5/Qt5Widget.cxx
@@ -602,6 +602,7 @@ Qt5Widget::Qt5Widget(Qt5Frame& rFrame, Qt::WindowFlags f)
     : QWidget(Q_NULLPTR, f)
     , m_rFrame(rFrame)
     , m_bNonEmptyIMPreeditSeen(false)
+    , m_bInInputMethodQueryCursorRectangle(false)
     , m_nDeltaX(0)
     , m_nDeltaY(0)
 {
@@ -776,11 +777,18 @@ QVariant Qt5Widget::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:
         {
-- 
2.35.1