[Libreoffice-commits] core.git: Branch 'distro/cib/libreoffice-6-1' - vcl/win

[Jan-Marek Glogowski (via logerrit)]

 vcl/win/window/salframe.cxx |   64 +++++++++++++++++++++++++++++++++++++-------
 1 file changed, 55 insertions(+), 9 deletions(-)

New commits:
commit f5f101b633c598c1dc66c31ea11d15f1a3cb2932
Author:     Jan-Marek Glogowski <jan-marek.glogowski at extern.cib.de>
AuthorDate: Tue Feb 25 10:02:25 2020 +0100
Commit:     Thorsten Behrens <Thorsten.Behrens at CIB.de>
CommitDate: Wed Mar 11 01:12:37 2020 +0100

    WIN prevent deadlock in SetForegroundWindow
    
    As mentioned in various blogs, like Raymon Chens "The old new
    thing", 2008-08-01, "I warned you: The dangers of attaching input
    queues", using AttachThreadInput to steal the input from an other
    thread, so SetForegroundWindow becomes more reliable, can
    deadlock in that call in win32u.dll!NtUserCallHwndLock.
    
    Stackoverflow also has a multitude of suggestions and links in
    "Win32 SetForegroundWindow unreliable", to circumvent Windows
    focus-stealing prevention mechanisms.
    
    A customer is experiencing these hangs reliably and often when
    opening LO windows via Java UNO, because the Window and the UNO
    thread are different and trigger this code path. Removing the
    calls to AttachThreadInput fixes the problem for them. This has
    started lately and nobody really knows why.
    I also know other customers with a similar Java UNO setup, which
    don't experience them.
    
    For better foreground handling, the calling app eventually should
    either use AllowSetForegroundWindow or CoAllowSetForegroundWindow
    (for COM servers), to give up the foreground / input handling.
    
    This is plus:
     WIN add bootstrap var to re-enable foreground hack
    
     We already found a regressed installation from commit
     518c0265efebf39ab6d1e90c4ec4e7cf52b701c6 ("WIN prevent deadlock
     in SetForegroundWindow").
    
     Finding a real fix might be impossible, so this just adds the
     bootstrap.ini boolean variable Win32.EnableAttachThreadInputHack
     to re-enable the previous AttachThreadInput hack on demand.
    
     Reviewed-on: https://gerrit.libreoffice.org/c/core/+/90235
    
    Change-Id: I8de0a17aaaa44c24b1ee728b2ef6ec3aea951c54
    Reviewed-on: https://gerrit.libreoffice.org/c/core/+/89518
    Tested-by: Thorsten Behrens <Thorsten.Behrens at CIB.de>
    Reviewed-by: Thorsten Behrens <Thorsten.Behrens at CIB.de>

diff --git a/vcl/win/window/salframe.cxx b/vcl/win/window/salframe.cxx
index 8b0a64232927..fcb7c3250a27 100644
--- a/vcl/win/window/salframe.cxx
+++ b/vcl/win/window/salframe.cxx
@@ -33,6 +33,12 @@
 
 #include <comphelper/windowserrorstring.hxx>
 
+#include <fstream>
+#include <boost/property_tree/ptree.hpp>
+#include <boost/property_tree/ini_parser.hpp>
+#include <osl/file.hxx>
+#include <osl/process.h>
+
 #include <rtl/string.h>
 #include <rtl/ustring.h>
 
@@ -1919,23 +1925,63 @@ void WinSalFrame::SetAlwaysOnTop( bool bOnTop )
     SetWindowPos( mhWnd, hWnd, 0, 0, 0, 0, SWP_NOMOVE | SWP_NOSIZE | SWP_NOACTIVATE );
 }
 
+static bool EnableAttachThreadInputHack()
+{
+    OUString aBootstrapUri;
+    if (osl_getProcessWorkingDir(&aBootstrapUri.pData) != osl_Process_E_None)
+        return false;
+    aBootstrapUri += "/bootstrap.ini";
+
+    OUString aSystemFileName;
+    if (osl::FileBase::getSystemPathFromFileURL(aBootstrapUri, aSystemFileName) != osl::FileBase::E_None)
+        return false;
+    if (aSystemFileName.getLength() > MAX_PATH)
+        return false;
+
+    // this uses the Boost ini parser, instead of tools::Config, as we already use it to read other
+    // values from bootstrap.ini in desktop/win32/source/loader.cxx, because that watchdog process
+    // can't access LO libs. This way the handling is consistent.
+    try
+    {
+        boost::property_tree::ptree pt;
+        std::ifstream aFile(o3tl::toW(aSystemFileName.getStr()));
+        boost::property_tree::ini_parser::read_ini(aFile, pt);
+        const bool bEnabled = pt.get("Win32.EnableAttachThreadInputHack", false);
+        SAL_WARN_IF(bEnabled, "vcl", "AttachThreadInput hack is enabled. Watch out for deadlocks!");
+        return bEnabled;
+    }
+    catch (...)
+    {
+        return false;
+    }
+}
+
 static void ImplSalToTop( HWND hWnd, SalFrameToTop nFlags )
 {
+    static const bool bEnableAttachThreadInputHack = EnableAttachThreadInputHack();
+
     WinSalFrame* pToTopFrame = GetWindowPtr( hWnd );
     if( pToTopFrame && (pToTopFrame->mnStyle & SalFrameStyleFlags::SYSTEMCHILD) )
         BringWindowToTop( hWnd );
 
     if ( nFlags & SalFrameToTop::ForegroundTask )
     {
-        // This magic code is necessary to connect the input focus of the
-        // current window thread and the thread which owns the window that
-        // should be the new foreground window.
-        HWND   hCurrWnd     = GetForegroundWindow();
-        DWORD  myThreadID   = GetCurrentThreadId();
-        DWORD  currThreadID = GetWindowThreadProcessId(hCurrWnd,nullptr);
-        AttachThreadInput(myThreadID, currThreadID,TRUE);
-        SetForegroundWindow_Impl(hWnd);
-        AttachThreadInput(myThreadID,currThreadID,FALSE);
+        // LO used to always call AttachThreadInput here, which resulted in deadlocks
+        // in some installations for unknown reasons!
+        if (bEnableAttachThreadInputHack)
+        {
+            // This magic code is necessary to connect the input focus of the
+            // current window thread and the thread which owns the window that
+            // should be the new foreground window.
+            HWND hCurrWnd = GetForegroundWindow();
+            DWORD myThreadID = GetCurrentThreadId();
+            DWORD currThreadID = GetWindowThreadProcessId(hCurrWnd,nullptr);
+            AttachThreadInput(myThreadID, currThreadID, TRUE);
+            SetForegroundWindow_Impl(hWnd);
+            AttachThreadInput(myThreadID, currThreadID, FALSE);
+        }
+        else
+            SetForegroundWindow_Impl(hWnd);
     }
 
     if ( nFlags & SalFrameToTop::RestoreWhenMin )