[LyX/master] Fix bug #11210

[Enrico Forestieri]

commit 83fc0f924cf30551615ed65c34941d0114e67a4f
Author: Enrico Forestieri <for...@lyx.org>
Date:   Thu Sep 27 21:21:49 2018 +0200

    Fix bug #11210
    
    On Windows, start viewers in detached processes in order to avoid
    a crash of the QProcess destructor when their thread terminates.
    The opening of a console window is avoided by redirecting to the
    null device all standard I/O channels.
---
 src/support/Systemcall.cpp |   32 +++++++++-----------------------
 1 files changed, 9 insertions(+), 23 deletions(-)

diff --git a/src/support/Systemcall.cpp b/src/support/Systemcall.cpp
index e658f91..ae224cb 100644
--- a/src/support/Systemcall.cpp
+++ b/src/support/Systemcall.cpp
@@ -258,28 +258,6 @@ int Systemcall::startscript(Starttype how, string const & 
what,
        SystemcallPrivate d(infile, outfile, errfile);
        bool do_events = process_events || how == WaitLoop;
 
-#ifdef Q_OS_WIN32
-       // QProcess::startDetached cannot provide environment variables. When 
the
-       // environment variables are set using the latexEnvCmdPrefix and the 
process
-       // is started with QProcess::startDetached, a console window is shown 
every
-       // time a viewer is started. To avoid this, we fall back on Windows to 
the
-       // original implementation that creates a QProcess object.
-       d.startProcess(cmd, path, lpath, false);
-       if (!d.waitWhile(SystemcallPrivate::Starting, do_events, -1)) {
-               if (d.state == SystemcallPrivate::Error) {
-                       LYXERR0("Systemcall: '" << cmd << "' did not start!");
-                       LYXERR0("error " << d.errorMessage());
-                       return NOSTART;
-               } else if (d.state == SystemcallPrivate::Killed) {
-                       LYXERR0("Killed: " << cmd);
-                       return KILLED;
-               }
-       }
-       if (how == DontWait) {
-               d.releaseProcess();
-               return OK;
-       }
-#else
        d.startProcess(cmd, path, lpath, how == DontWait);
        if (how == DontWait && d.state == SystemcallPrivate::Running)
                return OK;
@@ -295,7 +273,6 @@ int Systemcall::startscript(Starttype how, string const & 
what,
                        return KILLED;
                }
        }
-#endif
 
        if (!d.waitWhile(SystemcallPrivate::Running, do_events,
                         os::timeout_min() * 60 * 1000)) {
@@ -393,6 +370,15 @@ void SystemcallPrivate::startProcess(QString const & cmd, 
string const & path,
        cmd_ = cmd;
        if (detached) {
                state = SystemcallPrivate::Running;
+#ifdef Q_OS_WIN32
+               // Avoid opening a console window when a viewer is started
+               if (in_file_.empty())
+                       process_->setStandardInputFile(QProcess::nullDevice());
+               if (out_file_.empty())
+                       process_->setStandardOutputFile(QProcess::nullDevice());
+               if (err_file_.empty())
+                       process_->setStandardErrorFile(QProcess::nullDevice());
+#endif
                if (!QProcess::startDetached(toqstr(latexEnvCmdPrefix(path, 
lpath)) + cmd_)) {
                        state = SystemcallPrivate::Error;
                        return;