Adding upstream version 4.2.2.upstream/4.2.2

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 125 insertions, 0 deletions

diff --git a/ui/qt/glib_mainloop_on_qeventloop.cpp b/ui/qt/glib_mainloop_on_qeventloop.cpp
new file mode 100644
index 0000000..f715bbc
--- /dev/null
+++ b/ui/qt/glib_mainloop_on_qeventloop.cpp
@@ -0,0 +1,125 @@
+/** @file
+ *
+ * Copyright 2022 Tomasz Mon <desowin@gmail.com>
+ *
+ * SPDX-License-Identifier: GPL-2.0-or-later
+ */
+
+#include <QTimer>
+#include "glib_mainloop_on_qeventloop.h"
+
+GLibPoller::GLibPoller(GMainContext *context) :
+    mutex_(), dispatched_(),
+    ctx_(context), priority_(0),
+    fds_(g_new(GPollFD, 1)), allocated_fds_(1), nfds_(0)
+{
+    g_main_context_ref(ctx_);
+}
+
+GLibPoller::~GLibPoller()
+{
+    g_main_context_unref(ctx_);
+    g_free(fds_);
+}
+
+void GLibPoller::run()
+{
+    gint timeout;
+
+    mutex_.lock();
+    while (!isInterruptionRequested())
+    {
+        while (!g_main_context_acquire(ctx_))
+        {
+            /* In normal circumstances context is acquired right away */
+        }
+        g_main_context_prepare(ctx_, &priority_);
+        while ((nfds_ = g_main_context_query(ctx_, priority_, &timeout, fds_,
+                                             allocated_fds_)) > allocated_fds_)
+        {
+            g_free(fds_);
+            fds_ = g_new(GPollFD, nfds_);
+            allocated_fds_ = nfds_;
+        }
+        /* Blocking g_poll() call is the reason for separate polling thread */
+        g_poll(fds_, nfds_, timeout);
+        g_main_context_release(ctx_);
+
+        /* Polling has finished, dispatch events (if any) in main thread so we
+         * don't have to worry about concurrency issues in GLib callbacks.
+         */
+        emit polled();
+        /* Wait for the main thread to finish dispatching before next poll */
+        dispatched_.wait(&mutex_);
+    }
+    mutex_.unlock();
+}
+
+GLibMainloopOnQEventLoop::GLibMainloopOnQEventLoop(QObject *parent) :
+    QObject(parent),
+    poller_(g_main_context_default())
+{
+    connect(&poller_, &GLibPoller::polled,
+            this, &GLibMainloopOnQEventLoop::checkAndDispatch);
+    poller_.setObjectName("GLibPoller");
+    poller_.start();
+}
+
+GLibMainloopOnQEventLoop::~GLibMainloopOnQEventLoop()
+{
+    poller_.requestInterruption();
+    /* Wakeup poller thread in case it is blocked on g_poll(). Wakeup does not
+     * cause any problem if poller thread is already waiting on dispatched wait
+     * condition.
+     */
+    g_main_context_wakeup(poller_.ctx_);
+    /* Wakeup poller thread without actually dispatching */
+    poller_.mutex_.lock();
+    poller_.dispatched_.wakeOne();
+    poller_.mutex_.unlock();
+    /* Poller thread will quit, wait for it to avoid warning */
+    poller_.wait();
+}
+
+void GLibMainloopOnQEventLoop::checkAndDispatch()
+{
+    poller_.mutex_.lock();
+    while (!g_main_context_acquire(poller_.ctx_))
+    {
+        /* In normal circumstances context is acquired right away */
+    }
+    if (g_main_depth() > 0)
+    {
+        /* This should not happen, but if it does warn about nested event loops
+         * so the issue can be fixed before the harm is done. To identify root
+         * cause, put breakpoint here and take backtrace when it hits. Look for
+         * calls to exec() and processEvents() functions. Refactor the code so
+         * it does not spin additional event loops.
+         *
+         * Ignoring this warning will lead to very strange and hard to debug
+         * problems in the future.
+         */
+        qWarning("Nested GLib event loop detected");
+    }
+    if (g_main_context_check(poller_.ctx_, poller_.priority_,
+                             poller_.fds_, poller_.nfds_))
+    {
+        g_main_context_dispatch(poller_.ctx_);
+    }
+    g_main_context_release(poller_.ctx_);
+    /* Start next iteration in GLibPoller thread */
+    poller_.dispatched_.wakeOne();
+    poller_.mutex_.unlock();
+}
+
+void GLibMainloopOnQEventLoop::setup(QObject *parent)
+{
+    /* Schedule event loop action so we can check if Qt runs GLib mainloop */
+    QTimer::singleShot(0, [parent]() {
+        if (g_main_depth() == 0)
+        {
+            /* Not running inside GLib mainloop, actually setup */
+            new GLibMainloopOnQEventLoop(parent);
+        }
+    });
+}