From c853ffb5b2f75f5a889ed2e3ef89b818a736e87a Mon Sep 17 00:00:00 2001
From: Daniel Baumann <daniel.baumann@progress-linux.org>
Date: Sat, 13 Apr 2024 13:50:49 +0200
Subject: Adding upstream version 1.3+ds.

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>
---
 src/async/channel.h | 184 ++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 184 insertions(+)
 create mode 100644 src/async/channel.h

(limited to 'src/async/channel.h')

diff --git a/src/async/channel.h b/src/async/channel.h
new file mode 100644
index 0000000..d58841e
--- /dev/null
+++ b/src/async/channel.h
@@ -0,0 +1,184 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/** \file Channel
+ * Thread-safe communication channel for asyncs.
+ */
+#ifndef INKSCAPE_ASYNC_CHANNEL_H
+#define INKSCAPE_ASYNC_CHANNEL_H
+
+#include <memory>
+#include <optional>
+#include <mutex>
+#include <utility>
+#include <glibmm/dispatcher.h>
+#include "util/funclog.h"
+
+namespace Inkscape {
+namespace Async {
+namespace Channel {
+namespace detail {
+
+class Shared final
+    : public std::enable_shared_from_this<Shared>
+{
+public:
+    Shared()
+    {
+        dispatcher->connect([this] {
+            auto ref = shared_from_this();
+            grab().exec_while([this] { return is_open; });
+        });
+    }
+
+    Shared(Shared const &) = delete;
+    Shared &operator=(Shared const &) = delete;
+
+    operator bool() const
+    {
+        auto g = std::lock_guard(mutables);
+        return is_open;
+    }
+
+    template <typename F>
+    bool run(F &&f) const
+    {
+        auto g = std::lock_guard(mutables);
+        if (!is_open) return false;
+        if (funclog.empty()) dispatcher->emit();
+        funclog.emplace(std::forward<F>(f));
+        return true;
+    }
+
+    void close()
+    {
+        disconnect_source();
+        dispatcher.reset();
+        funclog.clear();
+    }
+
+private:
+    mutable std::mutex mutables;
+    mutable std::optional<Glib::Dispatcher> dispatcher = std::make_optional<Glib::Dispatcher>();
+    mutable Util::FuncLog funclog;
+    bool is_open = true;
+
+    Util::FuncLog grab() const
+    {
+        auto g = std::lock_guard(mutables);
+        return std::move(funclog);
+    }
+
+    void disconnect_source()
+    {
+        auto g = std::lock_guard(mutables);
+        is_open = false;
+    }
+};
+
+struct Create;
+
+} // namespace detail
+
+class Source final
+{
+public:
+    Source() = default;
+    Source(Source const &) = delete;
+    Source &operator=(Source const &) = delete;
+    Source(Source &&) = default;
+    Source &operator=(Source &&) = default;
+
+    /**
+     * Check whether the channel is still open.
+     */
+    explicit operator bool() const { return shared && shared->operator bool(); }
+
+    /**
+     * Attempt to run a function on the main loop that the Channel was created in. This will
+     * either succeed and execute or destroy the function in the main loop's thread, or fail and
+     * leave it untouched.
+     *
+     * \return Whether the Channel is still open at the time of calling.
+     *
+     * Note that a return value of true doesn't indicate whether the function will actually run,
+     * because the Channel could be closed in the meantime. If it does run, it is guaranteed the
+     * Dest object still exists and \a close() has not been called on it.
+     */
+    template <typename F>
+    bool run(F &&f) const { return shared && shared->run(std::forward<F>(f)); }
+
+    /**
+     * Close the channel. No more functions submitted through run() will be run.
+     */
+    void close() { shared.reset(); }
+
+private:
+    std::shared_ptr<detail::Shared const> shared;
+    explicit Source(std::shared_ptr<detail::Shared> shared_) : shared(std::move(shared_)) {}
+    friend struct detail::Create;
+};
+
+class Dest final
+{
+public:
+    Dest() = default;
+    Dest(Dest const &) = delete;
+    Dest &operator=(Dest const &) = delete;
+    Dest(Dest &&) = default;
+    Dest &operator=(Dest &&) = default;
+    ~Dest() { close(); }
+
+    /**
+     * Close the channel. No further functions submitted by the other end will be run, and it will
+     * be notified of closure whenever it checks.
+     */
+    void close() { if (shared) { shared->close(); shared.reset(); } }
+
+    /**
+     * Check whether \a close() has already been called, or if the channel was never opened.
+     *
+     * Note: This does not check whether the corresponding \a close() method of Source has been
+     * called. In fact, this condition is meaningless without further synchronization. If you need
+     * to know whether the Source has closed, you can have it manually send this information
+     * over the Channel instead.
+     */
+    explicit operator bool() const { return (bool)shared; }
+
+private:
+    std::shared_ptr<detail::Shared> shared;
+    explicit Dest(std::shared_ptr<detail::Shared> shared_) : shared(std::move(shared_)) {}
+    friend struct detail::Create;
+};
+
+namespace detail {
+
+struct Create
+{
+    Create() = delete;
+
+    static auto create()
+    {
+        auto shared = std::make_shared<detail::Shared>();
+        auto src = Source(shared);
+        auto dst = Dest(std::move(shared));
+        return std::make_pair(std::move(src), std::move(dst));
+    }
+};
+
+} // namespace detail
+
+/**
+ * Create a linked Source - Destination pair forming a thread-safe communication channel.
+ *
+ * As long as the channel is still open, the Source can use it to run commands in the main loop of
+ * the creation thread and check if the channel is still open. Destructing either end closes the channel.
+ */
+inline std::pair<Source, Dest> create()
+{
+    return detail::Create::create();
+}
+
+} // namespace Channel
+} // namespace Async
+} // namespace Inkscape
+
+#endif // INKSCAPE_ASYNC_CHANNEL_H
-- 
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