[LyX/master] Reduce the amount of needed boost headers

Yuriy Skalko yuriy.skalko at gmail.com
Sun Dec 13 08:32:38 UTC 2020


> Compiles fine adding
>         #include <cstring>
> in src/support/ForkedCalls.cpp
> and
>         #include <unistd.h>
> in src/Sever.cpp
> 
>         Kornel


Kornel, thanks for trying and fixing the patch!

Seems like these headers were indirectly included via boost/signal.hpp 
-- I've already had to add <list> includes. I've moved <unistd.h> 
include into conditional branch since it is unavailable in MSVC.


Yuriy
-------------- next part --------------
From 14dca35b76a3b90fc23f82854663e5edf6862ec3 Mon Sep 17 00:00:00 2001
From: Yuriy Skalko <yuriy.skalko at gmail.com>
Date: Sat, 12 Dec 2020 17:36:22 +0200
Subject: [PATCH] Use new signal library `nod` instead of `boost::signals2`

---
 3rdparty/Makefile.am               |   6 +-
 3rdparty/nod/Makefile.am           |   3 +
 3rdparty/nod/README.md             | 257 +++++++++++
 3rdparty/nod/nod.hpp               | 680 +++++++++++++++++++++++++++++
 CMakeLists.txt                     |   2 +
 src/Server.cpp                     |   8 +-
 src/graphics/GraphicsConverter.cpp |  27 +-
 src/graphics/GraphicsConverter.h   |   6 +-
 src/graphics/GraphicsLoader.cpp    |   1 +
 src/graphics/PreviewLoader.cpp     |  19 +-
 src/graphics/PreviewLoader.h       |   7 +-
 src/support/ForkedCalls.cpp        |   2 +
 src/support/signals.h              |   4 +-
 13 files changed, 981 insertions(+), 41 deletions(-)
 create mode 100644 3rdparty/nod/Makefile.am
 create mode 100644 3rdparty/nod/README.md
 create mode 100644 3rdparty/nod/nod.hpp

diff --git a/3rdparty/Makefile.am b/3rdparty/Makefile.am
index ec12adb883..8a205fdff1 100644
--- a/3rdparty/Makefile.am
+++ b/3rdparty/Makefile.am
@@ -1,6 +1,6 @@
 include $(top_srcdir)/config/common.am
 
-DIST_SUBDIRS = boost dtl hunspell mythes libiconv zlib
+DIST_SUBDIRS = boost dtl hunspell mythes libiconv zlib nod
 
 if USE_INCLUDED_BOOST
 BOOST = boost
@@ -26,7 +26,9 @@ if BUILD_INCLUDED_DTL
 DTL=dtl
 endif
 
-SUBDIRS = $(BOOST) $(DTL) $(HUNSPELL) $(MYTHES) $(ICONV) $(ZLIB)
+NOD=nod
+
+SUBDIRS = $(BOOST) $(DTL) $(HUNSPELL) $(MYTHES) $(ICONV) $(ZLIB) $(NOD)
 
 EXTRA_DIST = \
 	scripts/evince_sync/evince_backward_search \
diff --git a/3rdparty/nod/Makefile.am b/3rdparty/nod/Makefile.am
new file mode 100644
index 0000000000..1b73dffdd9
--- /dev/null
+++ b/3rdparty/nod/Makefile.am
@@ -0,0 +1,3 @@
+include $(top_srcdir)/config/common.am
+
+EXTRA_DIST = README.md
diff --git a/3rdparty/nod/README.md b/3rdparty/nod/README.md
new file mode 100644
index 0000000000..0cf74f1d4f
--- /dev/null
+++ b/3rdparty/nod/README.md
@@ -0,0 +1,257 @@
+# Nod
+[![Build Status](https://travis-ci.org/fr00b0/nod.svg?branch=master)](https://travis-ci.org/fr00b0/nod)
+[![GitHub tag](https://img.shields.io/github/tag/fr00b0/nod.svg?label=version)](https://github.com/fr00b0/nod/releases)
+
+Dependency free, header only signals and slot library implemented with C++11.
+
+## Usage
+
+### Simple usage
+The following example creates a signal and then connects a lambda as a slot.
+
+```cpp
+// Create a signal which accepts slots with no arguments and void return value.
+nod::signal<void()> signal;
+// Connect a lambda slot that writes "Hello, World!" to stdout
+signal.connect([](){
+		std::cout << "Hello, World!" << std::endl;
+	});
+// Call the slots
+signal();
+```
+
+### Connecting multiple slots
+If multiple slots are connected to the same signal, all of the slots will be
+called when the signal is invoked. The slots will be called in the same order
+as they where connected.
+
+```cpp
+void endline() {
+	std::cout << std::endl;
+}
+
+// Create a signal
+nod::signal<void()> signal;
+// Connect a lambda that prints a message
+signal.connect([](){
+		std::cout << "Message without endline!";
+	});
+// Connect a function that prints a endline
+signal.connect(endline);
+
+// Call the slots
+signal();
+```
+
+#### Slot type
+The signal types in the library support connection of the same types that is
+supported by `std::function<T>`.
+
+### Slot arguments
+When a signal calls it's connected slots, any arguments passed to the signal
+are propagated to the slots. To make this work, we do need to specify the 
+signature of the signal to accept the arguments.
+
+```cpp
+void print_sum( int x, int y ) {
+	std::cout << x << "+" << y << "=" << (x+y) << std::endl;
+}
+void print_product( int x, int y ) {
+	std::cout << x << "*" << y << "=" << (x*y) << std::endl;
+}
+
+
+// We create a signal with two integer arguments.
+nod::signal<void(int,int)> signal;
+// Let's connect our slot
+signal.connect( print_sum );
+signal.connect( print_product );
+
+// Call the slots
+signal(10, 15);
+signal(-5, 7);	
+
+```
+
+### Disconnecting slots
+There are many circumstances where the programmer needs to diconnect a slot that
+no longer want to recieve events from the signal. This can be really important
+if the lifetime of the slots are shorter than the lifetime of the signal. That
+could cause the signal to call slots that have been destroyed but not
+disconnected, leading to undefined behaviour and probably segmentation faults.
+
+When a slot is connected, the return value from the  `connect` method returns
+an instance of the class `nod::connection`, that can be used to disconnect
+that slot.
+
+```cpp
+// Let's create a signal
+nod::signal<void()> signal;
+// Connect a slot, and save the connection
+nod::connection connection = signal.connect([](){
+								 std::cout << "I'm connected!" << std::endl;
+							 });
+// Triggering the signal will call the slot
+signal();
+// Now we disconnect the slot
+connection.disconnect();
+// Triggering the signal will no longer call the slot
+signal();
+```	
+
+### Scoped connections
+To assist in disconnecting slots, one can use the class `nod::scoped_connection`
+to capture a slot connection. A scoped connection will automatically disconnect
+the slot when the connection object goes out of scope.
+
+```cpp
+// We create a signal
+nod::signal<void()> signal;
+// Let's use a scope to control lifetime
+{ 
+	// Let's save the connection in a scoped_connection
+	nod::scoped_connection connection =
+		signal.connect([](){
+			std::cout << "This message should only be emitted once!" << std::endl; 
+		});
+	// If we trigger the signal, the slot will be called
+	signal();
+} // Our scoped connection is destructed, and disconnects the slot
+// Triggering the signal now will not call the slot
+signal();	
+```
+
+### Slot return values
+
+#### Accumulation of return values
+It is possible for slots to have a return value. The return values can be
+returned from the signal using a *accumulator*, which is a function object that
+acts as a proxy object that processes the slot return values. When triggering a
+signal through a accumulator, the accumulator gets called for each slot return
+value, does the desired accumulation and then return the result to the code
+triggering the signal. The accumulator is designed to work in a similar way as 
+the STL numerical algorithm `std::accumulate`.
+
+```cpp
+// We create a singal with slots that return a value
+nod::signal<int(int, int)> signal;
+// Then we connect some signals
+signal.connect( std::plus<int>{} );
+signal.connect( std::multiplies<int>{} );
+signal.connect( std::minus<int>{} );		
+// Let's say we want to calculate the sum of all the slot return values
+// when triggering the singal with the parameters 10 and 100.
+// We do this by accumulating the return values with the initial value 0
+// and a plus function object, like so:
+std::cout << "Sum: " << signal.accumulate(0, std::plus<int>{})(10,100) << std::endl;
+// Or accumulate by multiplying (this needs 1 as initial value):
+std::cout << "Product: " << signal.accumulate(1, std::multiplies<int>{})(10,100) << std::endl;
+// If we instead want to build a vector with all the return values
+// we can accumulate them this way (start with a empty vector and add each value):			
+auto vec = signal.accumulate( std::vector<int>{}, []( std::vector<int> result, int value ) {
+		result.push_back( value );
+		return result;
+	})(10,100);
+
+std::cout << "Vector: ";
+for( auto const& element : vec ) {
+	std::cout << element << " "; 
+}
+std::cout << std::endl;
+```
+#### Aggregation
+As we can see from the previous example, we can use the `accumulate` method if
+we want to aggregate all the return values of the slots. Doing the aggregation
+that way is not very optimal. It is both a inefficient algorithm for doing
+aggreagtion to a container, and it obscures the call site as the caller needs to
+express the aggregation using the verb *accumulate*. To remedy these
+shortcomings we can turn to the method `aggregate` instead. This is a template
+method, taking the type of container to aggregate to as a template parameter.
+
+```cpp
+// We create a singal
+nod::signal<int(int, int)> signal;
+// Let's connect some slots
+signal.connect( std::plus<int>{} );
+signal.connect( std::multiplies<int>{} );
+signal.connect( std::minus<int>{} );
+// We can now trigger the signal and aggregate the slot return values
+auto vec = signal.aggregate<std::vector<int>>(10,100);
+
+std::cout << "Result: ";
+for( auto const& element : vec ) {
+	std::cout << element << " "; 
+}
+std::cout << std::endl;
+```
+
+## Thread safety
+There are two types of signals in the library. The first is `nod::signal<T>`
+which is safe to use in a multi threaded environment. Multiple threads can read,
+write, connect slots and disconnect slots simultaneously, and the signal will 
+provide the nessesary synchronization. When triggering a slignal, all the
+registered slots will be called and executed by the thread that triggered the
+signal.
+
+The second type of signal is `nod::unsafe_signal<T>` which is **not** safe to
+use in a multi threaded environment. No syncronization will be performed on the
+internal state of the signal. Instances of the signal should theoretically be
+safe to read from multiple thread simultaneously, as long as no thread is
+writing to the same object at the same time. There can be a performance gain
+involved in using the unsafe version of a signal, since no syncronization
+primitives will be used.
+
+`nod::connection` and `nod::scoped_connection` are thread safe for reading from
+multiple threads, as long as no thread is writing to the same object. Writing in
+this context means calling any non const member function, including destructing
+the object. If an object is being written by one thread, then all reads and
+writes to that object from the same or other threads needs to be prevented.
+This basically means that a connection is only allowed to be disconnected from
+one thread, and you should not check connection status or reassign the
+connection while it is being disconnected.
+
+## Building the tests
+The test project uses [premake5](https://premake.github.io/download.html) to 
+generate make files or similiar.
+
+### Linux
+To build and run the tests using gcc and gmake on linux, execute the following
+from the test directory:
+```bash
+premake5 gmake
+make -C build/gmake
+bin/gmake/debug/nod_tests
+```
+
+### Visual Studio 2013
+To build and run the tests, execute the following from the test directory:
+
+```batchfile
+REM Adjust paths to suite your environment
+c:\path\to\premake\premake5.exe vs2013
+"c:\Program Files (x86)\Microsoft Visual Studio 12.0\Common7\Tools\vsvars32.bat"
+msbuild /m build\vs2013\nod_tests.sln
+bin\vs2013\debug\nod_tests.exe
+```
+
+## The MIT License (MIT)
+
+Copyright (c) 2015 Fredrik Berggren
+
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files (the "Software"), to deal
+in the Software without restriction, including without limitation the rights
+to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all
+copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+SOFTWARE.
diff --git a/3rdparty/nod/nod.hpp b/3rdparty/nod/nod.hpp
new file mode 100644
index 0000000000..5c4a93cb85
--- /dev/null
+++ b/3rdparty/nod/nod.hpp
@@ -0,0 +1,680 @@
+#ifndef IG_NOD_INCLUDE_NOD_HPP
+#define IG_NOD_INCLUDE_NOD_HPP
+
+#include <vector>       // std::vector
+#include <functional>   // std::function
+#include <mutex>        // std::mutex, std::lock_guard
+#include <memory>       // std::shared_ptr, std::weak_ptr
+#include <algorithm>    // std::find_if()
+#include <cassert>      // assert()
+#include <thread>       // std::this_thread::yield()
+#include <type_traits>  // std::is_same
+#include <iterator>     // std::back_inserter
+
+namespace nod {
+	// implementational details
+	namespace detail {
+		/// Interface for type erasure when disconnecting slots
+		struct disconnector {
+			virtual void operator()( std::size_t index ) const = 0;
+		};
+		/// Deleter that doesn't delete
+		inline void no_delete(disconnector*){
+		};
+	} // namespace detail
+
+	/// Base template for the signal class
+	template <class P, class T>
+	class signal_type;
+
+
+	/// Connection class.
+	///
+	/// This is used to be able to disconnect slots after they have been connected.
+	/// Used as return type for the connect method of the signals.
+	///
+	/// Connections are default constructible.
+	/// Connections are not copy constructible or copy assignable.
+	/// Connections are move constructible and move assignable.
+	///
+	class connection {
+		public:
+			/// Default constructor
+			connection() :
+				_index()
+			{}
+
+			// Connection are not copy constructible or copy assignable
+			connection( connection const& ) = delete;
+			connection& operator=( connection const& ) = delete;
+
+			/// Move constructor
+			/// @param other   The instance to move from.
+			connection( connection&& other ) :
+				_weak_disconnector( std::move(other._weak_disconnector) ),
+				_index( other._index )
+			{}
+
+			/// Move assign operator.
+			/// @param other   The instance to move from.
+			connection& operator=( connection&& other ) {
+				_weak_disconnector = std::move( other._weak_disconnector );
+				_index = other._index;
+				return *this;
+			}
+
+			/// @returns `true` if the connection is connected to a signal object,
+			///          and `false` otherwise.
+			bool connected() const {
+				return !_weak_disconnector.expired();
+			}
+
+			/// Disconnect the slot from the connection.
+			///
+			/// If the connection represents a slot that is connected to a signal object, calling
+			/// this method will disconnect the slot from that object. The result of this operation
+			/// is that the slot will stop receiving calls when the signal is invoked.
+			void disconnect();
+
+		private:
+			/// The signal template is a friend of the connection, since it is the
+			/// only one allowed to create instances using the meaningful constructor.
+			template<class P,class T> friend class signal_type;
+
+			/// Create a connection.
+			/// @param shared_disconnector   Disconnector instance that will be used to disconnect
+			///                              the connection when the time comes. A weak pointer
+			///                              to the disconnector will be held within the connection
+			///                              object.
+			/// @param index                 The slot index of the connection.
+			connection( std::shared_ptr<detail::disconnector> const& shared_disconnector, std::size_t index ) :
+				_weak_disconnector( shared_disconnector ),
+				_index( index )
+			{}
+
+			/// Weak pointer to the current disconnector functor.
+			std::weak_ptr<detail::disconnector> _weak_disconnector;
+			/// Slot index of the connected slot.
+			std::size_t _index;
+	};
+
+	/// Scoped connection class.
+	///
+	/// This type of connection is automatically disconnected when
+	/// the connection object is destructed.
+	///
+	class scoped_connection
+	{
+		public:
+			/// Scoped are default constructible
+			scoped_connection() = default;
+			/// Scoped connections are not copy constructible
+			scoped_connection( scoped_connection const& ) = delete;
+			/// Scoped connections are not copy assingable
+			scoped_connection& operator=( scoped_connection const& ) = delete;
+
+			/// Move constructor
+			scoped_connection( scoped_connection&& other ) :
+				_connection( std::move(other._connection) )
+			{}
+
+			/// Move assign operator.
+			/// @param other   The instance to move from.
+			scoped_connection& operator=( scoped_connection&& other ) {
+				reset( std::move( other._connection ) );
+				return *this;
+			}
+
+			/// Construct a scoped connection from a connection object
+			/// @param connection   The connection object to manage
+			scoped_connection( connection&& c ) :
+				_connection( std::forward<connection>(c) )
+			{}
+
+			/// destructor
+			~scoped_connection() {
+				disconnect();
+			}
+
+			/// Assignment operator moving a new connection into the instance.
+			/// @note If the scoped_connection instance already contains a
+			///       connection, that connection will be disconnected as if
+			///       the scoped_connection was destroyed.
+			/// @param c   New connection to manage
+			scoped_connection& operator=( connection&& c ) {
+				reset( std::forward<connection>(c) );
+				return *this;
+			}
+
+			/// Reset the underlying connection to another connection.
+			/// @note The connection currently managed by the scoped_connection
+			///       instance will be disconnected when resetting.
+			/// @param c   New connection to manage
+			void reset( connection&& c = {} ) {
+				disconnect();
+				_connection = std::move(c);
+			}
+
+			/// Release the underlying connection, without disconnecting it.
+			/// @returns The newly released connection instance is returned.
+			connection release() {
+				connection c = std::move(_connection);
+				_connection = connection{};
+				return c;
+			}
+
+			///
+			/// @returns `true` if the connection is connected to a signal object,
+			///          and `false` otherwise.
+			bool connected() const {
+				return _connection.connected();
+			}
+
+			/// Disconnect the slot from the connection.
+			///
+			/// If the connection represents a slot that is connected to a signal object, calling
+			/// this method will disconnect the slot from that object. The result of this operation
+			/// is that the slot will stop receiving calls when the signal is invoked.
+			void disconnect() {
+				_connection.disconnect();
+			}
+
+		private:
+			/// Underlying connection object
+			connection _connection;
+	};
+
+	/// Policy for multi threaded use of signals.
+	///
+	/// This policy provides mutex and lock types for use in
+	/// a multithreaded environment, where signals and slots
+	/// may exists in different threads.
+	///
+	/// This policy is used in the `nod::signal` type provided
+	/// by the library.
+	struct multithread_policy
+	{
+		using mutex_type = std::mutex;
+		using mutex_lock_type = std::unique_lock<mutex_type>;
+		/// Function that yields the current thread, allowing
+		/// the OS to reschedule.
+		static void yield_thread() {
+			std::this_thread::yield();
+		}
+		/// Function that defers a lock to a lock function that prevents deadlock
+		static mutex_lock_type defer_lock(mutex_type & m){
+			return mutex_lock_type{m, std::defer_lock};
+		}
+		/// Function that locks two mutexes and prevents deadlock
+		static void lock(mutex_lock_type & a,mutex_lock_type & b) {
+			std::lock(a,b);
+		}
+	};
+
+	/// Policy for single threaded use of signals.
+	///
+	/// This policy provides dummy implementations for mutex
+	/// and lock types, resulting in that no synchronization
+	/// will take place.
+	///
+	/// This policy is used in the `nod::unsafe_signal` type
+	/// provided by the library.
+	struct singlethread_policy
+	{
+		/// Dummy mutex type that doesn't do anything
+		struct mutex_type{};
+		/// Dummy lock type, that doesn't do any locking.
+		struct mutex_lock_type
+		{
+			/// A lock type must be constructible from a
+			/// mutex type from the same thread policy.
+			explicit mutex_lock_type( mutex_type const& ) {
+			}
+		};
+		/// Dummy implementation of thread yielding, that
+		/// doesn't do any actual yielding.
+		static void yield_thread() {
+		}
+		/// Dummy implemention of defer_lock that doesn't
+		/// do anything
+		static mutex_lock_type defer_lock(mutex_type &m){
+			return mutex_lock_type{m};
+		}
+		/// Dummy implemention of lock that doesn't
+		/// do anything
+		static void lock(mutex_lock_type &,mutex_lock_type &) {
+		}
+	};
+
+	/// Signal accumulator class template.
+	///
+	/// This acts sort of as a proxy for triggering a signal and
+	/// accumulating the slot return values.
+	///
+	/// This class is not really intended to instantiate by client code.
+	/// Instances are aquired as return values of the method `accumulate()`
+	/// called on signals.
+	///
+	/// @tparam S      Type of signal. The signal_accumulator acts
+	///                as a type of proxy for a signal instance of
+	///                this type.
+	/// @tparam T      Type of initial value of the accumulate algorithm.
+	///                This type must meet the requirements of `CopyAssignable`
+	///                and `CopyConstructible`
+	/// @tparam F      Type of accumulation function.
+	/// @tparam A...   Argument types of the underlying signal type.
+	///
+	template <class S, class T, class F, class...A>
+	class signal_accumulator
+	{
+		public:
+			/// Result type when calling the accumulating function operator.
+			using result_type = typename std::result_of<F(T, typename S::slot_type::result_type)>::type;
+
+			/// Construct a signal_accumulator as a proxy to a given signal
+			//
+			/// @param signal   Signal instance.
+			/// @param init     Initial value of the accumulate algorithm.
+			/// @param func     Binary operation function object that will be
+			///                 applied to all slot return values.
+			///                 The signature of the function should be
+			///                 equivalent of the following:
+			///                   `R func( T1 const& a, T2 const& b )`
+			///                  - The signature does not need to have `const&`.
+			///                  - The initial value, type `T`, must be implicitly
+			///                    convertible to `R`
+			///                  - The return type `R` must be implicitly convertible
+			///                    to type `T1`.
+			///                  - The type `R` must be `CopyAssignable`.
+			///                  - The type `S::slot_type::result_type` (return type of
+			///                    the signals slots) must be implicitly convertible to
+			///                    type `T2`.
+			signal_accumulator( S const& signal, T init, F func ) :
+				_signal( signal ),
+				_init( init ),
+				_func( func )
+			{}
+
+			/// Function call operator.
+			///
+			/// Calling this will trigger the underlying signal and accumulate
+			/// all of the connected slots return values with the current
+			/// initial value and accumulator function.
+			///
+			/// When called, this will invoke the accumulator function will
+			/// be called for each return value of the slots. The semantics
+			/// are similar to the `std::accumulate` algorithm.
+			///
+			/// @param args   Arguments to propagate to the slots of the
+			///               underlying when triggering the signal.
+			result_type operator()( A const& ... args ) const {
+				return _signal.trigger_with_accumulator( _init, _func, args... );
+			}
+
+		private:
+
+			/// Reference to the underlying signal to proxy.
+			S const& _signal;
+			/// Initial value of the accumulate algorithm.
+			T _init;
+			/// Accumulator function.
+			F _func;
+
+	};
+
+	/// Signal template specialization.
+	///
+	/// This is the main signal implementation, and it is used to
+	/// implement the observer pattern whithout the overhead
+	/// boilerplate code that typically comes with it.
+	///
+	/// Any function or function object is considered a slot, and
+	/// can be connected to a signal instance, as long as the signature
+	/// of the slot matches the signature of the signal.
+	///
+	/// @tparam P      Threading policy for the signal.
+	///                A threading policy must provide two type definitions:
+	///                 - P::mutex_type, this type will be used as a mutex
+	///                   in the signal_type class template.
+	///                 - P::mutex_lock_type, this type must implement a
+	///                   constructor that takes a P::mutex_type as a parameter,
+	///                   and it must have the semantics of a scoped mutex lock
+	///                   like std::lock_guard, i.e. locking in the constructor
+	///                   and unlocking in the destructor.
+	///
+	/// @tparam R      Return value type of the slots connected to the signal.
+	/// @tparam A...   Argument types of the slots connected to the signal.
+	template <class P, class R, class... A >
+	class signal_type<P,R(A...)>
+	{
+		public:
+			/// signals are not copy constructible
+			signal_type( signal_type const& ) = delete;
+			/// signals are not copy assignable
+			signal_type& operator=( signal_type const& ) = delete;
+			/// signals are move constructible
+			signal_type(signal_type&& other)
+			{
+				mutex_lock_type lock{other._mutex};
+				_slot_count = std::move(other._slot_count);
+				_slots = std::move(other._slots);
+				if(other._shared_disconnector != nullptr)
+				{
+					_disconnector = disconnector{ this };
+					_shared_disconnector = std::move(other._shared_disconnector);
+					// replace the disconnector with our own disconnector
+					*static_cast<disconnector*>(_shared_disconnector.get()) = _disconnector;
+				}
+			}
+			/// signals are move assignable
+			signal_type& operator=(signal_type&& other)
+			{
+				auto lock = thread_policy::defer_lock(_mutex);
+				auto other_lock = thread_policy::defer_lock(other._mutex);
+				thread_policy::lock(lock,other_lock);
+
+				_slot_count = std::move(other._slot_count);
+				_slots = std::move(other._slots);
+				if(other._shared_disconnector != nullptr)
+				{
+					_disconnector = disconnector{ this };
+					_shared_disconnector = std::move(other._shared_disconnector);
+					// replace the disconnector with our own disconnector
+					*static_cast<disconnector*>(_shared_disconnector.get()) = _disconnector;
+				}
+				return *this;
+			}
+
+			/// signals are default constructible
+			signal_type() :
+				_slot_count(0)
+			{}
+
+			// Destruct the signal object.
+			~signal_type() {
+				invalidate_disconnector();
+			}
+
+			/// Type that will be used to store the slots for this signal type.
+			using slot_type = std::function<R(A...)>;
+			/// Type that is used for counting the slots connected to this signal.
+			using size_type = typename std::vector<slot_type>::size_type;
+
+
+			/// Connect a new slot to the signal.
+			///
+			/// The connected slot will be called every time the signal
+			/// is triggered.
+			/// @param slot   The slot to connect. This must be a callable with
+			///               the same signature as the signal itself.
+			/// @return       A connection object is returned, and can be used to
+			///               disconnect the slot.
+			template <class T>
+			connection connect( T&& slot ) {
+				mutex_lock_type lock{ _mutex };
+				_slots.push_back( std::forward<T>(slot) );
+				std::size_t index = _slots.size()-1;
+				if( _shared_disconnector == nullptr ) {
+					_disconnector = disconnector{ this };
+					_shared_disconnector = std::shared_ptr<detail::disconnector>{&_disconnector, detail::no_delete};
+				}
+				++_slot_count;
+				return connection{ _shared_disconnector, index };
+			}
+
+			/// Function call operator.
+			///
+			/// Calling this is how the signal is triggered and the
+			/// connected slots are called.
+			///
+			/// @note The slots will be called in the order they were
+			///       connected to the signal.
+			///
+			/// @param args   Arguments that will be propagated to the
+			///               connected slots when they are called.
+			void operator()( A const&... args ) const {
+				for( auto const& slot : copy_slots() ) {
+					if( slot ) {
+						slot( args... );
+					}
+				}
+			}
+
+			/// Construct a accumulator proxy object for the signal.
+			///
+			/// The intended purpose of this function is to create a function
+			/// object that can be used to trigger the signal and accumulate
+			/// all the slot return values.
+			///
+			/// The algorithm used to accumulate slot return values is similar
+			/// to `std::accumulate`. A given binary function is called for
+			/// each return value with the parameters consisting of the
+			/// return value of the accumulator function applied to the
+			/// previous slots return value, and the current slots return value.
+			/// A initial value must be provided for the first slot return type.
+			///
+			/// @note This can only be used on signals that have slots with
+			///       non-void return types, since we can't accumulate void
+			///       values.
+			///
+			/// @tparam T      The type of the initial value given to the accumulator.
+			/// @tparam F      The accumulator function type.
+			/// @param init    Initial value given to the accumulator.
+			/// @param op      Binary operator function object to apply by the accumulator.
+			///                The signature of the function should be
+			///                equivalent of the following:
+			///                  `R func( T1 const& a, T2 const& b )`
+			///                 - The signature does not need to have `const&`.
+			///                 - The initial value, type `T`, must be implicitly
+			///                   convertible to `R`
+			///                 - The return type `R` must be implicitly convertible
+			///                   to type `T1`.
+			///                 - The type `R` must be `CopyAssignable`.
+			///                 - The type `S::slot_type::result_type` (return type of
+			///                   the signals slots) must be implicitly convertible to
+			///                   type `T2`.
+			template <class T, class F>
+			signal_accumulator<signal_type, T, F, A...> accumulate( T init, F op ) const {
+				static_assert( std::is_same<R,void>::value == false, "Unable to accumulate slot return values with 'void' as return type." );
+				return { *this, init, op };
+			}
+
+
+			/// Trigger the signal, calling the slots and aggregate all
+			/// the slot return values into a container.
+			///
+			/// @tparam C     The type of container. This type must be
+			///               `DefaultConstructible`, and usable with
+			///               `std::back_insert_iterator`. Additionally it
+			///               must be either copyable or moveable.
+			/// @param args   The arguments to propagate to the slots.
+			template <class C>
+			C aggregate( A const&... args ) const {
+				static_assert( std::is_same<R,void>::value == false, "Unable to aggregate slot return values with 'void' as return type." );
+				C container;
+				auto iterator = std::back_inserter( container );
+				for( auto const& slot : copy_slots() ) {
+					if( slot ) {
+						(*iterator) = slot( args... );
+					}
+				}
+				return container;
+			}
+
+			/// Count the number of slots connected to this signal
+			/// @returns   The number of connected slots
+			size_type slot_count() const {
+				return _slot_count;
+			}
+
+			/// Determine if the signal is empty, i.e. no slots are connected
+			/// to it.
+			/// @returns   `true` is returned if the signal has no connected
+			///            slots, and `false` otherwise.
+			bool empty() const {
+				return slot_count() == 0;
+			}
+
+			/// Disconnects all slots
+			/// @note This operation invalidates all scoped_connection objects
+			void disconnect_all_slots() {
+				mutex_lock_type lock{ _mutex };
+				_slots.clear();
+				_slot_count = 0;
+				invalidate_disconnector();
+			}
+
+		private:
+			template<class, class, class, class...> friend class signal_accumulator;
+			/// Thread policy currently in use
+			using thread_policy = P;
+			/// Type of mutex, provided by threading policy
+			using mutex_type = typename thread_policy::mutex_type;
+			/// Type of mutex lock, provided by threading policy
+			using mutex_lock_type = typename thread_policy::mutex_lock_type;
+
+			/// Invalidate the internal disconnector object in a way
+			/// that is safe according to the current thread policy.
+			///
+			/// This will effectively make all current connection objects to
+			/// to this signal incapable of disconnecting, since they keep a
+			/// weak pointer to the shared disconnector object.
+			void invalidate_disconnector() {
+				// If we are unlucky, some of the connected slots
+				// might be in the process of disconnecting from other threads.
+				// If this happens, we are risking to destruct the disconnector
+				// object managed by our shared pointer before they are done
+				// disconnecting. This would be bad. To solve this problem, we
+				// discard the shared pointer (that is pointing to the disconnector
+				// object within our own instance), but keep a weak pointer to that
+				// instance. We then stall the destruction until all other weak
+				// pointers have released their "lock" (indicated by the fact that
+				// we will get a nullptr when locking our weak pointer).
+				std::weak_ptr<detail::disconnector> weak{_shared_disconnector};
+				_shared_disconnector.reset();
+				while( weak.lock() != nullptr )	{
+					// we just yield here, allowing the OS to reschedule. We do
+					// this until all threads has released the disconnector object.
+					thread_policy::yield_thread();
+				}
+			}
+
+			/// Retrieve a copy of the current slots
+			///
+			/// It's useful and necessary to copy the slots so we don't need
+			/// to hold the lock while calling the slots. If we hold the lock
+			/// we prevent the called slots from modifying the slots vector.
+			/// This simple "double buffering" will allow slots to disconnect
+			/// themself or other slots and connect new slots.
+			std::vector<slot_type> copy_slots() const
+			{
+				mutex_lock_type lock{ _mutex };
+				return _slots;
+			}
+
+			/// Implementation of the signal accumulator function call
+			template <class T, class F>
+			typename signal_accumulator<signal_type, T, F, A...>::result_type trigger_with_accumulator( T value, F& func, A const&... args ) const {
+				for( auto const& slot : copy_slots() ) {
+					if( slot ) {
+						value = func( value, slot( args... ) );
+					}
+				}
+				return value;
+			}
+
+			/// Implementation of the disconnection operation.
+			///
+			/// This is private, and only called by the connection
+			/// objects created when connecting slots to this signal.
+			/// @param index   The slot index of the slot that should
+			///                be disconnected.
+			void disconnect( std::size_t index ) {
+				mutex_lock_type lock( _mutex );
+				assert( _slots.size() > index );
+				if( _slots[ index ] != nullptr ) {
+					--_slot_count;
+				}
+				_slots[ index ] = slot_type{};
+				while( _slots.size()>0 && !_slots.back() ) {
+					_slots.pop_back();
+				}
+			}
+
+			/// Implementation of the shared disconnection state
+			/// used by all connection created by signal instances.
+			///
+			/// This inherits the @ref detail::disconnector interface
+			/// for type erasure.
+			struct disconnector :
+				detail::disconnector
+			{
+				/// Default constructor, resulting in a no-op disconnector.
+				disconnector() :
+					_ptr(nullptr)
+				{}
+
+				/// Create a disconnector that works with a given signal instance.
+				/// @param ptr   Pointer to the signal instance that the disconnector
+				///              should work with.
+				disconnector( signal_type<P,R(A...)>* ptr ) :
+					_ptr( ptr )
+				{}
+
+				/// Disconnect a given slot on the current signal instance.
+				/// @note If the instance is default constructed, or created
+				///       with `nullptr` as signal pointer this operation will
+				///       effectively be a no-op.
+				/// @param index   The index of the slot to disconnect.
+				void operator()( std::size_t index ) const override {
+					if( _ptr ) {
+						_ptr->disconnect( index );
+					}
+				}
+
+				/// Pointer to the current signal.
+				signal_type<P,R(A...)>* _ptr;
+			};
+
+			/// Mutex to synchronize access to the slot vector
+			mutable mutex_type _mutex;
+			/// Vector of all connected slots
+			std::vector<slot_type> _slots;
+			/// Number of connected slots
+			size_type _slot_count;
+			/// Disconnector operation, used for executing disconnection in a
+			/// type erased manner.
+			disconnector _disconnector;
+			/// Shared pointer to the disconnector. All connection objects has a
+			/// weak pointer to this pointer for performing disconnections.
+			std::shared_ptr<detail::disconnector> _shared_disconnector;
+	};
+
+	// Implementation of the disconnect operation of the connection class
+	inline void connection::disconnect() {
+		auto ptr = _weak_disconnector.lock();
+		if( ptr ) {
+			(*ptr)( _index );
+		}
+		_weak_disconnector.reset();
+	}
+
+	/// Signal type that is safe to use in multithreaded environments,
+	/// where the signal and slots exists in different threads.
+	/// The multithreaded policy provides mutexes and locks to synchronize
+	/// access to the signals internals.
+	///
+	/// This is the recommended signal type, even for single threaded
+	/// environments.
+	template <class T> using signal = signal_type<multithread_policy, T>;
+
+	/// Signal type that is unsafe in multithreaded environments.
+	/// No synchronizations are provided to the signal_type for accessing
+	/// the internals.
+	///
+	/// Only use this signal type if you are sure that your environment is
+	/// single threaded and performance is of importance.
+	template <class T> using unsafe_signal = signal_type<singlethread_policy, T>;
+} // namespace nod
+
+#endif // IG_NOD_INCLUDE_NOD_HPP
diff --git a/CMakeLists.txt b/CMakeLists.txt
index 1805a9c6b8..015fcc31b7 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -940,6 +940,8 @@ set(Lyx_Boost_Libraries)
 add_definitions(-DBOOST_USER_CONFIG=<config.h>)
 include_directories(${TOP_SRC_DIR}/3rdparty/boost)
 
+include_directories(${TOP_SRC_DIR}/3rdparty/nod)
+
 if(WIN32)
 	if(LYX_CONSOLE)
 		set(LYX_QTMAIN_LIBRARY)
diff --git a/src/Server.cpp b/src/Server.cpp
index 79340492c6..8d9e0c61db 100644
--- a/src/Server.cpp
+++ b/src/Server.cpp
@@ -60,8 +60,12 @@
 #include <iostream>
 
 #ifdef _WIN32
-#include <io.h>
-#include <QCoreApplication>
+# include <io.h>
+# include <QCoreApplication>
+#else
+# ifdef HAVE_UNISTD_H
+#  include <unistd.h>
+# endif
 #endif
 #include <QThread>
 
diff --git a/src/graphics/GraphicsConverter.cpp b/src/graphics/GraphicsConverter.cpp
index 1461fdb27c..66e198ace4 100644
--- a/src/graphics/GraphicsConverter.cpp
+++ b/src/graphics/GraphicsConverter.cpp
@@ -38,7 +38,7 @@ namespace graphics {
 class Converter::Impl {
 public:
 	///
-	Impl(FileName const & doc_fname,
+	Impl(Converter const & parent, FileName const & doc_fname,
 	     FileName const & from_file, string const & to_file_base,
 	     string const & from_format, string const & to_format);
 
@@ -59,6 +59,8 @@ public:
 	///
 	sig finishedConversion;
 
+	///
+	Converter const & parent_;
 	///
 	FileName const doc_fname_;
 	///
@@ -71,8 +73,6 @@ public:
 	bool valid_process_;
 	///
 	bool finished_;
-	///
-	Trackable tracker_;
 };
 
 
@@ -86,16 +86,10 @@ bool Converter::isReachable(string const & from_format_name,
 Converter::Converter(FileName const & doc_fname,
                      FileName const & from_file, string const & to_file_base,
                      string const & from_format, string const & to_format)
-	: pimpl_(new Impl(doc_fname, from_file, to_file_base, from_format, to_format))
+	: pimpl_(make_shared<Impl>(*this, doc_fname, from_file, to_file_base, from_format, to_format))
 {}
 
 
-Converter::~Converter()
-{
-	delete pimpl_;
-}
-
-
 void Converter::startConversion() const
 {
 	pimpl_->startConversion();
@@ -123,10 +117,10 @@ static void build_script(string const & doc_fname,
 		  ostream & script);
 
 
-Converter::Impl::Impl(FileName const & doc_fname,
+Converter::Impl::Impl(Converter const & parent, FileName const & doc_fname,
 		      FileName const & from_file, string const & to_file_base,
 		      string const & from_format, string const & to_format)
-	: doc_fname_(doc_fname), valid_process_(false), finished_(false)
+	: parent_(parent), doc_fname_(doc_fname), valid_process_(false), finished_(false)
 {
 	LYXERR(Debug::GRAPHICS, "Converter c-tor:\n"
 		<< "doc_fname:        " << doc_fname
@@ -188,9 +182,12 @@ void Converter::Impl::startConversion()
 	}
 
 	ForkedCall::sigPtr ptr = ForkedCallQueue::add(script_command_);
-	ptr->connect(ForkedCall::slot([this](pid_t pid, int retval){
-				converted(pid, retval);
-			}).track_foreign(tracker_.p()));
+	weak_ptr<Converter::Impl> this_ = parent_.pimpl_;
+	ptr->connect([this_](pid_t pid, int retval){
+			if (auto p = this_.lock()) {
+				p->converted(pid, retval);
+			}
+		});
 }
 
 
diff --git a/src/graphics/GraphicsConverter.h b/src/graphics/GraphicsConverter.h
index c038029bd8..7eb3689ad1 100644
--- a/src/graphics/GraphicsConverter.h
+++ b/src/graphics/GraphicsConverter.h
@@ -19,6 +19,7 @@
 
 #include "support/signals.h"
 
+#include <memory>
 
 namespace lyx {
 
@@ -39,9 +40,6 @@ public:
 		  support::FileName const & from_file, std::string const & to_file_base,
 		  std::string const & from_format, std::string const & to_format);
 
-	/// Needed for the pimpl
-	~Converter();
-
 	/// We are explicit about when we begin the conversion process.
 	void startConversion() const;
 
@@ -70,7 +68,7 @@ private:
 	/// Use the Pimpl idiom to hide the internals.
 	class Impl;
 	/// The pointer never changes although *pimpl_'s contents may.
-	Impl * const pimpl_;
+	std::shared_ptr<Impl> const pimpl_;
 };
 
 } // namespace graphics
diff --git a/src/graphics/GraphicsLoader.cpp b/src/graphics/GraphicsLoader.cpp
index f0a0934091..2316a4ac69 100644
--- a/src/graphics/GraphicsLoader.cpp
+++ b/src/graphics/GraphicsLoader.cpp
@@ -21,6 +21,7 @@
 #include "support/lassert.h"
 #include "support/Timeout.h"
 
+#include <list>
 #include <queue>
 #include <memory>
 #include <set>
diff --git a/src/graphics/PreviewLoader.cpp b/src/graphics/PreviewLoader.cpp
index d0590f6b28..e1177a8d87 100644
--- a/src/graphics/PreviewLoader.cpp
+++ b/src/graphics/PreviewLoader.cpp
@@ -226,8 +226,6 @@ private:
 	///
 	QTimer * delay_refresh_;
 	///
-	Trackable trackable_;
-	///
 	bool finished_generating_;
 
 	/// We don't own this
@@ -244,16 +242,10 @@ lyx::Converter const * PreviewLoader::Impl::pconverter_;
 //
 
 PreviewLoader::PreviewLoader(Buffer const & b)
-	: pimpl_(new Impl(*this, b))
+	: pimpl_(make_shared<Impl>(*this, b))
 {}
 
 
-PreviewLoader::~PreviewLoader()
-{
-	delete pimpl_;
-}
-
-
 PreviewImage const * PreviewLoader::preview(string const & latex_snippet) const
 {
 	return pimpl_->preview(latex_snippet);
@@ -721,9 +713,12 @@ void PreviewLoader::Impl::startLoading(bool wait)
 
 	// Initiate the conversion from LaTeX to bitmap images files.
 	ForkedCall::sigPtr convert_ptr = make_shared<ForkedCall::sig>();
-	convert_ptr->connect(ForkedProcess::slot([this](pid_t pid, int retval){
-				finishedGenerating(pid, retval);
-			}).track_foreign(trackable_.p()));
+	weak_ptr<PreviewLoader::Impl> this_ = parent_.pimpl_;
+	convert_ptr->connect([this_](pid_t pid, int retval){
+			if (auto p = this_.lock()) {
+				p->finishedGenerating(pid, retval);
+			}
+		});
 
 	ForkedCall call(buffer_.filePath());
 	int ret = call.startScript(command, convert_ptr);
diff --git a/src/graphics/PreviewLoader.h b/src/graphics/PreviewLoader.h
index ca22a9fa5c..5d0bf8e234 100644
--- a/src/graphics/PreviewLoader.h
+++ b/src/graphics/PreviewLoader.h
@@ -18,11 +18,12 @@
 #ifndef PREVIEWLOADER_H
 #define PREVIEWLOADER_H
 
+#include "ColorCode.h"
 #include "support/signals.h"
 
 #include <QObject>
 
-#include "ColorCode.h"
+#include <memory>
 
 namespace lyx {
 
@@ -39,8 +40,6 @@ public:
 	 *  LaTeX file.
 	 */
 	PreviewLoader(Buffer const & buffer);
-	///
-	~PreviewLoader();
 
 	/** Is there an image already associated with this snippet of LaTeX?
 	 *  If so, returns a pointer to it, else returns 0.
@@ -108,7 +107,7 @@ private:
 	/// Use the Pimpl idiom to hide the internals.
 	class Impl;
 	/// The pointer never changes although *pimpl_'s contents may.
-	Impl * const pimpl_;
+	std::shared_ptr<Impl> const pimpl_;
 };
 
 } // namespace graphics
diff --git a/src/support/ForkedCalls.cpp b/src/support/ForkedCalls.cpp
index 7718a745ae..387f8561bf 100644
--- a/src/support/ForkedCalls.cpp
+++ b/src/support/ForkedCalls.cpp
@@ -24,6 +24,8 @@
 #include "support/bind.h"
 
 #include <cerrno>
+#include <cstring>
+#include <list>
 #include <queue>
 #include <sstream>
 #include <utility>
diff --git a/src/support/signals.h b/src/support/signals.h
index f768f2f873..18bc03e117 100644
--- a/src/support/signals.h
+++ b/src/support/signals.h
@@ -12,13 +12,13 @@
 #ifndef LYX_SIGNALS_H
 #define LYX_SIGNALS_H
 
-#include <boost/signals2/signal.hpp>
+#include "nod.hpp"
 
 #include <memory>
 
 namespace lyx {
 
-namespace signals2 = ::boost::signals2;
+namespace signals2 = ::nod;
 
 namespace support {
 
-- 
2.28.0.windows.1



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