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scoped_connection: new wrapper to auto-disconnect…
…a contained sigc::connection, when the scoped_connection is destructed. #87
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‎sigc++/connection.h

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* Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
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*
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*/
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#ifndef SIGC_CONNECTION_HPP
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#define SIGC_CONNECTION_HPP
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#include <sigc++config.h>
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#include <sigc++/functors/slot_base.h>
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#include <sigc++/weak_raw_ptr.h>
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* This may be used to disconnect the referred slot at any time (disconnect()).
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* @ref sigc::signal_with_accumulator::connect() "sigc::signal::connect()"
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* returns a %sigc::connection.
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*
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* @code
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* sigc::connection conn = sig.connect(sigc::mem_fun(a, &A::foo));
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* @endcode
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*
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* If the slot has already been destroyed, disconnect() does nothing. empty() or
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* operator bool() can be used to test whether the connection is
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* still active. The connection can be blocked (block(), unblock()).
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*
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* sigc::connection doesnʼt disconnect the slot automatically upon destruction.
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* You do not need to keep the sigc::connection object to retain the connection
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* of the slot to the signal. See also @ref sigc::scoped_connection, which does
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* diconnect automatically when the connection object is destroyed or replaced.
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*
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* @ingroup signal
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*/
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struct SIGC_API connection

‎sigc++/filelist.am

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@@ -24,6 +24,7 @@ sigc_public_h = \
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member_method_trait.h \
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reference_wrapper.h \
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retype_return.h \
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scoped_connection.h \
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signal.h \
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signal_base.h \
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slot.h \

‎sigc++/meson.build

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source_cc_files = [
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'connection.cc',
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'scoped_connection.cc',
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'signal_base.cc',
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'trackable.cc',
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'functors' / 'slot_base.cc',
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'member_method_trait.h',
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'reference_wrapper.h',
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'retype_return.h',
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'scoped_connection.h',
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'signal.h',
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'signal_base.h',
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'slot.h',

‎sigc++/scoped_connection.cc

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/*
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* Copyright 2023, The libsigc++ Development Team
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*
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* This library is free software; you can redistribute it and/or
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* modify it under the terms of the GNU Lesser General Public
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* License as published by the Free Software Foundation; either
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* version 2.1 of the License, or (at your option) any later version.
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*
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* This library is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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* Lesser General Public License for more details.
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*
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* You should have received a copy of the GNU Lesser General Public
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* License along with this library; if not, write to the Free Software
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* Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
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*
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*/
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#include <sigc++/scoped_connection.h>
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#include <utility>
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namespace sigc
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{
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// All we are doing is assigning weak_raw_ptr, which is noexcept, so declare it.
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// connectionʼs copy operators can be noexcept for that reason, if breaking ABI.
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scoped_connection::scoped_connection(connection c) noexcept
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: conn_(std::move(c))
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{
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}
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scoped_connection&
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scoped_connection::operator=(connection c)
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{
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conn_.disconnect();
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conn_ = std::move(c);
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return *this;
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}
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// We do not implement move-ctor in terms of move-assign, so we can be noexcept,
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// as we do not need to call the maybe-throwing disconnect() for obvious reason.
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scoped_connection::scoped_connection(scoped_connection&& sc) noexcept
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: conn_(std::exchange(sc.conn_, connection()))
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{
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}
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scoped_connection&
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scoped_connection::operator=(scoped_connection&& sc)
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{
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conn_.disconnect();
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conn_ = std::exchange(sc.conn_, connection());
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return *this;
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}
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scoped_connection::~scoped_connection()
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{
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conn_.disconnect();
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}
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bool
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scoped_connection::empty() const noexcept
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{
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return conn_.empty();
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}
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bool
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scoped_connection::connected() const noexcept
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{
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return conn_.connected();
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}
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bool
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scoped_connection::blocked() const noexcept
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{
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return conn_.blocked();
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}
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bool
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scoped_connection::block(bool should_block) noexcept
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{
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return conn_.block(should_block);
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}
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bool
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scoped_connection::unblock() noexcept
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{
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return conn_.unblock();
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}
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void
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scoped_connection::disconnect()
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{
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conn_.disconnect();
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}
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scoped_connection::operator bool() const noexcept
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{
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return conn_.operator bool();
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}
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// Swapping can be noexcept, as it does not need to disconnect either connection
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// because they will still stay alive, just in opposite instances post-swapping.
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void
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swap(scoped_connection &sca, scoped_connection &scb) noexcept
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{
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using std::swap;
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swap(sca.conn_, scb.conn_);
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}
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connection
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scoped_connection::release() noexcept
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{
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return std::exchange(conn_, connection());
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}
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} /* namespace sigc */

‎sigc++/scoped_connection.h

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/*
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* Copyright 2023, The libsigc++ Development Team
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*
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* This library is free software; you can redistribute it and/or
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* modify it under the terms of the GNU Lesser General Public
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* License as published by the Free Software Foundation; either
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* version 2.1 of the License, or (at your option) any later version.
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*
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* This library is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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* Lesser General Public License for more details.
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*
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* You should have received a copy of the GNU Lesser General Public
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* License along with this library; if not, write to the Free Software
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* Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
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*
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*/
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#ifndef SIGC_SCOPED_CONNECTION_HPP
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#define SIGC_SCOPED_CONNECTION_HPP
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#include <sigc++/connection.h>
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namespace sigc
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{
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/** Convenience class for safe disconnection, including automatic disconnection
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* upon destruction.
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*
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* This is a variant of @ref sigc::connection which also disconnect()s the slot
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* automatically when the scoped_connection is destructed or re-assigned. Refer
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* to @ref sigc::connection for full information about the common functionality.
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*
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* You will use sigc::scoped_connection by constructing it from a ‘normal’,
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* unscoped @ref sigc::connection, such as those returned by
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* @ref sigc::signal_with_accumulator::connect() "sigc::signal::connect()", thus
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* ‘wrapping’ the connection in a scoped_connection, adding auto-disconnection.
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* It can also be assigned from an unscoped connection, in which case, if there
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* was a previous slot referred to by the scoped connection, it is disconnected.
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*
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* Once a connection is scoped, it canʼt be copied as that would make it unclear
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* which of the copies would hold responsibility to auto-disconnect the slot. It
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* can, however, be moved, so itʼs usable in containers or so ‘ownership’ of the
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* connection/auto-disconnect can be moved to another instance. Moving from the
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* scoped_connection clears its reference to the slot so it wonʼt disconnect it.
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*
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* If you want a reference-counted scoped_connection, wrap in a std::shared_ptr.
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*
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* @code
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* // Automatic disconnection:
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* {
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* sigc::scoped_connection sconn = sig.connect(&some_function);
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* // Do stuff that requires the slot to be connected & called.
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* }
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* // The scoped_connection was destroyed, so the slot is no longer connected.
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*
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* // ***
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*
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* // Moving ownership:
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* {
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* sigc::scoped_connection sconn = sig.connect(&some_function);
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* // Do stuff that requires the slot to be connected & called.
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* take_ownership(std::move(sconn)); // Pass by rvalue.
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* }
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* // Now our `sconn` no longer referred to slot, so it did NOT auto-disconnect.
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*
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* // ***
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*
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* // Shared ownership:
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* {
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* auto shconn = std::make_shared<sigc::scoped_connection>(sig.connect(&some_function));
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* take_copy(shconn); // Pass by copy/value
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* // Now we AND take_copy() must destroy our shared_ptr to auto-disconnect().
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* }
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* // take_copy() may still hold a shared_ptr reference, keeping the slot alive.
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* @endcode
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*
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* @ingroup signal
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* @newin{3,6}
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*/
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struct SIGC_API scoped_connection final
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{
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/** Constructs an empty scoped connection object. */
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[[nodiscard]] scoped_connection() noexcept = default;
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/** Constructs a scoped connection object from an unscoped connection object.
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* The source connection still refers to the slot and can manually disconnect.
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* @param c The connection object to make a copy from, whose slot weʼll
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* automatically disconnect when the scoped_connection object is destroyed.
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*/
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[[nodiscard]] scoped_connection(connection c) noexcept;
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/** Overrides this scoped connection object copying an unscoped connection.
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* The current slot, if any, will be disconnect()ed before being replaced.
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* The source connection still refers to the slot and can manually disconnect.
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* @param c The connection object to make a copy from, whose slot weʼll
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* automatically disconnect when the scoped_connection object is destroyed.
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*/
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scoped_connection& operator=(connection c);
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/// scoped_connection canʼt be copied as it would confuse ownership—see intro.
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scoped_connection& operator=(const scoped_connection&) = delete;
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/// scoped_connection canʼt be copied as it would confuse ownership—see intro.
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scoped_connection(const scoped_connection&) = delete;
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/** Constructs a scoped connection object moving an existing one.
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* The source scoped connection will no longer refer to / disconnect the slot.
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* @param sc The scoped connection object to move from.
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*/
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scoped_connection(scoped_connection&& sc) noexcept;
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/** Overrides this scoped connection object moving another one.
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* The current slot, if any, will be disconnect()ed before being replaced.
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* The source scoped connection will no longer refer to / disconnect the slot.
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* @param sc The scoped connection object to move from.
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*/
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scoped_connection& operator=(scoped_connection&& sc);
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/// Swap two scoped connections.
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friend void swap(scoped_connection &sca, scoped_connection &scb) noexcept;
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/// scoped_connection disconnects the referred slot, if any, upon destruction.
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~scoped_connection();
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/** Returns whether the connection is still active.
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* @return @p false if the connection is still active.
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*/
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[[nodiscard]] bool empty() const noexcept;
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/** Returns whether the connection is still active.
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* @return @p true if the connection is still active.
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*/
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[[nodiscard]] bool connected() const noexcept;
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/** Returns whether the connection is blocked.
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* @return @p true if the connection is blocked.
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*/
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[[nodiscard]] bool blocked() const noexcept;
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/** Sets or unsets the blocking state of this connection.
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* See slot_base::block() for details.
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* @param should_block Indicates whether the blocking state should be set or unset.
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* @return @p true if the connection has been in blocking state before.
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*/
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bool block(bool should_block = true) noexcept;
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/** Unsets the blocking state of this connection.
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* @return @p true if the connection has been in blocking state before.
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*/
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bool unblock() noexcept;
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/// Disconnects the referred slot. This will also happen upon destruction.
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void disconnect();
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/** Returns whether the connection is still active.
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* @return @p true if the connection is still active.
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*/
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[[nodiscard]] explicit operator bool() const noexcept;
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/** Releases the connection from a scoped connection object.
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* The scoped connection will no longer refer to / disconnect the slot.
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* @return An unscoped connection object referring to the same slot.
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*/
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[[nodiscard]] connection release() noexcept;
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private:
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sigc::connection conn_;
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};
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void swap(scoped_connection &sca, scoped_connection &scb) noexcept;
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} /* namespace sigc */
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#endif /* SIGC_SCOPED_CONNECTION_HPP */

‎sigc++/sigc++.h

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#include <sigc++/signal.h>
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#include <sigc++/connection.h>
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#include <sigc++/scoped_connection.h>
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#include <sigc++/trackable.h>
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#include <sigc++/adaptors/adaptors.h>
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#include <sigc++/functors/functors.h>

‎tests/Makefile.am

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test_retype \
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test_retype_return \
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test_rvalue_ref \
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test_scoped_connection \
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test_signal \
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test_signal_move \
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test_size \

‎tests/meson.build

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[[], 'test_retype', ['test_retype.cc', 'testutilities.cc']],
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[[], 'test_retype_return', ['test_retype_return.cc', 'testutilities.cc']],
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[[], 'test_rvalue_ref', ['test_rvalue_ref.cc', 'testutilities.cc']],
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[[], 'test_scoped_connection', ['test_scoped_connection.cc', 'testutilities.cc']],
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[[], 'test_signal', ['test_signal.cc', 'testutilities.cc']],
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[[], 'test_signal_move', ['test_signal_move.cc', 'testutilities.cc']],
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[[], 'test_size', ['test_size.cc', 'testutilities.cc']],

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