RAII and Qt signals - c++

Question

I'm trying to understand and use RAII and wanted opinions on this implementation:
I want the RAII PauseProcessRAII to emit a signal and another one in the destructor. Example:
// Header
public:
PauseProcessRAII(QObject *parent = 0);
void Execute();
~PauseProcessRAII();
signals:
void PauseProcess(bool pause_process);
// Source
PauseProcessRAII::~PauseProcessRAII()
{
emit PauseProcess(false);
}
void PauseProcessRAII::Execute()
{
emit PauseProcess(true);
}
// MainWindow code
void MainWindow::OnPauseProcessRAII(bool pause_process)
{
qDebug() << "pause_process: " << pause_process;
}
void MainWindow::OnButtonSaveClicked()
{
PauseProcessRAII pauseProcessRAII(this);
connect(&pauseProcessRAII, &PauseProcessRAII::PauseProcess, this, &MainWindow::OnPauseProcess);
pauseProcessRAII.Execute();
// ... Some code runs
// ... pauseRAII desctructor is called
}
When I run the code both emits are firing as expected. My question is this a good solution? At first I though the emit call in PauseProcessRAII destructor wouldn't have worked because it may have destroyed the signal and slot connection. Of course that would mean I would have to add the connect to every function that I use it on.

Answer 1

The whole idea is fundamentally broken if your premise is that the code indicated by "Some code runs" runs long enough to block the GUI. If so: don't do that. The only code that is supposed to ever execute in the GUI thread is short, run-to-completion code that doesn't take long enough for the user to notice.
If the time taken by "Some code runs" is very short - on the order of single milliseconds at most - then you can certainly use such a construct. The term RAII doesn't apply here, as you're dealing with some sort of a scope guard.
If you wish, you can forgo the execute method and perform the connection in the constructor:
// https://github.com/KubaO/stackoverflown/tree/master/questions/scopeguard-signal-34910879
// main.cpp
#include <QtCore>
class ScopeSignaller : public QObject {
Q_OBJECT
public:
Q_SIGNAL void inScope(bool);
template <typename F>
ScopeSignaller(QObject * target, F && slot, QObject * parent = 0) : QObject(parent) {
connect(this, &ScopeSignaller::inScope, target, std::forward<F>(slot));
inScope(true);
}
~ScopeSignaller() {
inScope(false);
}
};
int main(int argc, char ** argv) {
QCoreApplication app{argc, argv};
ScopeSignaller s(&app, +[](bool b){ qDebug() << "signalled" << b; });
}
#include "main.moc"