CODEWITHSUNDEEP
c++qt
crep4ever
crep4ever

Reputation: 93

Unresolved overloaded function type when using QtConcurrent for QImage::fill

I'm trying to call QImage::fill() asynchronously using the QtConcurrent module. The invert pixels example works fine but a similar syntax for the fill method does not:

#include <QApplication>
#include <QImage>
#include <QFuture>
#include <QtConcurrent/QtConcurrentRun>

int main(int argc, char *argv[])
{
  QApplication app(argc, argv);
  QImage image(1920, 1080, QImage::Format_ARGB32_Premultiplied);
  QFuture<void> future = QtConcurrent::run(&image, &QImage::fill, Qt::transparent); // ko
  //QFuture<void> future = QtConcurrent::run(&image, &QImage::invertPixels, QImage::InvertRgba); // ok
  future.waitForFinished();
  return app.exec();
}

Compilation fails with the following error:

error: no matching function for call to ‘run(QImage*, <unresolved overloaded function type>, Qt::GlobalColor)’
   10 |   QFuture<void> future = QtConcurrent::run(&img, &QImage::fill, Qt::transparent); // ko
      |                                                                                ^
In file included from /usr/include/x86_64-linux-gnu/qt5/QtConcurrent/QtConcurrentRun:1,
                 from /home/romain/code/qt/main.cc:4:
/usr/include/x86_64-linux-gnu/qt5/QtConcurrent/qtconcurrentrun.h:72:12: note: candidate: ‘template<class T> QFuture<T> QtConcurrent::run(T (*)())’
   72 | QFuture<T> run(T (*functionPointer)())
      |            ^~~
/usr/include/x86_64-linux-gnu/qt5/QtConcurrent/qtconcurrentrun.h:72:12: note:   template argument deduction/substitution failed:
/home/romain/code/qt/main.cc:10:80: note:   mismatched types ‘T()’ and ‘QImage’
   10 |   QFuture<void> future = QtConcurrent::run(&img, &QImage::fill, Qt::transparent); // ko
      |                                                                                ^

Is it possible to help the compiler by marking some template types explicitly?

Upvotes: 1

Views: 298

Answers (1)

G.M.
G.M.

Reputation: 12899

The problem is that QImage::fill has multiple overloads. You need to disambiguate using either static_cast...

QFuture<void> future = QtConcurrent::run(&image, static_cast<void(QImage::*)(Qt::GlobalColor)>(&QImage::fill), Qt::transparent);

or (since this is Qt) QOverload...

QFuture<void> future = QtConcurrent::run(&image, qOverload<Qt::GlobalColor>(&QImage::fill), Qt::transparent);

Upvotes: 2

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