QtConcurrent::run errors with Qt6

SGaist

Hi and welcome to devnet,

From a quick look at the documentation, you are not passing the arguments in the correct order. You need pass the member method first and then the rest of the parameters.

mpvx

If I enter the right form

ThreadAssembly.setFuture(QtConcurrent::run(&cEncodeVideo::Assembly,this,Frame,PreviousFrame,&RenderMusic,&ToEncodeMusic,Continue));

I get this error

engine/_EncodeVideo.cpp:930:55:   required from here
/usr/include/x86_64-linux-gnu/qt6/QtConcurrent/qtconcurrentstoredfunctioncall.h:189:64: error: static assertion failed: The first argument of passed callable object isn't a QPromise<T> & type. Did you intend to pass a callable which takes a QPromise<T> & type as a first argument? Otherwise it's not possible to invoke the function with passed arguments.

SGaist

Can you provide a minimal example that shows that issue ?
It will be easier to check what might be going wrong.

mpvx

_EncodeVideo.cpp

bool cEncodeVideo::DoEncode() {
...
if ((!PreviousFrame)||(PreviousFrame->RenderedImage.isNull()))          ThreadAssembly.setFuture(QtConcurrent::run(&cEncodeVideo::Assembly,this,Frame,PreviousFrame,&RenderMusic,&ToEncodeMusic,Continue));
...
}

void cEncodeVideo::Assembly(cDiaporamaObjectInfo *Frame,cDiaporamaObjectInfo *PreviousFrame,cSoundBlockList *RenderMusic,cSoundBlockList *ToEncodeMusic,bool &Continue) {
...
}

Asperamanca

Is cEncodeVideo::Assembly a member function?
Not sure QtConcurrent::run is able to bind together &cEncodeVideo::Assembly and the 'this' argument.
Try wrapping that part of the call into a lambda, or use std::mem_fn
Or some of the other arguments has a type mismatch.

JonB

@Asperamanca said in QtConcurrent::run errors with Qt6:

Is cEncodeVideo::Assembly a member function?
Not sure QtConcurrent::run is able to bind together &cEncodeVideo::Assembly and the 'this' argument.

We do not know, because the OP has been asked to provide an example for us to check and they simply paste a couple of lines out of any context so nobody can tell....

mpvx

cEncodeVideo::Assembly is a class::function

mpvx

In other files with QtConcurrent::run ffDiaporama 2.1 works well only not in _EncodeVideo.cpp.

gons@debian:~/Dokumente/_prog/_ffdiaporama/_qt6/_work_20250102/_work2/ffdiaporama-2.1$ find . -name '*' -type f -exec grep -q QtConcurrent::run {} \; -print
./src/ffDiaporama/wgt_QVideoPlayer/wgt_QVideoPlayer.cpp
./src/ffDiaporama/engine/_Diaporama.cpp
./src/ffDiaporama/engine/_EncodeVideo.cpp
./src/ffDiaporama/DlgExportProject/DlgExportProject.cpp
./src/ffDiaporama/DlgRenderVideo/DlgRenderVideo.cpp
./src/ffDiaporama/wgt_QMultimediaBrowser/QCustomFolderTable.cpp

Asperamanca

It's a bit frustrating. You mention code we can't know, instead of providing sufficient source code to identify and name the problem (even when asked to do so).
I have given you leads on how to identify and fix the problem yourself, but you did not answer them.

mpvx

The code is here (ffDiaporama 2.1)
https://sourceforge.net/projects/ffdiaporama/files/ffdiaporama_bin_2.1.2014.0209.tar.gz
The translation in Qt6 is here
https://sourceforge.net/projects/ffdiaporama/files/qt6/ffdiaporama_2.1-1.diff.gz

mpvx

If I use

ThreadAssembly.setFuture(QtConcurrent::run([=]{Assembly(Frame,PreviousFrame,&RenderMusic,&ToEncodeMusic,Continue)}));

as solution corresponding to link text
I get

engine/_EncodeVideo.cpp: In lambda function:
engine/_EncodeVideo.cpp:930:89: error: invalid conversion from ‘const cSoundBlockList*’ to ‘cSoundBlockList*’ [-fpermissive]
  930 |             ThreadAssembly.setFuture(QtConcurrent::run([=]{Assembly(Frame,PreviousFrame,&RenderMusic,&ToEncodeMusic,Continue)}));
      |                                                                                         ^~~~~~~~~~~~
      |                                                                                         |
      |                                                                                         const cSoundBlockList*
engine/_EncodeVideo.h:126:111: note:   initializing argument 3 of ‘void cEncodeVideo::Assembly(cDiaporamaObjectInfo*, cDiaporamaObjectInfo*, cSoundBlockList*, cSoundBlockList*, bool&)’
  126 |     void            Assembly(cDiaporamaObjectInfo *Frame,cDiaporamaObjectInfo *PreviousFrame,cSoundBlockList *RenderMusic,cSoundBlockList *ToEncodeMusic,bool &Continue);
      |                                                                                              ~~~~~~~~~~~~~~~~~^~~~~~~~~~~
engine/_EncodeVideo.cpp:930:102: error: invalid conversion from ‘const cSoundBlockList*’ to ‘cSoundBlockList*’ [-fpermissive]
  930 |             ThreadAssembly.setFuture(QtConcurrent::run([=]{Assembly(Frame,PreviousFrame,&RenderMusic,&ToEncodeMusic,Continue)}));
      |                                                                                                      ^~~~~~~~~~~~~~
      |                                                                                                      |
      |                                                                                                      const cSoundBlockList*
engine/_EncodeVideo.h:126:140: note:   initializing argument 4 of ‘void cEncodeVideo::Assembly(cDiaporamaObjectInfo*, cDiaporamaObjectInfo*, cSoundBlockList*, cSoundBlockList*, bool&)’
  126 |     void            Assembly(cDiaporamaObjectInfo *Frame,cDiaporamaObjectInfo *PreviousFrame,cSoundBlockList *RenderMusic,cSoundBlockList *ToEncodeMusic,bool &Continue);
      |                                                                                                                           ~~~~~~~~~~~~~~~~~^~~~~~~~~~~~~
engine/_EncodeVideo.cpp:930:117: error: binding reference of type ‘bool&’ to ‘const bool’ discards qualifiers
  930 |             ThreadAssembly.setFuture(QtConcurrent::run([=]{Assembly(Frame,PreviousFrame,&RenderMusic,&ToEncodeMusic,Continue)}));
      |                                                                                                                     ^~~~~~~~
engine/_EncodeVideo.h:126:160: note:   initializing argument 5 of ‘void cEncodeVideo::Assembly(cDiaporamaObjectInfo*, cDiaporamaObjectInfo*, cSoundBlockList*, cSoundBlockList*, bool&)’
  126 |     void            Assembly(cDiaporamaObjectInfo *Frame,cDiaporamaObjectInfo *PreviousFrame,cSoundBlockList *RenderMusic,cSoundBlockList *ToEncodeMusic,bool &Continue);
      |                                                                                                                                                          ~~~~~~^~~~~~~~
engine/_EncodeVideo.cpp: In member function ‘bool cEncodeVideo::DoEncode()’:
engine/_EncodeVideo.cpp:930:56: error: use of deleted function ‘cSoundBlockList::cSoundBlockList(const cSoundBlockList&)’
  930 |             ThreadAssembly.setFuture(QtConcurrent::run([=]{Assembly(Frame,PreviousFrame,&RenderMusic,&ToEncodeMusic,Continue)}));
      |                                                        ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Asperamanca

@mpvx
Here is what I would recommend you to do:

Create a static dummy function without parameters
Test whether calling QtConcurrent::run with that dummy function works
Create a member dummy function without parameters
Test whether you can call them
One by one, start adding your parameters to the dummy function. It does not need to do anything with them, just accept them
Find out at which point the code no longer compiles

If, at that point, you cannot figure out what exactly the problem is, post

your dummy function
the code that calls the dummy function

mpvx

I use now only the command

Assembly(Frame,PreviousFrame,&RenderMusic,&ToEncodeMusic,Continue);

and it works.

jawadulhassan

It looks like Qt6’s QtConcurrent::run no longer supports passing a raw pointer to a member function the way Qt5 did. You’ll need to use a lambda or std::bind to wrap the member function call. For example:
ThreadAssembly.setFuture(QtConcurrent::run(= {
this->Assembly(Frame, PreviousFrame, &RenderMusic, &ToEncodeMusic, Continue);
}));
This way, the function becomes a callable object compatible with Qt6’s QtConcurrent::run. It should fix the operator() / ArgResolver errors you’re seeing.