Need help with using `wxMediaCtrl`.

[apoorv569]

I am only about a week in learning C++, I have been learn python for last 2-3 months, I was using Tkinter for making a GUI music player application as a practice project, I recently discovered about wxWidgets, specifically wxPython, so I started using that instead of Tkinter, but I wanted to learn some stuff in future for which python is not really a good language. So I decided to learn C++, and I started using `wxWidgets` with C++, most of the code is carried over from my python version of the same application, I am still not very comfortable with C++, but I understand some things, so I finally made the GUI part of my application working yesterday, and I am trying to handle events, I started with a file dialog widget, so I can load songs in a list box widget, that is working, but today I started working on actually playing the selected item in list box widget, but I cannot seem to make `wxMediaCtrl` work, I don't understand how it works. For now I only have 2 `.cpp` files, one called `app.cpp` and other `frame.cpp`, in the `frame.cpp` file I only have one class called Frame, and the part where I am trying to setup `wxMediaCtrl` looks like this

In my `frame.hpp` header file I have

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#include <wx/mediactrl.h>

class Frame : public wxFrame

and somewhere down I have

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    protected:
       wxMediaCtrl* mediaCtrl;

and in my `frame.cpp` file I have

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    playButton = new wxButton(panel, 1000, wxT("|>"), wxDefaultPosition, wxDefaultSize, 0);
    playButton->Connect(1000, wxEVT_MEDIA_PLAY, (wxObjectEventFunction) (wxEventFunction) (wxMediaEventFunction) &Frame::Play);

and somewhere down I have

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mediaCtrl = new wxMediaCtrl(panel, wxID_ANY, wxEmptyString, wxDefaultPosition, wxDefaultSize, 0, wxEmptyString);

and somewhere even down the file I have this function

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void Frame::Play(wxMediaEvent& event)
{
//    stopped = false;

    int song_index = playlistBox->GetSelection();
    wxString song_str = playlistBox->GetString(song_index);

    std::string song;
    wxString wxsong;
    song = std::string(wxsong);

    song = "/home/apoorv/Music/mod/%s", "song_str";

//    std::cout << song << std::endl;

    mediaCtrl->Load(song);
    mediaCtrl->Play();

    event.Skip();

//    timer->Start(1000);
}

but when I try to compile it, it gives me error during linking

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/usr/include/wx-3.0/wx/mediactrl.h:137: undefined reference to `vtable for wxMediaCtrl'
/usr/bin/ld: /usr/include/wx-3.0/wx/mediactrl.h:138: undefined reference to `wxMediaCtrl::Create(wxWindow*, int, wxString const&, wxPoint const&, wxSize const&, long, wxString const&, wxValidator const&, wxString const&)'
/usr/bin/ld: warning: creating DT_TEXTREL in a PIE
collect2: error: ld returned 1 exit status
ninja: build stopped: subcommand failed.
./build.sh: line 12: ./musicApp: No such file or directory

I am using Arch Linux, I have installed wxgtk3 package from pacman, for wxWidgets, and I am using Meson for configuring and compiling. I can provide a link for full code if needed.

[doublemax]

The error indicates that you didn't link the "media" library do your project.

How does your build command look like?
Can you build the "mediaplayer" sample that comes with wxWidgets?

[apoorv569]

I tried building example here - https://github.com/wxWidgets/wxWidgets/ ... player.cpp

I tried using `gcc`

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❯ g++ wx.cpp
In file included from wx.cpp:40:
/usr/include/wx-3.0/wx/wxprec.h:12:10: fatal error: wx/defs.h: No such file or directory
   12 | #include "wx/defs.h"
      |          ^~~~~~~~~~~
compilation terminated.

then I copied my meson file and edited it to build this, then it gave this error

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❯ meson compile -j 1
Found runner: ['/usr/bin/ninja']
ninja: Entering directory `.'
[1/2] Compiling C++ object wx.p/wx.cpp.o
FAILED: wx.p/wx.cpp.o
g++ -Iwx.p -I. -I.. -I/usr/lib/wx/include/gtk2-unicode-3.0 -I/usr/include/wx-3.0 -fdiagnostics-color=always -pipe -Wall -Winvalid-pch -Wnon-virtual-dtor -g -D_FILE_OFFSET_BITS=64 -DWXUSINGDLL -D__WXGTK__ -pthread -MD -MQ wx.p/wx.cpp.o -MF wx.p/wx.cpp.o.d -o wx.p/wx.cpp.o -c ../wx.cpp
../wx.cpp:77:14: fatal error: ../sample.xpm: No such file or directory
   77 |     #include "../sample.xpm"
      |              ^~~~~~~~~~~~~~~
compilation terminated.
ninja: build stopped: subcommand failed.

And for my own project I have a `meson.build` file that looks like this

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project('Music Player', 'cpp')

src = [

  'src/app.cpp',
  'src/frame.cpp',

  ]

wx = dependency('wxwidgets')

executable('musicApp', src,
  dependencies : [wx])

and I have a script that builds the project and runs it, it looks like this

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#! /bin/bash

# cd where the script is
cd "$(dirname "$0")"

# rm -r build
CXX=g++ meson build
cd build
meson compile -j 1

# run the program
./musicApp

Here is a link to my full project if it helps. - https://gitlab.com/apoorv569/cpp-projec ... c%20Player

[doublemax]

I don't work under Linux myself, and i've never heard of meson files, so i can't help with this.

Try to get the wxWidgets sources and build the libraries yourself. Then building the samples with the provided makefiles should be easy.
https://wiki.wxwidgets.org/Compiling_an ... requisites

During the "configure" step check for messages regarding "gstreamer". If that's not found, the mediactrl support will be disabled.

[ONEEYEMAN]

Hi,

I tried building example here - https://github.com/wxWidgets/wxWidgets/ ... player.cpp

I tried using `gcc`

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❯ g++ wx.cpp
In file included from wx.cpp:40:
/usr/include/wx-3.0/wx/wxprec.h:12:10: fatal error: wx/defs.h: No such file or directory
   12 | #include "wx/defs.h"
      |          ^~~~~~~~~~~
compilation terminated.

Are you using wxWidgets installed frpm the official repository or you build the library yourself?
If you build it yourself, the Makefile should be created for you inside wxWidgets/<builddir>/samples/mediactrl.
If not - try this:

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g++ mediactrl.cpp `wx-config --cxxflags --libs std,media` -o media

then I copied my meson file and edited it to build this, then it gave this error

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❯ meson compile -j 1
Found runner: ['/usr/bin/ninja']
ninja: Entering directory `.'
[1/2] Compiling C++ object wx.p/wx.cpp.o
FAILED: wx.p/wx.cpp.o
g++ -Iwx.p -I. -I.. -I/usr/lib/wx/include/gtk2-unicode-3.0 -I/usr/include/wx-3.0 -fdiagnostics-color=always -pipe -Wall -Winvalid-pch -Wnon-virtual-dtor -g -D_FILE_OFFSET_BITS=64 -DWXUSINGDLL -D__WXGTK__ -pthread -MD -MQ wx.p/wx.cpp.o -MF wx.p/wx.cpp.o.d -o wx.p/wx.cpp.o -c ../wx.cpp
../wx.cpp:77:14: fatal error: ../sample.xpm: No such file or directory
   77 |     #include "../sample.xpm"
      |              ^~~~~~~~~~~~~~~
compilation terminated.
ninja: build stopped: subcommand failed.

And for my own project I have a `meson.build` file that looks like this

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project('Music Player', 'cpp')

src = [

  'src/app.cpp',
  'src/frame.cpp',

  ]

wx = dependency('wxwidgets')

executable('musicApp', src,
  dependencies : [wx])

and I have a script that builds the project and runs it, it looks like this

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#! /bin/bash

# cd where the script is
cd "$(dirname "$0")"

# rm -r build
CXX=g++ meson build
cd build
meson compile -j 1

# run the program
./musicApp

Here is a link to my full project if it helps. - https://gitlab.com/apoorv569/cpp-projec ... c%20Player

Are you running any kind of IDE?
Or you are building from the Terminal?

Thank you.

[apoorv569]

I am for now using Emacs specifically Doom Emacs, but I have vscodium also installed.

[ONEEYEMAN]

Hi,
Try to compile the sample and see if it works.

I gave an instruction on how to do that for both cases - self-compiled and installed from the repository.

Thank you.

[apoorv569]

I got it working, meson needed some configuration, I added modules `std` and `media`, and it compiles fine now. Thank you everyone for help

[stahta01]

I got it working, meson needed some configuration, I added modules `std` and `media`, and it compiles fine now. Thank you everyone for help

So, it likely passes the modules to wx-config.

Tim S.

[apoorv569]

Yes, I found the information here - https://mesonbuild.com/Dependencies.html#wxwidgets

I still need help with `wxMediaCtrl` I have set my code to open file dialog, and insert the file in list box, and I have set play button to play the current selected item in playlist, but it does not play anything, according the documentation, I need to capture the `EVT_MEDIA_LOADED` event, but I'm not sure how to do that. The example/sample `mediaplayer` file, is not really beginner to C++ friendly.

I have connected my play button like this

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    playButton = new wxButton(panel, 1000, wxT("|>"), wxDefaultPosition, wxDefaultSize, 0);
    playButton->Connect(1000, wxEVT_MEDIA_PLAY, (wxObjectEventFunction) (wxEventFunction) (wxMediaEventFunction) &Frame::Play);

and the play function looks like this

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void Frame::Play(wxMediaEvent& event)
{
//    stopped = false;

    int song_index = playlistBox->GetSelection();

    std::string song_str;
    wxString wxsong_s;

    wxsong_s = playlistBox->GetString(song_index);

    song_str = std::string(wxsong_s);

    std::string song;
    wxString wxsong;
    song = std::string(wxsong);

    song = "/home/apoorv/Music/mod/" + song_str;

    std::cout << "wxString: " << song_str << std::endl;
    std::cout << "Song: " << song << std::endl;

    mediaCtrl->Load(song);
    mediaCtrl->Play();

//    event.Skip();

//    timer->Start(1000);
}

[ONEEYEMAN]

Hi,
You can't handle EVT_MEDIA event in the wxButton.
Try to handle it in the media player you made.

And check the documentation of what event is handled by what class.

Thank you.

[doublemax]

This is the line from the sample:

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this->Connect(wxID_MEDIACTRL, wxEVT_MEDIA_PLAY, wxMediaEventHandler(wxMediaPlayerNotebookPage::OnMediaPlay));

It catches the event at the wxFrame. Note that this works, because all events that derive from wxCommandEvent propagate upwards in the window hierarchy until they are handled. E.g. this would not work for wxMouseEvents.

[apoorv569]

Sorry, I don't understand properly understand how does this `EVT_MEDIA_PLAY` and LOADED and all work. I can't seem to get them working, compiling fails. But I did manage to make it work, by simply binding the button to the play function and simply loading and playing the file using `wxMediaCtrl`. I'm very new to c++, I don't fully understand the code that I am writing either, like I don't know how pointers work and all. But I do have a general idea of what they do. I am not like blindly copy pasting. I am still very much trying to only do stuff that I at least some what understand, I know, learning python for 2 months, I struggled a lot, when the project gets bigger, it gets harder to manage, if you don't understand what/how your code works.

I binded my button like this

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    playButton = new wxButton(panel, 1000, wxT("|>"), wxDefaultPosition, wxDefaultSize, 0);
    playButton->Bind(wxEVT_BUTTON, &Frame::Play, this);

and my play functions looks like this.

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void Frame::Play(wxCommandEvent& event)
{
//    stopped = false;

    int song_index = playlistBox->GetSelection();

    std::string song_str;
    wxString wxsong_s;

    wxsong_s = playlistBox->GetString(song_index);

    song_str = std::string(wxsong_s);

    std::string song;
    wxString wxsong;
    song = std::string(wxsong);

    song = "/home/apoorv/Music/mod/" + song_str;

    std::cout << "wxString: " << song_str << std::endl;
    std::cout << "Song: " << song << std::endl;

    mediaCtrl->Load(song);
    mediaCtrl->Play();

//    event.Skip();

//    timer->Start(1000);
}

I think it works for me as of now. As I only need to be able to play pause stop and do general stuff with music. I do need to implement seeking capability with a seek bar, and volume control with a volume slider. Does this seek bar and volume functionality needs use of `EVT_MEDIA_XXX`?

[doublemax@work]

I'm sorry, i copied the wrong line. This one is the crucial one:

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Bind(wxEVT_MEDIA_LOADED, &wxMediaPlayerFrame::OnMediaLoaded, this,  wxID_MEDIACTRL);

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    mediaCtrl->Load(song);
    mediaCtrl->Play();

There is no guaranee that this will always work. Please try again using the wxEVT_MEDIA_LOADED event. If you can't get it to work, please post / attach your whole code.

[apoorv569]

I'm sorry, i copied the wrong line. This one is the crucial one:

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Bind(wxEVT_MEDIA_LOADED, &wxMediaPlayerFrame::OnMediaLoaded, this,  wxID_MEDIACTRL);

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    mediaCtrl->Load(song);
    mediaCtrl->Play();

There is no guaranee that this will always work. Please try again using the wxEVT_MEDIA_LOADED event. If you can't get it to work, please post / attach your whole code.

I see it uses some function called `OnMediaLoaded`, I don't know what to put there. It also has some ID `wxID_MEDIACTRL`. I get errors when I paste this line you shared, use of undeclared identifier.

I am facing another problem today, I was trying to make volume slider adjust volume according to the level of slider. I made this function,

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void Frame::Volume(wxScrollEvent& event)
{
    int getVolume = mediaCtrl->GetVolume() * 100;

    std::cout << "wxMediaCtrl Vol: " << getVolume << std::endl;
    std::cout << "Slider Vol: " << volumeSlider->GetValue() << std::endl;

    mediaCtrl->SetVolume(volumeSlider->GetValue() / 100);
}

and I made a slider and binded it like this

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    volumeSlider = new wxSlider(panel, wxID_ANY, 100, 0, 100, wxDefaultPosition, wxDefaultSize, wxSL_HORIZONTAL);
    volumeSlider->Bind(wxEVT_SCROLL, &Frame::Volume, this);

I get error when compiling

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../src/frame.cpp:48:24: error: ‘wxEVT_SCROLL’ was not declared in this scope; did you mean ‘EVT_SCROLL’?
   48 |     volumeSlider->Bind(wxEVT_SCROLL, &Frame::Volume, this);
      |                        ^~~~~~~~~~~~
      |                        EVT_SCROLL

You can check out the full project here - https://gitlab.com/apoorv569/cpp-projec ... c%20Player