Apps for AppImage - any recommendations for programmers?

Developers
1

Hi
I strugle with AppImage and I have some success (AppImage is created and my app can run from it).
But I have strange problem: When I start my app (writen with C++ and Qt) I setup all dirs suposed to use by my app (this is due to operating systems differences). Especially I have dir to images. I setup these dirs simply related to my exe (argv[0] main function parameter). Problem is that I have message like this:


Error: Exception occurs!
File: /home/szyk/!-EnergoKod/!-Libs/EnergoKodEditor1/Src/LineNumberArea.cpp, in line: 68, in function: loadSettings
Error code: 6, Error message: Bookmark image not found! Missing file: /home/szyk/!-EnergoKod/Textprofan2/Installers/Linux/share/Textprofan2-x86_64.AppImage/Images/bookmark.svg
Module: Energo Kod Editor 1 library
Code: 6

In this case I suppose (on Linux) my exe is located in /usr/bin and images are in /usr/share/Textprofan2/Images
I want to write my app properly so I want to know how should I setup my internaly used dirs.

So my question is:
How shoud I access my app resources? In case it is working inside AppImage package. It require some special hanling? Or I lame in my code?

Best regards
Szyk Cech

2

Hi and welcome.

You could use QCoreApplication::applicationDirPath()
and construct a relative path to your resources from there.

http://doc.qt.io/qt-5/qcoreapplication.html#applicationDirPath

1 Like
3

Thank you! You are avesome expert!!!

4

Your solution cover cases:

  1. when I run my app from AppImage package
  2. when I run my app from sources (from /usr/local/bin dir)
  3. when user use custom command e.g.: cmake .. -DCMAKE_INSTALL_PREFIX=/usr -DCMAKE_BUILD_TYPE=Release

But it does not cover one importand case:
4) compile from Ide in debug mode and run without install. In this case relay on exe position is useless.

Do you have any advices how to manage 4. case?

I can see two solutions:
I. Add function which search some default directories (e.g.: /usr/share , /usr/local/share , ../share )
II. Create ../share/MyApp dir above build dir

But I don’t know what is “recomended” way…

5

But it does not cover one importand case:
4) compile from Ide in debug mode and run without install. In this case relay on exe position is useless.

I found the solution in Qt: Let assume we have /usr/local/share/APP_NAME/Images dir. In order to access it properly we have to set our internal directories with QStandardPaths::locate function. This function search ~/.local/share, /usr/local/share, /usr/share dirs in order to find dirs or files given by parameter. The function is so kind that it properly handle subdirs like: gProgramName + '/' + QStringLiteral("Images"). So if you want to have reliable access to the images try some thing like this:

QString Application::findSharedPath(QString aSubPath)
{
    if(aSubPath[0] == '/')
        aSubPath = aSubPath.mid(1);

    QString lInstallBasePath(gPath(QCoreApplication::applicationDirPath()));
    QString lRelatedSharePath = QStringLiteral("%1/share/%2").arg(lInstallBasePath).arg(gBaseName(QCoreApplication::applicationFilePath()));
    QString lPath = lRelatedSharePath + '/' + aSubPath;
    if(!QFileInfo::exists(lPath))
        lPath = QStandardPaths::locate(QStandardPaths::GenericDataLocation, gProgramName + '/' + aSubPath, QStandardPaths::LocateDirectory);
    if(!QFileInfo::exists(lPath))
    {
        lPath = lRelatedSharePath + '/' + aSubPath;
        NOTIFY_WARNING(tr("Path not found! Missing path: %1").arg(lPath), gComponent, eErrorCode::eFileDoesNotExists);
    }
    return lPath;
}
1 Like
6

Hello, to help you further It would be very helpful if you could post a link to your source code, ideally on GitHub or GitLab. Thank you very much.