Qdebug June 2022

One 、Qt Widgets Problem communication

Two 、Qt Quick Problem communication

1.QML The program does not start properly on some graphics cards  

Environmental Science ：Window10  MSVC2019  Qt5.15.2-64bit( Lower versions will also )

The phenomenon ： The notebook + The expansion screen has two screens ,Windows The main screen of the setting can normally display QML Of Window window , The auxiliary screen will be stuck during startup （ A black or white window is stuck there ; The default operation focus will pop up on which screen , So the program can be started by dragging it to the corresponding screen ）. Disable the integrated graphics card that comes with the notebook , The main screen and auxiliary screen can be started normally .

Later learned Qt You can set the blacklist of the graphics card .Qt Quick application OpenGL The order of implementation is desktop,angle,software, To use Qt Quick 2 Work needs to be provided OpenGL2.1 And above , This requires disabling some pairs of   OpenGL Support problematic graphics cards , And then use angle perhaps software .

Qt file ：https://doc.qt.io/qt-5/windows-requirements.html

my Demo：https://github.com/gongjianbo/MyTestCode2021/tree/master/Qml/OpenGLBlackList

Write the problematic graphics card information to a json In file , And then in the environment variable QT_OPENGL_BUGLIST Appoint json Path to file （ To facilitate the resource file path I use here ）：

{
    "name": "Qt built-in GPU driver blacklist",
    "version": "5.14",
    "entries": [
        {
           "id": 1,
           "description": "Intel(R) UHD Graphics",
           "vendor_id": "0x8086",
           "device_id": ["0x9ba4"],
           "os": {
               "type": "win"
           },
           "features": [
               "disable_desktopgl"
           ]
        }
    ]
}

int main(int argc, char *argv[])
{
    qputenv("QT_OPENGL_BUGLIST", ":/opengl-blacklist.json");
    QGuiApplication app(argc, argv);
    ... ...
    return app.exec();
}

This type of graphics card is disabled in the settings desktop opengl, Will try angle and software The implementation of the .

json File each graphics card mainly distinguishes two parameters , manufacturer id And equipment id, It can be downloaded from Windows View... In device manager , This VEN The last four hexadecimal digits are the manufacturers id, DEV The next four hexadecimal digits are the device id：

  

There are many types of graphics cards that may be incompatible , It will be updated to the blacklist .

2.QML FileDialog Pick up to url The path is formatted as a local path

QML Of FileDialog The obtained file or directory path is url Format , Except that the path is preceded by "file:///"  start , And escape #%^{} Equal special symbol .

Qt C++ Of QUrl Class provides two interfaces for url Conversion with local path format ：

//url Convert to local path 
QString QUrl::toLocalFile() const
// Generate based on local path url
QUrl QUrl::fromLocalFile(const QString &localFile) //static

3、 ... and 、 other

1.QString Remove blanks

    QString str=" a b\t\tc\n\nd ";
    // Remove any white space 
    str.remove(QRegularExpression("\\s")); //"abcd"
    str.remove(QRegExp("\\s")); //"abcd"
    // Remove the head blank 
    str.remove(QRegExp("^ +\\s*")); //"a b\t\tc\n\nd "
    // Remove trailing blanks 
    str.remove(QRegExp("\\s* +$")); //" a b\t\tc\n\nd"
    // Remove the blank on both sides 
    str=str.trimmed(); //"a b\t\tc\n\nd"
    // Remove the blank on both sides , And replace the internal white space with a single space 
    str=str.simplified(); //"a b c d"
    qDebug()<<str;

2.FTH: ( Numbers ): ***Fault tolerant heap shim applied to current process. This is usually due toprevious crashes. ***

Microsoft documentation ：https://docs.microsoft.com/en-us/windows/win32/win7appqual/fault-tolerant-heap

Qt Creator The error prompt appears when running the program in , Most likely, the runtime crashed before . After the error prompt appears, you need to modify the registry to set , Otherwise, this error will be prompted every time .

Refer to Microsoft documentation , Fault tolerant heap （Fault Tolerant Heap,FTH） yes Windows 7 A subsystem of , Responsible for monitoring application crashes and autonomously applying mitigation measures , To prevent future crashes on every application . But I didn't find any specific use , Should it collapse or will it collapse .

First find the registry FTH Set up ：

 Computer \HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\FTH

take Enabled One from 1 Set to 0（ I also took FTH/State A message under the directory that is the same as the program name is deleted ）

The document says restart the computer after setting ,FTH Will no longer activate for new applications （ But the actual measurement does not restart and there is no problem ）

After setting, execute CMD Command to clear all FTH Application records ：

Rundll32.exe fthsvc.dll,FthSysprepSpecialize