But I dont know how to bind this to the qt c++ code.

Don't know what this means.

So if could give me the links to the grammar rules of the qtstylesheet

https://doc.qt.io/qt-6/stylesheet-reference.html
https://doc.qt.io/qt-6/stylesheet-examples.html
In particular: https://doc.qt.io/qt-6/stylesheet-syntax.html

Your particular example is an "advanced" one:

.IconfontBtn[white_bk="true"]:disabled

This *selector" applies to:

1. A widget of a C++ class named IconfontBtn....
2. ...which has a dynamic property set whose name is white_bk and which has a value of true...
3. ...and it is currently set to disabled.

Thanks .I just need the links.
And by the way,in the project that some ui objects were created by the codes.

I assume you mean that some code was generated to match a UI you built in Qt Creator (or Designer). The names in this code will match the names you see in Designer. So if you have a form named MyForm containing a widget with name pathLineEdit in the UI design then the generated code will contain a variable pathLineEdit that you can (usually) access your own code through a the ui pointer like this:

ui->pathLineEdit->setText("blah");

The actual generated code will be in the build directory in a file called ui_MyWidget.h that you will see as:

#include "ui_MyWidget.h"

in your MyForm class sources.

But I dont know how to bind this to the qt c++ code.

Don't know what this means.

So if could give me the links to the grammar rules of the qtstylesheet

https://doc.qt.io/qt-6/stylesheet-reference.html
https://doc.qt.io/qt-6/stylesheet-examples.html
In particular: https://doc.qt.io/qt-6/stylesheet-syntax.html

Your particular example is an "advanced" one:

.IconfontBtn[white_bk="true"]:disabled

This *selector" applies to:

1. A widget of a C++ class named IconfontBtn....
2. ...which has a dynamic property set whose name is white_bk and which has a value of true...
3. ...and it is currently set to disabled.