19. QT_NO_CLIPBOARD

19.1 problem description

void test()
{
  int argc = 1; 
  char* argv[] = {"libnative-lib.so"};
  QApplication  application(argc,argv);
}

the function test() is broken when init the resources in Android Environment,

when debug that funtion ‘QApplication application(argc,argv);’

step into when hit the following function which has the Macro ‘QT_NO_CLIPBOARD’;

#ifndef QT_NO_CLIPBOARD
    m_androidPlatformClipboard = new QAndroidPlatformClipboard();
#endif

continue to step into ‘new QAndroidPlatformClipboard()’;
some jni methods has been called ,but we cannot find the method,so program sink without any return ;

19.2 method

1. to find the method is the essential way;
2. but here we use another way in case that we have no so much information about the clipboard jni method;So if we do not call that logic function,just pass over it, the program do not sink;

19.2.1 HOW to pass over it?

we can define the Macro ‘QT_NO_CLIPBOARD’ to pass over it;

next we exam the method;

1. search the macro ‘QT_NO_CLIPBOARD’ in the source code folder;
   we get many hits in serveral modules ,such as gui | android platform | widget | modbus | assitant tools;
   but there is no hit about ‘define QT_NO_CLIPBOARD’;
   WHERE to deine the macro?

2. check some *.h or *.cpp files in which hit the macro;
   find the common includes, ‘#include <QtGui/private/qtguiglobal_p.h>’

   in qtguiglobal_p.h ,then locate :

    #include <QtGui/qtguiglobal.h>
    #include <QtCore/private/qglobal_p.h>
    #include <QtGui/private/qtgui-config_p.h>
   

   in qtguiglobal.h,locate:

    #include <QtCore/qglobal.h>
    #include <QtGui/qtgui-config.h>
   

   in qglobal.h or qglobal_p.h, we cannot find any macro defination;

   for qtgui-config_p.h or qtgui-config.h, firstly we cannot find them in the source code folder;
   we find them in the compile folder which has been created when run the configure command;
   in qtgui-config_p.h or qtgui-config.h, we can find many macro definition;

3. we edit the file ‘qtgui-config_p.h’ by appending the definition of the macro QT_NO_CLIPBOARD ;
   then compile the source code again and test the code;
   OK,we success; prove that that method is OK;

4. But WHY we need edit the file?

19.2.2 WHY we need edit the file?

is there another way to define the macro?

1. in file qtgui-config.h, when we search key words ‘clipboard’ ,
   we find ‘#define QT_FEATURE_clipboard 1’;

   so what create the file qtgui-config.h and define FEATURE_clipboard?

2. in the folder which locate the file qtgui-config.h, we find file qtgui-config.pri;

QT.gui.enabled_features = accessibility action opengles2 clipboard colornames cssparser cursor desktopservices imageformat_xpm draganddrop opengl imageformatplugin highdpiscaling im image_heuristic_mask image_text imageformat_bmp imageformat_jpeg imageformat_png imageformat_ppm imageformat_xbm movie pdf picture sessionmanager shortcut standarditemmodel systemtrayicon tabletevent texthtmlparser textodfwriter validator vulkan whatsthis wheelevent
QT.gui.disabled_features = angle combined-angle-lib dynamicgl opengles3 opengles31 opengles32 openvg
QT.gui.QT_CONFIG = accessibility action opengles2 clipboard colornames cssparser cursor desktopservices imageformat_xpm draganddrop opengl egl freetype imageformatplugin harfbuzz highdpiscaling ico im image_heuristic_mask image_text imageformat_bmp imageformat_jpeg imageformat_png imageformat_ppm imageformat_xbm movie pdf picture sessionmanager shortcut standarditemmodel systemtrayicon tabletevent texthtmlparser textodfwriter validator whatsthis wheelevent

in file qtgui-config.pri,clipboard is the enabled feature;
just list above;

3. so what create the file qtgui-config.pri? How to make clipboard disabled ?

19.2.3 How to make clipboard disabled ?

1. in source code folder, search key words ‘clipboard’ ,

2. locate file ‘configure.json’; the configure script use this json file to configure;

3. in json file,
   CHANGE from

   "clipboard": {
   	"label": "QClipboard",
   	"purpose": "Provides cut and paste operations.",
   	"section": "Kernel",
   	"condition": "!config.integrity && !config.qnx",
   	"output": [ "publicFeature", "feature" ]
   },

   into

   "clipboard": {
   	"label": "QClipboard",
   	"purpose": "Provides cut and paste operations.",
   	"section": "Kernel",
   	"autoDetect": "config.msvc",
   	"condition": "!config.integrity && !config.qnx",
   	"output": [ "publicFeature", "feature" ]
   },

4. save the changes and reconfigure,
   locate the file qtgui-config.h , there is no QT_FEATURE_clipboard defination;
   but we find ‘#define QT_NO_CLIPBOARD ‘;

5. bingo! we have made FEATURE clipboard disabled;

6. recompile the source code and retest the demo;OK;