qt - Set background of QMainWindow central widget -

using qt 4.8.4 on windows 7 (msvc 2010) have standard qmainwindow in app toolbar. want toolbar stay grey, central widget should have white background. calling centralwidget->setstylesheet("background-color: white;") @ first seemed job, using designer-generated widget (a q_object) doesn't. subsequently toyed around various other methods set style sheet (also using designer) no avail.

to see effect, add or remove q_object line in test.h. when it's there, label gets white bg. if q_object commented out, whole central widget white. of course, want whole area white, need q_object.

here's files:

main.cpp:

#include "test.h"  class testwin : public qmainwindow { public:     qwidget     *centralwidget;     qtoolbar    *maintoolbar;      testwin(qwidget *parent = 0) : qmainwindow(parent) {         centralwidget = new test(this);         setcentralwidget(centralwidget);         maintoolbar = new qtoolbar(this);         this->addtoolbar(qt::toptoolbararea, maintoolbar);     };      ~testwin() {}; };  int main(int argc, char *argv[]) {     qapplication a(argc, argv);     testwin w;     w.centralwidget->setstylesheet("background-color: white;");     w.show();     return a.exec(); } 

test.h:

#include <qtgui>  class test : public qwidget {     q_object    // remove  public:     qlabel *label;      test(qwidget *parent = 0) {         resize(400, 300);         label = new qlabel(this);         label->settext("test");     }; }; 

status update:

• setstylesheet("qwidget { background-color: white; }") not solve issue
• i succeed in making every widget (including popup dialogs) white, that's not want.

ok, proper answer can found here, or alternatively reading documentation. need implement paintevent test class:

class test : public qwidget {     q_object    // remove  public:     qlabel *label;      test(qwidget *parent = 0) {         resize(400, 300);         label = new qlabel(this);         label->settext("test");     };      void paintevent(qpaintevent *)     {         qstyleoption opt;         opt.init(this);         qpainter p(this);         style()->drawprimitive(qstyle::pe_widget, &opt, &p, this);     }  }; 

also many 1+1=2 read manual me @ the qt project forum.