具有完全透明背景的Qt小部件

Question

I need to create a qt widget, which will act as a parent for some other widgets, and which will order them.

Now, the question is how do I make it's background fully transparent?

I thought to do it like this :

struct Imp
{
  Imp( QWidget *parent ) : thisWidget( new QWidget( parent ) )
  {
    thisWidget->setAttribute( Qt::WA_TranslucentBackground, true );
  }

  QWidget *thisWidget;
};

Do you think that I need to set the attribute, or is it going to work fine without it?

Answer 1

By default in Qt4, a QWidget will draw nothing for its own background, and only its children will be drawn. If you want to override that, you specifically have to tell the widget to draw its background via one of its properties. Note that some widgets derived from QWidget will automatically draw backgrounds.

Answer 2

You should be able to do all the drawing customisation you need by changing the style of your widget i think

MyWidget {background-color: none;}

should work, stylesheets can very easily be tested in the designer

Answer 3

You may want to look at:

setAttribute( Qt::WA_NoSystemBackground, true );

and

setAttribute( Qt::WA_OpaquePaintEvent, false );

Answer 4

The solution that worked for me (I was setting a transparent background for a QTextEditor):

auto editorPalette = editorWidget->palette();
editorPalette.setColor(QPalette::Active, QPalette::Base, Qt::transparent);
editorPalette.setColor(QPalette::Inactive, QPalette::Base, Qt::transparent);
editorWidget->setPalette(editorPalette);

Answer 5

Don't know if it fully solves your problem but it is discussed in this article

Documentation is at http://doc.qt.nokia.com/4.1/qwidget.html#transparency-and-double-buffering

The solution is for Qt4.1 but should be relevent.