C++ 使 QWidget 透明
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Make QWidget transparent
提问by sorush-r
I have a QWidget-based overlay widget which should paint some text and take place over the central widget of my application. The problem is that I can't set background of overlay widget to be transparent. What I already tried:
我有一个QWidget基于覆盖的小部件，它应该绘制一些文本并在我的应用程序的中央小部件上进行。问题是我无法将覆盖小部件的背景设置为透明。我已经尝试过的：
setPalette(Qt::transparent);setAttribute( Qt::WA_TranslucentBackground, true );setAttribute( Qt::WA_OpaquePaintEvent, true );setAutoFillBackground(false);setStyleSheet("QWidget{background-color: transparent;}");setAttribute(Qt::WA_NoSystemBackground);
setPalette(Qt::transparent);setAttribute( Qt::WA_TranslucentBackground, true );setAttribute( Qt::WA_OpaquePaintEvent, true );setAutoFillBackground(false);setStyleSheet("QWidget{background-color: transparent;}");setAttribute(Qt::WA_NoSystemBackground);
回答by Antonio Dias
My best guess to show an overlay widget, is convert the widget to a window, resize it to it's contents and move them to the desired position manually.
我最好的猜测是显示一个覆盖小部件，是将小部件转换为窗口，将其调整为它的内容，然后手动将它们移动到所需的位置。
MainWindow Example, showing the overlay widget in the center of the video widget:
MainWindow 示例，在视频小部件的中心显示覆盖小部件：
Mwindow::Mwindow()
{
widget = new Widget(this);
}
void Mwindow::widgetSizeMove()
{
if (widget->width() <= videoWidget->width() && widget->height() <= videoWidget->height())
{
widget->setWindowOpacity(1); // Show the widget
QPoint p = videoWidget->mapToGlobal(videoWidget->pos());
int x = p.x() + (videoWidget->width() - widget->width()) / 2;
int y = p.y() + (videoWidget->height() - widget->height()) / 2;
widget->move(x, y);
widget->raise();
}
else
{
widget->setWindowOpacity(0); // Hide the widget
}
}
bool Mwindow::event(QEvent *event)
{
switch (event->type())
{
case QEvent::Show:
widget->show();
QTimer::singleShot(50, this, SLOT(widgetSizeMove()));
//Wait until the Main Window be shown
break;
case QEvent::WindowActivate:
case QEvent::Resize:
case QEvent::Move:
widgetSizeMove();
break;
default:
break;
}
return QMainWindow::event(event);
}
Widget Example:
小部件示例：
Widget::Widget(QWidget *parent) : QWidget(parent)
{
setWindowFlags(Qt::Window | Qt::FramelessWindowHint);
setAttribute(Qt::WA_NoSystemBackground);
setAttribute(Qt::WA_TranslucentBackground);
setAttribute(Qt::WA_PaintOnScreen);
setAttribute(Qt::WA_TransparentForMouseEvents);
}
void Widget::paintEvent(QPaintEvent*)
{
QPainter p(this);
QString text = "Some foo goes here";
QFontMetrics metrics(p.font());
resize(metrics.size(0, text));
p.drawText(rect(), Qt::AlignCenter, text);
}
Example when showing a video with LibVLC:
使用 LibVLC 显示视频的示例：
回答by Slawek Rewaj
The best solution is provided by G?kmen G?kselin one of the comments of this article
G?kmen G?ksel在本文的评论之一中提供了最佳解决方案
setStyleSheet("background-color: rgba(0,0,0,0)");
回答by UndeadDragon
On Linux works with:
在 Linux 上使用：
setWindowFlags(Qt::FramelessWindowHint);
setAttribute(Qt::WA_NoSystemBackground);
setAttribute(Qt::WA_TranslucentBackground);
setAttribute(Qt::WA_TransparentForMouseEvents);
