[Webkit-unassigned] [Bug 29414] New: [Qt] [Regression] Transparent QWebView

Fri Sep 18 07:36:09 PDT 2009

https://bugs.webkit.org/show_bug.cgi?id=29414

           Summary: [Qt] [Regression] Transparent QWebView
           Product: WebKit
           Version: 528+ (Nightly build)
          Platform: Other
        OS/Version: Mac OS X 10.5
            Status: NEW
          Keywords: Qt
          Severity: Normal
          Priority: P2
         Component: New Bugs
        AssignedTo: webkit-unassigned at lists.webkit.org
        ReportedBy: vestbo at webkit.org

This bug report originated from issue QTBUG-3706
<http://bugreports.qt.nokia.com/browse/QTBUG-3706>

--- Description ---

The result of the code below is a fully-transparent background in the HTML
page, so that one can overlay it over an existing widget background. This
worked in Qt 4.4.3, but not anymore in 4.5.0. The page renders with a solid
white background instead.

Test case (needs an image):
//----------------------------------------------------

int main(int argc, char *argv[])
{
    QApplication a(argc, argv);
    QWidget *widget = new QWidget;
    widget->setStyleSheet("QWidget {background: url(background.png)}");
    QVBoxLayout *vbox = new QVBoxLayout(widget);
    QWebView *webView = new QWebView;
    vbox->addWidget(webView);
    QPalette p = webView->palette();
    p.setColor( QPalette::Dark, Qt::transparent );
    webView->setPalette(p);
    p = webView->page()->palette();
    p.setColor( QPalette::Window, Qt::transparent );
    webView->page()->setPalette(p);
    webView->setHtml("<body style='background: rgba(0,0,0,0)'>"
"<h1 style='color:white'>Test</h1></body>");
    widget->show();
    return a.exec();
}
//----------------------------------------------------

--- Comments ---

Note: qtuser: 03/09/09 03:32:05 PM:
Here's a fix/workaround for this issue:

The difference between Qt 4.4 and 4.5 is that in Qt 4.4, the background is
first filled with QPalette::Dark by the QWebView followed by QPalette::Window
by the QWebPage.  In Qt 4.5, the page background is only filled with the
QPalette::Base color.  Making that color transparent in the palette of the
QWebView allows the page to be transparent again.  However, a small change to
the Qt source is also necessary in order for painting to work properly:

In the file src/3rdparty/webkit/WebKit/qt/Api/qwebview.cpp, in
QWebView::setPage(), remove the following line:

setAttribute(Qt::WA_OpaquePaintEvent, d->page);

I would say the 4.5 behavior is better.  It's just different from 4.4 -- but
maybe nobody else was doing transparent QWebViews, so I'd rather stick with the
4.5 behavior (with the above fix).

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