[Webkit-unassigned] [Bug 28865] New: [Qt] Make cursor set cleaner in QtWebKit Api: eliminate SetCursorEvent hack.

[bugzilla-daemon at webkit.org]

https://bugs.webkit.org/show_bug.cgi?id=28865

           Summary: [Qt] Make cursor set cleaner in QtWebKit Api:
                    eliminate SetCursorEvent hack.
           Product: WebKit
           Version: 528+ (Nightly build)
          Platform: PC
        OS/Version: All
            Status: NEW
          Severity: Normal
          Priority: P2
         Component: WebKit Qt
        AssignedTo: webkit-unassigned at lists.webkit.org
        ReportedBy: tonikitoo at gmail.com
                CC: tonikitoo at gmail.com, hausmann at webkit.org,
                    ariya.hidayat at trolltech.com,
                    kenneth.christiansen at openbossa.org


[Background]

Instead of the default architecture flow commonly used when embedding through
by QtWebKit API (QWebView -> QWebPage -> QWebFrame), one has the following:
CustomWidget -> QWebPage -> QWebFrame (e.g. DUI's QFxWebView [1] or plasma's
WebView [2])

[1]
http://qt.gitorious.org/+qt-kinetic-developers/qt/kinetic/blobs/kinetic-declarativeui-gv/src/declarative/fx/qfxwebview.h
[2]
http://api.kde.org/4.x-api/kdelibs-apidocs/plasma/html/classPlasma_1_1WebView.html

[Bug description]

currently it is very hacky the way cursors are set to the QApplication. The
flow is +- :

1) an outer embedding widget (for example qwebview or any other custom web
widget) receives mouse events (like the 'mousemove' event)

2) mousemove event is sent to qwebpage (see QWebPage::event and then to
QWebPagePrivate::mouseMoveEvent) and then to WebCore.

3) When there is a cursor change, WidgetQt::setCursor method is called (see
quotation below).

#include "qwebframe_p.h" // <-- that includes qwebpage_p.h
(...)
void Widget::setCursor(const Cursor& cursor)
{
#ifndef QT_NO_CURSOR
    QWidget* widget = root()->hostWindow()->platformWindow();
(...)
    QCoreApplication::postEvent(widget, new SetCursorEvent(cursor.impl()));
#endif
(...)
}

4) 3_ sends an custom event back to QWebView and from within QWebView::event()
method, we have:

void QWebView::event() {
(...)
#ifndef QT_NO_CURSOR
        } else if (e->type() ==
static_cast<QEvent::Type>(WebCore::SetCursorEvent::EventType)) {
            d->setCursor(static_cast<WebCore::SetCursorEvent*>(e)->cursor());
#if QT_VERSION >= 0x040400
(...)

whereas a static_cast to a not exposed class happens. pontentially wrong
things:

* in WidgetQt::setCursor method we have

    ...
    QWidget* widget = root()->hostWindow()->platformWindow();
    if (!widget)
        return;
    ...

here, it is mandatory that platformWindow() returns a QWidget, which can be
problematic for non-QWidget subclasses (e.g. QGraphicsWidget subclass objects).

    ...
    QCoreApplication::postEvent(widget, new SetCursorEvent(cursor.impl()));
    ...

SetCursorEvent is defined in a private header, so this class wont be available
together with other API headers. In QWebView it is not a problem, since it
includes this private header, but it can be a problem on other situations,
including DUI and plasma's qgraphicswidget approaches.

this API needs some better implementation, imho

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