Resize cursor doesn't change back (qx11embedcontainer in qmdisubwindow in qmdiarea)

[bartsch]

Hi,

I'm writing some kind of a window manager. Therefor I'm embedding windows
within a QX11EmbedContainer in a QMdiSubWindow in a QMdiArea. That part
is working fine.

The problem is the resizing cursor, which doesn't change back into a normal
pointer when moving it from the edge of a QMdiSubWindow to the center,
where the QX11EmbedContainer is. When moving the cursor from the edge of
the QMdiSubWindow to the QMdiArea, the resize cursor changes back to a
normal pointer.

I think QX11EmbedContainer eats some events meant for the
QMdiSubWindow. So, the QMdiSubWindow doesn't notice when to reset the
cursor. But, i haven't figured out how to deal with that.

Here's a stripped down example showing the effect. You'll need to start an
application (i.e. I tested with `evince`) and pass the window id as argument
to the test application.

#include <QApplication>
#include <QDebug>
#include <QMdiArea>
#include <QMdiSubWindow>
#include <QObject>
#include <QTimer>
#include <QX11EmbedContainer>
 
class Container : public QX11EmbedContainer
{
	Q_OBJECT
public:
	Container(QMdiArea *_area, int client)
		:QX11EmbedContainer(),
		 area(_area)
	{
		QObject::connect
			(this, SIGNAL(clientClosed()),
			 SLOT(slot_client_closed()));
		QObject::connect
			(this, SIGNAL(clientIsEmbedded()),
			 SLOT(slot_client_is_embedded()));
		QObject::connect
			(this, SIGNAL(error(QX11EmbedContainer::Error)),
			 SLOT(slot_client_error(QX11EmbedContainer::Error)));
 
		frame = new QMdiSubWindow();
		frame->setWidget(this);
 
		embedClient(client);
	}
 
private:
	QMdiArea *area;
	QMdiSubWindow *frame;
	void exit(void) {QTimer::singleShot(250, qApp, SLOT(quit()));}
 
public slots:
	void slot_client_closed(void) {exit();}
	void slot_client_is_embedded(void)
	{
		area->addSubWindow(frame);
		frame->show();
	}
	void slot_client_error(QX11EmbedContainer::Error error)
	{
		qDebug() << "error #" << error;
		exit();
	}
};
 
/* ugly hack to prevent: undefined reference to `vtable... */
#include "main.moc"
 
int main(int argc, char *argv[])
{
	QApplication *app = new QApplication(argc, argv);
 
	if (app->arguments().count() != 2) {
		qFatal("Error - expected window id as argument");
		return 1;
	}
 
	QMdiArea *area = new QMdiArea();
	area->show();
 
	new Container(area, app->arguments()[1].toInt(0, 16));
 
	return app->exec();
}

#include <QApplication>
#include <QDebug>
#include <QMdiArea>
#include <QMdiSubWindow>
#include <QObject>
#include <QTimer>
#include <QX11EmbedContainer>

class Container : public QX11EmbedContainer
{
	Q_OBJECT
public:
	Container(QMdiArea *_area, int client)
		:QX11EmbedContainer(),
		 area(_area)
	{
		QObject::connect
			(this, SIGNAL(clientClosed()),
			 SLOT(slot_client_closed()));
		QObject::connect
			(this, SIGNAL(clientIsEmbedded()),
			 SLOT(slot_client_is_embedded()));
		QObject::connect
			(this, SIGNAL(error(QX11EmbedContainer::Error)),
			 SLOT(slot_client_error(QX11EmbedContainer::Error)));

		frame = new QMdiSubWindow();
		frame->setWidget(this);

		embedClient(client);
	}

private:
	QMdiArea *area;
	QMdiSubWindow *frame;
	void exit(void) {QTimer::singleShot(250, qApp, SLOT(quit()));}

public slots:
	void slot_client_closed(void) {exit();}
	void slot_client_is_embedded(void)
	{
		area->addSubWindow(frame);
		frame->show();
	}
	void slot_client_error(QX11EmbedContainer::Error error)
	{
		qDebug() << "error #" << error;
		exit();
	}
};

/* ugly hack to prevent: undefined reference to `vtable... */
#include "main.moc"

int main(int argc, char *argv[])
{
	QApplication *app = new QApplication(argc, argv);

	if (app->arguments().count() != 2) {
		qFatal("Error - expected window id as argument");
		return 1;
	}

	QMdiArea *area = new QMdiArea();
	area->show();

	new Container(area, app->arguments()[1].toInt(0, 16));

	return app->exec();
}

To copy to clipboard, switch view to plain text mode 

[bartsch]

Just found a solution - raw XEvents:
- register an event filter
- search for an EnterNotify with a matching subwindow id
- set the desired cursor

#include <QApplication>
#include <QDebug>
#include <QMdiArea>
#include <QMdiSubWindow>
#include <QObject>
#include <QTimer>
#include <QX11EmbedContainer>
#include <QX11Info>
 
#include <X11/cursorfont.h>
#include <X11/Xlib.h>
 
class Container : public QX11EmbedContainer
{
	Q_OBJECT
public:
	Container(QMdiArea *_area, Window _client)
		:QX11EmbedContainer(),
		 area(_area)
	{
		QObject::connect
			(this, SIGNAL(clientClosed()),
			 SLOT(slot_client_closed()));
		QObject::connect
			(this, SIGNAL(clientIsEmbedded()),
			 SLOT(slot_client_is_embedded()));
		QObject::connect
			(this, SIGNAL(error(QX11EmbedContainer::Error)),
			 SLOT(slot_client_error(QX11EmbedContainer::Error)));
 
		frame = new QMdiSubWindow();
		frame->setWidget(this);
 
		embedClient(_client);
	}
 
private:
	QMdiArea *area;
	QMdiSubWindow *frame;
	void exit(void) {QTimer::singleShot(250, qApp, SLOT(quit()));}
 
public slots:
	void slot_client_closed(void) {exit();}
	void slot_client_is_embedded(void)
	{
		area->addSubWindow(frame);
		frame->show();
	}
	void slot_client_error(QX11EmbedContainer::Error error)
	{
		qDebug() << "error #" << error;
		exit();
	}
};
 
class X11EventFilter
{
public:
	static bool x11_event_filter(void *msg, long *res)
	{
		XEvent *ev = reinterpret_cast<XEvent*>(msg);
		if (ev->xany.type != EnterNotify) return NULL;
 
		if (X11EventFilter::client == ev->xcrossing.subwindow) {
			XDefineCursor
				(QX11Info::display(), X11EventFilter::client,
				 XCreateFontCursor
					(QX11Info::display(), XC_left_ptr));
		}
 
		return false;
	}
 
	static Window client;
};
Window X11EventFilter::client = 0;
 
/* ugly hack to prevent: undefined reference to `vtable... */
#include "main.moc"
 
int main(int argc, char *argv[])
{
	QApplication *app = new QApplication(argc, argv);
 
	if (app->arguments().count() != 2) {
		qFatal("Error - expected window id as argument");
		return 1;
	}
 
	app->setEventFilter(X11EventFilter::x11_event_filter);
 
	QMdiArea *area = new QMdiArea();
	area->show();
 
	X11EventFilter::client = app->arguments()[1].toInt(0, 16);
	new Container(area, X11EventFilter::client);
 
	return app->exec();
}

#include <QApplication>
#include <QDebug>
#include <QMdiArea>
#include <QMdiSubWindow>
#include <QObject>
#include <QTimer>
#include <QX11EmbedContainer>
#include <QX11Info>

#include <X11/cursorfont.h>
#include <X11/Xlib.h>

class Container : public QX11EmbedContainer
{
	Q_OBJECT
public:
	Container(QMdiArea *_area, Window _client)
		:QX11EmbedContainer(),
		 area(_area)
	{
		QObject::connect
			(this, SIGNAL(clientClosed()),
			 SLOT(slot_client_closed()));
		QObject::connect
			(this, SIGNAL(clientIsEmbedded()),
			 SLOT(slot_client_is_embedded()));
		QObject::connect
			(this, SIGNAL(error(QX11EmbedContainer::Error)),
			 SLOT(slot_client_error(QX11EmbedContainer::Error)));

		frame = new QMdiSubWindow();
		frame->setWidget(this);

		embedClient(_client);
	}

private:
	QMdiArea *area;
	QMdiSubWindow *frame;
	void exit(void) {QTimer::singleShot(250, qApp, SLOT(quit()));}

public slots:
	void slot_client_closed(void) {exit();}
	void slot_client_is_embedded(void)
	{
		area->addSubWindow(frame);
		frame->show();
	}
	void slot_client_error(QX11EmbedContainer::Error error)
	{
		qDebug() << "error #" << error;
		exit();
	}
};

class X11EventFilter
{
public:
	static bool x11_event_filter(void *msg, long *res)
	{
		XEvent *ev = reinterpret_cast<XEvent*>(msg);
		if (ev->xany.type != EnterNotify) return NULL;

		if (X11EventFilter::client == ev->xcrossing.subwindow) {
			XDefineCursor
				(QX11Info::display(), X11EventFilter::client,
				 XCreateFontCursor
					(QX11Info::display(), XC_left_ptr));
		}

		return false;
	}

	static Window client;
};
Window X11EventFilter::client = 0;

/* ugly hack to prevent: undefined reference to `vtable... */
#include "main.moc"

int main(int argc, char *argv[])
{
	QApplication *app = new QApplication(argc, argv);

	if (app->arguments().count() != 2) {
		qFatal("Error - expected window id as argument");
		return 1;
	}

	app->setEventFilter(X11EventFilter::x11_event_filter);

	QMdiArea *area = new QMdiArea();
	area->show();

	X11EventFilter::client = app->arguments()[1].toInt(0, 16);
	new Container(area, X11EventFilter::client);

	return app->exec();
}

To copy to clipboard, switch view to plain text mode 

Well, it works as I want. But, it doesn't look like the best solution to me.
Any suggestions for improvements? A plain Qt solution?

---

Added after 1 26 minutes:

The solution with XDefineCursor() was not that perfect - as expected. Now, instead of
using XDefineCursor(), I "find" and call unsetCursor() of the underlying QMdiSubWindow.

If I don't report back. I haven't found any other issues with that solution.