The gui is not start

[ugiwgh]

When I start my program. It is run, but the paintEvent() is not executed. So the gui is not start.
Any help will be appreciated.

Qt: 4.5.1
OS: redhat 6.0

Sometimes it outputs the following log.
X Error: BadIDChoice (invalid resource ID chosen for this connection) 14
Major opcode: 55 (X_CreateGC)
Resource id: 0x2023c
X Error: BadLength (poly request too large or internal Xlib length error) 16
Major opcode: 11 (X_UnmapSubwindows)
Resource id: 0x2023c
X Error: BadRequest (invalid request code or no such operation) 1
Extension: 255 (Uknown extension)
Minor opcode: 0 (Unknown request)
Resource id: 0x2023c

[anda_skoa]

Are you calling show() on the window/widget?
Are you calling exec() on the application?
Can you reproduce with a minimal main() that uses a standard widget, e.g. a QLabel?

Cheers,
_

[ugiwgh]

My code is following.

int main(int argc,char **argv)
{
  qDebug()<<"Main Begin";
  QApplication app(argc,argv);
 
  QWidget *widget=new QWidget;
 
  widget->show();
  //widget->showFullScreen();
 
  app.exec();
  delete widget;
  qDebug()<<"Main End";
  return 0;
}

int main(int argc,char **argv)
{
  qDebug()<<"Main Begin";
  QApplication app(argc,argv);

  QWidget *widget=new QWidget;

  widget->show();
  //widget->showFullScreen();

  app.exec();
  delete widget;
  qDebug()<<"Main End";
  return 0;
}

To copy to clipboard, switch view to plain text mode 

[anda_skoa]

That should work.
It will be a very tiny window since you did not resize the widget, but it should show.

Cheers,
_

[ugiwgh]

I add QPixmap in GUI slot function. Maybe this is the root cause, because when I remove it, the GUI show.

[anda_skoa]

Any relevant code you'd like to share?

Cheers,
_

[aamer4yu]

When I start my program. It is run, but the paintEvent() is not executed. So the gui is not start.

But from the code you shared -

QWidget *widget=new QWidget;
 
  widget->show();

QWidget *widget=new QWidget;

  widget->show();

To copy to clipboard, switch view to plain text mode 

You are creating a normal QWidget, and not a custom widget.
So where do you expect the paintEvent to get hit ? How are you checking if paintEvent was hit,, and of which class ?

[ugiwgh]

Yes, the following is the simple code.

main.h

class MRender : public QThread
{
	Q_OBJECT
public:
	MRender(){}
signals:
	void renderedPixmap(const QImage &image);
protected:
	void run();
};
 
class MCanvas : public QWidget
{
	Q_OBJECT
public:
	MCanvas(){}
public slots:
	updatePixmap(const QImage &image);
protected:
	void paintEvent(QPaintEvent *e);
private:
	QPixmap pixmap_;
};

class MRender : public QThread
{
	Q_OBJECT
public:
	MRender(){}
signals:
	void renderedPixmap(const QImage &image);
protected:
	void run();
};

class MCanvas : public QWidget
{
	Q_OBJECT
public:
	MCanvas(){}
public slots:
	updatePixmap(const QImage &image);
protected:
	void paintEvent(QPaintEvent *e);
private:
	QPixmap pixmap_;
};

To copy to clipboard, switch view to plain text mode 

main.cpp

#include "main.h"
 
MRender::run()
{
	while(1)
	{
		QPainter painter;
		QImage image(400,400,QImage::Formage_RGB32);
		image.fill(0xFFFFFF);
		painter.begin(&image);
		QRectF textRect(0,0,400,400);
		painter.drawText(textRect,Qt::AlignCenter,QString("Who are you?"));
		painter.end();
		emit renderedPixmap(image);
		sleep(1);
	}
}
 
MCanvas::updatePixmap(const QImage &image)
{
	pixmap_=QPixmap::fromImage(image);
}
MCanvas::paintEvent(QPaintEvent *e)
{
	QPianter painter;
	painter.begin(this);
	painter.drawPixmap(0,0,pixmap_);
	painter.end();
}
 
int main(int argc,char **argv);
{
	QApplication app(argc,argv);
 
	MCanvas canvas=new MCanvas;
	MRender render=new MRender;
 
	QObject::connect(render,SIGNAL(renderedPixmap(const QImage &)),canvas,SLOT(updatePixmap(const QImage &)),Qt::DirectConnection);
 
	QWidget *widget=new QWidget;
	QGridLayout *layout=new QGridLayout(widget);
	layout->addWidget(canvas);
	widget->setLayout(layout);
 
 
	widget->show();
	app.exec();
	delete widget;
	return 0;
}

#include "main.h"

MRender::run()
{
	while(1)
	{
		QPainter painter;
		QImage image(400,400,QImage::Formage_RGB32);
		image.fill(0xFFFFFF);
		painter.begin(&image);
		QRectF textRect(0,0,400,400);
		painter.drawText(textRect,Qt::AlignCenter,QString("Who are you?"));
		painter.end();
		emit renderedPixmap(image);
		sleep(1);
	}
}

MCanvas::updatePixmap(const QImage &image)
{
	pixmap_=QPixmap::fromImage(image);
}
MCanvas::paintEvent(QPaintEvent *e)
{
	QPianter painter;
	painter.begin(this);
	painter.drawPixmap(0,0,pixmap_);
	painter.end();
}

int main(int argc,char **argv);
{
	QApplication app(argc,argv);
	
	MCanvas canvas=new MCanvas;
	MRender render=new MRender;
	
	QObject::connect(render,SIGNAL(renderedPixmap(const QImage &)),canvas,SLOT(updatePixmap(const QImage &)),Qt::DirectConnection);
	
	QWidget *widget=new QWidget;
	QGridLayout *layout=new QGridLayout(widget);
	layout->addWidget(canvas);
	widget->setLayout(layout);


	widget->show();
	app.exec();
	delete widget;
	return 0;
}

To copy to clipboard, switch view to plain text mode 

The porblem is "pixmap_=QPixmap::fromImage(image);" and "painter.drawPixmap(0,0,pixmap_);".

[wysota]

You cannot create pixmap in threads other than the main thread. Your connect in line #38 cannot be a Qt::DirectConnection, it has to be Qt::QueuedConnection.

[ugiwgh]

If use Qt::QueuedConnection, when I resize the window many times, but not release mouse, the buffer queued. And as I resize the window, it take up memory will be more and more, until I release mouse.

And why you think it should use Qt::QueuedConnection?

[wysota]

If use Qt::QueuedConnection, when I resize the window many times, but not release mouse, the buffer queued.

When you don't, your program doesn't work.

And why you think it should use Qt::QueuedConnection?

Because if you use direct connection, the slot is executed in the context of the caller, which happens to be the worker thread which cannot access pixmaps. I don't know where you copied the code from but if you have to copy someone's code then at least try to understand what it does.