Just wanted to share this code with you:

#ifndef DBGHELPER_H
#include <QString>
#ifndef QT_NO_DEBUG
#    define DEBUG_FUNC_NAME DbgHelper dbgHelper(Q_FUNC_INFO);
#else
#    define DEBUG_FUNC_NAME
#endif
 
class DbgHelper {
public:
    DbgHelper(const QString &t);
    ~DbgHelper();
private:
    QString txt;
    static int indent;
    static int colorIndex;
    int myColor;
};
#endif

#include "dbghelper.h"
#ifdef DBGHELPER_USES_PRINTF
#include <stdio.h>
#else
#include <QtDebug>
#endif
 
int DbgHelper::indent = 0;
int DbgHelper::colorIndex = 0;
 
 
static void DbgHelper_output(int color, int indent, 
                             const QString &prefix, const QString &funcName) {
  QString text = QString(4*indent, ' ')+QString(prefix+" "+funcName);
  if(color>=0){
    text.prepend("\x1b[3"+QString::number(1+color)+"m");
    text.append("\x1b[39m");
  }
#ifndef DBGHELPER_USES_PRINTF
  qDebug() << text;
#else
  fprintf(stderr, "%s\n", qPrintable(text));
#endif
}
 
DbgHelper::DbgHelper(const QString &t) {
    txt = t;
#ifdef NO_COLOR
    myColor=-1;
#else
    myColor = colorIndex;
    colorIndex = (colorIndex+1) % 7;
#endif
    DbgHelper_output(myColor, indent, "BEGIN", txt);
    ++indent;
}
 
DbgHelper::~DbgHelper() {
    --indent;
    DbgHelper_output(myColor, indent, "END", txt);
}

Now you can do this:

#include "dbghelper.h"
#include <QtDebug>
 
class Cls {
public:
  Cls(){
    DEBUG_FUNC_NAME
  }
  ~Cls() {
    DEBUG_FUNC_NAME
  }
  void method(const QString &str) {
    DEBUG_FUNC_NAME
    int x = anotherMethod();
  }
  int anotherMethod() {
    DEBUG_FUNC_NAME
    qDebug() << "Regular output";
    return 7;
  }
};
 
int main(){
 Cls c;
 c.method("foobar");
 return 0;
}

And obtain a nice colorful (where ANSI escape sequences are supported) output:

BEGIN Cls::Cls()
END Cls::Cls()
BEGIN void Cls::method(const QString&)
    BEGIN int Cls::anotherMethod()
Regular output
    END int Cls::anotherMethod()
END void Cls::method(const QString&)
BEGIN Cls::~Cls()
END Cls::~Cls()

If you want, you can extend it to take argument values as well or print the file and line numbers where a particular method is defined.

What do you think? Do you have your own macros or classes that help you with debugging?

In relation to what I wrote earlier I am happy to say that it seems that finally the problem of UIC not being able to handle custom container widgets has been solved – at least partially.

I’ve been playing with Qt 4.4 Technical Preview and I noticed that finally the issue of being unable to create correct Designer forms with multipage widgets has a solution.

In your domXml() method of the custom widget plugin you need to inform UIC about the name of the method your class uses to add pages to itself. The solution is limited as it expects the name of a method taking a pointer to QWidget only, but at least that will render containers usable.

To have a working container widget plugin you need to make sure domXml() returns something like the following:

  
    QwwNavigationBar
    QWidget
    addWidget
  

This informs UIC that QwwNavigationBar is a widget derived from QWidget that uses QwwNavigationBar::addWidget() for adding pages.

Of course I couldn’t resist myself from implementing the algorithm I have written about in the previous post.

Images below have been scaled to fit on the page. The second one was scaled down using the application.

QRetargetScale download

Some time ago I’ve been asked if I wanted to write a review of one of the new books related to Qt. I agreed and soon after I had a copy of the book in my hands. Thanks go to Camille Herrera of No Starch Press for letting me do this. I’m certainly waiting for more!

The Book of Qt4 – The Art of Building Qt Applications review

If you do or don’t agree with my review, please leave your comment. Another review of the book is available here (the site seems to be currently down though).

I often write code that iterates over an XML document and performs actions on elements with some specifig tag. Usually I do it using code like the following:

for(QDomElement elem = parent.firstChildElement("tag");
                !elem.isNull();
                elem = elem.nextSiblingElement("tag")){
    doSomething(elem);
}

This is fine, but I thought it’d be nicer to do it using the foreach() loop offered by Qt. Out of the box Qt doesn’t allow to use foreach with xml documents, so I decided to do something about it

After 15 minutes the class was ready:

#include 
#include 
#include 

class DomElementContainer {
public:
  class const_iterator {
    friend class DomElementContainer;
  public:
      const_iterator(){}
      const_iterator &operator++(){
        m_e = m_e.nextSiblingElement(m_t);
        return *this;
      }
      const QDomElement & operator*(){
        return m_e;
      }
      bool operator==(const const_iterator &other) const {
        return (m_e==other.m_e && m_t==other.m_t);
      }
      bool operator!=(const const_iterator &other) const {
        return (m_e!=other.m_e || m_t!=other.m_t);
      }
  private:
      const_iterator(const QDomElement &e, const QString &t){
        m_e = e;
        m_t = t;
      }
      QDomElement m_e;
      QString m_t;
  };

  DomElementContainer(const QDomElement &e, const QString &tag=QString::null){
    m_tag = tag;
    m_elem = e;
  }
  DomElementContainer(const QDomDocument &d, const QString &tag=QString::null){
    m_tag = tag;
    m_elem = d.documentElement();
  }
  const_iterator begin() const{
    return const_iterator(m_elem.firstChildElement(m_tag), m_tag);
  }
  const_iterator end() const {
    return const_iterator(QDomElement(), m_tag);
  }
private:
  QDomElement m_elem;
  QString m_tag;
};

Now it’s possible to do the following:

#include "domelementcontainer.h"

const char *xml = "content 1content 2 "
                  "wrongcontent"
                  "content 3";

int main(){
    QDomDocument doc;
    doc.setContent(QString(xml));
    DomElementContainer c(doc, "tag");
    foreach(QDomElement e, c)
      qDebug("%s", qPrintable(e.text()));
    return 0;
}

Download available here.