How to replace old C code (printf) with C++/Qt for GUI application?

kahlenberg

I have a code that was written some years ago for command line. There are lots of printf codes that was writing on screen what is happening. Now I want to replace all printf codes and I want to show everything on GUI.

  int FLASH_Image(char *fname, unsigned StartAddr, unsigned imgSize)
   {   
     ....    
     for (i = StartSector; i < StartSector + NrOfSectors; i++) {
        printf("\rErasing sector %02d ...",i);
        FLASH_SectorErase((unsigned)i*SECTORSIZE);
     }
     ....
   }

If I use a parameter char *msg pointer for text messages, it will be "valid" after function ends. I want to "update" it during function runs. How is it possible?

? Offline

Hi! Are you familiar with Qt's concept of signals and slots? Your function could emit a signal that contains a string with the current text to be displayed. Your displaying UI component can be connected to that signal.

kahlenberg

@Wieland Yes I am familiar with signal/slots. But the problem is that there is no class in those old C code . Without object how can I emit a signal? It doesn't work even if I declare signal functions as static.
I have a UDP class in UDP.h, I have this old C code in flash.h and implementation in flash.c, Mainwindow.h includes flash.h, and flash.h includes udp.h, the include hieararchy is so:

udp.h (with object, signals and slots)  
           |
           V
flash.h (wihtout objects, only func declarations) 
           |
           V
mainwindow.h

jsulm

Replace printf() with your own function which then passes the strings to main window.
You could even name it printf() and remove the include <stdio.h> (and include your header file) from your C code, then you do not have to change anything else :-)

? Offline

I wouldn't mix UI components and business logic, e.g. access the MainWindow from flash.cpp. IMAO it's better to create an adapter for message passing:

msgadapter.h

#ifndef MSGADAPTER_H
#define MSGADAPTER_H

#include <QtCore>

class MsgAdapter : public QObject
{
    Q_OBJECT
public:
    MsgAdapter(QObject *parent = 0);
public:
    void printf(const char *format, ...);
signals:
    void msg(QString);
};

#endif // MSGADAPTER_H

msgadapter.cpp

#include "msgadapter.h"


MsgAdapter::MsgAdapter(QObject *parent)
    : QObject(parent)
{
}


void MsgAdapter::printf(const char *format, ...) {
    va_list args;
    va_start(args, format);
    char *result;
    const int n = vasprintf(&result, format, args);
    va_end(args);
    if (n>=0) {
        emit msg(result);
        free(result);
    }
}

flash.h

#ifndef FLASH_H
#define FLASH_H

class MsgAdapter;

void setMsgAdapter(MsgAdapter *msgAdapter);
void FLASH_Image();

#endif // FLASH_H

flash.cpp

#include "flash.h"

#include "msgadapter.h"

static MsgAdapter *g_msgAdapter = 0;


void setMsgAdapter(MsgAdapter *msgAdapter)
{
    g_msgAdapter = msgAdapter;
}


void FLASH_Image()
{
    g_msgAdapter->printf("\rErasing sector %02d ...", 23);
}

In mainwindow.cpp

#include "msgadapter.h"
#include "flash.h"


MainWindow::MainWindow(QWidget *parent) :
    QMainWindow(parent),
    ui(new Ui::MainWindow)
{
    ui->setupUi(this);

    MsgAdapter * msgAdapter = new MsgAdapter(this);
    setMsgAdapter(msgAdapter);
    connect(msgAdapter, SIGNAL(msg(QString)), ui->label, SLOT(setText(QString)));
}

MainWindow::~MainWindow()
{
    setMsgAdapter(0);
    delete ui;
}