Simple program with many errors

meolic · #1 16-May-2009, 12:04

Hi,

I am trying to prepare simple project for lab exercises (YES, we are trying to use fltk 1.1.9 in a course about C++ programming).

Well, I am new to this and I have problems with basic concepts. Here is a "should be simple" program which has some really bad erros, it doesn't even compile. And I am unable to prepare a correct version, Any suggestion will be of great help.

BTW: I have posted the same question also to fltk.org forum, please tell me, if you (GIDForums) do not like such flooding.

CPP / C++ / C Code:

#include <FL/Fl.H>
#include <FL/Fl_Window.H>
#include <FL/Fl_JPEG_Image.H>
#include <FL/Fl_Box.H>
#include <FL/Fl_Button.H>

#include <iostream>
using namespace std;

class MainWindow : public Fl_Window {

  public:
  MainWindow() : Fl_Window(800,600,"My program") {}
};

class Background : Fl_Box {

  public:
  Background(Fl_JPEG_Image bgimg) : Fl_Box(0,0,800,530) {
    image(bgimg);
  }
};

class Toolbar {

  public:
  Toolbar() {
    Fl_Button buttonPlus(100,0,50,50,"+");
    buttonPlus.labelsize(50);
    buttonPlus.callback(cb_buttonPlus);

    Fl_Button buttonMinus(0,0,50,50,"-");
    buttonMinus.labelsize(50);
    buttonMinus.callback(cb_buttonMinus);
  }

  private:
  static void cb_buttonPlus(Fl_Widget *w, void *data) {
    cout << "PLUS" << endl;
  }

  static void cb_buttonMinus(Fl_Widget *w, void *data) {
    cout << "MINUS" << endl;
  }
};

int main() {
  Fl_JPEG_Image slovenija("slovenija-800x530.jpg");
  MainWindow mainWindow;
  mainWindow.begin();
  Background background(slovenija);
  Toolbar toolbar;
  mainWindow.end();
  mainWindow.show();
  return Fl::run();
}

meolic · #2 21-May-2009, 07:22

Hi again,

I found all (?) mistakes and improved the program. It ended with 110 line and was already served as a demonstration example. Quite successful!

The first error was in the foolowing line:

Background(Fl_JPEG_Image bgimg) : Fl_Box(0,0,800,530) {

There is no copy constructor for Fl_JPEG_Image, thus a reference should be used. This was compiler error.

The second error was in the line (and similar a few lines down):

Fl_Button buttonPlus(100,0,50,50,"+");

Created buttonPlus is a local variable for Toolbar::Toolbar(), thus I get
runtime error becuase it does not exist after the constructor finishes.

I am sending here the final code (well, I used a picture called slovenia.jpg, it can be any JPEG, just change the name in the code). Any comments or suggestions?

Best regards, Robert

CPP / C++ / C Code:

// [email]meolic@uni-mb.si[/email], 2009
// This is based on FLTK documentation
// Build with: fltk-config --use-images --compile "%f"
// Build with: g++ -Wall "%f" -lfltk -lfltk_images -lfltk_jpeg -lXext

#include <FL/Fl.H>
#include <FL/Fl_Window.H>
#include <FL/Fl_JPEG_Image.H>
#include <FL/Fl_Box.H>
#include <FL/Fl_Button.H>

#include <iostream>
#include <string>

using namespace std;

void cbButtonPlus(Fl_Widget* w, void* data);
void cbButtonMinus(Fl_Widget* w, void* data);

class MainWindow : public Fl_Window {

  private:
  Fl_Image* imageOrg;
  Fl_Image* imageShown;
  Fl_Box workingBox;
  Fl_Button buttonPlus;
  Fl_Button buttonMinus;
  int zoom;

  public:
  MainWindow(string imageName, Fl_Image& thisImage);
  void zoomIn();
  void zoomOut();

  private:
  void showImage();
};

MainWindow::MainWindow(string imageName, Fl_Image& thisImage) :
    Fl_Window(800,600,imageName.c_str()),
    imageOrg(&thisImage),
    imageShown(0),
    workingBox(160,20,480,480),
    buttonPlus(350,550,50,50),
    buttonMinus(450,550,50,50),
    zoom(100)
{
  color(FL_BLACK); //window background

  begin();

  workingBox.box(FL_FLAT_BOX); //no border
  workingBox.color(FL_BLACK); //box background

  buttonPlus.label("+");
  buttonPlus.labelsize(50);
  buttonPlus.color(FL_YELLOW);
  buttonPlus.callback(cbButtonPlus);

  buttonMinus.label("-");
  buttonMinus.labelsize(50);
  buttonMinus.color(FL_YELLOW);
  buttonMinus.callback(cbButtonMinus);

  end();

  showImage();
}

void MainWindow::zoomIn() {
  if (zoom < 200) {
    zoom = zoom + 10;
    showImage();
  }
}

void MainWindow::zoomOut() {
  if (zoom > 10) {
    zoom = zoom - 10;
    showImage();
  }
}

void MainWindow::showImage() {
  delete(imageShown);
  imageShown = imageOrg->copy((480*zoom)/100,(480*zoom)/100);
  workingBox.image(*imageShown);
  workingBox.redraw();
}

int main() {
  Fl::visual(FL_DOUBLE|FL_INDEX); //recommended initialization
  string imageName = "slovenia.jpg";
  Fl_JPEG_Image image(imageName.c_str());
  MainWindow mainWindow(imageName,image);
  mainWindow.show();
  return Fl::run();
}

// Callback for buttonPlus
void cbButtonPlus(Fl_Widget* w, void* data) {
    MainWindow* mainWindow = ((MainWindow*) w->parent());
    mainWindow->zoomIn();
}

// Callback for button Minus
void cbButtonMinus(Fl_Widget* w, void* data) {
    MainWindow* mainWindow = ((MainWindow*) w->parent());
    mainWindow->zoomOut();
}

chandrashekhar · #3 08-Jun-2009, 01:56

Hey how do you compile it?

I tried to compile like this:
gcc -lfltk test2.cxx -o test2

but it's saying:

/tmp/cctxceop.o: In function `main':
test2.cxx:(.text+0x537): undefined reference to `Fl_JPEG_Image::Fl_JPEG_Image(char const*)'
collect2: ld returned 1 exit status

Can you give me the complete compile command?

chandrashekhar · #4 08-Jun-2009, 02:17

I tried to put the callback inside the class Main_window...but could not succeed...it's throwing a lot of errors.....can you tell me how to do that....it would be very much like java...

meolic · #5 08-Jun-2009, 03:06

Hi,

Compiler parameters depend on system and instalation method. For example:

1. On Linux you can use fltk-config which is a nice script:
fltk-config --use-images --compile test.cxx

2. On Linux/Ubuntu 9.04 + FLTK from repository the following line is working for me:
g++ -Wall test.cxx -lfltk -lfltk_images

3. On Linux/Ubuntu old + FLTK compiled from sources I am using:
g++ -Wall test.cxx -lfltk -lfltk_images -lfltk_jpeg -lXext

4. To compile on Windows + VC++ you must follow some instructions, e.g. from a book "Bjarne Stroustrup: Programming -- Principles and Practice Using C++".

Quote:

Originally Posted by chandrashekhar

I tried to put the callback inside the class Main_window...but could not succeed...it's throwing a lot of errors.....can you tell me how to do that....it would be very much like java...

Callback functions cannot be a class member. There will be a problem with types. An explanation for this is given here (but it is not an easy explanation):

http://www.parashift.com/c++-faq-lite/pointers-to-members.html

(Why I cannot post the complete link?? Search for "Pointers to member functions")

I like Java, too. But do not try to use to much Java style in C++ programs.
Going into details, C++ is a very different language!

Robert

chandrashekhar · #6 08-Jun-2009, 04:25

Thanks a lot for ur help...it compiled and ran perfectly....also ur explanation on not having callbacks as class members is quite satisfactory...

chandrashekhar · #7 08-Jun-2009, 04:48

Hey I succeeded in putting the callbacks inside the class......
Here's the code.......

CPP / C++ / C Code:

// [email]meolic@uni-mb.si[/email], 2009
// This is based on FLTK documentation
// Build with: fltk-config --use-images --compile "%f"
// Build with: g++ -Wall "%f" -lfltk -lfltk_images -lfltk_jpeg -lXext

#include <FL/Fl.H>
#include <FL/Fl_Window.H>
#include <FL/Fl_JPEG_Image.H>
#include <FL/Fl_Box.H>
#include <FL/Fl_Button.H>

#include <iostream>
#include <string>

using namespace std;


class MainWindow : public Fl_Window {

  private:
  Fl_Image* imageOrg;
  Fl_Image* imageShown;
  Fl_Box workingBox;
  Fl_Button buttonPlus;
  Fl_Button buttonMinus;
  int zoom;

  public:
  MainWindow(string imageName, Fl_Image& thisImage);
  void zoomIn();
  void zoomOut();

  private:
  static void cbButtonPlus(Fl_Widget* w, void* data);
  static void cbButtonMinus(Fl_Widget* w, void* data);
  void showImage();
};

MainWindow::MainWindow(string imageName, Fl_Image& thisImage) :
    Fl_Window(800,600,imageName.c_str()),
    imageOrg(&thisImage),
    imageShown(0),
    workingBox(160,20,480,480),
    buttonPlus(350,550,50,50),
    buttonMinus(450,550,50,50),
    zoom(100)
{
  color(FL_BLACK); //window background

  begin();

  workingBox.box(FL_FLAT_BOX); //no border
  workingBox.color(FL_BLACK); //box background

  buttonPlus.label("+");
  buttonPlus.labelsize(50);
  buttonPlus.color(FL_YELLOW);
  buttonPlus.callback(this->cbButtonPlus);

  buttonMinus.label("-");
  buttonMinus.labelsize(50);
  buttonMinus.color(FL_YELLOW);
  buttonMinus.callback(cbButtonMinus);

  end();

  showImage();
}

void MainWindow::zoomIn() {
  if (zoom < 200) {
    zoom = zoom + 10;
    showImage();
  }
}

void MainWindow::zoomOut() {
  if (zoom > 10) {
    zoom = zoom - 10;
    showImage();
  }
}

void MainWindow::showImage() {
  delete(imageShown);
  imageShown = imageOrg->copy((480*zoom)/100,(480*zoom)/100);
  workingBox.image(*imageShown);
  workingBox.redraw();
}

int main() {
  Fl::visual(FL_DOUBLE|FL_INDEX); //recommended initialization
  string imageName = "slovenia.jpg";
  Fl_JPEG_Image image(imageName.c_str());
  MainWindow mainWindow(imageName,image);
  mainWindow.show();
  return Fl::run();
}

// Callback for buttonPlus
void MainWindow::cbButtonPlus(Fl_Widget* w, void* data) {
    MainWindow* mainWindow = ((MainWindow*) w->parent());
    mainWindow->zoomIn();
}

// Callback for button Minus
void MainWindow::cbButtonMinus(Fl_Widget* w, void* data) {
    MainWindow* mainWindow = ((MainWindow*) w->parent());
    mainWindow->zoomOut();
}

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Simple program with many errors

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Re: Simple program with many errors

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