finalcut/doc/first-steps.md

First steps with the Final Cut widget toolkit

Table of Contents

• How to use the library
• Memory Management
• Event Processing
  • Event handler reimplementation
• Signals and Callbacks
  • Default signals
• Callback function
• Callback method
• Custom signals

How to use the library

At the beginning of this introduction to the Final Cut we will start with a small example.

The following example creates an empty 30×10 character dialog.

File: dialog.cpp

#include <final/final.h>

int main (int argc, char* argv[])
{
  finalcut::FApplication app(argc, argv);
  finalcut::FDialog dialog(&app);
  dialog.setText ("A dialog");
  const finalcut::FPoint position(25, 5);
  const finalcut::FSize size(30, 10);
  dialog.setGeometry (position, size);
  app.setMainWidget(&dialog);
  dialog.show();
  return app.exec();
}

(Note: You can close the dialog with the mouse, Shift+F10 or Ctrl+^)

After entering the source code in dialog.cpp you can compile the above program with gcc:

g++ -O2 -lfinal dialog.cpp -o dialog

How it works

#include <final/final.h>

All final cut programs must include the final.h header.

finalcut::FApplication app(argc, argv);

This line creates the finalcut::FApplication object app with the command line arguments argc and argv. This object manages the application main event loop. It receives keyboard and mouse events and sends them to the target widgets. You must create an application object before you can create a widgets object.

The next line

finalcut::FDialog dialog(&app);

creates the finalcut::FDialog object dialog with the object app as parent object. The finalcut::FDialog class is the base class for creating dialog windows.

dialog.setText ("A dialog");

The title bar of the dialog box gets the text "A dialog".

finalcut::FPoint position(25, 5);
finalcut::FSize size(30, 10);
dialog.setGeometry (position, size);

The dialog window gets a width of 30 and a height of 10 characters. The position of the window in the terminal is at x=25 and y=5 (note: x=1 and y=1 represents the upper left corner).

app.setMainWidget(&dialog);

The dialog object was now selected as the main widget for the application. When you close the main widget, the entire application quits.

dialog.show();

A window or widget is not visible directly after its creation. Only the call of show() makes it (and its child objects, if available) visible.

return app.exec();

The last line calls exec() to start the application and return the result to the operating system. The started application enters the main event loop. This loop does not end until the window is not closed.

Memory Management

To create a hierarchy of FObjects (or derived classes/widgets), a new FObject must initialize with its parent object.

FObject* parent = new FObject();
FObject* child  = new FObject(parent);

To deallocate the used memory of a parent FObject, the allocated memory of its child objects will also automatically deallocate.

An object can also be assigned to another object later via addChild().

FObject* parent = new FObject();
FObject* child = new FObject();
parent->addChild(child);

The child object assignment can also remove at any time with delChild().

FObject* parent = new FObject();
FObject* child  = new FObject(parent);
parent->delChild(child);

If an FObject with a parent will remove from the hierarchy, the destructor automatically deletes the object assignment from its parent object. If a class object doesn't derive from FObject, you must implement storage deallocation yourself.

File: memory.cpp

#include <final/final.h>

using namespace finalcut;

int main (int argc, char* argv[])
{
  FApplication app(argc, argv);

  // The object dialog is managed by app
  FDialog* dialog = new FDialog(&app);
  dialog->setText ("Window Title");
  dialog->setGeometry (FPoint(25, 5), FSize(40, 8));

  // The object input is managed by dialog
  FLineEdit* input = new FLineEdit("predefined text", dialog);
  input->setGeometry(FPoint(8, 2), FSize(29, 1));
  input->setLabelText (L"&Input");

  // The object label is managed by dialog
  FLabel* label = new FLabel ( "Lorem ipsum dolor sit amet, consectetur "
                               "adipiscing elit, sed do eiusmod tempor "
                               "incididunt ut labore et dolore magna aliqua."
                             , dialog );
  label->setGeometry (FPoint(2, 4), FSize(36, 1));
  app.setMainWidget(dialog);
  dialog->show();
  return app.exec();
}

(Note: You can close the window with the mouse, Shift+F10 or Ctrl+^)

After entering the source code in memory.cpp you can compile the above program with gcc:

g++ -O2 -lfinal memory.cpp -o memory

Event Processing

Calling FApplication::exec() starts the FINAL CUT main event loop. While the event loop is running, the system constantly checks whether an event has occurred and sends it to the application's currently focused object. The events of the terminal such as keystrokes, mouse actions or resizing the terminal are translated into FEvent objects and sent it to the active FObject. It is also possible to use FApplication::sendEvent() or FApplication::queueEvent() to send your own events to an object.

FObject-derived objects process incoming events by reimplementing the virtual method event(). The FObject itself calls only onTimer() or onUserEvent() and ignores all other events. The FObject-derived class FWidget also reimplements the event() method to handle further events. FWidget calls the FWidget::onKeyPress method when you press a key, or the FWidget::onMouseDown method when you click a mouse button.

Event handler reimplementation

An event in FINAL CUT is an object that inherits from the base class FEvent. There are several event types, represented by an enum value. For example, the method FEvent::type() returns the type fc::MouseDown_Event when you press down a mouse button.

Some event types have data that cannot store in an FEvent object. For example, a click event of the mouse must store which button it triggered where the mouse pointer was at that time. In classes derived from FEvent, such as FMouseEvent(), we store this data.

Widgets get their events from the event() method inherited from FObject. The implementation of event() in FWidget forwards the most common event types to specific event handlers such as FMouseEvent(), FKeyEvent() or FResizeEvent(). There are many other event types. It is also possible to create own event types and send them to other objects.

The FINAL CUT event types:

enum events
{
  None_Event,               // invalid event
  KeyPress_Event,           // key pressed
  KeyUp_Event,              // key released
  KeyDown_Event,            // key pressed
  MouseDown_Event,          // mouse button pressed
  MouseUp_Event,            // mouse button released
  MouseDoubleClick_Event,   // mouse button double click
  MouseWheel_Event,         // mouse wheel rolled
  MouseMove_Event,          // mouse move
  FocusIn_Event,            // focus in
  FocusOut_Event,           // focus out
  ChildFocusIn_Event,       // child focus in
  ChildFocusOut_Event,      // child focus out
  WindowActive_Event,       // activate window
  WindowInactive_Event,     // deactivate window
  WindowRaised_Event,       // raise window
  WindowLowered_Event,      // lower window
  Accelerator_Event,        // keyboard accelerator
  Resize_Event,             // terminal resize
  Show_Event,               // widget is shown
  Hide_Event,               // widget is hidden
  Close_Event,              // widget close
  Timer_Event,              // timer event occur
  User_Event                // user defined event
};

File: timer.cpp

#include <final/final.h>

using namespace finalcut;

class dialogWidget : public FDialog
{
  public:
    explicit dialogWidget (FWidget* parent = nullptr)
      : FDialog(parent)
    {
      setText ("Dialog");
      setGeometry (FPoint(25, 5), FSize(23, 4));
      label.setGeometry (FPoint(1, 1), FSize(10, 1));
      label.setAlignment (fc::alignRight);
      value.setGeometry (FPoint(11, 1), FSize(10, 1));
      id = addTimer(100);
    }

  private:
    virtual void onTimer (FTimerEvent* ev)
    {
      if ( id == ev->getTimerId() && n < 9999999999 )
      {
        value.setNumber(n);
        value.redraw();
        n++;
      }
    }

    FLabel label{"Counter: ", this};
    FLabel value{"0", this};
    long n{0};
    int id{0};
};

int main (int argc, char* argv[])
{
  FApplication app(argc, argv);
  dialogWidget dialog(&app);
  app.setMainWidget(&dialog);
  dialog.show();
  return app.exec();
}

(Note: You can close the window with the mouse, Shift+F10 or Ctrl+^)

After entering the source code in timer.cpp you can compile the above program with gcc:

g++ -O2 -lfinal -std=c++11 timer.cpp -o timer

Signals and Callbacks

The callback mechanism is essential for developing applications with FINAL CUT. Callback routines allow the programmer to connect different objects (which do not need to know each other). Connected objects notify each other when an action occurs in a widget. To uniquely identify a widget action, it uses signal strings. For example, if an FButton object gets clicked by a keyboard or mouse, it sends the string "clicked". A signal handler explicitly provided by Widget, in the form of a callback function or a callback method, can react to such a signal.

A callback function is always structured as follows:

void cb_function (FWidget* w, FDataPtr data)
{...}

The structure of a callback method is the same:

void classname::cb_methode (FWidget* w, FDataPtr data)
{...}

We use the addCallback() method of the FWidget class to connect to other widget objects.

For calling functions and static methods:

void FWidget::addCallback ( const FString& cb_signal
                          , FCallback cb_handler
                          , FDataPtr data )
{...}

For calling a member method of a specific instance:

void FWidget::addCallback ( const FString& cb_signal
                          , FWidget* cb_instance
                          , FMemberCallback cb_handler
                          , FDataPtr data )
{...}

There are two macros F_FUNCTION_CALLBACK and F_METHOD_CALLBACK to avoid having to deal with necessary type conversions. With delCallback() you can remove a connection to a signal handler or a widget. Alternatively, you can use delCallbacks() to remove all existing callbacks from an object.

The FINAL CUT widgets emit the following default signals

FButton

"clicked"

FCheckMenuItem

"clicked"
"toggled"

FLineEdit

"activate"
"changed"

FListBox

"clicked"
"row-changed"
"row-selected"

FListView

"clicked"
"row-changed"

FMenu

"activate"

FMenuItem

"activate"
"clicked"
"deactivate"

FRadioMenuItem

"clicked"
"toggled"

FScrollbar

"change-value"

FStatusBar

"activate"

FTextView

"changed"

FToggleButton

"clicked"
"toggled"

FWidget

"destroy"

 

Example of a callback function:

File: callback-function.cpp

#include <final/final.h>

using namespace finalcut;

void cb_changeText (FWidget* w, FDataPtr data)
{
  FButton& button = *(static_cast<FButton*>(w));
  FLabel& label = *(static_cast<FLabel*>(data));
  label.clear();
  label << "The " << button.getClassName() << " was pressed";
  label.redraw();
}

int main (int argc, char* argv[])
{
  FApplication app(argc, argv);
  FDialog dialog(&app);
  dialog.setText ("A dialog with callback function");
  dialog.setGeometry (FRect(25, 5, 45, 9));
  FLabel label (&dialog);
  label = "The button has never been pressed before";
  label.setGeometry (FPoint(2, 2), FSize(41, 1));
  FButton button (&dialog);
  // Character follows '&' will be used as the accelerator key
  button = "&Click me";
  button.setGeometry (FPoint(15, 5), FSize(14, 1));

  // Connect the button signal "clicked" with the callback function
  button.addCallback
  (
    "clicked",
    F_FUNCTION_CALLBACK (&cb_changeText),
    &label
  );

  app.setMainWidget(&dialog);
  dialog.show();
  return app.exec();
}

(Note: You can close the dialog with the mouse, Shift+F10 or Ctrl+^)

After entering the source code in callback-function.cpp you can compile the above program with gcc:

g++ -O2 -lfinal callback-function.cpp -o callback-function

 

Example of a callback method:

File: callback-method.cpp

#include <final/final.h>

using namespace finalcut;

class dialogWidget : public FDialog
{
  public:
    explicit dialogWidget (FWidget* parent = nullptr)
      : FDialog(parent)
    {
      setText ("Callback method");
      setGeometry (FPoint(25, 5), FSize(25, 7));
      button.setGeometry (FPoint(7, 3), FSize(10, 1));

      // Connect the button signal "clicked" with the callback method
      button.addCallback
      (
        "clicked",
        F_METHOD_CALLBACK (this, &FApplication::cb_exitApp),
        nullptr
      );
    }

  private:
    FButton button{"&Quit", this};
};

int main (int argc, char* argv[])
{
  FApplication app(argc, argv);
  dialogWidget dialog(&app);
  app.setMainWidget(&dialog);
  dialog.show();
  return app.exec();
}

(Note: You can close the window with the mouse, Shift+F10 or Ctrl+^)

After entering the source code in callback-method.cpp you can compile the above program with gcc:

g++ -O2 -lfinal -std=c++11 callback-method.cpp -o callback-method

 

Send custom signals

You can use the emitCallback() method to generate a user-defined signal. You can connect this signal later with the method addCallback() to a self-defined routine.

File: emit-signal.cpp

#include <final/final.h>

using namespace finalcut;

class dialogWidget : public FDialog
{
  public:
    explicit dialogWidget (FWidget* parent = nullptr)
      : FDialog(parent)
    {
      setGeometry (FPoint(25, 5), FSize(22, 7));
      setText ("Emit signal");
      FSize size(5, 1);
      label.setGeometry (FPoint(8, 1), size);
      label.setAlignment (fc::alignRight);
      label.setForegroundColor (fc::Black);
      plus.setGeometry (FPoint(3, 3), size);
      minus.setGeometry (FPoint(13, 3), size);
      plus.setNoUnderline();
      minus.setNoUnderline();

      // Connect the button signal "clicked" with the callback method
      plus.addCallback
      (
        "clicked",
        F_METHOD_CALLBACK (this, &dialogWidget::cb_plus)
      );

      minus.addCallback
      (
        "clicked",
        F_METHOD_CALLBACK (this, &dialogWidget::cb_minus)
      );

      // Connect own signals
      addCallback
      (
        "hot",
        F_METHOD_CALLBACK (this, &dialogWidget::cb_set_red)
      );

      addCallback
      (
        "regular",
        F_METHOD_CALLBACK (this, &dialogWidget::cb_set_black)
      );

      addCallback
      (
        "cold",
        F_METHOD_CALLBACK (this, &dialogWidget::cb_set_blue)
      );
    }

  private:
    void cb_plus (FWidget*, FDataPtr)
    {
      if ( t < 100 )
        t++;

      if ( t == 30 )
        emitCallback("hot");
      else if ( t == 1 )
        emitCallback("regular");

      setTemperature();
    }

    void cb_minus (FWidget*, FDataPtr)
    {
      if ( t > -99 )
        t--;

      if ( t == 0 )
        emitCallback("cold");
      else if ( t == 29 )
        emitCallback("regular");

      setTemperature();
    }

    void cb_set_blue (FWidget*, FDataPtr)
    {
      label.setForegroundColor (fc::Blue);
    }

    void cb_set_black (FWidget*, FDataPtr)
    {
      label.setForegroundColor (fc::Black);
    }

    void cb_set_red (FWidget*, FDataPtr)
    {
      label.setForegroundColor (fc::Red);
    }

    void setTemperature()
    {
      label.clear();
      label << t << "°C";
      label.redraw();
    }

    int t = 20;
    FLabel label{FString() << t << "°C", this};
    FButton plus {"&+", this};
    FButton minus {"&-", this};
};

int main (int argc, char* argv[])
{
  FApplication app(argc, argv);
  dialogWidget dialog(&app);
  app.setMainWidget(&dialog);
  dialog.show();
  return app.exec();
}

(Note: You can close the window with the mouse, Shift+F10 or Ctrl+^)

After entering the source code in emit-signal.cpp you can compile the above program with gcc:

g++ -O2 -lfinal -std=c++11 emit-signal.cpp -o emit-signal

The FINAL CUT widgets emit the following default signals: