finalcut/first-steps.md at eb8ae63b72e72a1650b062676d3ec8a4fbba7445

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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");
  dialog.setGeometry (25, 5, 30, 10);
  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".

dialog.setGeometry (25, 5, 30, 10);

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 (25, 5, 40, 8);

  // The object input is managed by dialog
  FLineEdit* input = new FLineEdit("predefined text", dialog);
  input->setGeometry(8, 2, 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 (2, 4, 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 (25, 5, 23, 4);
      label.setGeometry (1, 1, 10, 1);
      label.setAlignment (fc::alignRight);
      value.setGeometry (11, 1, 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();
}