first-steps.md

First steps with the FINAL CUT widget toolkit

Table of Contents

• Basic functions
• Widgets
• Widget tree
• How to use the library
• Memory Management
• Event Processing
  • Event handler reimplementation
  • Event types
  • Timer event
  • User event
• Signals and Callbacks
  • Default signals
  • Callback function
  • Callback lambda expression
  • Callback method
  • Custom signals
• Widget layout
  • Coordinates
  • Lengths
  • Areas
  • Dynamic layout
• Scroll view

Basic functions

FINAL CUT is a library for creating text-based terminal applications. It runs on several Unix-like platforms. The release of FINAL CUT is licensed under the terms of the GNU Lesser General Public License v3.0 (GNU LGPL v3), which allows flexible licensing of applications. FINAL CUT was written in the programming language C++. The object-oriented design allows the creation of fast and lean programs.

FINAL CUT is a widget toolkit. A user interface usually consists of several widgets. FINAL CUT draws widgets on virtual windows and then mapped them on a virtual terminal. It uses the terminal capabilities from the Termcap library to display the character matrix of the virtual terminal on the screen or a terminal emulator. It uses various optimization methods to improve the drawing speed.

Figure 1. Structure of a FINAL CUT application

Widgets

FINAL CUT has many widgets. It offers buttons, input fields, menus, and dialog boxes that cover the most common use cases. Widgets are visual elements that are combined to create user interfaces. Own widgets can be easily created by creating a derived class of FWidget or other existing widgets. All widgets are instances of FWidget or its subclasses.

A widget can contain any number of child widgets. Child widgets are displayed in the display area of the parent widget. Window widgets based on FWindow have their own virtual display area and are independent of the parent widget.

When a parent widget is disabled, hidden, or deleted, the same operation is used recursively to all its child widgets. The base class FObject implements the self-organized object tree behavior. For example, addChild() removes the child ownership from an existing parent object before assigning it to the new target. When a child becomes deleted, the parent-child relationship causes its reference in the parent object to be removed. An explicit delChild() is no longer required here.

Widget tree

An FApplication widget is the top-level widget of an application. It is unique and can not have a parent widget. The class FApplication manages all settings and assigns keyboard and mouse input to the different widgets.

Figure 2. Widget tree of a FINAL CUT application

The main widget of a FINAL CUT application is the only object that FApplication can have as a child. This main widget is usually a window object that contains all sub-widgets of the application. A sub-widget can also be another window.

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>

auto main (int argc, char* argv[]) -> int
{
  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);
  finalcut::FWidget::setMainWidget(&dialog);
  dialog.show();
  return app.exec();
}

Figure 3. A blank dialog

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

How it works

#include <final/final.h>

All final cut programs have to 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 have to 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).

finalcut::FWidget::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 to return the result to the operating system. The started application enters the main event loop. This loop does not end until the window is closed.

Memory Management

To create a hierarchy of FObjects (or derived classes/widgets), a new FObject has to be initialized with its parent object.

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

When the used memory of a parent FObject gets deallocated, the allocated memory of its child objects will also be deallocated automatically.

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 be removed at any time with delChild().

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

If an FObject with a parent gets removed from the hierarchy, the destructor automatically deletes the object assignment from its parent object. If a class object doesn't derive from FObject, you have to implement storage deallocation yourself.

File: memory.cpp

#include <final/final.h>

using namespace finalcut;

auto main (int argc, char* argv[]) -> int
{
  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});
  FWidget::setMainWidget(dialog);
  dialog->show();
  return app.exec();
}

Figure 4. FObject manages its child objects

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

Event Processing

Calling FApplication::exec() starts the FINAL CUT main event loop. While the event loop is running, the system checks all the time 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 terminal size changing, are translated into FEvent objects, and are sent to the active FObject. It is also possible to use FApplication::sendEvent() or FApplication::queueEvent() to send a specific event to an object.

FObject-derived objects process incoming events by reimplementing the virtual method event(). The FObject itself can only call its own events onTimer() and 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 Event::MouseDown when you press down a mouse button.

Some event types have data that cannot be stored in an FEvent object. For example, a click event of the mouse requires to store which button was triggered and the position of the mouse pointer 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. You can create your own event types and send them to other objects and widgets.

Available event types

enum class Event
{
  None,              // invalid event
  KeyPress,          // key pressed
  KeyUp,             // key released
  KeyDown,           // key pressed
  MouseDown,         // mouse button pressed
  MouseUp,           // mouse button released
  MouseDoubleClick,  // mouse button double click
  MouseWheel,        // mouse wheel rolled
  MouseMove,         // mouse move
  FocusIn,           // focus in
  FocusOut,          // focus out
  ChildFocusIn,      // child focus in
  ChildFocusOut,     // child focus out
  FailAtChildFocus,  // No further focusable child widgets
  TerminalFocusIn,   // terminal focus in
  TerminalFocusOut,  // terminal focus out
  WindowActive,      // activate window
  WindowInactive,    // deactivate window
  WindowRaised,      // raise window
  WindowLowered,     // lower window
  Accelerator,       // keyboard accelerator
  Resize,            // terminal resize
  Show,              // widget is shown
  Hide,              // widget is hidden
  Close,             // widget close
  Timer,             // timer event occur
  User               // user defined event
};

Using a timer event

The following example starts a periodic timer that triggers an FTimerEvent() every 100 ms. The virtual method onTimer() is then called each time in the same dialog object.

File: timer.cpp

#include <final/final.h>

using namespace finalcut;

class dialogWidget : public FDialog
{
  public:
    explicit dialogWidget (FWidget* parent = nullptr)
      : FDialog{parent}
    {
      label.setAlignment (Align::Right);
      id = addTimer(100);
    }

  private:
    void initLayout()
    {
      setText ("Dialog");
      setGeometry (FPoint{25, 5}, FSize{23, 4});
      label.setGeometry (FPoint{1, 1}, FSize{10, 1});
      value.setGeometry (FPoint{11, 1}, FSize{10, 1});
      FDialog::initLayout();
    }

    void onTimer (FTimerEvent* ev) override
    {
      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};
};

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

Figure 5. FObject::onTimer event handler

(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++ timer.cpp -o timer -O2 -lfinal -std=c++14

Using a user event

You can use the FUserEvent() to create a individual event and send it to a specific object. If you want to create more than one user event, you can specify an identification number (0 in the example below) to identify the different events. Afterwards this number can be retrieved with getUserId().

User events should be generated in the main event loop. For this purpose, the class FApplication provides the virtual method processExternalUserEvent(). This method can be overwritten in a derived class and filled with user code.

The following example reads the average system load and creates a user event when a value changes. This event sends the current values to an FLabel widget and displays them in the terminal.

File: user-event.cpp

#include <stdlib.h>
#include <final/final.h>
#define _BSD_SOURCE 1
#define _DEFAULT_SOURCE 1

using LoadAvg = double[3];
using namespace finalcut;

class extendedApplication : public FApplication
{
  public:
    extendedApplication (const int& argc, char* argv[])
      : FApplication(argc, argv)
    { }

  private:
    void processExternalUserEvent() override
    {
      if ( getMainWidget() )
      {
        if ( getloadavg(load_avg, 3) < 0 )
          FApplication::getLog()->error("Can't get load average values");

        if ( last_avg[0] != load_avg[0]
          || last_avg[1] != load_avg[1]
          || last_avg[2] != load_avg[2] )
        {
          FUserEvent user_event(Event::User, 0);
          user_event.setData (load_avg);
          FApplication::sendEvent (getMainWidget(), &user_event);
        }

        for (std::size_t i = 0; i < 3; i++)
          last_avg[i] = load_avg[i];
      }
    }

    // Data member
    LoadAvg load_avg{}, last_avg{};
};


class dialogWidget final : public FDialog
{
  public:
    explicit dialogWidget (FWidget* parent = nullptr)
      : FDialog{"User event", parent}
    { }

  private:
    void initLayout()
    {
      FDialog::setGeometry (FPoint{25, 5}, FSize{40, 6});
      loadavg_label.setGeometry (FPoint{2, 2}, FSize{36, 1});
      FDialog::initLayout();
    }

    void onUserEvent (FUserEvent* ev) override
    {
      const auto& lavg = ev->getData<LoadAvg>();
      std::setlocale(LC_NUMERIC, "C");
      loadavg_label.clear();
      loadavg_label << "Load average: " << lavg[0] << ", "
                                        << lavg[1] << ", "
                                        << lavg[2] << " ";
      loadavg_label.redraw();
    }

    FLabel loadavg_label{this};
};

auto main (int argc, char* argv[]) -> int
{
  extendedApplication app(argc, argv);
  dialogWidget dialog(&app);
  FWidget::setMainWidget(&dialog);
  dialog.show();
  return app.exec();
}

Figure 6. User event generation

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

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

g++ user-event.cpp -o user-event -O2 -lfinal -std=c++14

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 has no return value and can have various arguments:

void cb_function (FWidget* w, int* i, double* d, ...)
{...}

The structure of a callback method is the same:

void classname::cb_methode (FWidget* w, int* i, double* d, ...)
{...}

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

1. For calling functions or static methods via a pointer:

template< typename Function
        , typename FunctionPointer<Function>::type = nullptr
        , typename... Args >
void FWidget::addCallback ( const FString& cb_signal
                          , Function&&     cb_function
                          , Args&&...      args)
{...}

2. For calling functions or static methods via a reference:

template< typename Function
        , typename FunctionReference<Function>::type = nullptr
        , typename... Args >
void FWidget::addCallback ( const FString& cb_signal
                          , Function&      cb_function
                          , Args&&...      args)
{...}

3. For calling a member method of a specific instance:

template< typename Object
        , typename Function
        , typename ObjectPointer<Object>::type = nullptr
        , typename MemberFunctionPointer<Function>::type = nullptr
        , typename... Args >
void FWidget::addCallback ( const FString& cb_signal
                          , Object&&       cb_instance
                          , Function&&     cb_member
                          , Args&&...      args)
{...}

4. For calling a std::bind call wrapper or a lambda expression:

template< typename Function
        , typename ClassObject<Function>::type = nullptr
        , typename... Args >
void FWidget::addCallback ( const FString& cb_signal
                          , Function&&     cb_function
                          , Args&&...      args)
{...}

5. For calling a std::bind call wrapper to a specific instance:

template< typename Object
        , typename Function
        , typename ObjectPointer<Object>::type = nullptr
        , typename ClassObject<Function>::type = nullptr
        , typename... Args >
void FWidget::addCallback ( const FString& cb_signal
                          , Object&&       cb_instance
                          , Function&&     cb_function
                          , Args&&...      args)
{...}

6. For calling a lambda function that has been stored in a variable with the keyword auto:

template< typename Function
        , typename ClassObject<Function>::type = nullptr
        , typename... Args >
void FWidget::addCallback ( const FString& cb_signal
                          , Function&      cb_function
                          , Args&&...      args)
{...}

With delCallback(...) you can remove a connection to a signal handler or a widget instance. Alternatively, you can use delCallbacks() to remove all existing callbacks from an object.

1. To delete functions or static methods callbacks via a pointer:

template< typename FunctionPtr
        , typename FunctionPointer<FunctionPtr>::type = nullptr >
void FWidget::delCallback (FunctionPtr&& cb_func_ptr)
{...}

2. To delete functions or static methods callbacks via a reference:

template< typename Function
        , typename FunctionReference<Function>::type = nullptr >
void FWidget::delCallback (Function& cb_function)
{...}

3. To delete all callbacks from a specific instance:

template< typename Object
        , typename ObjectPointer<Object>::type = nullptr >
void FWidget::delCallback (Object&& cb_instance)
{...}

4. To delete all callbacks of a signal:

void delCallback (const FString& cb_signal)
{...}

5. To delete all callbacks of a signal and specific instance:

template< typename Object
        , typename ObjectPointer<Object>::type = nullptr >
void delCallback (const FString& cb_signal, Object&& cb_instance)
{...}

6. To delete all callbacks from a widget:

void delCallback()
{...}

The FINAL CUT widgets emit the following default signals

FApplication

"first-dialog-opened"
"last-dialog-closed"

FButton

"clicked"

FCheckMenuItem

"clicked"
"toggled"

FLineEdit

"activate"
"changed"

FListBox

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

FListView

"changed"
"clicked"
"row-changed"

FMenu

"activate"

FMenuItem

"activate"
"clicked"
"deactivate"

FRadioMenuItem

"clicked"
"toggled"

FScrollbar

"change-value"

FSpinBox

"changed"

FStatusBar

"activate"

FTextView

"changed"

FToggleButton

"clicked"
"toggled"

FWidget

"destroy"
"enable"
"disable"
"focus-in"
"focus-out"
"mouse-press"
"mouse-release"
"mouse-move"
"mouse-wheel-down"
"mouse-wheel-up"

 

Example of a callback function:

File: callback-function.cpp

#include <final/final.h>

using namespace finalcut;

void cb_changeText (const FButton& button, FLabel& label)
{
  label.clear();
  label << "The " << button.getClassName() << " was pressed";
  label.redraw();
}

auto main (int argc, char* argv[]) -> int
{
  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",          // Callback signal
    &cb_changeText,     // Function pointer
    std::cref(button),  // First function argument
    std::ref(label)     // Second function argument
  );

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

Figure 7. Button with a callback function

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

 

Example of an lambda expression callback:

File: callback-lambda.cpp

#include <final/final.h>

using namespace finalcut;

auto main (int argc, char* argv[]) -> int
{
  FApplication app(argc, argv);
  FDialog dialog(&app);
  dialog.setText ("Lambda expression as callback");
  dialog.setGeometry (FRect{25, 5, 45, 9});
  FButton button ("&bottom", &dialog);
  button.setGeometry (FPoint{15, 5}, FSize{14, 1});

  // Connect the button signal "clicked" with the lambda expression
  button.addCallback
  (
    "clicked",                          // Callback signal
    [] (FButton& button, FDialog& dgl)  // Lambda function
    {
      if ( button.getY() != 2 )
      {
        button.setPos (FPoint{15, 2});
        button.setText("&top");
      }
      else
      {
        button.setPos (FPoint{15, 5});
        button.setText("&bottom");
      }

      dgl.redraw();
    },
    std::ref(button),                   // First function argument
    std::ref(dialog)                    // Second function argument
  );

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

Figure 8. Button with lambda expression callback.

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

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

g++ callback-lambda.cpp -o callback-lambda -O2 -lfinal -std=c++14

 

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}
    {
      // Connect the button signal "clicked" with the callback method
      button.addCallback
      (
        "clicked",                            // Callback signal
        finalcut::getFApplication(),          // Class instance
        &finalcut::FApplication::cb_exitApp,  // Method pointer
        this                                  // Function argument
      );
    }

  private:
    void initLayout()
    {
      setText ("Callback method");
      setGeometry (FPoint{25, 5}, FSize{25, 7});
      button.setGeometry (FPoint{7, 3}, FSize{10, 1});
      FDialog::initLayout();
    }

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

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

Figure 9. Button with a callback method

(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++ callback-method.cpp -o callback-method -O2 -lfinal -std=c++14

 

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}
    {
      label.setAlignment (Align::Right);
      label.setForegroundColor (FColor::Black);
      plus.setNoUnderline();
      minus.setNoUnderline();

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

      // Connect own signals
      addCallback ("hot", this, &dialogWidget::cb_set_red);
      addCallback ("regular", this, &dialogWidget::cb_set_black);
      addCallback ("cold", this, &dialogWidget::cb_set_blue);
    }

  private:
    void initLayout()
    {
      setGeometry (FPoint{25, 5}, FSize{22, 7});
      setText ("Emit signal");
      const FSize size{5, 1};
      label.setGeometry (FPoint{8, 1}, size);
      plus.setGeometry (FPoint{3, 3}, size);
      minus.setGeometry (FPoint{3, 3} + FPoint{10, 0}, size);
      FDialog::initLayout();
    }

    void cb_plus()
    {
      if ( t < 100 )
        t++;

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

      setTemperature();
    }

    void cb_minus()
    {
      if ( t > -99 )
        t--;

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

      setTemperature();
    }

    void cb_set_blue()
    {
      label.setForegroundColor (FColor::Blue);
    }

    void cb_set_black()
    {
      label.setForegroundColor (FColor::Black);
    }

    void cb_set_red()
    {
      label.setForegroundColor (FColor::Red);
    }

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

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

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

Figure 10. Callbacks with custom signals

(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++ emit-signal.cpp -o emit-signal -O2 -lfinal -std=c++14

Widget layout

Coordinates

The positioning of a widget in the terminal works via a coordinate system. It consists of x characters in the horizontal and y characters in the vertical. The upper left corner has the coordinates (1, 1). With the commands getDesktopWidth() and getDesktopHeight(), the width and height of the terminal get retrieved. These two values result in the position of the lower right terminal corner. The position of a widget is retrievable with getX(), getY(), and getPos() or is definable with setX(), setY(), and setPos(). The data type for each coordinate is an int. All positions represent an FPoint object. The positioning of the widget is always relative to its parent widget. The top parent widget in a chain of children contains the terminal desktop. There the absolute terminal positions are still identical to the relative positions (getPos() = getTermPos()). In the case of a child widget, the positioning is corresponding to the upper left corner of the parent widget plus a possible padding space (can be determined with getLeftPadding() and getTopPadding()). If you want to ignore padding spaces, you have to force this with the ignorePadding() method.

Figure 11. Widget coordinates

int              getX() const;
int              getY() const;
const FPoint     getPos() const;
int              getTermX() const;
int              getTermY() const;
const FPoint     getTermPos() const;
virtual void     setX (int x, bool adjust = true);
virtual void     setY (int y, bool adjust = true);
virtual void     setPos (const FPoint& p, bool adjust = true);

If you set the value of adjust to false when calling setX(), setY(), or setPos(), this will prevent the explicit call of adjustSize() afterward. This is important to avoid adjustSize() loops or to block the adjustSize() call from being repeated unnecessarily often.

Lengths

The dimensions of a widget can be retrieved and defined separately in width and height. The methods getWidth() and getHeight() respectively setWidth() and setHeight() are used for this. Because a length cannot be negative, all lengths are of type std::size_t. The maximum size of a child widget automatically results from the size of the parent widget, which is retrievable with getClientWidth() and getClientHeight(). Some widgets have a border, a title bar, or both, which can reduce the maximum size of the child widget.

        widget width ≥ client widget width
        widget height ≥ client widget height

Corresponding padding space ensures the correct distance here. The padding space can be retrieved separately for all four sides with the widget methods getTopPadding(), getLeftPadding(), getBottomPadding(), and getRightPadding(). You can set the required padding space for the widget using the setTopPadding(), setLeftPadding(), setBottomPadding() and setRightPadding() methods.

        widget width = left padding + client width + right padding
        widget height = top padding + client height + bottom padding

Figure 12. Width and height of a widget

std::size_t    getWidth() const;
std::size_t    getHeight() const;
std::size_t    getClientWidth() const;
std::size_t    getClientHeight() const;
int            getTopPadding() const;
int            getLeftPadding() const;
int            getBottomPadding() const;
int            getRightPadding() const;
virtual void   setWidth (std::size_t width, bool adjust = true);
virtual void   setHeight (std::size_t height, bool adjust = true);
void           setTopPadding (int top, bool adjust = true);
void           setLeftPadding (int left, bool adjust = true);
void           setBottomPadding (int bottom, bool adjust = true);
void           setRightPadding (int right, bool adjust = true);

If the value of adjust is set to false for setWidth(), setHeight(), setTopPadding(), setLeftPadding(), setBottomPadding() or setRightPadding(), then adjustSize() is not explicitly called afterward. This is important to prevent adjustSize() loops or to avoid that adjustSize() is called unnecessarily often.

Areas

The terminal area in which a widget appears determines its geometry. The geometry of a widget is composed of its position and its size. A widget position is always of object type FPoint and a widget size of type FSize. The widget geometry can be retrieved as FRect object via the widget method getGeometry() and set with the method setGeometry(). The getTermGeometry() method gets the total values of the terminal geometry. If you are only interested in the size of a widget, you can also use the method getSize(). To set the widget size, you can use the method setSize(). The position of a shadow is outside the widget. The shadow size itself as FSize object is retrievable via the getShadow() method. You can set the widget shadow size with the setShadowSize() method. If you want to get the geometry values of a widget, including its shadow, you can use the method getGeometryWithShadow() from the FWidget class. If you want to have the entire geometry with shadow for the absolute geometry values as a FRect object, you can call the method getTermGeometryWithShadow().

Figure 13. Geometry of widgets

const FSize    getSize() const;
const FSize    getClientSize() const;
const FRect&   getGeometry() const;
const FRect&   getTermGeometry();
const FSize&   getShadow() const;
const FRect&   getGeometryWithShadow();
const FRect&   getTermGeometryWithShadow();
virtual void   setSize (const FSize& size, bool adjust = true);
virtual void   setGeometry (const FRect& box, bool adjust = true);
virtual void   setGeometry (const FPoint& p, const FSize& s, bool adjust = true);
virtual void   setShadowSize (const FSize& size);

If you explicitly set the value of adjust to false when using the setSize(), setGeometry() or setShadowSize() mutators, the adjustSize() method is no longer called automatically. This can be used to prevent recursive adjustSize() calls or to avoid unnecessary adjustSize() calls.

Dynamic layout

A modern terminal emulation like xterm has no fixed resolution. They offer the possibility to change the height and width of the terminal at any time. That triggers a resize-event that calls the adjustSize() method. This method allows adapting the widget to a changed terminal size. You can override the adjustSize() method to adjust the size and position of the widget. The method adjustSize() will also be called indirectly via calling methods setGeometry(), setX(), setY(), setPos(), setWidth(), setHeight(), setSize(), setTopPadding(), setLeftPadding(), setBottomPadding(), setRightPadding(), or setDoubleFlatLine().

Scalable dialogs derived from FDialog can change the dialog size by clicking on the lower right corner of the window. You can intercept a scaling action by overriding the setSize() method and adjusting the client widgets.

File: size-adjustment.cpp

#include <final/final.h>

using namespace finalcut;

class dialogWidget : public FDialog
{
  public:
    explicit dialogWidget (FWidget* parent = nullptr)
      : FDialog{parent}
    { }

  private:
    void initLayout()
    {
      setText ("Dialog");
      setResizeable();
      button.setGeometry (FPoint{1, 1}, FSize{12, 1}, false);
      input.setGeometry (FPoint{2, 3}, FSize{12, 1}, false);
      // Set dialog geometry and calling adjustSize()
      setGeometry (FPoint{25, 5}, FSize{40, 12});
      setMinimumSize (FSize{25, 9});
      FDialog::initLayout();
    }

    inline void checkMinValue (int& n)
    {
      if ( n < 1 )  // Checks and corrects the minimum value
        n = 1;
    }

    void centerDialog()
    {
      auto x = int((getDesktopWidth() - getWidth()) / 2);
      auto y = int((getDesktopHeight() - getHeight()) / 2);
      checkMinValue(x);
      checkMinValue(y);
      setPos (FPoint{x, y}, false);
    }

    void adjustWidgets()
    {
      const auto bx = int(getWidth() - button.getWidth() - 3);
      const auto by = int(getHeight() - 4);
      button.setPos (FPoint{bx, by}, false);
      input.setWidth (getWidth() - 4);
      const auto ly = int(getHeight() / 2) - 1;
      input.setY (ly, false);
    }

    void adjustSize() override
    {
      // Calling super class method adjustSize()
      FDialog::adjustSize();
      // Centers the dialog in the terminal
      centerDialog();
      // Adjust widgets before drawing
      adjustWidgets();
    }

    void draw() override
    {
      // Calling super class method draw()
      FDialog::draw();

      print() << FPoint{3, 3}
              << FColorPair{FColor::Black, FColor::White}
              << "Text on "
              << FColorPair{FColor::Blue, FColor::Yellow}
              << "top";
    }

    FLineEdit input{"Middle", this};
    FButton button{"&Bottom", this};
};

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

Figure 14. Dynamic layout

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

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

g++ size-adjustment.cpp -o size-adjustment -O2 -lfinal -std=c++14

Scroll view

The scroll view of the FScrollView class allows users to view content that is larger than the visible area. The FScrollView widget displays the horizontal and vertical scroll bar by default, only if the content size requires it. You can controll this behavior by the two methods setHorizontalScrollBarMode() and setVerticalScrollBarMode().

setHorizontalScrollBarMode (finalcut::ScrollBarMode);
setVerticalScrollBarMode (finalcut::ScrollBarMode);

You pass the scroll bar visibility mode as a value of the enum type finalcut::ScrollBarMode.

enum class ScrollBarMode
{
  Auto   = 0,  // Shows a scroll bar when area is larger than viewport
  Hidden = 1,  // Never shows a scroll bar
  Scroll = 2   // Always shows a scroll bar
};

You can add widgets to an FScrollView object as child objects and place them (with a widget positioning method) on the scrollable area. If a client widget gets the focus, it automatically scrolls the viewport to the focused widget. You can use the methods scrollTo(), scrollToX(), scrollToY() and scrollBy() to set the scroll position of the viewport directly.

The FButtonGroup widget uses FScrollView to display more buttons in the frame than the height allows.

File: scrollview.cpp

#include <utility>
#include <final/final.h>

using namespace finalcut;

class dialogWidget : public FDialog
{
  public:
    explicit dialogWidget (FWidget* parent = nullptr)
      : FDialog{parent}
    {
      scrollview.setGeometry(FPoint{1, 1}, FSize{22, 11});
      scrollview.setScrollSize(FSize{60, 27});
      // Attention: getColorTheme() requires an initialized terminal
      const auto& wc = getColorTheme();
      setColor (wc->label.inactive_fg, wc->dialog.bg);
      scrollview.clearArea();
      FColorPair red (FColor::LightRed, wc->dialog.bg);
      FColorPair black (FColor::Black, wc->dialog.bg);
      FColorPair cyan (FColor::Cyan, wc->dialog.bg);

      static std::vector<direction> d
      {
        {"NW", FPoint{3,  13}, FPoint{1,  1},  black},
        {"N",  FPoint{10, 13}, FPoint{21, 1},  red},
        {"NE", FPoint{17, 13}, FPoint{41, 1},  black},
        {"W",  FPoint{3,  15}, FPoint{1,  10}, black},
        {"*",  FPoint{10, 15}, FPoint{21, 10}, black},
        {"E",  FPoint{17, 15}, FPoint{41, 10}, black},
        {"SW", FPoint{3,  17}, FPoint{1,  19}, black},
        {"S",  FPoint{10, 17}, FPoint{21, 19}, cyan},
        {"SE", FPoint{17, 17}, FPoint{41, 19}, black}
      };

      for (auto&& b : d)
      {
        scrollview.print() << std::get<2>(b) + FPoint{10, 5}
                           << std::get<3>(b) << std::get<0>(b);
        auto edit = new FLineEdit("direction " + std::get<0>(b), &scrollview);
        edit->setGeometry(std::get<2>(b) + FPoint{1, 1}, FSize{17, 1});
        auto btn = new FButton(std::move(std::get<0>(b)), this);
        btn->setGeometry(std::get<1>(b), FSize{4, 1});
        btn->unsetShadow();
        btn->addCallback
        (
          "clicked",
          this, &dialogWidget::cb_button, std::get<2>(b)
        );
      }
    }

  private:
    typedef std::tuple<FString, FPoint, FPoint, FColorPair> direction;

    void initLayout()
    {
      setText ("Dialog");
      setGeometry (FPoint{28, 2}, FSize{24, 21});
      FDialog::initLayout();
    }

    void cb_button (const FPoint& p)
    {
      scrollview.scrollTo(p);
    }

    FScrollView scrollview{this};
};

auto main (int argc, char* argv[]) -> int
{
  FApplication app(argc, argv);
  app.initTerminal();  // Terminal initialization
  dialogWidget dialog(&app);
  FWidget::setMainWidget(&dialog);
  dialog.show();
  return app.exec();
}

Figure 15. Dialog with a scrolling viewport

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

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

g++ scrollview.cpp -o scrollview -O2 -lfinal -std=c++14