Sanko Robinson [三興]

NAME

FLTK::CheatSheet - FLTK... Cheat sheet. >_> Yeah.

Description

Here, you'll find common snippets and hints that should help get you started.

It's a work in progress.

Windows

There are a number of different Window types for various needs:

 Window  .  .  .  .  .  .  .  General purpose window class
 GlWindow   .  .  .  .  .  .  Allows OpenGL to be used directly in the window
 ShapedWindow  .  .  .  .  .  Custom shaped Window based on Image

Widgets

This is a list of major widgets:

 Button  .  .  .  .  .  .  .  You click it. It does stuff.
 ColorChooser  .  .  .  .  .  Pick a color (with alpha support)

Dialogs

FLTK has a number of built-in dialogs. Most are simple and function based but some are full fledged objects.

These simple dialogs are imported with the :dialog tag:

 alert   .  .  .  .  .  .  .  Same as message except for the '!' icon
 ask  .  .  .  .  .  .  .  .  Quickly ask the user a 'Yes' or 'No' question
 color_chooser .  .  .  .  .  Display a ColorChoser widget in a popup dialog
 choice  .  .  .  .  .  .  .  Query the user with up to three possible choices
 choice_alert  .  .  .  .  .  Same as choice except for the '!' icon
 dir_chooser   .  .  .  .  .  Pick a directory from the local filesystem
 file_chooser  .  .  .  .  .  Pick a file from the local filesystem
 input   .  .  .  .  .  .  .  Display a string and let the user edit it
 message .  .  .  .  .  .  .  Pop-up with a message and an 'OK' button
 password   .  .  .  .  .  .  Display a password field for the user

The more complex dialogs are found in their own packages under the FLTK namespace, are object based, and support varying degrees of user-interactivity:

 HelpDialog .  .  .  .  .  .  Basic HTML-based help viewer

Callbacks

Without user interaction, a user interface would be rather pointless. FLTK handles default user interaction with a simple callback system. By default, all activity triggers the callback but this can be modified in by subclassing existing widgets.

Creating Your Own Custom Widgets

New widgets are created by subclassing an existing FLTK widget which is as easy as setting inheritance. As an example of this see the following snippet taken from examples/cursor.pl:

  {
    package CursorBox;
    our @ISA = qw[FLTK::Widget];

    sub handle {
        my ($self, $event) = @_;
        if ($event == ::ENTER) {
            $self->cursor($cursors{$self->label()});
            return 0;
        }
        return 1 if ($event == ::PUSH);    # drag the cursor around
        return 0;
    }
  }

Once you've set the base class, you can override the methods which make the widget function including handle( ) which handles all events (keyboard, mouse activity, etc.) and draw( ). See the individual widgets' documentation for specific subclassing information and the section on subclassing in FLTK::Widget.

Handling Events

The virtual method handle( $event ) is called to handle each event assed to your custom widget. It can:

  • Change the state of the widget

  • Call redraw( ) if the widget needs to be redisplayed

  • Call redraw( $x ) if the widget needs a partial update (assuming you provide support for this in your custom draw( ) method)

  • Call do_callback( ) if a callback should be generated

  • Call handle( ) on child widgets

Events are identified by the $event argument. Other information about the most recent event can be acquired by calling the event_.*( ) functions. This information remains valid until another event is handled.

Here is another example handle( ) method. This custom widget would act as a pushbutton and also accept the keystroke 'x' to cause the callback:

  {
    package FLTKx::CSBox;
    our @ISA = qw[FLTK::Widget];
    my ($highlight);

    sub handle {
      my ($self, $event) = @_;
      if ($event == FLTK::PUSH) {
        $highlight = 1;
        $self->redraw();
        return 1;
      }
      elsif ($event == FLTK::DRAG) {
        my $t = FLTK::event_inside($self);
        $highlight = $t if $t != $highlight;
        $self->redraw();
        return 1;
      }
      elsif ($event == FLTK::RELEASE) {
        if ($highlight) {
          $highlight = 0;
          $self->redraw;
          $self->do_callback();
          # Never do anything after a callback, as
          # the callback may have deleted the widget
        }
        return 1;
      }
      elsif ($event == FLTK::SHORTCUT) {
        if (FLTK::event_key() == ord 'x') {
          $self->do_callback();
          return 1;
        }
      }
      return 0;
    }
  }

You must return non-zero if your handle( ) method uses the event. If you return zero, the default handle( ) method is called.

Drawing the Widget

TODO




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