15.7.1. Tk::Splashscreen

Figure 15-6. An HP-16C RPN calculator

Figure 15-7. tkhp16c initialization is 90% complete

Anyway, we keep the MacProgressBar widget reference in the global variable $MAC_PB, so we can access it throughout the various initialization subroutines. For our Splashscreen, we've use the -milliseconds option to specify that the Splashscreen remain posted for a minimum of three seconds.

$splash = $mw->Splashscreen(-milliseconds => 3000);
$splash->Label(-text => 'Building your HP 16C ...', -bg => $BLUE)->
    pack(qw/-fill both -expand 1/);
$MAC_PB = $splash->MacProgressBar(-width => 300);
$MAC_PB->pack(qw/-fill both -expand 1/);
$splash->Label(-image => $mw->Photo(-file => 'hp16c-splash.gif'))->pack;

Here's how we use the Splashscreen. First, withdraw the MainWindow and show the Splashscreen. Now perform program initialization. Note how we use the set method to update the MacProgressBar to 100% before destroying the Splashscreen. With the Splashscreen gone, redisplay the MainWindow containing the completed calculator.

my $mw = MainWindow->new;
$mw->withdraw;
$splash->Splash;                     # show Splashscreen

build_help_window;
build_calculator;

$MAC_PB->set($MAC_PB_P = 100);
$splash->Destroy;                    # tear down Splashscreen

$mw->deiconify;                      # show calculator

sub Splash {

    my ($self, $millis) = @_;

    $millis = $self->cget(-milliseconds) unless defined $millis;
    $self->{tm0} = Tk::timeofday;
    $self->configure(-milliseconds => $millis);
    $self->Popup;

} # end_splash

Destroy's first duty is to ensure that the Splashcreen remains visible for its allotted minimum time. It does this with a simple computation, which, if positive, gives the time to delay. If the result is negative, we set it to zero so there is no wait.

We then create a generic completion callback that does one final update call (to ensure all pending events are completed) and destroys the Splashscreen.

Now, if the program initialization has taken longer than the minimum Splashscreen time, we call the completion callback and return. Otherwise, we process all timer events, wait the requisite amount of time, and destroy the Splashscreen.

sub Destroy {

    my ($self, $millis) = @_;

    $millis = $self->cget(-milliseconds) unless defined $millis;
    my $t = Tk::timeofday;
    $millis = $millis - ( ($t - $self->{tm0}) * 1000 );
    $millis = 0 if $millis < 0;

    my $destroy_splashscreen = sub {
			$self->update;
			$self->after(100);			# ensure 100% of PB seen
			$self->destroy;
    };

    do { &$destroy_splashscreen; return } if $millis == 0;

    while ( $self->DoOneEvent (DONT_WAIT | TIMER_EVENTS)) {}

    $self->waitVariableX( [$millis, $destroy_splashscreen] );

} # end Destroy

These are the private methods responsible for moving a Splashscreen widget. On a button press, we record the cursor's x and y coordinates relative to the Splashscreen's top-left corner. When the button is released, we compute new x and y coordinates relative to the display's top-left corner and use geometry to move the Toplevel.

sub b3prs {
    my ($self, $x, $y) = @_;
    $self->{ofx} = $x;
    $self->{ofy} = $y;
} # end b3prs

sub b3rls {
    my($self, $X, $Y) = @_;
    $X -= $self->{ofx};
    $Y -= $self->{ofy};
    $self->geometry("+${X}+${Y}");
} # end b3rls

## Binding information for '.splashscreen', Tk::Splashscreen=HASH(0x83a6874) ##

1. Binding tag 'Tk::Splashscreen' has no bindings.

2. Binding tag '.splashscreen' has these bindings:
             <ButtonRelease-3> : Tk::Callback=ARRAY(0x83aaaf8)           
                                   Tk::Splashscreen=HASH(0x83a6874)
                                     'b3rls'
                                     Tk::Ev=SCALAR(0x83aab1c)               : 'X'
                                     Tk::Ev=SCALAR(0x83aab58)               : 'Y'
                    <Button-3> : Tk::Callback=ARRAY(0x83aaae0)           
                                   Tk::Splashscreen=HASH(0x83a6874)
                                     'b3prs'
                                     Tk::Ev=SCALAR(0x839a348)               : 'x'
                                     Tk::Ev=SCALAR(0x83aab04)               : 'y'

3. Binding tag 'all' has these bindings:
                     <Key-F10> : Tk::Callback=SCALAR(0x839a3fc)          
                                   'FirstMenu'
                     <Alt-Key> : Tk::Callback=ARRAY(0x839a390)           
                                   'TraverseToMenu'
                                     Tk::Ev=SCALAR(0x816e198)               : 'K'
                   <<LeftTab>> : Tk::Callback=SCALAR(0x839a360)          
                                   'focusPrev'
                     <Key-Tab> : Tk::Callback=SCALAR(0x839a264)          
                                   'focusNext'