NAME

Wx::Loader - using custom dll loaders with Wx

SYNOPSIS

#---------------------------------------
# For Packagers
#---------------------------------------

# the order of these use()s is important
use MyCustomWxLoader;
use Wx;

or .....

use threads;
use threads::shared;
use MyCustomLoader;
use Wx;

or - Wx::Perl::Splashfast special case
  
use MyCustomWxLoader;
use Wx::Perl::SplashFast ("./logo.jpg",5000);
use Wx;

............. meanwhile in MyCustomWxLoader.pm

package MyCustomWxLoader;
require Wx::Mini;
our @ISA = qw( Wx::Loader::Standard );
  
$Wx::wx_binary_loader = __PACKAGE__;
...... or
$Wx::wx_binary_loader = __PACKAGE__->new;

#-----------------------------------------
# For binary distributions
#-----------------------------------------

# Provide a custom Wx::Loader::Custom
# to be loaded by Wx::Mini

package Wx::Loader::Custom
our @ISA = qw( Wx::Loader::Standard );

# be polite if another loader is already in place

$Wx::wx_binary_loader = __PACKAGE__ if !$Wx::wx_binary_loader;
...... or
$Wx::wx_binary_loader = __PACKAGE__->new() if !$Wx::wx_binary_loader;

DESCRIPTION

If you are providing binary distributions of Wx or packaging Wx applications to run on machines without Perl (PAR, PerlApp),you may need to override dll loading methods. Providing a custom wx_binary_loader package allows you to do this.

Binary Distributions

A binary distribution my provide alternative sources and loading methods for the wxWidgets dlls. It achieves this by providing a Wx::Loader::Custom module in the distribution

package Wx::Loader::Custom
our @ISA = qw( Wx::Loader::Standard );

# be polite if another loader is already in place

$Wx::wx_binary_loader = __PACKAGE__ if !$Wx::wx_binary_loader;
...... or
$Wx::wx_binary_loader = __PACKAGE__->new() if !$Wx::wx_binary_loader;

# remember that Wx.pm has not necessarily been loaded so only
# Wx::Mini is available

Perl Application Packagers

Applications that package perl scripts to run on machines without
Perl (PAR, PerlApp etc) can override dll loading methods if necessary
by loading a custom package before wx

package MyCustomWxLoader;
require Wx::Mini;
our @ISA = qw( Wx::Loader::Standard );
  
$Wx::wx_binary_loader = __PACKAGE__;
...... or
$Wx::wx_binary_loader = __PACKAGE__->new;

# remember that Wx.pm has not necessarily been loaded so only
# Wx::Mini is available

METHODS

The following methods may be provided by custom loaders to override the
default behaviour

loader_info

should return an information string about the loader and MUST be provided.
The default loader has

sub loader_info { 'Standard Distribution'; }

so any custom loader should return something different

e.g.

sub loader_info { "Mark's Broken Distribution - it's all my fault"; }

set_binary_path

allows setting a custom path for the wxWidgets libraries.

sub set_binary_path {
  my $class_or_object = shift;
  
  ... work out binary path
  
  return $newbinarypath; # method MUST return a path
}

load_dll

Is called to load wxWidgets plugin dlls using a key for the $Wx::dlls hash
( see Wx::Mini )

sub load_dll {
  my ($class_or_object, $dllkey) = @_;
  ..... load dll - or maybe not
}

the default loader does nothing - dependencies are loaded automatically
and determined by the standard methods of the os:

an example of pre loading a known dependency 

sub load_dll {
  return if $^O !~ /^(mswin|linux)/i;
  local $ENV{PATH} = $Wx::wx_path . ';' . $ENV{PATH} if $Wx::wx_path;
  return unless exists $Wx::dlls->{$_[1]} && $Wx::dlls->{$_[1]};
  my $dll = $Wx::dlls->{$_[1]};
  $dll = $Wx::wx_path . '/' . $dll if $Wx::wx_path;
  Wx::_load_plugin( $dll );
}

unload_dll

Is called ONCE from within an END block
A custom loader may choose, for example to unload any dlls it has loaded

sub unload_dll {
  my $class_or_object = shift;
  
  ... carry out END actions
}

The default unload_dll is a noop ( sub unload_dll {} )

external_set_load

A deprecated method of replacing the load function for plugins
A custom loader may override this to prevent a legacy loader replacing
the loading methods.

external_set_unload

A deprecated method of replacing the unload function for plugins
A custom loader may override this to prevent a legacy loader replacing
the unloading methods.

boot_overload

For binary distributions and packaged applications, normal shared
library loading semantics may not work. A custom loader may provide
this method to use in place of, or to supplement the standard XS load
of Wx.dll (Wx.so).

The method MUST return true or false, depending on whether it has
loaded Wx.dll (Wx.so).

For example, to load the core wxWidgets dlls before Wx is loaded

sub boot_overload {
  shift; 
  require DynaLoader;
  for my $dll ( qw( base core adv ) ) {
    next unless exists $Wx::dlls->{$dll} && $Wx::dlls->{$dll};
    my $file = ( $Wx::wx_path ) ? $Wx::wx_path . '/' . $Wx::dlls->{$dll} : $Wx::dlls->{$dll};
    my $libref = DynaLoader::dl_load_file($file, 0);
    push(@DynaLoader::dl_librefs,$libref) if $libref;
    
    # Dynaloader should take care of unloading
  
  }
 
  #------------ IMPORTANT ----------
  return 0; # we have not loaded Wx
  #---------------------------------
}


Some packagers extract dlls at runtime, and then may attempt to remove them
at application close. This may fail for Wx. For example, on MSWin the directory
cleanup fails whilst on Linux the application will seg-fault on exit.
Packagers may avoid this by loading Wx.dll( Wx.so) from a non standard location
( perhaps a separate binary distribution of wx dlls ) that is not removed at
application exit.

For example

sub boot_overload {
  my $class = shift 
  require DynaLoader;
  for my $dll ( qw( base core adv ) ) {
    next unless exists $Wx::dlls->{$dll} && $Wx::dlls->{$dll};
    my $file = ( $Wx::wx_path ) ? $Wx::wx_path . '/' . $Wx::dlls->{$dll} : $Wx::dlls->{$dll};
    my $libref = DynaLoader::dl_load_file($file, 0);
    push(@DynaLoader::dl_librefs,$libref) if $libref;
    
    # Dynaloader should take care of unloading
  
  }
  
  package
     DynaLoader;
  
  my $file = $class->get_the_location_to_wx_xs_module;
  
  #------------------------------------------
  # From XSLoader
  #------------------------------------------
  
  my $module  = 'Wx';
  
  my $boots = "$module\::bootstrap";
  my $bootname = "boot_$module";
  $bootname =~ s/\W/_/g;
  @DynaLoader::dl_require_symbols = ($bootname);
  my $boot_symbol_ref;
  
  my $libref = dl_load_file($file, 0) or do {
      require Carp;
      Carp::croak("Can't load '$file' for module $module: " . dl_error());
  };
  push(@DynaLoader::dl_librefs,$libref);  # record loaded object

  my @unresolved = dl_undef_symbols();
  if (@unresolved) {
      require Carp;
      Carp::carp("Undefined symbols present after loading $file: @unresolved\n");
  }

  $boot_symbol_ref = dl_find_symbol($libref, $bootname) or do {
      require Carp;
      Carp::croak("Can't find '$bootname' symbol in $file\n");
  };

  push(@DynaLoader::dl_modules, $module); # record loaded module

  my $xs = dl_install_xsub($boots, $boot_symbol_ref, $file);

  push(@DynaLoader::dl_shared_objects, $file); # record files loaded
      
  #------------ IMPORTANT ----------
  return 1; # we have loaded Wx
  #---------------------------------
}

Full Custom Loader Example

################################################
# Custom loader for Wx distribution from
# http://www.wxperl.co.uk/repository
#
################################################

package Wx::Loader::Custom;
use strict;
use warnings;

our @ISA = qw( Wx::Loader::Standard );

$Wx::wx_binary_loader = __PACKAGE__ if !$Wx::wx_binary_loader;

sub loader_info { 'Linux PPM Distribution from http://www.wxperl.co.uk/repository'; }

sub boot_overload {
    shift; 
    require DynaLoader;
    for my $dll ( qw( base core adv ) ) {
      next unless exists $Wx::dlls->{$dll} && $Wx::dlls->{$dll};
      my $file = ( $Wx::wx_path ) ? $Wx::wx_path . '/' . $Wx::dlls->{$dll} : $Wx::dlls->{$dll};
      my $libref = DynaLoader::dl_load_file($file, 0);
      push(@DynaLoader::dl_librefs,$libref) if $libref;
      
      # Dynaloader should take care of unloading
    }
   return 0;
}

# Allow legacy packaging call to override our load method

my( $load_fun ) = ( \&_load_dll );

sub _load_dll {
    return unless exists $Wx::dlls->{$_[0]} && $Wx::dlls->{$_[0]};
    my $dll = $Wx::dlls->{$_[0]};
    $dll = $Wx::wx_path . '/' . $dll if $Wx::wx_path;
    return Wx::_load_plugin( $dll );  
}

sub external_set_load { $load_fun = $_[1] }

sub load_dll {
  shift;
  goto &$load_fun;
}