'Hello world', Button

The mandatory example:

$Spc::res_h{ blsc} = "hello";
$Spc::res_h{ hello_title} = { text => "Hello"}; 
$Spc::res_h{ hello_b1} = { name => "Press me",
			   command => sub { Util::log( "hello world");}};

The BLSCs can be found in the Misc popup menu of the TkI toplevel widget. The GUI is displayed in figure 14.1. It displays a button, 'Press me', which sends the string 'hello world' to the log window of the TkI toplevel widget once it is pressed. Here are some details about the code:

Figure 14.1: Hello World

• $Spc::res_h{ blsc} = "hello";
  There is only one BLSC widget, the generic name is hello.

• $Spc::res_h{ hello_title} = { text => "Hello"};
  The title of the widget, it is introduced by setting a component of the %Spc::res_h hash. The indexing string is composed of the generic name (hello) and the keyword title.

• $Spc::res_h{ hello_b1} = { name => "Press me", command => sub {...}}
  Directs Online to create a button, 'Press me' is displayed on the button. The command option specifies the callback routine for the button.

  hello_b1 is composed of the generic part, the letter 'b', which selects the button widget, and the number 1. The purpose of appending a number is to distinguish between several buttons.