[incr Tcl] 3.0

Porting Guide

As much as possible, I've tried to make itcl3.0 backward-compatible with earlier releases. The class definition syntax has not changed at all from itcl2.2, and the old itcl1.x syntax is still supported. But you'll notice changes related to namespaces. John Ousterhout adopted a slightly different namespace model for Tcl8. The syntax of the namespace command is different, as well as the semantics for command/variable lookups and imports. Also, John failed to adopt ensembles into the Tcl core, so itcl can't add functions like info objects and info classes into the usual info command. These functions have been moved to a new itcl::find command.
The [incr Widgets] package has changed quite a bit. There are many new widgets, and some of the existing widgets were streamlined--some of the widget options were removed to improve performance. For details, see the CHANGES file in the iwidgets3.0.0 directory. Because there are a lot of changes, this distribution also contains the iwidgets2.2.0 package, which is backward-compatible with the existing [incr Widgets].

It should be quite easy for most people to migrate their code to work with itcl3.0. I updated two releases of the entire [incr Widgets] library in a few hours.
Following is a quick summary of changes, to serve as a porting guide.
You have code like this... Change to this...
    namespace foo {...}
  
    namespace eval foo {...}
  
    delete namespace foo

    ::delete objects fred barney
  
    namespace delete foo

    itcl::delete objects fred barney
  
    info context
  
    namespace current
  
    info objects ...
  
    itcl::find objects ...
  
    info classes ...
  
    itcl::find classes ...
  
    info which -namespace $name
  
    if {![string match ::* $name]} {
        set name [namespace current]::$name    
    }
  
In itcl2.2, commands/classes could be found in any namespace in a hierarchy. So within a namespace like "iwidgets" you could use simple names like:
    Labeledwidget::alignlabels ...
    Pane #auto
  
In Tcl8.0, all commands/classes that are not in the global namespace must be qualified. For example, the "iwidgets" namespace has a bunch of classes within it. You must always refer to these classes with qualified names, like this:
    iwidgets::Labeledwidget::alignlabels ...
    iwidgets::Pane #auto
  
In itcl2.2, the global command was used to access variables in a namespace:
    namespace foo {
        variable x 0
        proc example {} {
            global x
            return $x
        }
    }
  
In Tcl8.0, the variable command is used to access variables in a namespace:
    namespace eval foo {
        variable x 0
        proc example {} {
            variable x
            return $x
        }
    }
  
    public itk_component add...
    protected itk_component add...
    private itk_component add...
  
    itk_component add ...
    itk_component add -protected ...
    itk_component add -private ...
  
    bind .foo <Enter> [code %q method]
    bind .foo <Enter> [code %Q method]
  
    bind .foo <Enter> [code %W method]
    bind .foo <Enter> [code $this method]
  

Other Differences
You can now use instance variables (along with the usual common variables) with the scope command. Thus, you're no longer forced to use the trick with a common array, such as: [scope modes($this)]

All widget/mega-widget access commands (e.g., .foo.bar) are installed in the global namespace. Therefore, they can be accessed from any namespace context.
The [incr Widgets] package used to be loaded by default. You must now use the package require command to load it explicitly:
    package require Iwidgets              <-- loads the lastest (iwidgets3.0.0)
    package require -exact Iwidgets 2.2   <-- loads the older release
Command/variable names are now reported with fully-qualified names in info inquiries and in error messages.

No public/protected/private declarations outside of class definitions

The scope command used to be more or less the same as the code command. In itcl3.x, scope is only for variables, and if a variable is not recognized, you'll get an error.

The code command used to return a value like "@scope ...". It now returns "namespace inscope ...", to be compatible with Tcl8.

The prototypes for Itcl_RegisterC and Itcl_FindC have changed. You can now include ClientDatawhen you register C functions. Also, there is a new Itcl_RegisterObjC function for (objc,objv)-style command handlers.

You have code like this...	Change to this...
namespace foo {...}	namespace eval foo {...}
delete namespace foo ::delete objects fred barney	namespace delete foo itcl::delete objects fred barney
info context	namespace current
info objects ...	itcl::find objects ...
info classes ...	itcl::find classes ...
info which -namespace $name	if {![string match ::* $name]} { set name [namespace current]::$name }
In itcl2.2, commands/classes could be found in any namespace in a hierarchy. So within a namespace like "iwidgets" you could use simple names like: Labeledwidget::alignlabels ... Pane #auto	In Tcl8.0, all commands/classes that are not in the global namespace must be qualified. For example, the "iwidgets" namespace has a bunch of classes within it. You must always refer to these classes with qualified names, like this: iwidgets::Labeledwidget::alignlabels ... iwidgets::Pane #auto
In itcl2.2, the `global` command was used to access variables in a namespace: namespace foo { variable x 0 proc example {} { global x return $x } }	In Tcl8.0, the `variable` command is used to access variables in a namespace: namespace eval foo { variable x 0 proc example {} { variable x return $x } }
public itk_component add... protected itk_component add... private itk_component add...	itk_component add ... itk_component add -protected ... itk_component add -private ...
bind .foo <Enter> [code %q method] bind .foo <Enter> [code %Q method]	bind .foo <Enter> [code %W method] bind .foo <Enter> [code $this method]