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<title>Eclipse Debug Platform [org.eclipse.debug.core.model]</title>
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<p>Defines interfaces for debug model elements, source lookup, and launching.</p>

<h2>Package Specification</h2>

<p>This package defines classes and interfaces known as the &quot;debug model&quot; 
  which support an extensible set of debug architectures and languages. The debug 
  model is a set of interfaces representing common artifacts in debuggable programs. 
  The debug plug-in itself does not provide an implementation of a debug model. 
  It is intended that third parties providing an integrated set of development 
  tools for a specific language will also implement a debug model for that language, 
  using an underlying debug architecture of their choice. For example, Java development 
  tooling provides an implementation of a debug model based on the standard Java 
  Platform Debug Architecture (JPDA).</p>

<h4>The Debug Model</h4>

<p>A client implements a debug model by
providing an implementation of the interfaces defined in this package. (There is no explicit
extension point that represents a debug model). Each debug model provides one or more
launch configuration types capable of initiating a debug session.</p>

<p>The common elements defined by the debug model are: 

<ul>
  <li>Debug Target - A debug target represents a debuggable program - for example, a virtual
    machine or a process.</li>
  <li>Thread - A debug target may contain one or more threads.</li>
  <li>Stack Frame - A suspended thread may contain one or more stack frames.</li>
  <li>Variable - A stack frame may contain variables.</li>
  <li>Value - Each variable has an associated value, and a value may contain more variables (to
  	represent complex data structures and objects).</li>
  <li>Register Group - A stack frame may (optionally) be associated with one or more register
    groups.</li>
  <li>Register - A register group contains one or more registers.</li>
  <li>Memory Blocks - A debug target may (optionally) support the retrieval of
    arbitrary contiguous segments of memory.</li>
  <li>Breakpoint - Breakpoints suspend the execution of a program.</li>
  <li>Expression -  An expression is a snippet of code that can be evaluated to
  	produce a value.</li>
</ul>

<p>A debug model implementation is responsible for firing debug events. A debug event
corresponds to an event in a program being debugged - for example the creation or
termination of a thread.</p>

<h4>Breakpoints</h4>

<p>Breakpoints are used to suspend the execution of a program being debugged. There are
many kinds of breakpoints - line breakpoints, conditional line breakpoints, hit count
breakpoints, exception breakpoints, etc. The kinds of breakpoints supported by each debug
architecture, and the information required to create those breakpoints
is dictated by each debug architecture. The debug platform supports an extensible
set of breakpoint via the breakpoints extension point.</p>

<p>The debug platform provides a breakpoint manager that maintains the collection 
  of all registered breakpoints. Clients add and remove breakpoints via this manager. 
  Breakpoints are implemented by instances of <b>IBreakpoint</b>. Each breakpoint 
  object has an associated marker, which provides persistence and presentation 
  in editors. The debug platform defines a generic breakpoint and line breakpoint, 
  as well as their corresponding marker definitions. Breakpoint creation is a 
  client responsibility - that is, defining the attributes of a breakpoint and 
  the resource to associate a breakpoint marker with.</p>

<p>Breakpoints are persisted via their underlying marker. Breakpoint markers defined 
  with the <b>persisted</b> attribute as <b>false</b> will not be persisted. Breakpoints 
  are restored at workspace startup time by the breakpoint manager - that is, 
  breakpoint objects are created for all persisted markers which are a subtype 
  of the root breakpoint marker and are added to the breakpoint manager. To allow 
  for selective persistence of breakpoints (of the same kind), the <b>IBreakpoint</b> 
  interface and root breakpoint implementation defines a &quot;persisted&quot; 
  attribute. If this value is set to false, the breakpoint will not be persisted 
  across workspace invocations.</p>

<p>As breakpoint markers are modified (created, removed, and changed), resource 
  deltas are created by the platform. The breakpoint manager translates pertinent 
  resource deltas into breakpoint change notifications (breakpoint added/removed/changed 
  messages). Interested listeners may register with the breakpoint manager. The 
  breakpoint manager only fires change notifications for registered breakpoints. 
  This simplifies breakpoint processing for clients, as resource delta traversal 
  and analysis is not required. Debug targets that support breakpoints should 
  register for breakpoint change notifications.</p>
<h4>New Features in the Debug Model, Eclipse 3.0</h4>
<blockquote> 
  <h4>Launch Delegate Enhancements<br>
  </h4>
  <p>Lanuch delegates can optionally implement the new interface <code>ILaunchConfigurationDelegate2</code>. 
    This allows launch delegates to provide a launch object to be used for a launch. 
    For example, when debugging on a server a delegate could create a new launch 
    object or may reuse an existing launch object if the server is already running 
    in debug mode. As well, the inteface provides a mechanism for performing a 
    scoped build prior to launching (i.e. scoped to the projects in the workspace 
    pertaining to the launch), and searching for errors in the workspace which 
    may prevent the launch from succeeding (for example, compilation errors).</p>
  <p></p>
  <h4>Extensible Watch Expressions</h4>
  <p>The debug platform provides an implementation of watch expressions. Debug 
    models can contribute watch expression delegates if they support watch expressions. 
    When a stack frame is selected, the associated delegate is queried to provide 
    a value for a watch expression in that context. The debug platform provides 
    persistence, enabling, disabling, entering, and editing of watch expressions.</p>
  <h4>Automatic Array Partitioning<br>
  </h4>
  <p>The debug plug-in supports automatic partitioning of indexed collections, 
    which partitions large arrays into sub-ranges in the variables view. This 
    is supported with the introduction of a new interface in the debug model representing 
    an indexed value - <code>IIndexedValue</code>. If a value implements this 
    interface, the variables view will automatically partition its elements as 
    required, into sub-ranges</p>
  <h4>Logical Structure Types<br>
  </h4>
  <p>Often, it is convenient to navigate complex data structures in terms of a 
    logical structure, rather than an implementation structure. For example, no 
    matter how a list is implemented (i.e. linked list, collection of arrays, 
    etc.), it is often convenient to be able to view the list as an ordered collection. 
    To facilitate the display of logical structures in the variables view, an 
    extension point has been added (<code>org.eclipse.debug.core.logicalStructureTypes</code>) 
    allowing debug models to contribute logical structures of its values, where 
    applicable. Debug models may contribute delegates to translate raw implementation 
    values into logical values. The variables view will display the logical values, 
    when the option to display logical structures is turned on. More than one 
    logical structure can be provided for a single value - the user can choose 
    which structure to display.</p>
  <h4>Step Filters<br>
  </h4>
  <p>To support step filters on all stepping functions (into, over, return), a 
    new interface has been added to the debug platform - <code>IStepFilters</code> 
    - which can be implemented by debug targets. This interface replaces <code>IFilteredStep</code>, 
    which is now deprecated. The debugger provides a global toggle that turns 
    step filters on/off for all stepping functions. Debug targets should implement 
    this new interface and honor the step filter enablement setting when stepping.</p>
  <p>This change maintains binary compatibility with previous releases. However, 
    targets wishing to leverage the new function must implement the new interface.<br>
  </p>
</blockquote>
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