NetBeans Architecture Answers for Diff module

General Information

Question (arch-what): What is this project good for?
Answer: The diff module provides the ability to visualize differences between source files. It also has a graphical conflicts resolver tool and built-in patch algorithm.

List of the main features:

• Simple APIs, that provide access to registered diff and merge engines and visualizers.
• Built in and external diff engines defined.
• Graphical diff vizualizer and conflicts resolver.
• Extensible with additional diff and merge engines and vizualizers.
• Patch algorithm implemented for UNIX-style, unidiff and contextual diff formats.
Question (arch-overall): Describe the overall architecture.
Answer:

Support to everything related to creation and visualization of diffs. This library allows registrations of various diff providers and visualizers and provides programatic access to their functionality.

Question (arch-usecases): Describe the main use cases of the new API. Who will use it under what circumstances? What kind of code would typically need to be written to use the module?
Answer:

Show a diff from action

From an action or wherever you like you can call this:

                                public void diff(final StreamSource local, final StreamSource remote){
    SwingUtilities.invokeLater(new Runnable() {
        public void run() {
            try {
                DiffView view = Diff.getDefault().createDiff(local, remote);
                showDiff(view);
            } catch (IOException ex) {
                Logger.getLogger(ThisClass.class.getName()).throwing(ex);
            }
        }
    });
}
public void showDiff(final DiffView view){
    SwingUtilities.invokeLater(new Runnable() {
        public void run() {
            //create our panel with our view
            //right now I am just going to use the diff component 
            // instead of a panel
            //create a topcomponent with our panel
            DiffTopComponent tc = new DiffTopComponent(view);
            tc.setName("MY_DIFF");
            tc.setDisplayName("Some display name");
            tc.open();
            tc.requestActive();
        }
    });
}

                            

Embeded into TopComponent

Here is a top component to display it:

                                public class DiffTopComponent extends TopComponent {
    /** Creates a new instance of DiffTopComponent */
    public DiffTopComponent(Component diffPanel) {
        setLayout(new BorderLayout());
        add(diffPanel, BorderLayout.CENTER);
        getAccessibleContext().setAccessibleName(
            NbBundle.getMessage(DiffTopComponent.class, 
            "ACSN_Diff_Top_Component")); // NOI18N
        
        getAccessibleContext().setAccessibleDescription(
            NbBundle.getMessage(DiffTopComponent.class, 
            "ACSD_Diff_Top_Component")); // NOI18N
    }
   
    public DiffTopComponent(DiffView view) {
        this(view.getComponent());
    }
    public int getPersistenceType(){
        return TopComponent.PERSISTENCE_NEVER;
    }
    protected String preferredID(){
        return "DiffTopComponent";    //NOI18N
    }
    public HelpCtx getHelpCtx() {
        return new HelpCtx(getClass());
    }
}

                            

Question (arch-time): What are the time estimates of the work?
Answer:

Finished in 2002.

Question (arch-quality): How will the quality of your code be tested and how are future regressions going to be prevented?
Answer:

XXX no answer for arch-quality

Question (arch-where): Where one can find sources for your module?
Answer:

The sources for the module are in the Apache Git repositories or in the GitHub repositories

Project and platform dependencies

Question (dep-nb): What other NetBeans projects and modules does this one depend on?
Answer: Several.
Question (dep-non-nb): What other projects outside NetBeans does this one depend on?
Answer: None.
Question (dep-platform): On which platforms does your module run? Does it run in the same way on each?
Answer: The module is 100% pure Java and runs on any platform.
Question (dep-jre): Which version of JRE do you need (1.2, 1.3, 1.4, etc.)?
Answer: Needs at least JRE 1.4.
Question (dep-jrejdk): Do you require the JDK or is the JRE enough?
Answer: JRE is enough.

Deployment

Question (deploy-jar): Do you deploy just module JAR file(s) or other files as well?
Answer:
• diff.jar - standard module jar file
Question (deploy-nbm): Can you deploy an NBM via the Update Center?
Answer: Yes.
Question (deploy-shared): Do you need to be installed in the shared location only, or in the user directory only, or can your module be installed anywhere?
Answer: Module can be installed anywhere.
Question (deploy-packages): Are packages of your module made inaccessible by not declaring them public?
Answer: All public packages are accessible, no restriction applied. Diff module contains DiffAPI. Some parts of VCS modules can use semi-private API DiffImplementationAPI, namely org.netbeans.modules.diff.builtin.DiffPresenter.
Question (deploy-dependencies): What do other modules need to do to declare a dependency on this one, in addition to or instead of the normal module dependency declaration (e.g. tokens to require)?
Answer: Nothing.

Compatibility with environment

Question (compat-i18n): Is your module correctly internationalized?
Answer: Yes.
Question (compat-standards): Does the module implement or define any standards? Is the implementation exact or does it deviate somehow?
Answer: The external diff engine expect the standard UNIX-style output of the external diff executable. The patching algorithm supports three diff formats:
• Standard UNIX-style diff format,
• Unidiff format,
• Contextual diff format.
Question (compat-version): Can your module coexist with earlier and future versions of itself? Can you correctly read all old settings? Will future versions be able to read your current settings? Can you read or politely ignore settings stored by a future version?
Answer: Only one version of the module can be installed at a time. The settings are shared across different versions, stored and read by Java serialization and will be read in future as well.
Question (compat-deprecation): How the introduction of your project influences functionality provided by previous version of the product?
Answer:

XXX no answer for compat-deprecation

Access to resources

Question (resources-file): Does your module use java.io.File directly?
Answer: Yes, for temporary files and for location of the patch file.
Question (resources-layer): Does your module provide own layer? Does it create any files or folders in it? What it is trying to communicate by that and with which components?
Answer: Yes. The module defines the provided diff and merge engines and visualizers so that they can be accessed by lookup. Also settings are defined there.
Question (resources-read): Does your module read any resources from layers? For what purpose?
Answer: No.
Question (resources-mask): Does your module mask/hide/override any resources provided by other modules in their layers?
Answer: No.
Question (resources-preferences): Does your module uses preferences via Preferences API? Does your module use NbPreferences or or regular JDK Preferences ? Does it read, write or both ? Does it share preferences with other modules ? If so, then why ?
WARNING: Question with id="resources-preferences" has not been answered!

Lookup of components

Question (lookup-lookup): Does your module use org.openide.util.Lookup or any similar technology to find any components to communicate with? Which ones?
Answer: Yes. Lookup is used to get all registered diff and merge engines and visualizers.
Question (lookup-register): Do you register anything into lookup for other code to find?
Answer: Yes. The module registers two diff engines, two diff visualizers and one merge visualizer (visual conflicts resolver).
Question (lookup-remove): Do you remove entries of other modules from lookup?
Answer: No.

Execution Environment

Question (exec-property): Is execution of your code influenced by any environment or Java system (System.getProperty) property? On a similar note, is there something interesting that you pass to java.util.logging.Logger? Or do you observe what others log?
Answer: user.dir - Used as a default directory in the file chooser, that is used by the patch action.
Question (exec-component): Is execution of your code influenced by any (string) property of any of your components?
Answer: No.
Question (exec-ant-tasks): Do you define or register any ant tasks that other can use?
Answer:

XXX no answer for exec-ant-tasks

Question (exec-classloader): Does your code create its own class loader(s)?
Answer: No.
Question (exec-reflection): Does your code use Java Reflection to execute other code?
Answer: No.
Question (exec-privateaccess): Are you aware of any other parts of the system calling some of your methods by reflection?
Answer: No.
Question (exec-process): Do you execute an external process from your module? How do you ensure that the result is the same on different platforms? Do you parse output? Do you depend on result code?
Answer: Yes, for an external diff engine. The standard UNIX diff output is expected, it's the responsibility of the user to supply the correct executable.
Question (exec-introspection): Does your module use any kind of runtime type information (instanceof, work with java.lang.Class, etc.)?
Answer: Yes.
• DiffAction needs to detect whether the provided diff component is a TopComponent or not in order to open it in an appropriate way.
• DiffPanel and MergePanel need to check whether the supplied document is a StyledDocument or not.
• DiffSettings needs to alter diff services when the default is changed and thus it needs to cast the service to InstanceDataObject
• LinesComponent needs to cast the settings objects retrieved from editor's settings
• MergeDialogComponent needs to check class types for presenting pop-up menu actions
• PatchAction in order to disable itself on InstanceDataObjects
Question (exec-threading): What threading models, if any, does your module adhere to? How the project behaves with respect to threading?
Answer:

XXX no answer for exec-threading

Question (security-policy): Does your functionality require modifications to the standard policy file?
Answer:

XXX no answer for security-policy

Question (security-grant): Does your code grant additional rights to some other code?
Answer:

XXX no answer for security-grant

Format of files and protocols

Question (format-types): Which protocols and file formats (if any) does your module read or write on disk, or transmit or receive over the network? Do you generate an ant build script? Can it be edited and modified?
Answer: Three diff formats:
• Standard UNIX-style diff format,
• Unidiff format,
• Contextual diff format.
Question (format-dnd): Which protocols (if any) does your code understand during Drag & Drop?
Answer: None.
Question (format-clipboard): Which data flavors (if any) does your code read from or insert to the clipboard (by access to clipboard on means calling methods on java.awt.datatransfer.Transferable?
Answer: No clipboard communication is implemented.

Performance and Scalability

Question (perf-startup): Does your module run any code on startup?
Answer: No.
Question (perf-exit): Does your module run any code on exit?
Answer: No.
Question (perf-scale): Which external criteria influence the performance of your program (size of file in editor, number of files in menu, in source directory, etc.) and how well your code scales?
Answer: Size of the files, that are diffing or patching.
Question (perf-limit): Are there any hard-coded or practical limits in the number or size of elements your code can handle?
Answer: No explicit limits. Technically, the available memory size is the limit...
Question (perf-mem): How much memory does your component consume? Estimate with a relation to the number of windows, etc.
Answer: TBD.
Question (perf-wakeup): Does any piece of your code wake up periodically and do something even when the system is otherwise idle (no user interaction)?
Answer: No.
Question (perf-progress): Does your module execute any long-running tasks?
Answer: The diff engines and patch action run in background to prevent blocking the AWT thread. The running time depends on the file size.
Question (perf-huge_dialogs): Does your module contain any dialogs or wizards with a large number of GUI controls such as combo boxes, lists, trees, or text areas?
Answer: No.
Question (perf-menus): Does your module use dynamically updated context menus, or context-sensitive actions with complicated and slow enablement logic?
Answer: No. Enabling logic is simple.
Question (perf-spi): How the performance of the plugged in code will be enforced?
Answer:

XXX no answer for perf-spi