Overview

# NetBeans Architecture Answers for Editor Code Completion module

- Author: dbalek@netbeans.org
- Answers as of: Dec 7, 2006
- Answers for questions version: 1.25
- Latest available version of questions: 1.26

WARNING: answering questions version 1.25 rather than the current 1.26.

## Interfaces table

##### Group of java interfaces

Interface Name | In/Out | Stability | Specified in What Document?
CodeCompletionAPI | Exported | Official | index.html
EditorModuleAPI | Imported | Friend |

## General Information

Question (arch-what): What is this project good for?

Answer:

Code Completion provides users with a list of suggested completions for partially typed texts in the editor and various dialog input fields.
The Code Completion module was created to replace the original legacy editor code completion which lacked several key requirements:

- Support for multiple independent code completion content providers.
- Implied requirement for ordering and prioritization of the completion items.
- Direct support for asynchronous completion result computation.
- Missing separation to the API and SPI and implementation parts.

Question (arch-overall): Describe the overall architecture.

Answer:

The Code Completion module is located under `/cvs/editor/completion` directory. It provides the CodeCompletionAPI with a simple API for showing and hiding of the completion located in `org.netbeans.api.editor.completion` and with SPI defining the completion providers that is located in `org.netbeans.spi.editor.completion`, and the implementation located in `org.netbeans.modules.editor.completion`.

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:

### API

#### Show or hide completion window

The API is small and it only allows to explicitly show or hide the completion window.
It's being used by code templates that need to explicitly show the code completion window when tabbing to a particular parameter.
There may be certain actions that want to ensure that the code completion is hidden at the time when they are invoked. For example the actions pasting the content of the completion item into the document.

### SPI

#### Provide completion content by independent providers

Completion infrastructure needs to obtain the results that are then displayed in the completion window.
There are three types of displayed results related to the current caret offset:

- Code completion items
- Documentation (e.g. the javadoc documentation)
- Tooltip (e.g. for method parameters)

For the purpose of obtaining these completion results CompletionProvider exists.
There may be an arbitrary number of independent completion providers for a single completion popup window.
The completion providers are registered through the xml layer into Editors/<mime-type>/CompletionProviders. Once the document with the particular mime-type gets loaded the corresponding completion providers will get instantiated and used.

Threading:
The code completion's infrastructure invokes the requests for the completion results in the AWT thread.
Therefore all the methods of the completion providers are invoked in AWT thread but they may reschedule their processing into other threads.

#### Provide completion results computed asynchronously

The completion provider creates a task that computes the resulting data that will then be displayed by the code completion infrastructure.
The task creation and computation are called synchronously from the AWT event dispatch thread.
However there can be potentially long-running tasks (e.g. working with MDR) that are not desirable to be run in AWT thread.
Therefore the completion infrastructure provides a listener to which the completion task notifies the results.
The support class AsyncCompletionTask allows to post the task computation into `RequestProcessor`.

#### Provide list of completion items fulfilling various requirements

The completion task computes a collection of completion items which are then collected by the completion infrastructure and displayed.
Displaying. Each completion item must be able to display itself in a `JList`.
Sorting. The completion items may come from different completion providers and they must be sorted before displaying. The sort order should not only be alphabetical but it should also allow a prioritization of the items according to their importance in the given context.
Actions. The interaction of the user with the completion item is done by interacting with item's input map and action map.
Documentation. The item may want to display additional detailed information in a documentation popup window.

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

Answer:

The prototype implementation of the module is available in cvs on the completion branch. Also, the prototype implementation of the Java completion provider exists in /cvs/java/editor on the completion branch. An additional time will be needed for cleaning-up the editor module from the existing code completion infrastructure (5 man-days), convering the existing completion supports (e.g. JSP Completion, XML Completion) into the completion providers (5 man-days), polishing the Code Completion module itself to e.g. work with the existing code completion options, etc. (3 working man-days), and the overall module stabilization (5 man-days).

There are no expected milestones yet.

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

Answer:

The unit tests will be created to cover the functionality testing.
The proper instantiation of the registered completion providers will be tested.
Asynchronous task execution.
Various semantics e.g. prohibition of repetitive result notification from the completion provider.

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

WARNING: Question with id="arch-where" has not been answered!

## Project and platform dependencies

Question (dep-nb): What other NetBeans projects and modules does this one depend on?

Answer:

The module has dependency on the EditorModuleAPI module. It uses this dependency to read the old code completion options stored as a part of the editor module.

Question (dep-non-nb): What other projects outside NetBeans does this one depend on?

Answer:

The module does not depend on any outside project.

Question (dep-platform): On which platforms does your module run? Does it run in the same way on each?

Answer:

The module runs on any platform that provides the required JRE.

Question (dep-jre): Which version of JRE do you need (1.2, 1.3, 1.4, etc.)?

Answer:

JRE 1.4 and higher.

Question (dep-jrejdk): Do you require the JDK or is the JRE enough?

Answer:

JRE is sufficient.

## Deployment

Question (deploy-jar): Do you deploy just module JAR file(s) or other files as well?

Answer:

No additional files.

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:

The module can be installed anywhere.

Question (deploy-packages): Are packages of your module made inaccessible by not declaring them public?

Answer:

Yes, only the Code Completion SPI is public.

Question (deploy-dependencies): What do other modules need to do to declare a dependency on this one?

Answer: OpenIDE-Module-Module-Dependecies: org.netbeans.modules.editor.completion/1 > 1.6.22

## 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 module does not define nor implement any standard.

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:

The Code Completion module should be able to read the existing code completion related options stored as part of the editor settings.
In a future, we plan to introduce some additional options related to e.g. sorting the code completion results, etc.

## Access to resources

Question (resources-file): Does your module use `java.io.File` directly?

Answer:

No.

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:

No.

Question (resources-read): Does your module read any resources from layers? For what purpose?

Answer:

The module reads CompletionProviders registered for the given mime-type from the `Editors/<mime-type>/CompletionProviders` folder.

Question (resources-mask): Does your module mask/hide/override any resources provided by other modules in their layers?

Answer:

No.

## 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:

No.

Question (lookup-register): Do you register anything into lookup for other code to find?

Answer:

No.

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?

Answer:

No.

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:

No.

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:

No.

Question (exec-introspection): Does your module use any kind of runtime type information (`instanceof`, work with `java.lang.Class`, etc.)?

Answer:

No.

Question (exec-threading): What threading models, if any, does your module adhere to?

Answer:

XXX no answer for exec-threading

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

Answer:

No.

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

Answer:

No.

## 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:

No files are read or written to the disk.

Question (format-dnd): Which protocols (if any) does your code understand during Drag & Drop?

Answer:

The module does not use Drag & Drop.

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:

The module does not work with the clipboard.

## Performance and Scalability

Question (perf-startup): Does your module run any code on startup?

Answer:

Singleton `org.netbeans.modules.editor.completion.Completion` is created on the module startup.

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:

Number of CompletionProviders registered for a document mime-type.

Question (perf-limit): Are there any hard-coded or practical limits in the number or size of elements your code can handle?

Answer:

There are no hard-coded limits. However, due to performance reasons, the number of CompletionProviders registered with a mime-type should be held as low as possible.

Question (perf-mem): How much memory does your component consume? Estimate with a relation to the number of windows, etc.

Answer:

No answer.

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:

Computing of the code completion results is potentially a long-running task. The Code Completion SPI is constructed in such a way that it provides CompletinProviders with a possibility to run their tasks asynchronously.

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.

Question (perf-spi): How the performance of the plugged in code will be enforced?

Answer:

Currently, there is no way to enforce the performance of the plugged in code.

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