How to Write Bad Eclipse Plug-ins Alex Blewitt @alblue Originally presented at Eclipse Night London 16 September 2015

Bad Eclipse Plug-ins • This talk will present anti-patterns for
 Eclipse plug-in development • Use these techniques in order to degrade a user's experience of Eclipse • Bad plug-ins don't just happen by accident!

Bad Eclipse Plug-ins • This talk will present anti-patterns for
 Eclipse plug-in development • Use these techniques in order to degrade a user's experience of Eclipse • Bad plug-ins don't just happen by accident!

First impressions • First impressions last - make them count • Display a splash screen specifically for your plug-in • Otherwise how will they know what plug-in they have installed? • Use new Shell() and resize to size of window for maximum effect • Preferably whilst they're in the middle of something

First impressions • First impressions last - make them count • Display a splash screen specifically for your plug-in • Otherwise how will they know what plug-in they have installed? • Use new Shell() and resize to size of window for maximum effect • Preferably whilst they're in the middle of something

Have a Dialog with user • If a splash screen won't fit then consider a Dialog instead • For maximum benefit, show whilst typing – easier to accidentally press one of the buttons • Register a KeyListener on the SWT container to receive notifications of when they are typing

Rentware • Dialogs are great for rentware • Remind the user to pay up or the software will stop working • Allow the dialog to be dismissed, but come back • Bonus points for having it in a different place • Punch the Money!

Rentware • Dialogs are great for rentware • Remind the user to pay up or the software will stop working • Allow the dialog to be dismissed, but come back • Bonus points for having it in a different place • Punch the Money!

Rentware • Dialogs are great for rentware • Remind the user to pay up or the software will stop working • Allow the dialog to be dismissed, but come back • Bonus points for having it in a different place • Punch the Money!

Rentware • Dialogs are great for rentware • Remind the user to pay up or the software will stop working • Allow the dialog to be dismissed, but come back • Bonus points for having it in a different place • Punch the Money!

Interactive dialog • Dialogs can be interactive too • Why not add a payment field into the dialog? • Take a credit card number • Add a field listener to validate number; use the LUHN check to determine if card is valid • Enable payment button when valid

Interactive dialog • Dialogs can be interactive too • Why not add a payment field into the dialog? • Take a credit card number • Add a field listener to validate number; use the LUHN check to determine if card is valid • Enable payment button when valid

Interactive dialog • Dialogs can be interactive too • Why not add a payment field into the dialog? • Take a credit card number • Add a field listener to validate number; use the LUHN check to determine if card is valid • Enable payment button when valid

Notifications • Another option is to use Mylyn Notifications • Pop-up dialogs in bottom right of screen • Problems with this approach • Notification goes away after inactivity • User doesn't get distracted • Limited click-through conversion rate!

Combine them! • Splash screen AND field input • What's not to like? • Use them to unlock functionality • Good way of populating marketing lists

Combine them! • Splash screen AND field input • What's not to like? • Use them to unlock functionality • Good way of populating marketing lists

Assume the Networks • Only successful people use Eclipse • Clearly they can afford in-flight WiFi ✈ • If their computer isn't connected, it's their fault • Make sure to log lots of errors (or just fail) • Automated Error Reporter is lonely • Who uses firewalls anyway? ⛔

On the Job – the UIJob • Your plug-in is the most important plug-in the user has installed • Instead of running a Job in the background, use UIJob instead • Especially if using the filesystem or network • Everyone loves the beachball!

Reporting Progress • IProgressMonitor allows progress to be reported • Can avoid giving any hints by avoiding setting amount of work - use UNKNOWN (-1) • Ignore cancellations • Pretty animations!

Bundle Activator • Bundle-Activator is an opportunity for delays • Eclipse start-up is serial activation of activators • Single bundle can take down Eclipse! • Thread.sleep(1000000…) • Even if bundle does nothing useful, leave the Activator in there – shows you used a template

Bundle Activator • Bundle-Activator is an opportunity for delays • Eclipse start-up is serial activation of activators • Single bundle can take down Eclipse! • Thread.sleep(1000000…) • Even if bundle does nothing useful, leave the Activator in there – shows you used a template 258 classes out of 762 bundles can't be wrong!

Activators are the • When you reference a class from a bundle it triggers activation automatically if the following: • Bundle-ActivationPolicy: lazy • Referring to a class is enough to cause delays! • Useful in combination with static blocks

Activators are the • When you reference a class from a bundle it triggers activation automatically if the following: • Bundle-ActivationPolicy: lazy • Referring to a class is enough to cause delays! • Useful in combination with static blocks static { ImageDescriptor img = … JFaceResources. getImageRegistry(). put(…,img) } Added 100k+ to application load by triggering ImageRegistry creation

Laziness is overrated • Why be lazy when you can be active? • Better to be fit • IStartup provides ultimate active extension • earlyStartup() – use resources actively at start • Use UIJob().schedule(0) for immediate effect • Don't use declarative services – multi threaded

IInterface and IImplementation • Eclipse ❤ Iinterfaces • Put IInterface and IImplementation in same bundle so they won't get lost • Bonus: refer to the interface, activate the bundle! • Ensure you always cast the interface to hidden internal implementation class to prevent reuse!

IInterface2 • Even better, interfaces can be versioned! • IInterface2 • IInterface3 • IInterface4 • IInterface∞ ! ! Never delete code! Never revoke an API! If it was good enough for Eclipse 2.1 then it is good enough for you!

Avoid new-fangled code • Most Eclipse APIs don't use generics – 
 why should you? • Avoid new annotations like @Inject and @EventTopic – these aren't yet decades old • Why use command and handler when Action is still used by the platform?

Graphics Leaks • SWT is a great library for being able to leak resources • ERROR_NO_HANDLES • Just forget to call dispose() on your Resource • Don't use: • ImageRegistry, ColorRegistry, FontRegistry • Sleak, SWTBot

Summary • Use splash screens, dialogs and interruptions • Rentware is highly popular • Assume the network is always available • Use UIJob instead of Job to block the interface • Don't estimate progress; or check for cancel

Summary • Put all your complex logic in Bundle Activators • Run tasks in IStartup with zero delay for priority • Use static blocks of code to avoid lazy code • Mix interface & implementation in same bundle • Avoid declarative services, @Inject, commands

Thank you and have fun Alex Blewitt @alblue