Implementation Support Introduction Elements of Windowing Systems
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Implementation support Introduction chapter 8 • programming tools How does HCI affect of the programmer? – levels of services for programmers • windowing systems Advances in coding have elevated programming – core support for separate and simultaneous user- hardware specific system activity → interaction-technique specific • programming the application and control of dialogue Layers of development tools • interaction toolkits – windowing systems (operating systems) – bring programming closer to level of user perception – interaction toolkits • user interface management systems – user interface management systems – controls relationship between presentation and functionality 1 2 Elements of windowing systems roles of a windowing system Device independence programming the abstract terminal device drivers image models for output and (partially) input Resource sharing achieving simultaneity of user tasks window system supports independent processes isolation of individual applications 3 4 Architectures of windowing The client-server architecture systems Need not be three possible software architectures on same machine – all assume device driver is separate – differ in how multiple application management is implemented 1. each application manages all processes – everyone worries about synchronization – reduces portability of applications 2. management role within kernel of operating system – applications tied to operating system 3. management role as separate application maximum portability 5 6 Programming the application Programming the application read-evaluation loop (macs) notification-based void main(String[] args) { Menu menu = new Menu(); menu.setOption(“Save”); menu.setOption(“Quit”); menu.setAction(“Save”,mySave) menu.setAction(“Quit”,myQuit) ... repeat } read-event(myevent) case myevent.type int mySave(Event e) { type_1: // save the current file do type_1 processing } type_2: do type_2 processing int myQuit(Event e) { ... // close down type_n: } do type_n processing end case end repeat 7 8 going with the grain Using toolkits • system style affects the interfaces Interaction objects – modal dialogue box – input and output intrinsically linked • easy with event-loop (just have extra read-event loop) • hard with notification (need lots of mode flags) – non-modal dialogue box • hard with event-loop (very complicated main loop) move press release move • easy with notification (just add extra handler) Toolkits provide this level of abstraction – programming with interaction objects (or beware! – techniques, widgets, gadgets) if you don’t explicitly design it will just happen – promote consistency and generalizability – through similar look and feel implementation should not drive design – amenable to object-oriented programming 9 10 UI development environment interfaces in Java (UIDE) • Java toolkit – AWT (abstract windowing toolkit) • e.g. Visual Studio, Delphi – Provide high level of support for • Java classes for buttons, menus, etc. programmer • Notification based; •but – AWT 1.0 – need to subclass basic widgets – Usually operating system specific – AWT 1.1 and beyond -– callback objects •Swing toolkit – built on top of AWT – higher level features – uses MVC architecture (see later) 11 12 User Interface Management UIMS as conceptual architecture Systems (UIMS) • UIMS add another level above toolkits • separation between application semantics and – toolkits too difficult for non-programmers presentation •improves: • roles of UIMS – portability – runs on different systems – conceptual architecture – reusability – components reused cutting costs – implementation techniques – multiple interfaces – accessing same functionality – support infrastructure – customizability – by designer and user • These issues will be more important as ‘anytime anywhere’ computing becomes a reality 13 14 Seeheim model MVC model - view - controller lexical syntactic semantic Dialogue Functionality view USERUSER Presentation (application APPLICATION Control interface) model switch controller – arose out of implementation experience • MVC is largely pipeline model: – but principal contribution is conceptual input → control → model → view → output – concepts part of ‘normal’ UI language • but in graphical interface – input only has meaning in relation to output e.g. mouse click –need to know what was clicked e.g. the lower box, the switch – controller has to decide what to do with click • needed for implementation – but view knows what is shown where! • in practice controller ‘talks’ to view • but not conceptual – separation not complete 15 16 PAC PAC model presentation - abstraction - control A P A P • PAC model closer to Seeheim C C – abstraction – logical state of component – presentation – manages input and output – control – mediates between them abstraction presentation • manages hierarchy and multiple views – control part of PAC objects communicate control • PAC cleaner in many ways … but MVC used more in practice (e.g. Java Swing) A P C A P C 17 18 Implementation of UIMS graphical specification • Techniques for dialogue controller • what it is • menu networks • state transition diagrams – draw components on screen • grammar notations • event languages – set actions with script or links to program • declarative languages • constraints • graphical specification • in use – with raw programming most popular technique – for most of these see chapter 16 – e.g. Visual Basic, Dreamweaver, Flash • N.B. constraints • local vs. global – instead of what happens say what should be true – hard to ‘see’ the paths through system – used in groupware as well as single user interfaces – focus on what can be seen on one screen (ALV -abstraction–link–view) see chapter 16 for more details on several of19 these 20 Trend Summary The drift of dialogue control • internal control Levels of programming support tools (e.g., read-evaluation loop) •Windowing systems – device independence –multiple tasks • external control • Paradigms for programming the application (independent of application semantics or presentation) – read-evaluation loop – notification-based • presentation control • Toolkits – programming interaction objects (e.g., graphical specification) •UIMS – conceptual architectures for separation – techniques for expressing dialogue 21 22.