Input - PDF document

�������������� � Input ����������������������� Fall 2005 6.831 UI Design and Implementation 1 Fall 2005 6.831 UI Design and Implementation 2 ����������������������������� ��������������������� � Console I/O uses blocking procedure calls � Raw input events print ( � Enter name: � ) � Mouse moved name = readLine(); � Mouse button pressed or released print ( � Enter phone number: � ) � Key pressed or released name = readLine(); � Translated input events � System controls the dialogue � Mouse click or double-click � GUI input uses event handling instead � Mouse entered or exited component � User has much more control over the dialogue � Keyboard focus gained or lost (loss of focus is � User can click on almost anything sometimes called � blur � ) � Character typed Fall 2005 6.831 UI Design and Implementation 3 Fall 2005 6.831 UI Design and Implementation 4 1

��������������������������� ������!���� � Events are stored in a queue � Mouse position (X,Y) � User input tends to be bursty � Mouse button state � Queue saves application from hard real � Modifier key state (Ctrl, Shift, Alt, Meta) time constraints (i.e., having to finish � Timestamp handling each event before next one might occur) � Why is timestamp important? � Mouse moves are coalesced into a single event in queue � If application can � t keep up, then sketched lines have very few points Fall 2005 6.831 UI Design and Implementation 5 Fall 2005 6.831 UI Design and Implementation 6 ���������� ������"��������#� ����$����� � Dispatch: choose target component for � While application is running � Block until an event is ready event � Get event from queue � Key event: component with keyboard focus � (sometimes) Translate raw event into higher-level events � Generates double-clicks, characters, focus, enter/exit, etc. � Mouse event: component under mouse � Translated events are put into the queue � Mouse capture : any component can grab � Dispatch event to target component mouse temporarily so that it receives all mouse � Who provides the event loop? events (e.g. for drag & drop) � High-level GUI toolkits do it internally (Java, VB, C#) � Propagation: if target component � Low-level toolkits require application to do it (MS Win, Palm, SWT) declines to handle event, the event passes up to its parent Fall 2005 6.831 UI Design and Implementation 7 Fall 2005 6.831 UI Design and Implementation 8 2

%��������� ������������ "���$���$���&��������� � Events propagate in different directions � A controller is a finite state machine on different browsers � Example: push button � Netscape 4: downwards from root to target � Internet Explorer: upwards from target to Armed press root mouse enter � W3C standardized by combining them release exit Idle Hover enter � Netscape 6+/Mozilla/Opera/W3C: first (invoke) mouse exit downwards ( � capturing � ), then upwards ( � bubbling � ) Disarmed release Fall 2005 6.831 UI Design and Implementation 9 Fall 2005 6.831 UI Design and Implementation 10 ����������� � Generic reusable controllers (Garnet and Amulet toolkits) � Selection interactor � Move/Grow interactor � New-point interactor � Text editing interactor � Rotating interactor � Hide the details of handling input events and finite state machines � Useful only in a component model � Parameterized � start, stop, abort events � start location, inside/outside predicates � feedback components � callback procedures on event transitions Fall 2005 6.831 UI Design and Implementation 11 3