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Project report (2003) - Using Flash MX Cursor-control component to enhance computer interaction for motion-impaired users
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Project report (2003) - Using Flash MX Cursor-control component to enhance computer interaction for motion-impaired users


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  • 1. Middlesex University (SAE Institute)Using Flash MX Cursor-control component to enhance computer interaction for motion-impaired users Amir Dotan Multimedia Arts degree program - SAE Institute London
  • 2. AbstractFor users with motion impairments, interacting with a computer can be a difficult task, one thatinvolves using special input and output devices.These people are often faced with interfaces that were designed for non-disabled people and inter-acting with them, despite any assistive technology that is being used, may sometime prove to bea time consuming task.This report describes the Cursor-control component, an accessibility component that was devel-oped for Macromedia Flash MX authoring software. It aims to enhance computer interaction formotion-impaired users by making point-and-click tasks easier.It outlines the preliminary research which preceded it followed by a description of the componentitself and how it is used. 1. IntroductionAccessing a computer and interacting with a wide range of the content it has to offer is not aprivilege - it’s a right every person has, regardless of his or hers physical and/or mental condition.Unfortunately, almost all systems and interfaces are designed for non-disabled people, making thetask of interacting with the computer for those with disabilities difficult and frustrating.Users with different motion impairments such as Cerebral Palsy, Muscular Dystrophy, spinal inju-ries to name but a few, tend to experience a number of symptoms that has a direct effect on theirability to interact with a computer. These symptoms may include spasms, tremors, poor coordina-tion, reduced muscle strength and restricted movement.Different kinds of assistive technologies are developed to help motion impaired users interact witha computer and cope with the various tasks with a relative ease and comfort.These technologies include input devices such as a special keyboard and mouse and other typesof hardware.Although they offer a valuable and important bridge between the user and the computer, the nextchallenge the user is faced with is an interface which has to be manipulated and explored with acursor in order to perform tasks and achieve goals.A specially designed mouse may help move a cursor on the screen, but an additional assistancemay and should be offered on the interface’s side to help reduce time when confronted with point-and-click tasks.
  • 3. Studies carried out at the department of engineering and the computer laboratory at CambridgeUniversity investigated different issues concerning motion-impaired users and how they interactwith the computer.One of the studies conducted looked into the use of force-feedback technology which uses a spe-cial mouse to assist users with target selection tasks.The mouse physically reacts to potential targets by moving the cursor toward them and the resultsshowed that the time needed to complete target selection tasks was reduced by over 50%. Figure 1. Cursor paths of one of the partici- pants in the study suffering from tremors and Friedrich’s Ataxia. In that task the participants were presented with 16 “target” circles and were required to select a random target generated by the soft- ware. This recording of the cursor path demostrates the cursor’s movements in 3 different situa- tions where force-feedback technology was used under various conditions.That study stood at the heart of the project detailed in this report and the goal was to implement thatlogic on the interface’s side using Macromedia Flash as the development tool.The result is a reusable component that can be used in any Flash project that is aimed specificallytoward users with motion impairments (Therapeutic applications, games, educational programmesetc.) or is partially targeted of users which might suffer from a form of motion impairments, includingelderly able-bodied population with conditions such as arthritis, strokes and Parkinson’s disease.This report also includes a detailed description of the component’s operational logic and currentconstraints of the current version as further development work alongside user testing are needed tomake this component reach its full potential.
  • 4. 2. The Cursor-control component overviewThe Flash environment, which is often criticized for its lack of accessibility support, can offer newand unexplored opportunities for software accessibility development.Its encapsulated nature and range of programming capabilities make it possible to bend UI conven-tions and paradigms. Too often these attributes seem to encourage usability nightmares but as thisreport will demonstrate, they can be used to do the exact opposite and support accessibility in waysnever tried before.The component was designed with the clear intent of offering developers an amount of flexibilitywhen using it and allows them to modify properties both for functional and aesthetic-visual reasonsmaking it completely independent and customizable.When the cursor is close to a target (proximity detection to be discussed later) a visual rectangleillustrated by a line appears surrounding the target and the cursor attaches to the centre of thetarget having changed to a pointing finger.At its current development stage the component offers developers to make the visual indicationinvisible, control the line’s height, transparency and colour. It also allows setting the amount ofsensitivity with which the cursor will be monitored for proximity and modify its colour. 3. The component’s logicThe main logic behind this component revolves around Flash’s ability to hide the system’s cursorand subsequently replace it with one of its own native visual objects that can be set to follow thehidden system cursor.Since the actual cursor can not be manipulated by the program it is replaced with a “virtual” onethat is much more controllable.The virtual cursor is a movie clip object and is a component asset, meaning its part of it and isplaced inside the host movie’s library once the component is dragged onto the host movie’s stage.When the component is initialized during runtime the actual cursor is hidden and the virtual cursoris placed on the stage and set to follow the invisible actual cursor. contact us Virtual cursor (visible Flash object) Actual cursor (invisible) Figure 2. Basic component logic
  • 5. The second important aspect that makes this component possible is the movie clip object’smethod getBounds() which returns the coordinates of an instance’s bounding box.The virtual cursor’s position on the screen is constantly monitored to check if it overlaps a click-able object’s bounding box but because the goal is to detect proximity and not full contact, thecoordinates are artificially “inflated” by the component to create “virtual” bounds thus allowing itto detect proximity. The difference between the actual and virtual bounding box is set by the devel-oper during authoring. contact us Object’s actual bounding box Object’s virtual bounding box Figure 3.”Inflating” the object’s bounding box*Note: Since the Button object doesn’t include the getBounds() method the Button class inheritsthe MovieClip class in order to allow the logic to work with button objects as well as movie clipsobject since both can be used to detect user interactions.When the component detects that the virtual cursor overlaps the virtual bounding box of a click-able object it disables the drag effect so it can reposition the virtual cursor in the centre of theobject and turn it from an arrow to a pointing finger, indicating it is clickable.Once the virtual cursor is on the target the dragging effect is re-established and the user controlsit again. contact us Figure 4.detects virtual cursor overlapping object’ virtual bounding box
  • 6. contact us Figure 6. The virtual cursor is positioned at the centre of the object and turns into a pointing finger.*Note: When the virtual cursor is placed in the centre of the target the actual cursor is still locatedin its original position since it can not be moved without the user’s mouse movement. This cre-ates an offset between the two that is maintained as long as the virtual cursor is inside a target’sbounding box area. Once the virtual cursor is outside a target it snaps back to the actual cursor’sposition which might at times look a bit crude. Figure 7. An example of the component in action
  • 7. 4. The component’s present state and constraintsThe Cursor-control component is an accessibility component, which assists motion-impaired userswith target selection tasks.At its current development stage it has some limitations and constraints but can still be fully utilizedif these constraints are taken into account by developers.Some are a result of the Flash development environment and its limitations, while others may beregarded as limitations imposed by the component’s own working logic.4.1 Detecting clickable objects in a moviePrior to the release of Flash MX, only button objects where commonly used to detect user interac-tions such as clicking at a specific location on the screen.The latest incarnation of Flash offers developers more ways of detecting user interactions and but-tons event handlers can be implemented with movie clip objects as well.This along with the ability to define event handlers as functions outside the object itself posed achallenge when developing the component to detect all the possible scenarios.When the component is initialized it performs a search for button objects and movie clip objectswhich have button event handler functions. The search includes all the objects in the movie on anygiven timeline and scope and is carried once the host movie has finished loading.The component will not detect and include the following:1. Movie clip objects that have a button event handler defined locally (e.g. on(press){//do something} as oppose to myClip.onPress=function(){//do something} ).2. Linked text in a text box which is assigned with a URL.3. Objects that do not exist in any timeline or scope and reside in the library to be used later in the movie (e.g. attachMovie() method).4. Objects that were created via code after the movie has loaded (e.g. createEmptyMov ieClip() method etc.).5. Objects that reside in external movies loaded into the host movie (e.g. loadMovie() method).At the moment, no way has been found to detect if a movie clip object has a locally defined buttonevent handler or if a text in a text box is linkable. Also, without events such as onAttachMovie it isgoing to be very difficult to detect new clickable objects that are introduced during runtime.Performing a constant update for new objects may put an extra computing strain on the processorthat will effect the overall performance of the host movie.
  • 8. 4.2 Operating speedThe constant monitoring of whether the virtual cursor’s overlaps any given target on the screen isa important and basic operation of the component, However, to avoid intensive resources usageon the part of the component that will have a negative effect on the host movie, the rate at whichthe operation is being carried out is lower than what it potentially could be.The component’s detection speed is frame rate dependent and uses the enterFrame event handlerto generate a constant loop.This means that when running a movie at a low frame rate a decrease in speed detection maybe experienced, resulting in slight delay from the time the cursor enters a target’s area to beingattached to its centre.The detection speed is also dependent on the number of clickable objects the component has tomonitor against the cursor’s position. 5. Design considerations when using the componentThe Cursor-control component was designed to offer developers using it a fair amount of flexibilityand customisation capabilities.Colour control, line height and bounding box visibility are all aimed at making the component’sintegration into projects as manageable as possible, helping to make it part of the surroundings andnot be considered an intrusive element.Despite all that, the functionality of the component may require some design considerations suchas additional spacing between clickable elements to avoid overlapping during runtime, which mayresult in an unpleasant visual effect.Designers intending to use the component for special projects targeted specifically for users withmotion impairments are encouraged to integrate it into the design process and examine how itperforms in a given visual environment.Figure 8. The component’s properties panel allowing developrs to modify the component in various ways
  • 9. 6. Installing and using the componentThe Cursor-control component can be downloaded from the ZIP file has been extrected, the FLA file named cursorcontrol.fla should be placed intothe First Run folder which is located inside Flash MX application folder.Once in place, the component will appear in the components panel after being selected using theback arrow at the top right corner of the panel.All that is left do to is drag it onto the stage and publish the movie. 7. ConclusionsAs was described earlier the component is far from being perfect but it marks an important step inaccessibility components development and should pave the way for more innovations in this field.Although it may be regarded by some as less exciting and challenging than mainstream componentdevelopment, the opposite is true if only to create code that helps users and not just other develop-ers.The Cursor-control component was designed to offer assistance to motion impaired users interact-ing with Flash content, whether it is online or offline.It was developed based on academic studies that showed how taking control over the user’s cursorcan be very helpful in reducing time it takes to perform target selection tasks and implemented thatapproach in a Flash environment, which is becoming a standard in multimedia authoring.The current version of the component may be regarded as a prototype since it hasn’t yet beentested with its target audience and such testing will probably have a direct impact on its functionalityand operation.This report briefly described the theoretical background behind the development process and out-lined the components functionality, constraints and logic.Future work will strive to add a mechanism that triggers an event in a clickable object after anamount of time has elapsed seeing has how some motion impaired users find it difficult to click atarget once reaching it.That alongside other limitations mentioned will hopefully be addressed in the future as well, asFlash offers more opportunities and further wok is carried out in the area of motion impairmentaccessibility.
  • 10. 8. BibliographyHwang. F., Langdon. P., Keates. S., Clarkson. J., Haptic Assistance to Improve ComputerAccess for Motion-Imaired Users, Engineering Desgin Centre, University of Cambridge P., Langdon. P., Keates. S., Clarkson. J., Investigating the cursor movementparameters for haptic assistance of motion-impaired users, Department of Engineering,University of Cambridge., Computer Laboratory, University of Cambridge S., Clarkson. P.J., Robinson. P., Cognitive considerations in the design of mul-timodel input systems, Engineering Desgin Centre, University of Cambridge., ComputerLaboratory, University of Cambridge P., Langdon. P., Keates. S., Clarkson. J., Using haptic feedback to enhancecomputer interaction for motion-impaired users, Engineering Desgin Centre, University ofCambridge., Computer Laboratory, University of Cambridge S., Clarkson. P.J., Investigating the applicability of user models for motion-impairedusers, Engineering Desgin Centre, University of Cambridge., Computer Laboratory, Universityof Cambridge J., Castillo. D., Creating a Flash MX Component, Flashcomponents.net