Lecture 8
Leftover Demos: JPEGEncoder,
Animation-demos. Translucency demos.
Internationalization, Customization
Accessibility
History of Animation/Early Cinema
Animation how-to
Example: Dungeon Dregs
Internationalization
2 System properties are typically used
to customize program interface:
user.language and user.region
There is a standardized set of 2-letter
ISO codes for these. Languages: en, fr,
de, es, sw, etc. Regions: US, FR, CA,
CH, DE, GB, etc.
Also called Localization
I18N How-To
1. Subclass ResourceBundle once for
every supported Locale. All localityspecific resources go in here.
2. Load ResourceBundle corresponding
to user’s preference.
3. Get all locale-specific Strings and
other resources from the bundle. Use
wherever appropriate.
I18N Demo1 Notes
Some redundancy is required and
desirable. MyResources, MyResources_en and
MyResources_en_US are identical. These
provide defaults in case not all system
properties are set.
Watch for pitfalls: String resources may
not be the expected size. Meanings
may change in subtle ways.
Formats
To get accents and special characters, need
to know some Unicode. \u####
NumberFormat, DateFormat.
Constructing sentences from pieces is not so
easy anymore. Languages differ in sentence
structure and ordering.

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Move all sentence-constructing into bundles.
Use MessageFormat class. Bundle format strings.
Beyond Strings
Can customize look and feel for
different locales. ResourceBundles can
contain filenames, such as image files,
and can even contain customized
classes such as dialogs or frames.
ResourceBundles can inherit from one
another. Might have a single resource
file with common data for Europe.
Customization
User may want to change language
preference for your program only, or
alter other settings from the defaults.
Easy to do for one session. Just
modify the attributes.
Would also like preferences to persist
from one session to another. Need to
create a preferences file.
Preferences files
Location

Preferred location varies with system.
Program directory for single-user PCs, user
directory for multi-user systems.
Format


Serialized objects? Easy. Hard to edit.
Custom format. Must deal with syntax.
Preferences class
Define a preferences class along the
same lines as ResourceBundle.
Basically a Map or Hashtable of keys
and values.
Write preference file using Serialize or
entry by entry.
On startup, load the preferences from
the stored file. Defaults if this fails.
What to customize
A good topic for use case analysis and
user surveys. What will the product be
used for? What do users ask for?
Better to offer users a limited set of
ready-made preference sets than to
make them choose everything
individually.
Options to turn “features” off.
What not to customize
Everything. Want to be able to explain
to users how to do any given task,
without having to worry about how they
customized the application.
Menus. Makes sense to have all
commands accessible through menus in
fixed locations. Customizable toolbars
for commonly-used commands.
(This isn’t a hard-and-fast rule)
Accessibility
Swing components have methods to
support assistive technologies, which
for example may allow vocal control
and audio display of a GUI interface.
Can play with this: download Monkey.
To take advantage, you need to label
components with informative text.
Making components accessible
1. Label all JComponents using
method. This also
serves as help for new users.
2. When JLabels are meant to label
something, use JLabel.setLabelFor()
setToolTipText(String)
3. JComponent.getAccessibleContext().setA
ccessible*()
Description.
where *=Name or
History of the Magic Lantern
Projected Images have been around in
one form or another since at least 1420.
By 1700’s, used for popular
entertainment.
Special effects such as rear-projection
onto a translucent screen, projection
onto cloud of smoke, dissolving views.
1895: Cinematographe invented.
Pre-history of Cinema
As early as 1674, idea of quick
succession of glass slides.
1832: Fantoscope, Stroboscope.
Illusion of motion created
by “persistence of vision”
1870’s: combined with
photography.
1890’s: celluloid film.
Persistence of Vision
Images remain on the retina for about
1/14 of a second. Small delay between
bright images not visible.
Frame rate of 30Hz is generally
considered flicker-free.
Typical monitor refresh rate is 70130Hz. (Hz = Hertz = * per second).
Basic Animation
Display image sequence at intervals.
Images must line up exactly

can detect 1-pixel shift on most monitors
Intervals must be same length

movement will appear jerky
Intervals should be short.

probably no benefit beyond 1/30 second
User expectations vary with application
Corollaries
Must ensure adequate computational
resources. Small delays lead to jerks.
Example: scrolling in IE.
Less computationally demanding to
animate small images, or simple images
such as rectangles filled by solid color.
Rendering text especially slow in Java.
Simple animation in Swing
Use javax.swing.Timer to generate
ticks every N milliseconds.
On tick, display current frame, then
compute next frame.

Order matters: computing frame may take
variable time; displaying should not.
Speed-up tricks: downloads
Downloading: slow, and speed varies.

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Track downloads with a MediaTracker.
Start animations after downloads complete.
Fewer HTTP connections saves time.
Combine images into 1 file; extract with
graphics operations. Better still: put all
images and source into a jar file, and
extract locally.
Generate graphics locally if possible.
Speed-up tricks: precompute
Compute once, draw many times.
Avoid Graphics.drawString (very slow)


Precompute GlyphVectors or Images for
strings which you draw more than once.
Same for digits of numeric displays.
Use antialias and transparency effects
in precomputing. For actual display,
just copy in the BufferedImage.
More speed tricks
Don’t repeat graphics ops wastefully

e.g. Triple buffering (next slide).
Minimize area to redraw.

Small rectangles can be updated faster.
Graphics.setRenderHints(…RENDER_SPEED)
Ask user not to run other jobs.
Case-study: “Dungeon Dregs”
About the lamest of many cool games
at J*va On The Brain by Karl Hörnell.
In public domain.
Lots of game applets on the site,
together with notes about their
creation, including design choices and
implementation details. Go browse it!
Welcome to the Dungeon
Dungeon Graphics
All the graphics for this game have been stored in a
single .gif file. This is downloaded and stored as an
Image. The individual pieces are copied out
as needed. This method reduces download time.
Triple-Buffering
There are 2 buffers, farBuffer and
nearBuffer (both class Image).
farBuffer contains background
elements, and is changed rarely.
(e.g. crate smashed or prisoner freed).
nearBuffer is redrawn frequently, with
all the moving elements.
nearBuffer drawn to Panel when done.
Triple-Buffering
farBuffer: static elements
nearBuffer: farBuffer + mobile elements
screen: nearBuffer, but drawn in 1 step.
Animation Loop
Since this is an Applet, it uses
Thread.sleep instead of a Timer.
Every 85ms, tick occurs. New positions
are computed, farBuffer and nearBuffer
are updated, and screen is refreshed.
Finite state machine is simulated to
minimize processing time. Slow tasks
are spread over several ticks.