scalable layouts : Java Glossary

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scalable layouts

Java has a problem when Applets or applications are run on very small or very big screen, or very low resolution or very high resolution screens. The essential problem is Java is based around physical pixels. Ideally, applications should scale to maintain an acceptable viewing size. The layouts should rearrange and shrink, removing optional fields or labels and otherwise simplify in low-real estate situations and expand when screen real estate is abundant.

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PostScript	Tools
Problem Areas	Learning More
Solutions	Links

PostScript

PostScript was invented long before Java, yet supports resolution independence with a floating point API (Application Programming Interface) that is scaled to physical pixels. This lets you render the same image on a 640 × 479 screen or a 1024 dpi typsetter without modification. Even it has to bow to the physical pixel reality with font rendering hints and special rounding to pixel boundaries. At one point Java was about to adopt Bravo PostScript rendering, then the project faded away without explanation.

Problem Areas

What are the problem areas for autoscaling?

Fonts. Sizes are specified in non-scaling points/pixels.
Images. *.png, *.gif images are specified in non-scaling pixels. *.jpg will scale.
The sizes of Frames, Panels etc. are specified in non-scaling pixels.
setSize, setLocation etc. are specified in non-scaling pixels.
Layouts are in general not smart enough to do things like remove optional fields, remove labeling or shorten fields when the real-estate gets tight.
There is no general way to query the user’s visual acuity to know the smallest point size the user can tolerate.
There is nothing like the Microsoft dialog unit for the API to use that generates auto-scaling displays.
Knowing the width of the physical screen in pixels and the width of the application window in pixels still gives only an approximation to the best point size/dialog unit to use.

Solutions

There are no totally satisfactory solutions, however, there are a number of band-aids. Karsten Lentzsch of JGoodies has done most of the research and documenting of the problem. Read his white papers and use his tools.

There are some techniques you can work with:

Component-level scaling: use a Look & Feel like Substance or JGoodies Looks Plastic Look & Feel family or JGoodies Looks Windows Look & Feel that let you be very precise for the most popular resolutions between 80dpi and 140dpi.
Since the dialog font scales with the resolution and the desktop font setting, if any, you may want to look for a Swing Look & Feel that honors these two settings, e.g. Substance, Plastic and the JGoodies Windows.
JLabel, JTextField and JTextArea will scale correctly because they are defined by the number of characters displayed.
JComboBox and JList have prototype values that are used to determine the width and height and thus will automatically scale too.
MigLayout and JGoodies FormLayout provide conversions from scalable units to pixels, so you can define sizes, gaps and borders in a resolution-independent way. You can avoid using physical pixel units for screen positions, widths and heights.
Microsoft Windows uses DLU (Dialog Units) for precise resolution-independence. On Windows, a button should have a minimum width of 50 dlu. And the width of a JTree in a JScrollPane should be defined by its content or in a resolution-independent way, often in dlu.

Tools

Learning More

Oracle’s Javadoc on getScreenSize class : available:

on the web at Oracle.com
in the current JDK 1.8.0_131 on your local Windows J: drive.

Oracle’s Javadoc on getScreenResolution class : available:

on the web at Oracle.com
in the current JDK 1.8.0_131 on your local Windows J: drive.

biometric pica
coordinates
digital TV
JGoodies Forms layout system
MigLayout
monitor
pixel
PostScript
Pushing Pixels Blog: tips on resolution-independent images
resolution
review of JGoodies
Substance

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