"I have a mind like a steel... uh... thingy." Patrick Logan's weblog.

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Wednesday, August 15, 2007

Don't Fidget With Widgets, Draw!

The best thing I came across, between MCV in the 1980s and the web in the 1990s was Joel Bartlett's Scheme library (for his fantastic Scheme->C system, oh, that was something) called EZDraw...

This report describes a graphics server, ezd, that sits between an application program and the X server and allows both existing and new programs easy access to structured graphics. Programs may draw, edit, and sense user events in terms of application-defined graphical objects. When run on workstations with 10 MIPS or faster processors, interactive response is excellent, indicating that ezd’s simple structured graphics drawing model can be widely applied. The enthusiastic response of ezd’s initial users and the variety of uses to which they have put it to suggest that there is a tremendous pent-up urge to draw with programs and that ezd has lowered the barriers to doing so.
Here's an image of an application using EZDraw to draw map graphics and display weather information from the location clicked on the map. A "mashup" in its day, I suppose...

5.3. Weather Forecasts

National Weather Service forecasts for the United States are sometimes available for network access. The ezd application shown in Figure 6 was constructed to fetch such forecasts for the contiguous 48 states. The mouse-sensitive diamonds on the map identify cities that issue forecasts. When the mouse is positioned over a diamond, text describing the region covered by the forecast is displayed. When the mouse is clicked on a diamond, the forecast is obtained via the network and displayed in the text area at the bottom of the window. The text is scrolled using the scroll bar on the left of the text. The mouse can be used to select areas of text for copying into other X applications. The radio buttons DISC, ZONE, WARN, and EXTEND select the type of forecast, the HELP push button replaces the forecast text with help text, and the QUIT push button terminates the application.

Every graphical element of this application, a 300 line Scheme program running entirely in the ezd server, is constructed using ezd. The text area, slider, check buttons, and push buttons are drawn with a library of interactors that use the basic ezd drawing capabilities. A simple ezdbased drawing tool was used to collect the 133 line segments and 50 city locations defining the the map by tracing a newspaper weather map (copied onto a transparency and taped over the display) and then positioning the cities on it.

The application graphics are automatically positioned based upon the size of the window. This is done by grouping the graphics into three drawings: one containing the map, one containing the buttons, and one containing the text area and slider. When the window is initially created or resized, the drawings are overlayed onto the window by centering the map at the top of the window, attaching the buttons to the right side of the window, and using the rest of the window below the buttons for the text area. Even though ezd does no automatic window layout, explicit layout requires only 5 ezd commands, generated by a 22 line Scheme procedure.

"National Weather Service forecasts for the United States are sometimes available for network access." How about that!

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Portland, Oregon, United States
I'm usually writing from my favorite location on the planet, the pacific northwest of the u.s. I write for myself only and unless otherwise specified my posts here should not be taken as representing an official position of my employer. Contact me at my gee mail account, username patrickdlogan.