Documentation

Open a new window and display an infrequently updated picture.

Once the window is open you can use the same commands as with display.

• This wrapper is intended for mostly static pictures that do not need to be updated more than once per second. For example, the picture could show network activity over the last minute, a daily stock price, or a weather forecast. If you want to show a real-time animation where the frames are redrawn more frequently then use the animate wrapper instead.
• The provided picture generating action will be invoked, and the display redrawn in two situation: 1) We receive a display event, like someone clicks on the window. 2) When controllerSetRedraw has been set, some indeterminate time between the last redraw, and one second from that.
• Note that calling controllerSetRedraw indicates that the picture should be redrawn, but does not cause this to happen immediately, due to limitations in the GLUT and GLFW window managers. The display runs on a one second timer interrupt, and if there have been no display events we need to wait for the next timer interrupt before redrawing. Having the timer interrupt period at 1 second keeps the CPU usage due to the context switches at under 1%.
• Also note that the picture generating action is called for every display event, so if the user pans the display then it will be invoked at 10hz or more during the pan. If you are generating the picture by reading some on-disk files then you should track when the files were last updated and cache the picture between updates. Caching the picture avoids repeatedly reading and re-parsing your files during a pan. Consider storing your current picture in an IORef, passing an action that just reads this IORef, and forking a new thread that watches your files for updates.

Functions to asynchronously control a Gloss display.