5 World Operations
Every canvas comes with an associated world. A client program can set the world, start the world’s clock, stop the world’s clock, and deal with tick events (the clock ticks) and keyboard inputs (keyevents).
| ((init-world viewport) v) → void? |
| viewport : viewport? |
| v : any/c |
Sets the initial value of viewport’s world to v.
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| viewport : viewport? | |||||||||||||||||||||
| secs : real? | |||||||||||||||||||||
| update-callback : (any/c . -> . any/c) |
For viewport, sets update-callback to be invoked to
transform the world value every secs seconds. Only one
callback is installed at a time.
Stops updating viewport’s world via a callback installed with
set-on-tick-event.
| ((set-on-key-event viewport) key-callback) → void? |
| viewport : viewport? |
| key-callback : (any/c any/c . -> . any/c) |
Sets key-callback as the function to call whenever a key
event is received for viewport. The key-callback is
given a key event and the current world, and it produces an updated
world.