On Mon, Oct 3, 2016 at 3:49 PM, CodeDmitry <dimamakh...@gmail.com> wrote: > a JavaScript timeout is a function that takes a block and a period of time, > and after this period of time, puts the block at the end of the event > queue, to be executed as soon as the runtime is done performing the tasks in > front of it. > > I am not sure if Pharo has an event queue, so it's a bit harder to do > it(since without one you can't ensure only one thing happens at a time, and > strange things can happen). > > That said, in simplest terms, imagine writing a clock app for Pharo, which > updates time every second, in JS this would be done by setting an interval > that ticks every 1000ms, and each time places the callback function(block) > at the end of the event queue. > > Related: https://www.youtube.com/watch?time_continue=1&v=8aGhZQkoFbQ
Pharo has a single threaded VM, but multiple green threads can run concurrently. The closest to the event loop you are thinking of most likely the Morphic UI Process which you can see using World > Tools > Process Browser. When you execute code from Playground it runs in that Process (note what Smalltalk historically (circa 1970s?) has called a Process is today more commonly know as a Green Thread) If you select Morphic UI Process you will see its call stack on the right, where an interesting method is WorldState>>doOneCycleFor: You can gain some insight by turning on auto-update in the Process Browser, then open a Browser on WorldState>>doOneCycleFor: and put "self haltOnce" at the top, then enable it via... Pharo 5: World > System > Enable halt/inspect once. Pharo 6: World > Debugging > Enable all break/inspect once. You will see in the Process Browser that a new Morphic UI Process is spawned, and the original Morphic UI Process call stack now has #debugProcess at the top and a debug window appears that you can step through. Note, since two UI loops are executing here, the image may lock up, but usually its fine so hey! live on the edge! In #runStepMethodsIn: you'll see "queue := self class deferredUIMessages" for which you enqueue items like this... http://forum.world.st/Issue-3562-in-pharo-Deferred-UI-messages-executed-slowly-td3228060.html After processing the deferred UI messages, each Morph's #step method is processed by #runLocalStepMethodsIn: refer... http://wiki.squeak.org/squeak/2096 The display is then rendered by #displayWorldSafely: calling... --> #displayWorld --> #displayWorld:submorphs: which then is a lot to trace through, but depending on the graphics back end eventually ends up calling... Canvas>>fullDrawMorph: which ultimately invokes one of many #drawOn: or... AthensCanvas>>fullDrawMorph: which ultimately invokes one of many #drawOnAthensCanvas: So, for a regular timed UI animation, you would define your custom morph's #step and #stepTime methods, and for lower level stuff you would fork like Dennis suggests. cheers -ben
