m.startComputation / m.endComputation
Typically, m.startComputation / m.endComputation don't need to be called from application space. These methods are only intended to be used by people who are writing libraries that do things asynchronously.
If you need to do custom asynchronous calls without using Mithril's API, and find that your views are not redrawing, or that you're being forced to call m.redraw manually, you should consider using m.startComputation / m.endComputation so that Mithril can intelligently auto-redraw once your custom code finishes running.
In order to integrate an asynchronous code to Mithril's autoredrawing system, you should call m.startComputation BEFORE making an asynchronous call, and m.endComputation after the asynchronous callback completes.
//this service waits 1 second, logs "hello" and then notifies the view that
//it may start redrawing (if no other asynchronous operations are pending)
var doStuff = function() {
m.startComputation(); //call `startComputation` before the asynchronous `setTimeout`
setTimeout(function() {
console.log("hello");
m.endComputation(); //call `endComputation` at the end of the callback
}, 1000);
};To integrate synchronous code, call m.startComputation at the beginning of the method, and m.endComputation at the end.
window.onfocus = function() {
m.startComputation(); //call before everything else in the event handler
doStuff();
m.endComputation(); //call after everything else in the event handler
}For each m.startComputation call a library makes, it MUST also make one and ONLY one corresponding m.endComputation call.
You should not use these methods if your code is intended to run repeatedly (e.g. by using setInterval). If you want to repeatedly redraw the view without necessarily waiting for user input, you should manually call m.redraw within the repeatable context.
Note that failing to call endComputation after a respective startComputation call will halt the redrawing system. It's a good idea to wrap exception-prone code in a try block and call m.endComputation from within the respective finally block, in order to prevent rendering from halting.
window.onfocus = function() {
m.startComputation();
try {
doStuff();
}
finally {
m.endComputation(); //redraw regardless of whether `doStuff` threw errors
}
}Integrating multiple execution threads
When integrating with third party libraries, you might find that you need to call asynchronous methods from outside of Mithril's API.
In order to integrate non-trivial asynchronous code to Mithril's auto-redrawing system, you need to ensure all execution threads call m.startComputation / m.endComputation.
An execution thread is basically any amount of code that runs before other asynchronous threads start to run.
Integrating multiple execution threads can be done in a two different ways: in a layered fashion or in comprehensive fashion
Layered integration
Layered integration is recommended for modular code where many different APIs may be put together at the application level.
Below is an example where various methods implemented with a third party library can be integrated in layered fashion: any of the methods can be used in isolation or in combination.
Notice how doBoth repeatedly calls m.startComputation since that method calls both doSomething and doAnother. This is perfectly valid: there are three asynchronous computations pending after the jQuery.when method is called, and therefore, three pairs of m.startComputation / m.endComputation in play.
var doSomething = function(callback) {
m.startComputation(); //call `startComputation` before the asynchronous AJAX request
return jQuery.ajax("/something").done(function() {
if (callback) callback();
m.endComputation(); //call `endComputation` at the end of the callback
});
};
var doAnother = function(callback) {
m.startComputation(); //call `startComputation` before the asynchronous AJAX request
return jQuery.ajax("/another").done(function() {
if (callback) callback();
m.endComputation(); //call `endComputation` at the end of the callback
});
};
var doBoth = function(callback) {
m.startComputation(); //call `startComputation` before the asynchronous synchronization method
jQuery.when(doSomething(), doAnother()).then(function() {
if (callback) callback();
m.endComputation(); //call `endComputation` at the end of the callback
})
};Comprehensive integration
Comprehensive integration is recommended if integrating a monolithic series of asynchronous operations. In contrast to layered integration, it minimizes the number of m.startComputation / m.endComputation to avoid clutter.
The example below shows a convoluted series of AJAX requests implemented with a third party library.
var doSomething = function(callback) {
m.startComputation(); //call `startComputation` before everything else
jQuery.ajax("/something").done(function() {
doStuff();
jQuery.ajax("/another").done(function() {
doMoreStuff();
jQuery.ajax("/more").done(function() {
if (callback) callback();
m.endComputation(); //call `endComputation` at the end of everything
});
});
});
};Integrating to legacy code
If you need to add separate widgets to different places on a same page, you can simply initialize each widget as you would a regular Mithril application (i.e. use m.render, m.module or m.route).
There's just one caveat: while simply initializing multiple "islands" in this fashion works, their initialization calls are not aware of each other and can cause redraws too frequently. To optimize rendering, you should add a m.startComputation call before the first widget initialization call, and a m.endComputation after the last widget initialization call in each execution thread.
m.startComputation()
m.module(document.getElementById("widget1-container"), widget1)
m.module(document.getElementById("widget2-container"), widget1)
m.endComputation()Signature
void startComputation()void endComputation()