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Script to be pasted into developer tools to log calls to programmatic scrolling APIs. Currently tested just on Chrome and Firefox.
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| (function(){ | |
| // Override function in given prototype to add a log statement | |
| function logMethod(prototype, fname) { | |
| var name = prototype.constructor.name + '.' + fname; | |
| if (!(fname in prototype)) { | |
| console.warn("Warning: can't instrument " + name); | |
| return; | |
| } | |
| console.log("Instrumenting " + name); | |
| var original = prototype[fname]; | |
| prototype[fname] = function() { | |
| // Want single line output but with optional callstack - abuse 'error' for this. | |
| // console.trace is also good but expands the callstack by default.' | |
| console.error(name + ' invoked with ' + JSON.stringify(Array.prototype.slice.call(arguments))); | |
| // debugger; | |
| original.apply(this, arguments); | |
| }; | |
| } | |
| // Override property setter to add a log statement | |
| function logSetter(prototype, property, errContext) { | |
| var name = prototype.constructor.name + '.' + property; | |
| var original = Object.getOwnPropertyDescriptor(prototype, property); | |
| if (!original) { | |
| console.warn("Warning: can't instrument " + name + '. ' + errContext); | |
| return; | |
| } | |
| console.log("Instrumenting " + name); | |
| Object.defineProperty(prototype, property, { | |
| set: function(v) { | |
| var changed = v !== original.get.call(this); | |
| console.error(name + ' set to:' + v + (changed?' (changed)':' (not changed)')); // add changed indicator | |
| // debugger; | |
| original.set.call(this, v); | |
| }, | |
| get: original.get | |
| }); | |
| } | |
| var win = window; | |
| // Work around for http://crbug.com/475587 | |
| if ('scrollBy' in window && !window.hasOwnProperty('scrollBy')) | |
| win = Window.prototype; | |
| for (var m of ['scrollBy', 'scrollTo', 'scroll']) | |
| logMethod(win, m); | |
| for (var m of ['scrollIntoView', 'scrollIntoViewIfNeeded', 'focus']) | |
| if (m in Element.prototype) | |
| logMethod(Element.prototype, m); | |
| for (var p of ['scrollTop', 'scrollLeft']) | |
| logSetter(Element.prototype, p, "Chrome 43+ required (http://crbug.com/43394)"); | |
| })(); |
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