Chrome specific issue that happens when destroying a chart and re-creating it immediately (same animation frame?). The CSS animation used to detect when the canvas become visible is not re-evaluated, breaking responsiveness. Accessing the `offsetParent` property will force a reflow and re-evaluate the CSS animation.
If `window` or `document` are `undefined`, a minimal platform implementation is used instead, which one only returns a context2d read from the given canvas/context.
Allow to create a chart on a canvas not yet attached to the DOM (detection based on CSS animations described in https://davidwalsh.name/detect-node-insertion). The resize element (IFRAME) is added only when the canvas receives a parent or when `style.display` changes from `none`. This change also allows to re-parent the canvas under a different node (the resizer element following). This is a preliminary work for the DIV based resizer.
Properly export helpers and remove dependencies to `Chart.helpers`. Helpers can now be accessed from `src/helpers/index.js` (`var helpers = require('path/to/helpers/index')`, instead of `var helpers = Chart.helpers`).
Deprecate `addEvent` and `removeEvent`, and move implementation in `platform.dom.js`. Add 'options' feature detection to register event listeners as passive and prevent warning in Chrome.
Move some of the "core" and "canvas" utils in `helpers.core.js` and `helpers.canvas.js` and introduce the new `isNullOrUndef` and `isObject` helpers. Deprecate `indexOf` and rename `drawRoundedRectangle` to `roundedRect` which now creates a simple `rect` path if radius is 0. Write missing unit tests for the moved helpers.
`instanceof HTMLCanvasElement/CanvasRenderingContext2D` fails when the item is inside an iframe or when running in a protected environment. We could guess the types from their toString() value but let's keep things flexible and assume it's a sufficient condition if the item has a context2D which has item as `canvas`.
Move base platform definition and logic in src/platform/platform.js and simplify the browser -> Chart.js event mapping by listing only different naming then fallback to the native type.
Replace `createEvent` by `add/removeEventListener` methods which dispatch Chart.js IEvent objects instead of native events. Move `add/removeResizeListener` implementation into the DOM platform which is now accessible via `platform.add/removeEventListener(chart, 'resize', listener)`.
Finally, remove `bindEvent` and `unbindEvent` from the helpers since the implementation is specific to the chart controller (and should be private).
Refactoring to put browser specific code in a new class, BrowserPlatform.
BrowserPlatform implements IPlatform. Chart.Platform is the constructor for the platform object that is attached to the chart instance.
Plugins are notified about the event using the `onEvent` call. The legend plugin was converted to use onEvent instead of the older private `handleEvent` method.
Wrote test to check that plugins are notified about events
