In case of charts with over 4000 points, smallestLabelSeparation
calculation contributes significantly to total cpu usage (about 25% according
to built-in Chrome profiler). Important thing to note is that result
of this calculation is not used at all.
Related commits:
* 677c249b61
introduced smallestLabelSeparation. It was used in calculateBaseWidth
function.
* d198157fb8
removed last use of smallestLabelSeparation. Since then the calculated
value was never used.
Previously, calling getLabelMoment with an out of bound index would cause an
error such as this:
```
Uncaught TypeError: Cannot read property 'null' of undefined
```
This happens because there is not always guaranteed to be a labelMoment on
at the current datasetIndex.
One example of this is practice comes from a this function call:
```js
// since the are not always guaranteed to be at least two labelMoments
// \ / this index can be out of bounds
// |
var tickWidth = me.getPixelForTick(1) - me.getPixelForTick(0) - 6;
```
This patch simply ensures that the `labelMoments` for the `datasetIndex` are
defined before accessing properties on it.
* Category scale can now read from the xLabels and yLabels properties.
* Update docs with section regarding the data object.
* Add sample file with non numeric Y and fix animations
This change allows for smaller minified code in the final version, resulting in a smaller file size. Some files had previously used _this, but that has been changed to me to keep consistency throughout the project.
New Chart.Element.hidden bool flag storing the visibility state of its associated data. Since elements belong to a specific chart, this change allows to manage data visibility per chart (e.g. when clicking the legend of some charts).
This commit also changes (fixes?) the polar chart animation when data visibility changes. Previous implementation was affected by an edge effect due to the use of NaN as hidden implementation.
Introduced a new meta.hidden 3 states flag (null|true|false) to be able to override dataset.hidden when interacting with the chart (i.e., true or false to ignore the dataset.hidden value). This is required in order to be able to correctly share dataset.hidden between multiple charts.
For example: 2 charts are sharing the same data and dataset.hidden is initially false: the dataset will be displayed on both charts because meta.hidden is null. If the user clicks the legend of the first chart, meta.hidden is changed to true and the dataset is only hidden on the first chart. If dataset.hidden changes, only the second chart will have the dataset visibility updated and that until the user click again on the first chart legend, switching the meta.hidden to null.
Dataset effective type is now stored under meta.type, allowing many charts to share the same dataset but with different types. Also move dataset.bar flag to meta.bar.
Meta info are now scoped by chart and moved under the dataset._meta map { chart.id -> meta }. Meta for a specific chart (and dataset) can be accessed using chart.getDatasetMeta(datasetIndex) or from the dataset controller using getMeta(). Note that helpers.uid() now generates an int (instead of a string) to make lookups in the _meta map faster.
