Plotly

Added
- Add top-level methods `Plotly.toImage` to convert a plotly graph to an image
data URL (svg, png, jpg, and webp are supported) and `Plotly.downloadImage` to
download a plotly graph as an image [446]
- Add the ability to add arbitrary images loaded from a url to a plot's layout
[525]
- Add the option of making legend span horizontally [535]
- Add `connectgaps` attribute to `scattergl` traces [449]
- Add new 'relative' bar mode which stacks on top of one another with negative
values below the axis, positive values above [517]
- Add support for the 'winkel tripel' projection in geo subplots [492]
- Event `plotly_relayout` is now emitted on gl2d subplot drag/pan/zoom
interactions [466]
- Add support for fill coloring in `contourgl` traces [522, 543]

Changed
- Cartesian on-hover routine is now uses a 50ms interval between search calls
instead of 100ms for smoother displaying hover labels [514]
- [Internal change] fullLayout `_has` fields are replaced by a `_has` method
which checks if a particular plot type is present on a graph [491]

Fixed
- Bar widths of traces with null coordinates are now correctly computed [542]
- Error bar spans on bar traces with null coordinates are now correctly computed
[542]
- All promises spawn in `Plotly.plot` are now guaranteed to be resolved before
the final resolve [521]
- Restyling `scatterternary` data attributes is now working [540]
- Error bar of 0 length in log axes are not included in hover labels (instead of
showing `NaN`s) [533]

Fixed
- Subplot and range slider clip paths are now functional in AngularJS [509]
- `relayout` call involving axis `categoryorder` and `categoryarray` are now
working [510]
- Annotation drag interactions in `editable: true` mode are now functional (bug
introduced in 1.10.0)[505]
- Improved attribute description for shape `xref` and `yref` [506]

Fixed
- Resizing a graph (e.g. via `Plotly.relayout` or Plotly.Plots.resize)
properly updates the plot area clip paths (bug introduced in 1.10.0) [490]
- `Plotly.Snapshot.toSVG` is now functional again in IE11 and old version of
Chrome and FF (bug introduced in 1.10.0) [489]
- Hover labels of superimposed traces when 'hovermode' is set to 'closest' are
properly displayed (bug introduced in 1.10.0) [495]
- Surface contour highlights are toggleable [459]
- Surface contour highlights style attributes are lower cased [459]
- Zoom overlay are drawn over shapes [448]
- Legend are draggable in `editable: true` contexts (bug introduced in 1.6.0)
[487]
- Legend scroll box are drawn outside the legend [478]

Added
- Beta version of two new 2D WebGL trace types: `heatmapgl` and `contourgl`
[427, 434]
- Two new `scatter` line `fill` modes: `'toself'` and `'tonext'` [462]
- Fills for `scatterternary` traces are now supported [462]
- Configurable axis category ordering with `categoryorder` and an optional
`categoryarray` axis attributes [419]
- Configurable shapes layer position with shape attribute `layer` [439]
- Configurable range slider range (so that the initial xaxis range can differ
from the range slider range) [473]

Changed
- Nested SVG elements in SVG image exports are removed, making the to-image mode
bar button work in RStudio and SVG export compatible with Adobe Illustrator
[415, 454, 442]
- Use `country-regex` npm package instead of hard-coded file of ISO-3 code to
country regular expressions [461]

Fixed
- Legend positioning does not break on negative `x` and `y` settings (bug
introduced in 1.6.0) [417]
- Shapes are properly deleted when clearing all of them at once (bug introduced
in 1.9.0) [465]
- Promise are return after first render in gl3d and gl2d plots [421]
- Click and hover events are properly triggered when trace `hoverinfo` is set to
`'none'` [438]
- `plotly_unhover` events is now properly triggered on geo trace types [429]
- `plotly_relayout` event is now properly triggered on gl3d set camera [458]
- RGBA colors are now supported in `scatter` and `bar` custom color scales
[422]
- Range slider is now functional with `x0`/`dx` data [441]
- Range slider is now compatible with mode bar axis range buttons and double
click [471]

Fixed
- Fixed issue in offline mode related to the inability to reload plotly.js on page refresh and extra init_notebook_mode calls.

Added
- SSL support for streaming.