Tooltip 
Add custom tooltips over the viewer.
To add a tooltip you must call viewer.createTooltip(), this will a return a tooltip instance with methods : move(), update() and hide(). This allows to have multiple tooltips at the same time.
Example 
This example adds a persistent tooltip following the cursor.
Methods 
viewer.createTooltip(config) 
Create a tooltip.
| option | type | |
|---|---|---|
| content(required) | string | HTML content of the tooltip. | 
| top&left(required) | number | Pixel coordinates of the tooltip relative to the top-left corner of the viewer. | 
| position(defaulttop center) | string | Tooltip position toward it's arrow tip. Accepted values are combinations of top,center,bottomandleft,center,right. | 
| className | string | Additional CSS class added to the tooltip. | 
| data | any | User data associated to the tooltip (useful for events). | 
tooltip.move(config) 
Updates the position of the tooltip, the parameters are the same top, left and position as above.
tooltip.update(content) 
Updates the content of the tooltip.
tooltip.hide() 
Hide and destroy the tooltip.
Events 
show-tooltip(data) 
Triggered when a tooltip is shown.
hide-tooltip(data) 
Triggered when a tooltip is hidden.
