Boss Bar Overlay
Boss bar overlays are generally similar to action bar overlays, with the difference that they're rendered at boss bar position, can be moved vertically, and have a built-in way to dynamically position themselves above/below other overlays.
Vertically Moved Fonts
Boss bars in Minecraft generally have a fixed spacing of 19px. However, we need to be able to move overlays at 1px increments, which is why Nova gets rid of all vanilla boss bars and re-renders them using custom characters that have a boss bar texture. Additionally, we also create what we call "vertically moved fonts", which are variations of a font that are moved on the vertical axis.
When creating a custom font for a boss bar overlay, you will also need to create those vertically moved font variations.
Vertically moved fonts for minecraft:default will be automatically generated if the boss bar overlay is enabled in main config.
After you've created your vertically moved fonts, you can start implementing the boss bar overlay in code.
For that, you'll need to create a BossBarOverlayCompound consisting of at least one BossBarOverlay.
BossBarOverlay
Each BossBarOverlay defines a Component to be rendered at one specific vertical position.
| property | description |
|---|---|
| offset | The vertical offset of this BossBarOverlay inside the BossBarOverlayCompound. |
| centerX | The x coordinate at which the component should be centered at, with 0 being the middle of the screen. Can be null if no centering logic should be applied. |
| component | The component to display. |
Similar to action bar overlays, you can override the getWidth and also the getVerticalRange methods to improve performance.
BossBarOverlayCompound
A BossBarOverlayCompound is a collection of BossBarOverlays. The overlays in this compound will never be seperated.
| property | description |
|---|---|
| overlays | The list of BossBarOverlays that are part of the BossBarOverlayCompound. |
| positioning | The BarPositioning that specifies at which position the BossBarOverlayCompound should be rendered. |
| hasChanged | Whether any component of the included overlays have been changed and should be re-rendered. If you set this boolean to true, the BossBarOverlayManager will update your overlay and set the boolean to false again. |
The BossBarOverlayCompound can then be registered:
BossBarOverlayManager.registerOverlay(player, compound)
BossBarOverlayManager.unregisterOverlay(player, compound)
BarPositioning
The BarPositioning determines where your overlay should be rendered. You can choose between BarPositioning.Fixed and
BarPositioning.Dynamic, where the latter will automatically move your overlay to prevent it from overlapping with other
overlays or vanilla boss bars. Both types of positioning also allow you to define BarMatchers, which are used to determine
whether your overlay should be placed above or below another overlay.
BarMatchers can be both hard-coded or deserialized from a yaml configuration using ConfigurationSection.getDeserialized<BarMatcher>(path).
See Configuration - WAILA Positioning for a more detailed explanation.