# LinearCanvasBaseDisplay
Auto-generated from the config schema in the source — see the [config guide](https://jbrowse.org/jb2/docs/config_guide) for concepts. Provided by the `canvas` plugin. [View source](https://github.com/GMOD/jbrowse-components/blob/main/plugins/canvas/src/LinearBasicDisplay/baseConfigSchema.ts).
Holds the slots shared by the canvas-drawn linear feature displays, which
stack overlapping features in rows (pileup-style glyphs).
## Related links
- **Extended by:** [LinearBasicDisplay](../linearbasicdisplay)
- **Extended by:** [LinearVariantDisplay](../linearvariantdisplay)
- **State model:** [runtime API](../../models/linearcanvasbasedisplay)
- **Base config:** [BaseLinearDisplay](../baselineardisplay)
## Config slots
`LinearCanvasBaseDisplay` is a shared base schema, not a type you name in a config. Set these slots on one of the configs under **Extended by** above, each of which lists them as inherited and shows the shape in its own example. Slot types (`fileLocation`, `frozen`, ...) are explained in the [config slot types reference](https://jbrowse.org/jb2/docs/config_guides/slot_types). Slots a base configuration contributes are listed here too, so this table is the whole surface.
| Slot | Description |
| --- | --- |
| **mouseover**
[`string`](https://jbrowse.org/jb2/docs/config_guides/slot_types#string) = 'jexl:get(feature,'_mouseOver')||get(feature,'name')||get(feature,'function')||get(feature,'id')' | text to display when the cursor hovers over a feature
_callback args:_ `feature` |
| **maxFeatureScreenDensity**
[`number`](https://jbrowse.org/jb2/docs/config_guides/slot_types#number) = 1 | maximum features per pixel before showing a "too many features" message
_advanced_ |
| **showLegend**
[`boolean`](https://jbrowse.org/jb2/docs/config_guides/slot_types#boolean) = true | show the display's color key when it has one: the key a `color` field derives, or a variant track's consequence-impact / SV-type presets. |
| **showLabels**
[`stringEnum`](https://jbrowse.org/jb2/docs/config_guides/slot_types#stringenum) (auto, nameAndDescription, name, description, none) = 'auto' | Label text drawn beside each feature: "auto" adapts to zoom, dropping descriptions at maxDescriptionFeatureDensity and names at maxLabelFeatureDensity; "nameAndDescription", "name", "description", and "none" pin a choice at every zoom. Defaults to `auto`. Replaces the former showLabels on/off enum + showDescriptions boolean pair |
| **maxLabelFeatureDensity**
[`number`](https://jbrowse.org/jb2/docs/config_guides/slot_types#number) = 0.2 | In "auto" showLabels mode, hide labels when visible feature density (features/pixel) exceeds this value
_advanced_ |
| **maxDescriptionFeatureDensity**
[`number`](https://jbrowse.org/jb2/docs/config_guides/slot_types#number) = 0.1 | In "auto" showLabels mode, hide descriptions when visible feature density (features/pixel) exceeds this value. Lower than maxLabelFeatureDensity so descriptions drop before names
_advanced_ |
| **color**
[FeatureColor](../featurecolor) | The main fill of each feature: a CSS color or a jexl expression (`"goldenrod"`, `"jexl:…"`), or `{ field, domain, range }` to paint each value of a field its own `range` color, with a key. |
| **showOutline**
[`boolean`](https://jbrowse.org/jb2/docs/config_guides/slot_types#boolean) = false | draw an outline around each feature |
| **outlineColor**
[`maybeColor`](https://jbrowse.org/jb2/docs/config_guides/slot_types#the-maybe-types) | the outline's color while showOutline draws one; unset takes the theme's |
| **featureHeight**
[`number`](https://jbrowse.org/jb2/docs/config_guides/slot_types#number) = 10 | height in pixels of the main body of each feature
_callback args:_ `feature` |
| **displayMode**
[`stringEnum`](https://jbrowse.org/jb2/docs/config_guides/slot_types#stringenum) (normal, compact, superCompact, collapsed) = 'normal' | Feature height preset, `normal` by default; `compact` and `superCompact` shrink the rows, and `collapsed` packs every feature onto a single row with all labels hidden |
| **facet**
[SectionFacet](../sectionfacet) | One labelled section of the track per value of a field: `"strand"`, or `{ field, domain }` with the order its sections stack in. |
| **labels.name**
[`featureField`](https://jbrowse.org/jb2/docs/config_guides/slot_types#featurefield) = 'jexl:get(feature,'name') || get(feature,'id')' | the field each feature's name label reads, such as `gene_name`, or a `jexl:` expression over `feature`; the default reads the name, else the ID, and an empty value draws no name |
| **labels.description**
[`featureField`](https://jbrowse.org/jb2/docs/config_guides/slot_types#featurefield) = 'jexl:get(feature,'note') || get(feature,'description') || get(feature,'function')' | the field each feature's description line reads, such as `note`, or a `jexl:` expression over `feature`; the default reads `note`, else `description`, else `function`, and an empty value draws no description |
| **heightMode**
[`stringEnum`](https://jbrowse.org/jb2/docs/config_guides/slot_types#stringenum) (fixed, grow, fit) = 'fit' | Track-sizing strategy — how the track responds when there are more features than fit (shared vocabulary with the alignments display, exposed in the "Track sizing" menu). `fit` (the default) keeps the track height and gives up descriptions, then isoforms, then names, then squeezes boxes down to 2px, and scrolls only what still overflows; `fixed` keeps a scrollable fixed height; `grow` expands the track to show all features. Orthogonal to the per-feature size set by `displayMode`, which fit never enlarges. |
| **growMaxHeight**
[`number`](https://jbrowse.org/jb2/docs/config_guides/slot_types#number) = 800 | Ceiling in pixels for the "autogrow track height" sizing mode; a track with more content than this grows to the ceiling and scrolls the rest. Does not apply to the fixed or fit modes
_advanced_ |
| **filter**
[`expressionArray`](https://jbrowse.org/jb2/docs/config_guides/slot_types#expressionarray) = [] | jexl: expressions a feature must pass to be drawn |
| Inherited from [BaseLinearDisplay](../baselineardisplay) | 3 slots |
| **height**
[`number`](https://jbrowse.org/jb2/docs/config_guides/slot_types#number) = 100 | default height for the track |
| **fetchSizeLimit**
[`number`](https://jbrowse.org/jb2/docs/config_guides/slot_types#number) = 1_000_000 | maximum data to attempt to download for a given track, used if adapter doesn't specify one
_advanced_ |
| **forceLoad**
[`boolean`](https://jbrowse.org/jb2/docs/config_guides/slot_types#boolean) = false | Declarative equivalent of the "Force load" button on the "too much data" banner: when true the display always renders, however large the region or dense the features. Off by default (the gate guards against huge downloads). Set it on a view no one can interact with — an embedded / notebook view, or a screenshot — where the region is known and you want it drawn without a click.
_advanced_ |