Tracking issue for full vector tile styling support

[Maximkaaa]

We want to achieve parity of styling options between Galileo and MapLibre vector tile styles: https://docs.maptiler.com/gl-style-specification/. These are the features that should be implemented to achieve this:

• Configuring min/max zoom levels (or, rather, resolution) for a layer (style rule)
• Property values interpolation for numbers and colors
  • Interpolation based on zoom level (using stops, steps, functions)
  • Interpolation from a feature property value (including match, get, case expressions)
• Styling and representation
  • Using icons for points and labels
  • Line styling (caps, joins, mitters)
  • Placement properties (particularly, placing labels along the lines)
  • Patterns and gradients
    • Line and fill patterns
    • Line dasharrays feat: Support rendering lines with dasharrays #330
    • Line gradients
  • Icon halos
• "in" expressions for text attributes
• Building 3d extrusion

There is an example of conversion of map-tiles style JSON into Galileo vector tile layer here: https://github.com/galileo-map/galileo_vt_styler/blob/main/src/maptiler_style/converter.rs . Ultimately, we want to have a separate crate (in a separate repo under the organization) that will contain an implementation for MapBoxLayer, that you can initialize by giving it just the difinition of the style, and it will create the layer, and allow the user to easily configure the Map and the Renderer (for example, for max/min zoom levels, sky colors etc.).

[shri-acha]

I looked into adding configuration for min/max zoom levels on Layers( i hope that means for the visibility of layers on basis of zoom level ),
As the spec mentions: https://docs.maptiler.com/gl-style-specification/layers/

I believe we could modify VectorTileStyle for zoom min/max and check zoom with max/min while rendering layers, and we would need checks for zoom levels within the render() method, no?

[shri-acha]

Also, on looking into https://openlayers.org/en/latest/apidoc/module-ol_layer_Tile-TileLayer.html and it has two distinct field of max/min resolutions and zoom, yet in this case I assume it is resolution....?

[Maximkaaa]

@shri-acha The whole layer set of a maptiler style is represented by a single layer in Galileo, which means min/max zoom parameters should be translated into style rules, not the whole style. And yes, we should translate zoom levels from the JSON spec into actual resolution values and use those in the Galileo layer styles. You can do it easily by using layer's tile schema. The only slightly tricky part is that I believe in MapTiler spec you can use non-integer zoom-level values, which should be translated into resolution using logarithmic, not linear interpolation.

[shri-acha]

@Maximkaaa If i'm not mistaken, it seems relatively forwards as it seems that you've already used logarithmic interpolation in below snippet.

I was thinking of just creating a function that is able to handle zoom levels into resolution from the TileSchema in a similar way.

[nrbnlulu]

@Maximkaaa I'd split that to sub issues if possible..

We want to achieve parity of styling options between Galileo and MapLibre vector tile styles

how would this affect 4rd party vector tile providers? mapbox / esri etc..

[Maximkaaa]

@Maximkaaa I'd split that to sub issues if possible..

As I suggested to @shri-acha in Discord, the best approach would be whenever someone starts working on any of this points, they should create a separate ticket, describe in more details how it works in MapLibre and how we are planning to translate it into Galileo architecture. So that we can discuss it before trying to implement.

I'm not fan of creating a ton of empty in advance tickets, and writing a good problem statement is already like 30% of the work...

We want to achieve parity of styling options between Galileo and MapLibre vector tile styles

how would this affect 4rd party vector tile providers? mapbox / esri etc..

Mapbox uses basically the same styling specification as MapLibre. I'm not sure how much was added there since MapLibre was forked off, they seem to mostly have worked on the glob view and other 3d stuff, not on vector tiles styling. I know nothing about ESRI vector tile styling, so cannot tell you what what extra capabilities they have or don't have.

[shri-acha]

@Maximkaaa @nrbnlulu
I'll make separate tickets for issues following this, as much of the problems in the first part of the issue have already have been discussed here .

[nrbnlulu]

Mapbox uses basically the same styling specification as MapLibre. I'm not sure how much was added there since MapLibre was forked off, they seem to mostly have worked on the glob view and other 3d stuff, not on vector tiles styling. I know nothing about ESRI vector tile styling, so cannot tell you what what extra capabilities they have or don't have.

IDRC about extra bizarre features for now. im just saying that this should be flexible enough that you could add compat for other providers in the future..

[TomBeckett]

@Maximkaaa Id also like to see interpolated label font sizes. At present, the TextStyle struct uses a plain f32 for font_size, not a StyleValue<f32> that would support interpolation.