Create a struct for ZoomLevel

[Drabble]

We probably should add a struct for ZoomLevel.

Originally posted by @maxammann in #87 (comment)

🤔 Expected Behavior

Zoom is a f64 which represents the current zoom on the map. It needs to be a floating number because we want to be able to zoom smoothly on the map.

ZoomLevel is a u8 which represents the level of a tile within the map's quad tree. ZoomLevel 0 would be one tile that contains the entire map, ZoomLevel 1 would be a part of the map if it was split in 4, etc.

We can derive the current ZoomLevel from the Zoom using the constant ZOOM_BOUNDS defined in the coords.rs file.

😯 Current Behavior

Currently ZoomLevel is always stored as a u8 directly.

💁 Possible Solution

We should create a custom type or a struct to store the zoom level.

🔦 Context

It would make the code easier to read.

💻 Examples

The function below could be changed from:

pub fn scale_to_zoom_level(&self, z: u8) -> f64

to:

pub fn scale_to_zoom_level(&self, z: ZoomLevel) -> f64

[ybiletskyi]

I'll try to pick up this issue. Can any one assign it to me?

[maxammann]

Sure! If you have any questions feel free to contact me on matrix

[nyurik]

should this be an enum with either z8 or f32 values? This way we can work with it transparently, while still enjoying the u8 perf optimizations... Although this could be a case of premature optimization, and instead it should just be two values -- TileZoom(u8) and ViewportZoom(f32), and each function will be clear which one it is using.

[maxammann]

I think both "zoomes" are conceptionally quite different and their documentation will also differ. While zoom is a property of the "viewport", the zoom level is a property of a tile (like you said).
Accepting a f32 for a function which expects the zoom level of the currently displayed layer out of tiles probably does not make sense.

[ybiletskyi]

Should this be a type alias instead of creating a new struct? If it's just need for improving code reading.

[maxammann]

I think a new struct makes sense, so we can actually define functions on a ZoomLevel and make sure people understand what this u8 means.