Merge pull request #235 from podusowski/use-max-parallel-dls-as-chann…

…el-size

use MAX_PARALLEL_DOWNLOADS as channel size

CHANGELOG.md

@@ -2,6 +2,10 @@
 
 All notable changes to this project will be documented in this file.
 
+## Unreleased
+
+* Tile download optimized by no longer queueing older requests.
+
 ## 0.30.0
 
 * Add option for changing the zoom speed

walkers/src/download.rs

@@ -153,7 +153,7 @@ async fn download_complete(
 
 /// Maximum number of parallel downloads. Following modern browsers' behavior.
 /// https://stackoverflow.com/questions/985431/max-parallel-http-connections-in-a-browser
-const MAX_PARALLEL_DOWNLOADS: usize = 6;
+pub(crate) const MAX_PARALLEL_DOWNLOADS: usize = 6;
 
 async fn download_continuously_impl<S>(
     source: S,

walkers/src/tiles.rs

@@ -4,7 +4,7 @@ use futures::channel::mpsc::{channel, Receiver, Sender};
 use image::ImageError;
 use lru::LruCache;
 
-use crate::download::{download_continuously, HttpOptions};
+use crate::download::{download_continuously, HttpOptions, MAX_PARALLEL_DOWNLOADS};
 use crate::io::Runtime;
 use crate::mercator::TileId;
 use crate::sources::{Attribution, TileSource};
@@ -104,8 +104,8 @@ impl HttpTiles {
     where
         S: TileSource + Send + 'static,
     {
-        // Minimum value which didn't cause any stalls while testing.
-        let channel_size = 20;
+        // This ensures that newer requests are prioritized.
+        let channel_size = MAX_PARALLEL_DOWNLOADS;
 
         let (request_tx, request_rx) = channel(channel_size);
         let (tile_tx, tile_rx) = channel(channel_size);