cleanup and comments

src/tile-fetching.jl

@@ -110,32 +110,42 @@ function get_tiles_for_area(m::Map{Axis}, scheme::Halo2DTiling, area::Union{Rect
     layer_range = max(min_zoom(m), zoom - depth):zoom
     # Get the tiles around the mouse first
     xpos, ypos = Makie.mouseposition(m.axis.scene)
+    # Use the closest in-bounds point
+    xpos = max(min(xpos, area.X[2]), area.X[1])
+    ypos = max(min(ypos, area.Y[2]), area.Y[1])
+    # Define a 1% resolution extent around the mouse
     xspan = (area.X[2] - area.X[1]) * 0.01
     yspan = (area.Y[2] - area.Y[1]) * 0.01
     mouse_area = Extents.Extent(; X=(xpos - xspan, xpos + xspan), Y=(ypos - yspan, ypos + yspan))
     # Define a halo around the area to download last, so pan/zoom are filled already
     halo_area = grow_extent(area, scheme.halo) # We don't mind that the middle tiles are the same, the OrderedSet will remove them
 
+    # Set up empty tile lists
     foreground = OrderedSet{Tile}()
     background = OrderedSet{Tile}()
     offscreen = OrderedSet{Tile}()
+    # Fill tiles for each z layer
     for z in layer_range
-        # Make a halo around the mouse tile to load next,
-        # intersecting area so we don't download outside the plot
-        for ext_scale in 1:2:100
+        # Get rings of tiles around the mouse, intersecting 
+        # area so we don't get tiles outside the plot
+        for ext_scale in 1:4:100
+            # Get an extent
             mouse_halo_area = grow_extent(mouse_area, ext_scale)
+            # Check if it intersects the plot area
             ext = Extents.intersection(mouse_halo_area, area)
+            # No intersection so continue
             isnothing(ext) && continue
-            tilegrid = collect(MapTiles.TileGrid(ext, z, m.crs))
+            tilegrid = MapTiles.TileGrid(ext, z, m.crs)
             if z == zoom
-                union!(foreground, OrderedSet(tilegrid))
+                union!(foreground, tilegrid)
             else
                 union!(background, tilegrid)
             end
         end
-        # Get just the halo ring tiles to load offscreen
+        # Get the halo ring tiles to load offscreen
         area_grid = MapTiles.TileGrid(area, z, m.crs)
         halo_grid = MapTiles.TileGrid(halo_area, z, m.crs)
+        # Remove tiles inside the area grid
         halo_tiles = setdiff(halo_grid, area_grid)
         union!(offscreen, halo_tiles)
     end