avoid reffing g:line_to in loop

it makes a difference on the flame graph but not a noticeable one in
top

pkgs/maps/main.fnl

@@ -150,38 +150,38 @@ label.readout {
 
 (local cq (cqueues.new))
 
-(fn road-width-for [line offset]
-  (+ (or offset 0)
-     (case (?. line :tags :highway)
-       :motorway 18
-       :trunk 17
-       :primary 16
-       :secondary 14
-       :cycleway 4
-       :footway 4
-       other 12)))
-
-(fn cairo-road-path [g [[sx sy] & points] bounds width]
-  (g:save)
-  (g:set_line_width width)
-  (g:move_to (* tile-size (- sx bounds.min.x))
-             (* tile-size (- sy bounds.min.y)))
-  (each [_ [x y] (ipairs points)]
-    (let [x1 (* tile-size (- x bounds.min.x))
-          y1 (* tile-size (- y bounds.min.y))]
-      (g:line_to x1 y1)))
-  (g:stroke)
-  (g:restore))
+(fn road-width-for [line]
+  (case (?. line :tags :highway)
+    :motorway 18
+    :trunk 17
+    :primary 16
+    :secondary 14
+    :cycleway 4
+    :footway 4
+    other 12))
 
+(fn cairo-road-path [g [[sx sy] & points] bounds]
+  (let [min bounds.min
+        { : line_to } g]
+    (g:move_to (* tile-size (- sx min.x))
+               (* tile-size (- sy min.y)))
+    (each [_ [x y] (ipairs points)]
+      (let [x1 (* tile-size (- x min.x))
+            y1 (* tile-size (- y min.y))]
+        (line_to g x1 y1)))))
 
 (fn cairo-roads [g lines bounds]
-  (let [road-width 14]
-    (g:set_source_rgb 0 0 0)
-    (each [_ line (pairs lines)]
-      (cairo-road-path g line.points bounds (road-width-for line)))
-    (g:set_source_rgb 1 1 1)
-    (each [_ line (pairs lines)]
-      (cairo-road-path g line.points bounds (road-width-for line -2)))))
+  (g:set_source_rgb 0 0 0)
+  (each [_ line (pairs lines)]
+    (g:set_line_width (road-width-for line))
+    (cairo-road-path g line.points bounds )
+    (g:stroke))
+  (g:set_source_rgb 1 1 1)
+  (each [_ line (pairs lines)]
+    (g:set_line_width (- (road-width-for line) 2))
+    (cairo-road-path g line.points bounds)
+    (g:stroke)))
+
 
 (var map-surface nil)