From 4aa140c264412c5c2da9dc13215523371ba622ff Mon Sep 17 00:00:00 2001
From: Daniel Barlow <dan@telent.net>
Date: Mon, 9 Jun 2025 13:30:11 +0100
Subject: [PATCH] always use callback in tiles.fetch (formerly polylines)

---
 pkgs/maps/main.fnl  | 13 ++++++++++---
 pkgs/maps/tiles.fnl | 33 +++++++++++++--------------------
 2 files changed, 23 insertions(+), 23 deletions(-)

diff --git a/pkgs/maps/main.fnl b/pkgs/maps/main.fnl
index 8bd73bd..2a1183f 100644
--- a/pkgs/maps/main.fnl
+++ b/pkgs/maps/main.fnl
@@ -67,6 +67,7 @@ label.readout {
             :zoom 17
             :course 0 ; direction of travel
             :orientation 0 ; map rotation angle from north
+            :tiles {}
             }
  )
 
@@ -198,6 +199,13 @@ label.readout {
 
 (var map-surface nil)
 
+(fn fetch-tiles [bounds tbl zoom]
+  (for [x bounds.min.x bounds.max.x]
+    (for [y bounds.min.y bounds.max.y]
+      (let [k (tiles.name x y zoom)]
+        (when (not (. tbl k))
+          (tiles.fetch cq x y zoom #(tset tbl k $1)))))))
+
 (fn draw-onto-map-surface [surface bounds zoom]
   (let [{ : num-tiles-x : num-tiles-y } bounds
         road-width 14
@@ -205,9 +213,7 @@ label.readout {
 
     (for [x bounds.min.x bounds.max.x]
       (for [y bounds.min.y bounds.max.y]
-        (merge lines (tiles.polylines cq x y zoom
-                                      #(set map-surface nil)
-                                      ))))
+        (merge lines (or (. app-state.tiles (tiles.name x y zoom)) {}))))
 
     (let [seen-road-names {}
           g (cairo.Context.create surface)]
@@ -314,6 +320,7 @@ label.readout {
     (let [bounds
           (map-bounds app-state.lat app-state.lon app-state.zoom)]
       (when (not (bounds= old-bounds bounds))
+        (fetch-tiles bounds app-state.tiles app-state.zoom)
         (set map-surface nil)))
     (set app-state.orientation
          (+ app-state.orientation
diff --git a/pkgs/maps/tiles.fnl b/pkgs/maps/tiles.fnl
index 436bf6e..d269b26 100644
--- a/pkgs/maps/tiles.fnl
+++ b/pkgs/maps/tiles.fnl
@@ -112,33 +112,26 @@
 (fn tile-name [x y zoom]
   (.. x "_" y "_" zoom))
   
-(fn polylines [cq x y zoom cb]
-  (let [k (tile-name  x y zoom)
+(fn fetch [cq x y zoom cb]
+  (let [k (tile-name x y zoom)
         pathname (.. "/tmp/tiles/" k ".json")]
     (if (file-exists? pathname)
-        (let [data (with-open [i (io.open pathname :r)] (i:read "*a"))]
-          (if (= data "")
-              []
-              (canvas (. (json.decode data) :elements) zoom)))
+        (let [payload (with-open [i (io.open pathname :r)] (i:read "*a"))]
+          (when (not (= payload ""))
+            (cb (canvas (. (json.decode payload) :elements) zoom))))
         (let [out (io.open pathname :w)]
           (cq:wrap (fn []
                      (print "getting " k)
-                     (var json nil)
+                     (var payload nil)
                      (with-open [f out]
-                       (while (not json)
-                         (set json (unparsed-for-xyz x y zoom))
-                         (when (not json)
+                       (while (not payload)
+                         (set payload (unparsed-for-xyz x y zoom))
+                         (when (not payload)
                            (print "sleeping " k)
                            (cqueues.sleep (math.random 2 6))))
                        (print "got " k)
-                       (f:write json)
-                       (cb)
-                       true)))
-          [] ; return no lines for now
-          ))))
+                       (f:write payload)
+                       (cb (canvas (. (json.decode payload) :elements) zoom))
+                       true)))))))
 
-
-
-
-
-{ : polylines : latlon->tile :name tile-name }
+{ : fetch : latlon->tile :name tile-name }