biscuit

commit 173a440bd6f57149bc3c96d56ad36a8a8f6cd6d1
parent 6b921e2c253d1dc8559ba23b4820a67351be8096
Author: Daniel Barlow <dan@telent.net>
Date:   Sun, 15 Jun 2025 17:52:06 +0100

rotate the offscreen map

this takes us from 60% cpu to about 20% (on my laptop, your hardware
may vary) when we're travelling in a straight line, as we render the
offscreen map only when the bounds change or the target orientation
changes, not every time we move

Diffstat:
M
pkgs/maps/main.fnl
 | 
37
++++++++++++++++++++++++++++++-------

1 file changed, 30 insertions(+), 7 deletions(-)
diff --git a/pkgs/maps/main.fnl b/pkgs/maps/main.fnl
@@ -134,17 +134,23 @@ label.readout {
               :x (* tile-size num-tiles-x)
               :y (* tile-size num-tiles-y)
               }
+     :centre {
+              :x (/ (+ min-tile-x max-tile-x 1) 2)
+              :y (/ (+ min-tile-y max-tile-y 1) 2)
+              }
      }))
 
 ;; diagonal radius is 538 pixels, 2.1 tiles
 
 (let [bounds (map-bounds-tile 65539.5 45014.5)]
   (expect= bounds.min {:x 65537 :y 45012})
-  (expect= bounds.max {:x 65541 :y 45016}))
+  (expect= bounds.max {:x 65541 :y 45016})
+  (expect= bounds.centre {:x 65539.5 :y 45014.5}))
 
 (let [bounds (map-bounds-tile 65539.0 45014.0)]
   (expect= bounds.min {:x 65536 :y 45011})
   (expect= bounds.max {:x 65541 :y 45016})
+  (expect= bounds.centre {:x 65539 :y 45014})
   )
 
 (fn map-bounds [lat lon zoom]
@@ -217,6 +223,10 @@ label.readout {
       (g:rectangle 0 0 bounds.pixels.x bounds.pixels.y)
       (g:fill)
 
+      (g:translate (+ (// bounds.pixels.x 2))  (+ (// bounds.pixels.y 2)))
+      (g:rotate (* (/ (- app-state.orientation-target) 180) math.pi))
+      (g:translate (- (// bounds.pixels.x 2))  (- (// bounds.pixels.y 2)))
+
       (cairo-roads g lines bounds)
 
       (g:set_source_rgb 0.2 0.2 0.2)
@@ -246,8 +256,16 @@ label.readout {
 (fn on-osm-draw [widget g]
   (let [(tile-x tile-y) (tiles.latlon->tile app-state.lat app-state.lon app-state.zoom)
         bounds (map-bounds-tile tile-x tile-y)
-        offset-x (- (* tile-size (- tile-x bounds.min.x)) (/ viewport-width 2))
-        offset-y (- (* tile-size (- tile-y bounds.min.y)) (/ viewport-height 2))]
+        offset-x (/ (- viewport-width bounds.pixels.x) 2)
+        offset-y (/ (- viewport-height bounds.pixels.y) 2)
+        x-to-centre (- tile-x bounds.centre.x)
+        y-to-centre (- tile-y bounds.centre.y)
+        angle (- (/ (* math.pi app-state.orientation-target) 180))
+        x-to-centre-rot (- (* x-to-centre (math.cos angle))
+                           (* y-to-centre (math.sin angle)))
+        y-to-centre-rot (+ (* x-to-centre (math.sin angle))
+                           (* y-to-centre (math.cos angle)))
+        ]
 
     (when (not map-surface)
       (let [window (widget:get_window)]
@@ -259,11 +277,16 @@ label.readout {
                   bounds.pixels.y)
                (draw-onto-map-surface bounds app-state.zoom)))))
 
-    (g:translate (+ (/ viewport-width 2))  (+ (/ viewport-height 2)))
-    (g:rotate (* (/ (- 360 app-state.orientation-actual) 180) math.pi))
-    (g:translate (- (/ viewport-width 2))  (- (/ viewport-height 2)))
 
-    (g:set_source_surface map-surface (- offset-x) (- offset-y))
+    (when (not (= app-state.orientation-actual app-state.orientation-target))
+      (print (- app-state.orientation-actual app-state.orientation-target))
+      (g:translate (+ (/ viewport-width 2))  (+ (/ viewport-height 2)))
+      (g:rotate (* (/ (- 360 (- app-state.orientation-actual app-state.orientation-target)) 180) math.pi))
+      (g:translate (- (/ viewport-width 2))  (- (/ viewport-height 2))))
+
+    (g:set_source_surface map-surface
+                          (- offset-x (* tile-size x-to-centre-rot))
+                          (- offset-y (* tile-size y-to-centre-rot)))
     (g:set_operator cairo.Operator.SOURCE)
     (g:paint)))