Periodically free memory in the middle of screenshot test, to avoid

running out on my current machine. Fixes #671.

Finally regenerate screenshots for the first time in ages... just
blindly accepting everything, because the slightly different screen size
means everything was slightly shifted down.

data/MANIFEST.json

@@ -641,9 +641,9 @@
       "compressed_size_bytes": 3360875
     },
     "data/input/gb/great_kneighton/screenshots/center.zip": {
-      "checksum": "691b1100a3024d75e40fa5421804816b",
-      "uncompressed_size_bytes": 40408055,
-      "compressed_size_bytes": 40392956
+      "checksum": "d63d28848433aee9583f9cda45055cb6",
+      "uncompressed_size_bytes": 40511903,
+      "compressed_size_bytes": 40497136
     },
     "data/input/gb/halsnead/osm/center.osm": {
       "checksum": "9b4aedf25220e29e11d0970cf7c70a26",
@@ -1381,9 +1381,9 @@
       "compressed_size_bytes": 4109889
     },
     "data/input/pl/krakow/screenshots/center.zip": {
-      "checksum": "29a86e25c6eccfb37af0b59e202b0e14",
-      "uncompressed_size_bytes": 29802245,
-      "compressed_size_bytes": 29797624
+      "checksum": "166d773faf1b288a220fc0b695d014cb",
+      "uncompressed_size_bytes": 29954067,
+      "compressed_size_bytes": 29949440
     },
     "data/input/pl/warsaw/osm/center.osm": {
       "checksum": "b41830dd375674ffc9f7ec15d6cf9c0c",
@@ -1861,9 +1861,9 @@
       "compressed_size_bytes": 439447
     },
     "data/input/us/phoenix/screenshots/tempe.zip": {
-      "checksum": "f4f15a4f48ef39cb9b7266cb40d2be9a",
-      "uncompressed_size_bytes": 7339279,
-      "compressed_size_bytes": 7336881
+      "checksum": "45a9cfd163b3841fe31ef0c562492c33",
+      "uncompressed_size_bytes": 7522637,
+      "compressed_size_bytes": 7520470
     },
     "data/input/us/providence/osm/downtown.osm": {
       "checksum": "463b986adc83ae4d1174496a4ce744d1",
@@ -2166,24 +2166,24 @@
       "compressed_size_bytes": 6482033
     },
     "data/input/us/seattle/screenshots/downtown.zip": {
-      "checksum": "541b6e45836d37d797bed7531a03e421",
-      "uncompressed_size_bytes": 22965800,
-      "compressed_size_bytes": 22957392
+      "checksum": "dafeea78cd662199cc321aef8494295f",
+      "uncompressed_size_bytes": 22998289,
+      "compressed_size_bytes": 22990295
     },
     "data/input/us/seattle/screenshots/lakeslice.zip": {
-      "checksum": "ac9a50dd97577178494561ea1fd7951f",
-      "uncompressed_size_bytes": 22290371,
-      "compressed_size_bytes": 22283926
+      "checksum": "1a8bd605773e4a8e36a66a9292dee20c",
+      "uncompressed_size_bytes": 22427709,
+      "compressed_size_bytes": 22421438
     },
     "data/input/us/seattle/screenshots/montlake.zip": {
-      "checksum": "fd66ccdc843e1c085d5e6c33f239f8d3",
-      "uncompressed_size_bytes": 4363199,
-      "compressed_size_bytes": 4362963
+      "checksum": "0a750cdfe36c6250fe793c98e05ee1d7",
+      "uncompressed_size_bytes": 4381887,
+      "compressed_size_bytes": 4381657
     },
     "data/input/us/seattle/screenshots/udistrict.zip": {
-      "checksum": "9d0723df3ae3a9f19d67d3c0bff819bb",
-      "uncompressed_size_bytes": 11021512,
-      "compressed_size_bytes": 11018263
+      "checksum": "c9903c981ab1cccd9d3bd6cda788bfcc",
+      "uncompressed_size_bytes": 11086681,
+      "compressed_size_bytes": 11083687
     },
     "data/input/us/seattle/trips_2014.csv": {
       "checksum": "d4a8e733045b28c0385fb81359d6df03",

game/src/app.rs

@@ -864,6 +864,10 @@ impl SharedAppState for App {
     fn before_quit(&self, canvas: &Canvas) {
         CameraState::save(canvas, self.primary.map.get_name());
     }
+
+    fn free_memory(&mut self) {
+        self.primary.draw_map.free_memory();
+    }
 }
 
 /// Load an extra GeoJSON file, and add the area to the map dynamically.

map_gui/src/render/building.rs

@@ -228,6 +228,10 @@ impl DrawBuilding {
             );
         }
     }
+
+    pub fn clear_rendering(&mut self) {
+        *self.label.borrow_mut() = None;
+    }
 }
 
 impl Renderable for DrawBuilding {

map_gui/src/render/intersection.rs

@@ -151,6 +151,10 @@ impl DrawIntersection {
         .make_polygons(Distance::meters(0.3));
         Some((octagon, pole, last_line.angle()))
     }
+
+    pub fn clear_rendering(&mut self) {
+        *self.draw_default.borrow_mut() = None;
+    }
 }
 
 impl Renderable for DrawIntersection {

map_gui/src/render/lane.rs

@@ -179,6 +179,10 @@ impl DrawLane {
 
         batch
     }
+
+    pub fn clear_rendering(&mut self) {
+        *self.draw_default.borrow_mut() = None;
+    }
 }
 
 impl Renderable for DrawLane {

map_gui/src/render/map.rs

@@ -514,4 +514,23 @@ impl DrawMap {
         }
         self.draw_all_building_driveways = ctx.upload(batch);
     }
+
+    pub fn free_memory(&mut self) {
+        // Clear the lazily evaluated zoomed-in details
+        for r in &mut self.roads {
+            r.clear_rendering();
+        }
+        for l in self.lanes.values_mut() {
+            l.clear_rendering();
+        }
+        for i in &mut self.intersections {
+            i.clear_rendering();
+        }
+        for b in &mut self.buildings {
+            b.clear_rendering();
+        }
+        for pl in &mut self.parking_lots {
+            pl.clear_rendering();
+        }
+    }
 }

map_gui/src/simple_app.rs

@@ -315,6 +315,10 @@ impl<T: 'static> SharedAppState for SimpleApp<T> {
     fn before_quit(&self, canvas: &Canvas) {
         CameraState::save(canvas, self.map.get_name());
     }
+
+    fn free_memory(&mut self) {
+        self.draw_map.free_memory();
+    }
 }
 
 struct SimpleWarper {

widgetry/src/app_state.rs

@@ -19,6 +19,10 @@ pub trait SharedAppState {
     fn dump_before_abort(&self, _: &Canvas) {}
     /// Called before a normal exit, like window close
     fn before_quit(&self, _: &Canvas) {}
+
+    /// If widgetry determines the video card is low on memory, this may be called. The application
+    /// should make its best effort to delete any unused Drawables.
+    fn free_memory(&mut self) {}
 }
 
 pub(crate) struct App<A: SharedAppState> {

widgetry/src/runner.rs

@@ -158,6 +158,10 @@ impl<A: SharedAppState> State<A> {
         prerender.inner.draw_finished(g.inner);
         naming_hint
     }
+
+    pub(crate) fn free_memory(&mut self) {
+        self.app.shared_app_state.free_memory();
+    }
 }
 
 /// Customize how widgetry works. Most of these settings can't be changed after starting.

widgetry/src/tools/screenshot.rs

@@ -31,12 +31,23 @@ pub(crate) fn screenshot_everything<A: SharedAppState>(
     state.canvas.cam_zoom = zoom;
     std::fs::create_dir_all(dir_path)?;
 
+    // See https://github.com/a-b-street/abstreet/issues/671 for context. Some maps are so large
+    // and detailed that they drain all memory on some video cards. As a workaround, just free up
+    // some of the objects in the middle of this test.
+    let free_memory_frequency = 10;
+    let mut cnt = 0;
+
     for tile_y in 0..num_tiles_y {
         for tile_x in 0..num_tiles_x {
             timer.next();
             state.canvas.cam_x = (tile_x as f64) * dims.width;
             state.canvas.cam_y = (tile_y as f64) * dims.height;
 
+            cnt += 1;
+            if cnt % free_memory_frequency == 0 {
+                state.free_memory();
+            }
+
             let suffix = state.draw(prerender, true).unwrap_or_else(String::new);
 
             // Sometimes the very first image captured is of the debug mode used to launch this. Not