dirt simple hack to cache rendered text. reasonable!

ezgui/src/assets.rs

@@ -1,7 +1,12 @@
-// TODO We don't need refcell maybe
+use crate::GeomBatch;
+use std::cell::RefCell;
+use std::collections::HashMap;
+
+// TODO We don't need refcell maybe? Can we take &mut Assets?
 pub struct Assets {
     pub default_line_height: f64,
     pub font_size: usize,
+    text_cache: RefCell<HashMap<String, GeomBatch>>,
 }
 
 impl Assets {
@@ -9,6 +14,7 @@ impl Assets {
         let mut a = Assets {
             default_line_height: 0.0,
             font_size,
+            text_cache: RefCell::new(HashMap::new()),
         };
         a.default_line_height = a.line_height(a.font_size);
         a
@@ -18,4 +24,14 @@ impl Assets {
         // TODO Ahhh this stops working.
         font_size as f64
     }
+
+    pub fn get_cached_text(&self, key: &str) -> Option<GeomBatch> {
+        self.text_cache.borrow().get(key).cloned()
+    }
+
+    pub fn cache_text(&self, key: String, geom: GeomBatch) {
+        self.text_cache.borrow_mut().insert(key, geom);
+        //println!("cache has {} things",
+        // abstutil::prettyprint_usize(self.text_cache.borrow().len()));
+    }
 }

ezgui/src/text.rs

@@ -1,7 +1,9 @@
 use crate::assets::Assets;
 use crate::{Color, GeomBatch, Prerender, ScreenDims};
 use geom::Polygon;
+use std::collections::hash_map::DefaultHasher;
 use std::fmt::Write;
+use std::hash::Hasher;
 use textwrap;
 
 const FG_COLOR: Color = Color::WHITE;
@@ -191,7 +193,12 @@ impl Text {
         self.render(assets).get_dims()
     }
 
-    pub fn render(self, _: &Assets) -> GeomBatch {
+    pub fn render(self, assets: &Assets) -> GeomBatch {
+        let hash_key = self.hash_key();
+        if let Some(batch) = assets.get_cached_text(&hash_key) {
+            return batch;
+        }
+
         // TODO Bad guess
         let empty_line_height = 30.0;
 
@@ -232,12 +239,19 @@ impl Text {
             output_batch.push(color, poly);
         }
 
+        assets.cache_text(hash_key, output_batch.clone());
         output_batch
     }
 
     pub fn render_to_batch(self, prerender: &Prerender) -> GeomBatch {
         self.render(&prerender.assets).realign()
     }
+
+    fn hash_key(&self) -> String {
+        let mut hasher = DefaultHasher::new();
+        hasher.write(format!("{:?}", self).as_ref());
+        format!("{:x}", hasher.finish())
+    }
 }
 
 fn render_text(spans: Vec<TextSpan>) -> GeomBatch {