High-res textures built on first use: no cost in the pixel-art style, the 128x128 atlas only when zoomed in

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

src/gfx.rs

@@ -101,11 +101,11 @@ pub const T_EGG: u32 = 222; // 2 variants: a painted egg (Easter)
 pub struct Gfx {
     pub atlas: Texture2D,
     pub sprites: Texture2D,
-    pub hd_sprites: Texture2D,   // detailed sprites, 64x64 level (see HD_SPRITES, hd_picture)
-    pub hd_sprites32: Texture2D, // the same, 32x32 level
-    pub gear: Texture2D,         // their gear parts (see GEAR_HELMET etc.)
-    pub atlas_hd: Texture2D,   // the tile atlas of the high-res style, 64x64 tiles (see HD_TILES)
-    pub atlas_hd2: Texture2D,  // the same with 128x128 tiles (close up)
+    pub hd_sprites: LazyTex,   // detailed sprites, 64x64 level (see HD_SPRITES, hd_picture)
+    pub hd_sprites32: LazyTex, // the same, 32x32 level
+    pub gear: LazyTex,         // their gear parts (see GEAR_HELMET etc.)
+    pub atlas_hd: LazyTex,     // the tile atlas of the high-res style, 64x64 tiles (see HD_TILES)
+    pub atlas_hd2: LazyTex,    // the same with 128x128 tiles (close up)
     pub materials: [Texture2D; 9],    // furniture materials, high-res (see crate::props::Mat)
     pub materials_px: [Texture2D; 9], // the same for the pixel-art style (16x16)
     pub cursors: Texture2D, // mouse pointer frames, 16x16 each (see CURSOR_*)
@@ -347,6 +347,32 @@ pub fn high_res_ui() -> bool {
     HIGH_RES_UI.with(|h| h.get())
 }
 
+// a texture with nearest filtering
+fn tex(img: &Image) -> Texture2D {
+    let t = Texture2D::from_image(img);
+    t.set_filter(FilterMode::Nearest);
+    t
+}
+
+// a texture built on first use (it derefs to the texture)
+pub struct LazyTex {
+    cell: std::cell::OnceCell<Texture2D>,
+    make: Box<dyn Fn() -> Texture2D>,
+}
+
+impl LazyTex {
+    fn new(make: impl Fn() -> Texture2D + 'static) -> LazyTex {
+        LazyTex { cell: std::cell::OnceCell::new(), make: Box::new(make) }
+    }
+}
+
+impl std::ops::Deref for LazyTex {
+    type Target = Texture2D;
+    fn deref(&self) -> &Texture2D {
+        self.cell.get_or_init(|| (self.make)())
+    }
+}
+
 // ---- furniture materials (crate::props::Mat order): grey detail the furniture's colours tint
 // (the page keeps its colours), 64x64 and 16x16; see art/generated/textures/materials/
 macro_rules! material {
@@ -2939,17 +2965,30 @@ impl Gfx {
         cursors.set_filter(FilterMode::Nearest);
         let badges = Texture2D::from_image(&crate::badges::gen_badges());
         badges.set_filter(FilterMode::Nearest);
-        let atlas_hd = Texture2D::from_image(&gen_hd_atlas(HD_TILE));
-        atlas_hd.set_filter(FilterMode::Nearest);
-        let atlas_hd2 = Texture2D::from_image(&gen_hd_atlas(HD_TILE2));
-        atlas_hd2.set_filter(FilterMode::Nearest);
-        let (hd64, hd32) = gen_hd_sprites();
-        let hd_sprites = Texture2D::from_image(&hd64);
-        hd_sprites.set_filter(FilterMode::Nearest);
-        let hd_sprites32 = Texture2D::from_image(&hd32);
-        hd_sprites32.set_filter(FilterMode::Nearest);
-        let gear = Texture2D::from_image(&gen_gear());
-        gear.set_filter(FilterMode::Nearest);
+        // the high-res textures are built when first used (the pixel-art style never needs them)
+        let atlas_hd = LazyTex::new(|| tex(&gen_hd_atlas(HD_TILE)));
+        let atlas_hd2 = LazyTex::new(|| tex(&gen_hd_atlas(HD_TILE2)));
+        // both levels of the detailed sprites come from one pass (which also measures the gear anchors)
+        let both: std::rc::Rc<std::cell::OnceCell<(Texture2D, Texture2D)>> = Default::default();
+        let both2 = both.clone();
+        let make = move |b: &std::cell::OnceCell<(Texture2D, Texture2D)>| {
+            b.get_or_init(|| {
+                let (a, c) = gen_hd_sprites();
+                (tex(&a), tex(&c))
+            })
+            .clone()
+        };
+        let hd_sprites = LazyTex::new(move || make(&both).0);
+        let hd_sprites32 = LazyTex::new(move || {
+            both2
+                .get_or_init(|| {
+                    let (a, c) = gen_hd_sprites();
+                    (tex(&a), tex(&c))
+                })
+                .1
+                .clone()
+        });
+        let gear = LazyTex::new(|| tex(&gen_gear()));
         let mat = |b: &[u8]| {
             let t = Texture2D::from_file_with_format(b, Some(ImageFormat::Png));
             t.set_filter(FilterMode::Nearest);
@@ -3097,7 +3136,7 @@ impl Gfx {
     // an atlas cell in the interface (tool and room buttons); the high-res style shows the
     // high-res atlas, so the room buttons show the rooms' new floors
     pub fn draw_cell(&self, id: u32, x: f32, y: f32, w: f32, h: f32, color: Color) {
-        let (tex, k) = if HIGH_RES_UI.with(|h| h.get()) { (&self.atlas_hd, (HD_TILE / 16) as f32) } else { (&self.atlas, 1.0) };
+        let (tex, k): (&Texture2D, f32) = if HIGH_RES_UI.with(|h| h.get()) { (&self.atlas_hd, (HD_TILE / 16) as f32) } else { (&self.atlas, 1.0) };
         let r = Self::cell(id);
         draw_texture_ex(
             tex,
@@ -3357,6 +3396,33 @@ mod hd_atlas_tests {
     }
 }
 
+#[cfg(test)]
+mod startup_timing {
+    use super::*;
+
+    // `cargo test --release --bins startup_timing -- --ignored --nocapture`: how long building
+    // the textures takes at the start
+    #[test]
+    #[ignore]
+    fn startup_timing() {
+        let t = std::time::Instant::now();
+        let _ = gen_atlas();
+        println!("atlas 16: {:?}", t.elapsed());
+        let t = std::time::Instant::now();
+        let _ = gen_sprites();
+        println!("sprites: {:?}", t.elapsed());
+        let t = std::time::Instant::now();
+        let _ = gen_hd_atlas(HD_TILE);
+        println!("hd atlas 64: {:?}", t.elapsed());
+        let t = std::time::Instant::now();
+        let _ = gen_hd_atlas(HD_TILE2);
+        println!("hd atlas 128: {:?}", t.elapsed());
+        let t = std::time::Instant::now();
+        let _ = gen_hd_sprites();
+        println!("hd sprites: {:?}", t.elapsed());
+    }
+}
+
 #[cfg(test)]
 mod atlas_dump {
     use super::*;

src/render3d.rs

@@ -1406,7 +1406,7 @@ impl R3d {
                         lava_fresh = true;
                     }
                     let ch = &mut self.chunks[(cz * self.ncx + cx) as usize];
-                    let atlas = if self.chunks_hd { &gfx.atlas_hd } else { &gfx.atlas };
+                    let atlas: &Texture2D = if self.chunks_hd { &gfx.atlas_hd } else { &gfx.atlas };
                     let [m, o, l, k] = build_chunk(&g.map, a, &self.lava, cx, cz, atlas, self.wall_sub, self.chunks_hd);
                     ch.mesh = m;
                     ch.overlay = o;
@@ -1652,8 +1652,8 @@ impl R3d {
         };
         let atlas = match tile {
             16 => &gfx.atlas,
-            crate::gfx::HD_TILE => &gfx.atlas_hd,
-            _ => &gfx.atlas_hd2,
+            crate::gfx::HD_TILE => &*gfx.atlas_hd,
+            _ => &*gfx.atlas_hd2,
         };
         for ch in self.chunks.iter_mut() {
             for mesh in [&mut ch.mesh, &mut ch.overlay].into_iter().flatten() {
@@ -1808,6 +1808,11 @@ impl R3d {
         // high) gives every texel nearly a pixel; fewer pixels would only turn it into noise
         let hd = self.pixel_rows >= crate::settings::HIGH_RES_ROWS as u32;
         let px_per_tile = world_rows / cam.view_h().max(0.1);
+        if hd {
+            // the detailed sprites are built on first use; that also measures the gear anchors,
+            // which the gear below needs
+            let _: &Texture2D = &gfx.hd_sprites;
+        }
         for e in &g.ents {
             if !e.alive || e.held || unit_hidden(g, e) {
                 continue;