Add helper type for fixed-point layer sorts

src/editor/map_renderer.rs

@@ -335,7 +335,7 @@ impl RenderPop {
             ofs_x: sprite.ofs_x,
             ofs_y: sprite.ofs_y,
             plane: sprite.plane,
-            layer: sprite.layer,
+            layer: sprite.layer.encode(),
         })
     }
 

src/tools/minimap.rs

@@ -158,7 +158,7 @@ pub fn generate(ctx: Context, icon_cache: &IconCache) -> Result<Image, ()> {
                     };
                     if !aboveground.is_empty() {
                         add_overlay!(aboveground);
-                        atom.sprite.layer = -5_000;
+                        atom.sprite.layer = Layer::from(-5);
                     }
                 } else if subtype(p, "/obj/machinery/power/apc/") {
                     use dmi::*;
@@ -460,6 +460,39 @@ impl<'a> GetVar<'a> for TypeRef<'a> {
 // ----------------------------------------------------------------------------
 // Renderer-agnostic sprite structure
 
+/// A guaranteed sortable representation of a `layer` float.
+#[derive(Default, Debug, Clone, Copy, Ord, PartialOrd, Eq, PartialEq, Hash)]
+pub struct Layer {
+    whole: i16,
+    frac: u16,
+}
+
+impl Layer {
+    /// Encode this layer as an `i32` for FFI representation.
+    pub fn encode(self) -> i32 {
+        ((self.whole as i32) << 16) | (self.frac as i32)
+    }
+}
+
+impl From<i16> for Layer {
+    fn from(whole: i16) -> Layer {
+        Layer { whole, frac: 0 }
+    }
+}
+
+impl From<i32> for Layer {
+    fn from(whole: i32) -> Layer {
+        use std::convert::TryFrom;
+        Layer { whole: i16::try_from(whole).expect("layer out of range"), frac: 0 }
+    }
+}
+
+impl From<f32> for Layer {
+    fn from(f: f32) -> Layer {
+        Layer { whole: f as i16, frac: ((f.fract() + 1.).fract() * 65536.) as u16 }
+    }
+}
+
 /// A Sprite is a fragment of an atom's appearance.
 ///
 /// Every atom has a default sprite, which may be disabled, and a list of
@@ -481,7 +514,7 @@ pub struct Sprite<'s> {
 
     // sorting
     pub plane: i32,
-    pub layer: i32,
+    pub layer: Layer,
 }
 
 impl<'s> Sprite<'s> {
@@ -518,7 +551,7 @@ impl<'s> Default for Sprite<'s> {
             ofs_x: 0,
             ofs_y: 0,
             plane: 0,
-            layer: 0,
+            layer: Layer::default(),
         }
     }
 }
@@ -547,13 +580,13 @@ fn plane_of<'s, T: GetVar<'s> + ?Sized>(objtree: &'s ObjectTree, atom: &T) -> i3
     }
 }
 
-fn layer_of<'s, T: GetVar<'s> + ?Sized>(objtree: &'s ObjectTree, atom: &T) -> i32 {
+fn layer_of<'s, T: GetVar<'s> + ?Sized>(objtree: &'s ObjectTree, atom: &T) -> Layer {
     match atom.get_var("layer", objtree) {
-        &Constant::Int(i) => (i % 1000) * 1000,
-        &Constant::Float(f) => ((f % 1000.) * 1000.) as i32,
+        &Constant::Int(i) => Layer::from(i),
+        &Constant::Float(f) => Layer::from(f),
         other => {
             eprintln!("not a layer: {:?} on {:?}", other, atom.get_path());
-            2_000
+            Layer::from(2)
         }
     }
 }

src/tools/render_passes/mod.rs

@@ -1,6 +1,6 @@
 use dm::objtree::*;
 use dm::constants::Constant;
-use minimap::{Atom, GetVar, Sprite};
+use minimap::{Atom, GetVar, Sprite, Layer};
 
 pub mod transit_tube;
 pub mod random;
@@ -287,30 +287,30 @@ impl RenderPass for FancyLayers {
     }
 }
 
-fn fancy_layer_for_path(p: &str) -> Option<i32> {
+fn fancy_layer_for_path(p: &str) -> Option<Layer> {
     use dm::objtree::subpath as subtype;
     Some(if subtype(p, "/turf/open/floor/plating/") || subtype(p, "/turf/open/space/") {
-        -10_000  // under everything
+        Layer::from(-10)  // under everything
     } else if subtype(p, "/turf/closed/mineral/") {
-        -3_000   // above hidden stuff and plating but below walls
+        Layer::from(-3)   // above hidden stuff and plating but below walls
     } else if subtype(p, "/turf/open/floor/") || subtype(p, "/turf/closed/") {
-        -2_000   // above hidden pipes and wires
+        Layer::from(-2)   // above hidden pipes and wires
     } else if subtype(p, "/turf/") {
-        -10_000  // under everything
+        Layer::from(-10)  // under everything
     } else if subtype(p, "/obj/effect/turf_decal/") {
-        -1_000   // above turfs
+        Layer::from(-1)   // above turfs
     } else if subtype(p, "/obj/structure/disposalpipe/") {
-        -6_000
+        Layer::from(-6)
     } else if subtype(p, "/obj/machinery/atmospherics/pipe/") && !p.contains("visible") {
-        -5_000
+        Layer::from(-5)
     } else if subtype(p, "/obj/structure/cable/") {
-        -4_000
+        Layer::from(-4)
     } else if subtype(p, "/obj/machinery/power/terminal/") {
-        -3_500
+        Layer::from(-3.5)
     } else if subtype(p, "/obj/structure/lattice/") {
-        -8_000
+        Layer::from(-8)
     } else if subtype(p, "/obj/machinery/navbeacon/") {
-        -3_000
+        Layer::from(-3)
     } else {
         return None
     })

src/tools/render_passes/structures.rs

@@ -66,7 +66,7 @@ impl RenderPass for GravityGen {
             sprite.icon_state = icon_state;
             sprite.plane = 0;  // TODO: figure out plane handling for real
             if count <= 3 {
-                sprite.layer = 4_250;  // WALL_OBJ_LAYER
+                sprite.layer = Layer::from(4.25);  // WALL_OBJ_LAYER
             }
             if count == 5 {
                 // energy overlay goes above the middle part