bcca2f1 | plum | pyrossh

git clone https://git.pyrossh.dev/plum

A statically typed, imperative programming language inspired by rust, python

bcca2f1 — Peter John 2026-11-02T17:42:31+05:30

plum_bridge: render-target textures are premultiplied (unpremultiply on sample, premultiplied clear), bound the bind-group cache; rendertarget fixture covers a translucent target

Files changed (3) hide show

plum-game/web-test/fixtures/rendertarget.plum +8 -2
plum-game/web-test/tests/web_check.rs +1 -1
plum-game/web/plum_bridge.js +9 -3

plum-game/web-test/fixtures/rendertarget.plum CHANGED Viewed

@@ -8,6 +8,8 @@
 #  4. Screen (700,100): rgb(0.5,0.5,0.5) gives (153,153,153)
 #  5. Normal with alpha 0.5 (850,100): red gives (153,26,26)
 #  6. a second 16x16 blue target drawn at (400,300)
+#  7. a 16x16 target holding red at alpha 0.5 drawn at (400,400): translucent target
+#     contents blend once, giving (153,26,26) like item 5
 module rendertarget
 import std/Str
 import std/Int
@@ -16,10 +18,10 @@ import std/Vec2
 import std/Color
 import std/Game
-record Targets(big: Int, small: Int, t: Int)
+record Targets(big: Int, small: Int, glass: Int, t: Int)
 export fun init() -> Targets =
-  Targets(big: textureCreate(64, 64), small: textureCreate(16, 16), t: 0)
+  Targets(big: textureCreate(64, 64), small: textureCreate(16, 16), glass: textureCreate(16, 16), t: 0)
 export fun update(g: Targets, dt: Float) =
   g.t = g.t + 1
@@ -32,6 +34,9 @@ export fun draw(g: Targets) =
   drawRect(32.0, 32.0, 32.0, 32.0, Color.rgb(0.0, 1.0, 0.0))
   renderTarget(g.small)
   clear(Color.rgb(0.0, 0.0, 1.0))
+  renderTarget(g.glass)
+  clear(Color.Transparent)
+  drawRect(0.0, 0.0, 16.0, 16.0, Color(r: 1.0, g: 0.0, b: 0.0, a: 0.5))
   renderTarget(-1)
   clear(Color.rgb(0.2, 0.2, 0.2))
   drawTexture(g.big, 60.0, 50.0, Color.White)
@@ -45,5 +50,6 @@ export fun draw(g: Targets) =
   blendMode(Blend.Normal)
   drawRect(850.0, 100.0, 100.0, 100.0, Color(r: 1.0, g: 0.0, b: 0.0, a: 0.5))
   drawTexture(g.small, 400.0, 300.0, Color.White)
+  drawTexture(g.glass, 400.0, 400.0, Color.White)
   drawText("frame {g.t}", 20.0, 500.0, 16.0, Color.White)
   drawRect(Float(g.t % 600), 600.0, 40.0, 6.0, Color.Yellow)

plum-game/web-test/tests/web_check.rs CHANGED Viewed

@@ -97,7 +97,7 @@ fn render_target_pixels() {
         eprintln!("SKIP: Playwright Chromium not installed (see plum-game/web-test/README.md)");
         return;
     }
-    let pixels = ["130,130,255,0,0", "196,196,0,255,0", "130,196,51,51,51", "450,150,102,153,204", "600,150,26,51,26", "750,150,153,153,153", "900,150,153,26,26", "408,308,0,0,255"];
+    let pixels = ["130,130,255,0,0", "196,196,0,255,0", "130,196,51,51,51", "450,150,102,153,204", "600,150,26,51,26", "750,150,153,153,153", "900,150,153,26,26", "408,308,0,0,255", "408,408,153,26,26"];
     let opts = Options { expect_pixels: pixels.iter().map(|p| plum_web_test::ExpectPixel::parse(p).unwrap()).collect(), ..Options::default() };
     let rt = tokio::runtime::Runtime::new().unwrap();
     let file = repo_root().join("plum-game/web-test/fixtures/rendertarget.plum");

plum-game/web/plum_bridge.js CHANGED Viewed

@@ -246,6 +246,7 @@
   const ATLAS_W = 2048;
   const ATLAS_H = 1024;
   const SDF_BIT = 512; // the texture is the glyph atlas: alpha holds a distance field
+  const PREM_BIT = 1024; // the texture is a render target: its colour is premultiplied by its alpha
   const MAX_SEGMENTS = 96;
   function clamp01(v) {
@@ -352,7 +353,7 @@
         t.slot = cur.n;
         cur.slots[cur.n++] = t;
       }
-      slotBits = t.slot | (t.smooth ? SMOOTH_BIT : 0) | (t.sdf ? SDF_BIT : 0);
+      slotBits = t.slot | (t.smooth ? SMOOTH_BIT : 0) | (t.sdf ? SDF_BIT : 0) | (t.target ? PREM_BIT : 0);
     }
     function vert(x, y, u, v, c) {
@@ -595,7 +596,10 @@ ${cases}    default: { return vec4f(1.0); }
 }
 fn shade(i: VOut) -> vec4f {
   let fw = max(fwidth(i.uv.x), fwidth(i.uv.y));
-  let texel = pick(i.slot, i.uv);
+  var texel = pick(i.slot, i.uv);
+  if ((i.slot & ${PREM_BIT}u) != 0u) {
+    texel = vec4f(texel.rgb / max(texel.a, 0.0001), texel.a);
+  }
   if ((i.slot & ${SDF_BIT}u) != 0u) {
     let w = clamp(fw * ${ATLAS_W}.0 / ${2 * GLYPH_SPREAD}.0 * 0.75, 0.02, 0.5);
     return vec4f(i.c.rgb, i.c.a * smoothstep(0.5 - w, 0.5 + w, texel.a));
@@ -767,6 +771,7 @@ fn shade(i: VOut) -> vec4f {
     // Bind groups by the textures of a draw's slots (unused slots hold the white texture).
     function bindGroup(batch) {
+      if (groups.size > 512) groups.clear(); // bounded: every distinct set of 16 textures is a key
       let key = "";
       for (let i = 0; i < SLOTS; i++) key += (i < batch.n ? batch.slots[i].uid : white.uid) + ",";
       let bg = groups.get(key);
@@ -832,11 +837,12 @@ fn shade(i: VOut) -> vec4f {
           if (pass) pass.end();
           const screen = !target;
           const clearing = clearValue || (screen && !screenCleared ? [0, 0, 0, 1] : null);
+          const k = clearing && !screen ? clearing[3] : 1; // a target holds premultiplied colour
           if (screen) screenCleared = true;
           pass = enc.beginRenderPass({
             colorAttachments: [{
               view: screen ? ctx.getCurrentTexture().createView() : target.view,
-              clearValue: clearing ? { r: clearing[0], g: clearing[1], b: clearing[2], a: screen ? 1 : clearing[3] } : undefined,
+              clearValue: clearing ? { r: clearing[0] * k, g: clearing[1] * k, b: clearing[2] * k, a: screen ? 1 : clearing[3] } : undefined,
               loadOp: clearing ? "clear" : "load",
               storeOp: "store",
             }],