update zig example

fixes carts running too slow in chrome

examples/zig/build.zig

@@ -5,11 +5,7 @@ pub fn build(b: *std.build.Builder) void {
 
     const lib = b.addSharedLibrary("cart", "main.zig", .unversioned);
     lib.setBuildMode(mode);
-    lib.setTarget(.{
-        .cpu_arch = .wasm32,
-        .os_tag = .freestanding,
-        .cpu_features_add = std.Target.wasm.featureSet(&.{ .nontrapping_fptoint })
-    });
+    lib.setTarget(.{ .cpu_arch = .wasm32, .os_tag = .freestanding, .cpu_features_add = std.Target.wasm.featureSet(&.{.nontrapping_fptoint}) });
     lib.import_memory = true;
     lib.initial_memory = 262144;
     lib.max_memory = 262144;
@@ -18,19 +14,13 @@ pub fn build(b: *std.build.Builder) void {
     lib.install();
 
     if (lib.install_step) |install_step| {
-        const run_filter_exports = b.addSystemCommand(&[_][]const u8{
-            "uw8", "filter-exports", "zig-out/lib/cart.wasm", "zig-out/lib/cart-filtered.wasm"
-        });
+        const run_filter_exports = b.addSystemCommand(&[_][]const u8{ "uw8", "filter-exports", "zig-out/lib/cart.wasm", "zig-out/lib/cart-filtered.wasm" });
         run_filter_exports.step.dependOn(&install_step.step);
 
-        const run_wasm_opt = b.addSystemCommand(&[_][]const u8{
-            "wasm-opt", "-Oz", "-o", "zig-out/cart.wasm", "zig-out/lib/cart-filtered.wasm"
-        });
+        const run_wasm_opt = b.addSystemCommand(&[_][]const u8{ "wasm-opt", "--enable-nontrapping-float-to-int", "-Oz", "-o", "zig-out/cart.wasm", "zig-out/lib/cart-filtered.wasm" });
         run_wasm_opt.step.dependOn(&run_filter_exports.step);
 
-        const run_uw8_pack = b.addSystemCommand(&[_][]const u8{
-            "uw8", "pack", "-l", "9", "zig-out/cart.wasm", "zig-out/cart.uw8"
-        });
+        const run_uw8_pack = b.addSystemCommand(&[_][]const u8{ "uw8", "pack", "-l", "9", "zig-out/cart.wasm", "zig-out/cart.uw8" });
         run_uw8_pack.step.dependOn(&run_wasm_opt.step);
 
         const make_opt = b.step("make_opt", "make size optimized cart");

examples/zig/main.zig

@@ -1,11 +1,11 @@
 extern fn atan2(x: f32, y: f32) f32;
 extern fn time() f32;
 
-pub const FRAMEBUFFER: *[320*240]u8 = @intToPtr(*[320*240]u8, 120);
+pub const FRAMEBUFFER: *[320 * 240]u8 = @intToPtr(*[320 * 240]u8, 120);
 
 export fn upd() void {
     var i: u32 = 0;
-    while(true) {
+    while (true) {
         var t = time() * 63.0;
         var x = @intToFloat(f32, (@intCast(i32, i % 320) - 160));
         var y = @intToFloat(f32, (@intCast(i32, i / 320) - 120));
@@ -13,8 +13,10 @@ export fn upd() void {
         var u = atan2(x, y) * 512.0 / 3.141;
         var c = @intCast(u8, (@floatToInt(i32, d + t * 2.0) ^ @floatToInt(i32, u + t)) & 255) >> 4;
 
-        FRAMEBUFFER[@as(usize, i)] = c;
+        FRAMEBUFFER[i] = c;
         i += 1;
-        if(i >= 320*240) { break; }
+        if (i >= 320 * 240) {
+            break;
+        }
     }
-}
+}

src/run_native.rs

@@ -181,10 +181,12 @@ impl super::Runtime for MicroW8 {
         if let Some(mut instance) = self.instance.take() {
             let time = (now - instance.start_time).as_millis() as i32;
             let next_frame = {
-                let offset = ((time as u32 as i64 * 6) % 100 - 50) / 6;
-                let max = now + Duration::from_millis(17);
-                let next_center = now + Duration::from_millis((16 - offset) as u64);
-                next_center.min(max)
+                let frame = (time as u32 as u64 * 6 / 100) as u32;
+                let cur_offset = (time as u32).wrapping_sub((frame as u64 * 100 / 6) as u32);
+                let next_time =
+                    ((frame as u64 + 1) * 100 / 6 + cur_offset.max(1).min(4) as u64) as u32;
+                let offset = next_time.wrapping_sub(time as u32);
+                now + Duration::from_millis(offset as u64)
             };
 
             {

web/src/microw8.js

@@ -274,7 +274,7 @@ export default function MicroW8(screen, config = {}) {
     
                 try {
                     let restart = false;
-                    let thisFrame;
+                    let nextFrame = 0;
                     if (!isPaused) {
                         let gamepads = navigator.getGamepads();
                         let gamepad = 0;
@@ -321,13 +321,12 @@ export default function MicroW8(screen, config = {}) {
                         }
                         canvasCtx.putImageData(imageData, 0, 0);
 
-                        let timeOffset = ((time * 6) % 100 - 50) / 6;
-                        thisFrame = startTime + time - timeOffset / 8;
-                    } else {
-                        thisFrame = Date.now();
+                        let thisFrame = Math.floor(time * 6 / 100);
+                        let timeOffset = time - thisFrame * 100 / 6;
+                        nextFrame = Math.ceil(startTime + (thisFrame + 1) * 100 / 6 + Math.min(4, timeOffset));
                     }
                     let now = Date.now();
-                    let nextFrame = Math.max(thisFrame + timePerFrame, now);
+                    nextFrame = Math.max(nextFrame, now);
     
                     if (restart) {
                         runModule(currentData);