update zig example

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

@@ -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)
             };
 
             {