Integer overflow crash in Linux on FPSCounter.update

[DownloadableFox]

Executing the simple "Hello World" example from the README.md page on Linux causes an instant crash after rendering the initial text. This is because FpsCounter.update is attempting to cache the time it took to generate 60 frames and constantly substracting and adding that time to the total_time variable.

// In animation.zig
pub fn update(self: *FpsCounter, delta_ms: u32) void {
    self.total_time -= self.frame_times[self.index];
    // ^ Integer underflow here! I am unsure of the causes.

    self.frame_times[self.index] = delta_ms;
    self.total_time += delta_ms;
    self.index = (self.index + 1) % 60;
}

In theory this shouldn't be a problem but for some reason on my machine running the latest version of Fedora the simple example program crashes instantly.

I've fixed it on my end by just calculating the total time rather than using a cashed value.

/// FPS counter
pub const FpsCounter = struct {
    frame_times: [60]u32 = undefined,
    index: usize = 0,

    pub fn init() FpsCounter {
        var f: FpsCounter = .{};
        f.index = 0;
        for (0..60) |i| {
            f.frame_times[i] = 16;
        }
        return f;
    }

    pub fn update(self: *FpsCounter, delta_ms: u32) void {
        self.frame_times[self.index] = delta_ms;
        self.index = (self.index + 1) % 60;
    }

    pub fn getFps(self: *FpsCounter) u32 {
        var total_time: u32 = 0;
        for (0..60) |i| {
            total_time += self.frame_times[i];
        }

        if (total_time == 0) return 0;
        const avg_ms: u32 = total_time / 60;
        if (avg_ms == 0) return 0;
        return 60000 / avg_ms;
    }
};

Of course, this doesn't solve why the issue is presented in the first place, as I don't see why it would crash when subtracting values that should have been added before.

[teleyos]

I Claude fixed it with #2