Macroquad Panic Handler Doesn't Work On WASM

Apr 19, 2025 by ADMIN 45 views

Macroquad Panic Handler Doesn't Work on WASM: A Deep Dive into the Issue

Introduction

Macroquad is a popular Rust library for creating games and interactive applications. It provides a wide range of features, including a panic handler that allows developers to customize the behavior of their application when it encounters an error. However, when it comes to the WASM (WebAssembly) platform, the panic handler doesn't quite work as expected. In this article, we'll delve into the issue and explore the reasons behind it.

Expected Behavior

On desktop platforms, the panic handler works as intended. When an error occurs, the application will display a recovery UI to the user, providing them with options to recover from the error or quit the application. This is achieved through the set_panic_handler function, which takes a closure as an argument. This closure is responsible for displaying the error message and backtrace to the user.

use macroquad::prelude::*;
use macroquad::ui;

#[macroquad::main("Panic crash")]
async fn main() {
    set_panic_handler(|msg, backtrace| async move {
        // Display error message and backtrace to the user
        loop {
            clear_background(RED);
            ui::root_ui().label(None, &msg);
            for line in backtrace.split('\n') {
                ui::root_ui().label(None, line);
            }
            next_frame().await;
        }
    });

    // Rest of the application code...
}

Observed Behavior

However, when we run the same application on the WASM platform, the panic handler doesn't work as expected. Instead of displaying a recovery UI to the user, the application will simply crash and display a generic error message. This is because the WASM platform doesn't support displaying UI components in the same way as desktop platforms.

use macroquad::prelude::*;
use macroquad::ui;

#[macroquad::main("Panic crash")]
async fn main() {
    set_panic_handler(|msg, backtrace| async move {
        // Error message and backtrace are not displayed to the user
        loop {
            clear_background(RED);
            // No UI components are displayed
            next_frame().await;
        }
    });

    // Rest of the application code...
}

Why Does This Happen?

The reason behind this behavior is due to the way WASM handles errors. When an error occurs in a WASM application, the runtime will terminate the application and display a generic error message to the user. This is because WASM is designed to be a low-level, platform-agnostic language that can run on a wide range of platforms, including web browsers and embedded systems.

In contrast, desktop platforms like Windows and macOS have a more robust error handling system that allows applications to display custom error messages and UI components to the user. This is why the panic handler works as expected on desktop platforms, but not on WASM.

Conclusion

In conclusion, the panic handler in Macroquad doesn't work as expected on the WASM platform. This is due to the way WASM handles errors, which is designed to be platform-agnostic and low-level. While this may seem like a limitation, it's actually a design choice that allows WASM to run on a wide range of platforms.

If you developing a game or interactive application using Macroquad, you may want to consider using a different error handling mechanism that's specifically designed for the WASM platform. Alternatively, you can use a library like wasm-bindgen to create a custom error handling system that works with the WASM platform.

Example Use Case

Here's an example use case that demonstrates how to create a custom error handling system using wasm-bindgen:

use macroquad::prelude::*;
use wasm_bindgen::prelude::*;

#[wasm_bindgen]
pub fn handle_error(msg: &str, backtrace: &str) {
    // Display error message and backtrace to the user
    let error_element = document().create_element("div");
    error_element.set_inner_html(&format!("Error: {}\n{}", msg, backtrace));
    document().body().append_child(&error_element);
}

#[macroquad::main("Panic crash")]
async fn main() {
    // Set up custom error handling system
    set_panic_handler(|msg, backtrace| async move {
        handle_error(msg, backtrace);
    });

    // Rest of the application code...
}

In this example, we use wasm-bindgen to create a custom error handling system that displays the error message and backtrace to the user using a custom HTML element. This allows us to work around the limitations of the WASM platform and create a more robust error handling system for our application.
Macroquad Panic Handler Doesn't Work on WASM: A Q&A Article

Introduction

In our previous article, we explored the issue of the Macroquad panic handler not working on the WASM platform. We discussed the reasons behind this behavior and provided an example use case for creating a custom error handling system using wasm-bindgen. In this article, we'll answer some frequently asked questions about this issue and provide additional guidance for developers who are experiencing similar problems.

Q&A

Q: Why doesn't the panic handler work on WASM?

A: The panic handler doesn't work on WASM because the WASM platform doesn't support displaying UI components in the same way as desktop platforms. When an error occurs in a WASM application, the runtime will terminate the application and display a generic error message to the user.

Q: Is there a way to make the panic handler work on WASM?

A: Unfortunately, there isn't a straightforward way to make the panic handler work on WASM. However, you can use a library like wasm-bindgen to create a custom error handling system that works with the WASM platform.

Q: What are the limitations of the WASM platform?

A: The WASM platform has several limitations, including:

Limited support for UI components
Limited support for error handling
Limited support for file I/O
Limited support for networking

Q: How can I work around these limitations?

A: There are several ways to work around the limitations of the WASM platform, including:

Using a library like wasm-bindgen to create a custom error handling system
Using a library like web-sys to access web APIs
Using a library like file-sys to access file I/O
Using a library like net to access networking

Q: What are some best practices for error handling on WASM?

A: Here are some best practices for error handling on WASM:

Use a custom error handling system that works with the WASM platform
Display error messages and backtraces to the user in a user-friendly way
Provide options for the user to recover from errors or quit the application
Use logging to track errors and debug issues

Q: What are some common pitfalls to avoid when working with WASM?

A: Here are some common pitfalls to avoid when working with WASM:

Not checking for errors when using web APIs
Not handling errors properly when using file I/O or networking
Not displaying error messages and backtraces to the user in a user-friendly way
Not using logging to track errors and debug issues

Conclusion

In conclusion, the panic handler in Macroquad doesn't work on the WASM platform due to the limitations of the WASM platform. However, you can use a library like wasm-bindgen to create a custom error handling system that works with the WASM platform. By following best practices for error handling on WASM and avoiding common pitfalls, you can create robust and reliable applications that work on a wide range of platforms.

Example Use Case

Here's an example use case that demonstrates how to create a custom error handling system using wasm-bindgen:

use macroquad::prelude::*;
use wasm_bindgen::prelude::*;

#[wasm_bindgen]
pub fn handle_error(msg: &str, backtrace: &str) {
    // Display error message and backtrace to the user
    let error_element = document().create_element("div");
    error_element.set_inner_html(&format!("Error: {}\n{}", msg, backtrace));
    document().body().append_child(&error_element);
}

#[macroquad::main("Panic crash")]
async fn main() {
    // Set up custom error handling system
    set_panic_handler(|msg, backtrace| async move {
        handle_error(msg, backtrace);
    });

    // Rest of the application code...
}