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2026-03-109 min read

JS Graphics (C++)

Learn JS Graphics (C++) step by step with clear examples and exercises.

Title: JS Graphics (C++) - A full guide for Creating Graphics in C++ Using JavaScript bindings

Why This Matters

In the realm of software development, creating graphics is an essential skill that can significantly enhance user experience in various applications such as games, simulations, and data visualization tools. While C++ provides a robust foundation for developing high-performance applications, it lacks native support for modern web technologies like JavaScript. However, by leveraging JavaScript bindings, we can harness the power of both languages to create graphics that run on the web.

By learning how to use C++ with JavaScript bindings, you will be able to:

  1. Write high-performance graphics code in C++ and execute it within a web page.
  2. use the strengths of both C++ and JavaScript for creating powerful graphics applications.
  3. Create cross-platform graphics solutions that can run on desktop and mobile browsers without the need for plugins.
  4. Improve the performance of your graphics applications by taking advantage of C++'s low-level control over hardware resources.
  5. Reduce development time by reusing existing C++ libraries in web projects.
  6. use the vast ecosystem of JavaScript libraries and frameworks to enhance the functionality of your graphics applications.

Prerequisites

To follow this guide, you should have a good understanding of:

  1. C++ programming basics, including data types, functions, and classes
  2. JavaScript programming fundamentals, such as variables, functions, and objects
  3. Familiarity with the concept of binding two or more languages together in a single application
  4. Basic knowledge of web development concepts like HTML, CSS, and browser APIs
  5. Experience with popular C++ graphics libraries like GLFW, OpenGL, or SFML
  6. Familiarity with Emscripten SDK and its capabilities for compiling C++ code to asm.js
  7. Understanding of modern web development practices, such as responsive design and progressive enhancement
  8. Knowledge of version control systems like Git and collaborative development workflows

Core Concept

To create graphics using C++ and JavaScript, we will use a popular library called Emscripten (emcc). Emscripten is a toolchain that compiles C and C++ code to asm.js, a low-level subset of JavaScript that can run in any browser without the need for plugins. By using Emscripten, we can write our graphics code in C++ and execute it within a web page.

Steps to create a basic graphics application with Emscripten:

  1. Install Emscripten SDK: Follow the installation guide provided by Emscripten here.
  2. Create a new C++ project and write your code for creating graphics using standard C++ libraries like GLFW, OpenGL, or SFML.
  3. Compile the C++ code using Emscripten's compiler (emcc) with appropriate flags and options.
  4. Include the generated JavaScript file in an HTML page and call the functions from your compiled C++ code to create graphics on the web.
  5. use JavaScript libraries like jQuery, React, or Angular to handle user interactions, animations, and other front-end functionality.
  6. use browser APIs like WebGL for more advanced graphics rendering capabilities.
  7. Optimize your C++ code for performance by taking advantage of Emscripten's optimizations and techniques.
  8. Use version control systems like Git to manage your project and collaborate with other developers.
  9. Test your application on various browsers and devices to ensure cross-platform compatibility.

Best Practices for Organizing Your Project Structure

Organize your project into separate directories for source files, header files, and generated JavaScript files. Use consistent naming conventions and keep your code modular to make it easier to manage and maintain. Consider using a build system like CMake or Makefile to automate the build process.

Worked Example

Let's create a simple example of drawing a rotating cube using OpenGL, GLFW, and Emscripten. First, you need to set up a new project with the following steps:

  1. Create a new directory for your project (e.g., opengl_cube).
  2. Inside the project directory, create two subdirectories: src and out.
  3. In the src directory, create a new C++ file called main.cpp with the following content:
#include <GLFW/glfw3.h>

// ... (Include necessary headers and set up OpenGL context and window)

int main() {
// Initialize OpenGL, GLFW, and other resources...

// Set up vertex array objects, vertex buffer objects, and shader programs for the cube

// Main render loop with animation...

glfwTerminate();
return 0;
}
  1. In the src directory, create a header file called glfw_bindings.h with the following content:
#ifndef GLFW_BINDINGS_H
#define GLFW_BINDINGS_H

extern "C" {
void glfwInit();
void glfwTerminate();
}

#endif // GLFW_BINDINGS_H
  1. Create a header file called shaders.h in the src directory with the following content:
#ifndef SHADERS_H
#define SHADERS_H

// ... (Include necessary headers and define shader program functions)

#endif // SHADERS_H
  1. Create a header file called vertex_data.h in the src directory with the following content:
#ifndef VERTEX_DATA_H
#define VERTEX_DATA_H

// ... (Include necessary headers and define vertex array object, vertex buffer object, and vertex attribute pointer functions)

#endif // VERTEX_DATA_H
  1. Compile the C++ code using Emscripten's compiler (emcc) with the following command:
emcc -O3 -I /path/to/glfw/include main.cpp glfw_bindings.h shaders.h vertex_data.h -o out/main.js -s ALLOW_MEMORY_GROWTH=1 -s MODULARIZE=1 -s EXPORT_NAME="init()"

Replace /path/to/glfw/include with the path to the GLFW include directory in your system. This command will generate a JavaScript file called out/main.js.

  1. Create an HTML file (e.g., index.html) in the project root directory:
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>OpenGL Cube Example</title>
<script src="out/main.js"></script>
</head>
<body>
<script>
function main() {
init();
}

window.onload = main;
</script>
</body>
</html>
  1. Open the generated HTML file in a web browser to see the rotating cube being rendered using your compiled C++ code.

Common Mistakes

  1. Forgetting to include necessary headers and libraries: Make sure you have included all the required header files for both C++ and JavaScript libraries, such as GLFW, OpenGL, and Emscripten SDK.
  2. Not setting up the OpenGL context correctly: Ensure that you have initialized the OpenGL context and window properly before rendering anything on the screen.
  3. Misunderstanding Emscripten's compilation flags and options: Familiarize yourself with Emscripten's compiler options to optimize your code for web performance and compatibility.
  4. Not handling errors and exceptions: Make sure you handle potential errors and exceptions that might occur during the execution of your C++ code, such as failed OpenGL function calls or window resizing events.
  5. Incorrectly linking Emscripten's JavaScript bindings: Ensure that you have correctly linked Emscripten's JavaScript bindings for the libraries you are using, like GLFW and OpenGL.
  6. Not optimizing your C++ code for web performance: Use Emscripten's optimization techniques to improve the performance of your compiled C++ code on the web.
  7. ### Subheadings under Common Mistakes:
  • Forgetting to include necessary header files and libraries for both C++ and JavaScript
  • Failing to initialize OpenGL context and window properly
  • Misunderstanding Emscripten's compilation flags and options
  • Not handling errors and exceptions in your C++ code
  • Incorrectly linking Emscripten's JavaScript bindings for libraries like GLFW and OpenGL
  • Not optimizing your C++ code for web performance

Practice Questions

  1. Modify the example provided to draw a spinning sphere instead of a rotating cube.
  2. Implement a simple animation where the size, position, or color of the drawn shape changes over time.
  3. Create a simple menu system using JavaScript that allows users to select different shapes (e.g., sphere, cone, cylinder) and materials (e.g., texture mapping, lighting) to be rendered on the screen.
  4. Add support for loading and rendering images using OpenGL and Emscripten.
  5. Implement a particle system using GLFW and Emscripten to create an engaging visual effect.
  6. Create a simple physics simulation using Box2D and Emscripten to demonstrate the power of combining C++ and JavaScript for graphics applications.
  7. Use WebGL to create more advanced graphics rendering capabilities, such as real-time 3D models or complex shaders.
  8. use JavaScript libraries like React or Angular to handle user interactions and animations in your Emscripten project.
  9. Optimize your C++ code for web performance using Emscripten's optimization techniques.
  10. Test your application on various browsers and devices to ensure cross-platform compatibility.

FAQ

  1. Why can't I use standard JavaScript libraries like p5.js or Three.js with Emscripten?

While it is possible to use some JavaScript libraries with Emscripten, they may not be optimized for performance or may require significant modifications to work correctly with asm.js. It is usually more efficient to write custom graphics code in C++ and compile it using Emscripten.

  1. What are some best practices for organizing my project structure when using Emscripten?

Organize your project into separate directories for source files, header files, and generated JavaScript files. Use consistent naming conventions and keep your code modular to make it easier to manage and maintain. Consider using a build system like CMake or Makefile to automate the build process.

  1. Why does my compiled C++ code run slower than expected in the browser?

There are several reasons why your compiled C++ code may run slower in the browser, such as memory limitations, JavaScript garbage collection, or suboptimal compilation settings. Experiment with different optimization flags and techniques to improve performance.

  1. How can I add audio support to my Emscripten project?

You can use Emscripten's Web Audio API bindings to add audio support to your project. Follow the official guide on adding sound for more information.

  1. Why can't I use standard C++ libraries like STL or Boost with Emscripten?

While it is possible to use some parts of the Standard Template Library (STL) and Boost with Emscripten, they may not be optimized for performance or may require significant modifications to work correctly with asm.js. It is usually more efficient to use alternative libraries designed for web development or write custom code in C++ that can be compiled using Emscripten.

  1. Why does my JavaScript bindings code not seem to call the correct functions from my C++ code?

Ensure that you have correctly linked Emscripten's JavaScript bindings for the libraries you are using, like GLFW and OpenGL. Check that the function names in your JavaScript code match the exported function names in your C++ code.

  1. Why does my compiled C++ code not seem to be executing as expected?

Make sure that you have correctly compiled your C++ code with Emscripten's compiler (emcc) and included the generated JavaScript file in an HTML page. Check for any compilation errors or warnings, and ensure that your C++ code is free of logic errors.

  1. ### Subheadings under FAQ:
  • Why can't I use standard JavaScript libraries like p5.js or Three.js with Emscripten?
  • What are some best practices for organizing my project structure when using Emscripten?
  • Why does my compiled C++ code run slower than expected in the browser?
  • How can I add audio support to my Emscripten project?
  • Why can't I use standard C++ libraries like STL or Boost with Emscripten?
  • Why does my JavaScript bindings code not seem to call the correct functions from my C++ code?
  • Why does my compiled C++ code not seem to be executing as expected?
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