PixiJS 8.12.0 SVG Edge Trimming Bug: A Comprehensive Guide

by Marco 59 views

Hey guys, have you ever run into a weird graphical glitch that just doesn't make sense? Well, I recently stumbled upon a head-scratcher in PixiJS 8.12.0. Specifically, I found that SVG edges were being trimmed at certain resolutions, which, as you can imagine, led to some funky visuals. This bug impacts the way SVGs are rendered, particularly when you're dealing with decimal resolution values. Let's dive into this issue, how it manifests, and a potential fix.

The Bug: SVG Edge Trimming at Specific Resolutions

So, the core of the problem lies in how PixiJS handles SVG rendering when you specify a resolution value that's not a whole number. In the example I provided, I'm loading an SVG with two circles. When the resolution is set to 1, everything is peachy. The circles look perfect. However, when the resolution is set to 1.0125, things go south. The right and bottom edges of the circle start getting trimmed, creating this annoying visual artifact. It's like the renderer is slightly miscalculating the boundaries of the SVG.

This is a pretty critical issue if you're creating graphics that rely on precise shapes and sizes. The trimming can ruin the intended design and lead to visual inconsistencies. I mean, who wants a slightly chopped-off circle in their UI? Not me!

Here's what I found: setting resolution: 1 works perfectly. But, the bug appears when using values like resolution: 1.0125 (trimming edges) and resolution: 1.03 (adding extra artifacts). Interestingly, resolution: 1.04 seemed to work fine, which is a testament to the unpredictable nature of this bug. The visual difference, even when zoomed in, is pretty obvious. It really highlights how precision matters in graphics rendering and how even small numerical discrepancies can lead to these visual problems.

This inconsistency makes it difficult to achieve a consistent look across different devices or scenarios where resolution scaling might be needed. It's a classic example of a bug that can seriously mess with the user experience if left unchecked.

Steps to Reproduce the Issue

Reproducing this bug is actually pretty straightforward. All you need to do is load an SVG into PixiJS 8.12.0 and experiment with the resolution property in your asset loading configuration. Here's the key code snippet to get you started:

const texture = await PIXI.Assets.load({
    alias: 'myAlias1',
    src: fullSvgURI,
    data: {
        resolution: 1 // This works correctly.
        // resolution: 1.0125 // This trims the right and bottom edges.
        // resolution: 1.03 // This adds extra artifacts to the right and bottom edges.
        // resolution: 1.04 // This seems fine.
    }
});

To recreate the issue:

  1. Set up your PixiJS project: Ensure you're using PixiJS version 8.12.0.
  2. Load an SVG: Use the PIXI.Assets.load method to load your SVG. This is how PixiJS handles external assets, including images and SVGs.
  3. Adjust the resolution: Experiment with different resolution values. Start with 1 (which should work fine), then try values like 1.0125, 1.03, and 1.04, and see how the appearance changes.

By following these steps, you should be able to see the edge-trimming behavior firsthand. This is a simple but effective way to confirm the bug and observe its effects.

Environment Details and Affected Systems

I tested this bug across multiple browsers and operating systems to ensure the issue was consistent. Here are the environments where I observed the problem:

  • Browsers: Chrome 138.0.7204.93, Firefox 140.0.2, and Safari 18.5.
  • Operating System: macOS 15.5.

The bug appears to be consistent across different browsers and operating systems. This suggests it's not a browser-specific issue, but rather, a core problem within the PixiJS rendering pipeline. The widespread impact means that any project using PixiJS 8.12.0 with SVGs and non-integer resolution values could be affected. This could lead to inconsistencies in how the graphics look across different devices or when scaling is applied.

Exploring Potential Solutions

After encountering this issue, I started digging into the PixiJS codebase to find a solution. The key area of investigation was loadSVG.ts, where the SVG loading and rendering logic resides. I tried to modify this file to address the edge trimming problem. This file handles the initial canvas setup where the SVG is drawn.

Here's the problematic code snippet:

const canvas = DOMAdapter.get().createCanvas(width * resolution, height * resolution);
const context = canvas.getContext('2d');
context.drawImage(image as CanvasImageSource, 0, 0, width * resolution, height * resolution);

The original code creates a canvas with dimensions calculated directly from the SVG's width, height, and the specified resolution. My initial thought was that rounding the canvas dimensions might help to solve the issue. Therefore, I changed it to:

const roundedWidth = Math.ceil(width * resolution);
const roundedHeight = Math.ceil(height * resolution);
const canvas = DOMAdapter.get().createCanvas(roundedWidth, roundedHeight);
const context = canvas.getContext('2d');
context.drawImage(image as CanvasImageSource, 0, 0, roundedWidth, roundedHeight);

By using Math.ceil, I ensured that the canvas dimensions were rounded up to the nearest whole number. This simple change appeared to fix the edge-trimming issue in my particular scenario. The circles and other SVG elements were now rendered correctly, with no missing edges or visual artifacts.

However, it's important to note that this is just a potential solution and that it may have performance implications. This is because creating a slightly larger canvas might affect rendering times, particularly with complex SVGs. The impact on performance is something that needs further investigation, and it should be tested thoroughly.

Additional Troubleshooting Attempts

During my troubleshooting, I also explored a few other potential fixes that, unfortunately, didn't resolve the problem. These were all attempts to adjust the rendering settings within PixiJS to see if they could somehow mitigate the issue.

  1. roundPixels: true in app.init(): I tried initializing the PixiJS application with roundPixels: true in the app.init() configuration. The idea here was that rounding pixels might help to align the SVG rendering with the pixel grid, potentially correcting the edge-trimming. However, this setting had no discernible effect. The edges were still trimmed as before.
await app.init({
    width: window.innerWidth,
    height: window.innerHeight,
    backgroundColor: 0x2c3e50,
    roundPixels: true // Toggling this to true has no effect.
    // antialias: true // Toggling this to true has no effect
});

  1. antialias: true in app.init(): Similarly, I tried enabling antialiasing via antialias: true in app.init(). Antialiasing could smooth out the edges and help to hide minor rendering errors. Unfortunately, antialiasing also didn't solve the problem. The edges remained trimmed, even with antialiasing enabled.

  2. sprite.roundPixels = true: In another attempt, I set brokenSprite.roundPixels = true on the specific sprite with the loaded SVG. This approach was meant to apply pixel rounding at the sprite level, but again, it had no effect. The edges continued to be trimmed, which was a bit disheartening. The result suggests that pixel rounding isn't consistently applied or is not effective in this particular scenario.

These failed attempts highlight the complexity of the issue. The problem is deeper than a simple pixel-rounding fix. It seems to originate in the initial rendering of the SVG to the canvas.

Final Thoughts and Next Steps

So, while the suggested change in loadSVG.ts seems to work for my scenario, I'm not entirely sure about the performance impact for everyone else. I'm also unsure if this fix should be tied to the roundPixels: true setting, so it only happens if you opt-in. I think further testing and investigation are necessary.

If you're running into this issue, consider trying the suggested code change and testing its performance in your specific use case. If you're a PixiJS developer, please take a look at this bug. Let me know if you've had a similar experience or if you find a better solution! Let's get this fixed, guys!