ZEBAS204 / moz-safari-toolbar

⚠PROOF OF CONCEPT⚠ Firefox extension that simulates the dynamic colored Safari tab bar (halted until FF supports WebGPU)

preview.mp4

Warning This is just a proof of concept.

I recommend using Adaptive Tab Bar Colour (source) as this extension in its current state is not suited for normal users.

If you are still interested in using this extension, please read the following installation guide:

• Clone this repository or download the source ZIP
• Enter about:debugging in the URL bar
• Click "This Firefox" and then click on "Load Temporary Add-on"
• Open the extension's directory and select any file inside the extension, or select the packaged extension (.zip file)

Problems

This extension works by capturing a tiny portion of the top page and converting it to an image, blur it and set as a theme background.

• WebGPU does not work in Firefox (August 2023). This extension uses canvas powered by CPU.

• Capturing the page can be done only (or as far as I know) in two ways:

  1. (extension only - currently in use) Using the browser.tabs.captureTab/browser.tabs.captureVisibleTab (or DrawWindow message in older versions) to take a screenshot of the current tab and process it on a <canvas> element.

  2. Using the WebCodecs API to draw a video stream of the current tab on a <video> element and later extract it into a <canvas> element to process it. One drawback to the Canvas approach is that there is no guarantee that all video frames get processed.

Limitations

This extension uses the Theme API to change the background of the toolbar and the status bar. Thus, is limited by how Firefox allows and processes theme changes:

• Does not work properly with multiple Firefox instances. The background will change in all Firefox windows, including incognito (as Firefox does not support split permission)

• Blobs backgrounds (blob://...) do not. Firefox only allows local image URLs defined in the extension manifest.

• Excessive use of cache: to prevent flickering (example here) of the background when changing, we use additional_backgrounds to stack the next image and "cache it" so when displayed is already loaded.

Discarded ideas

1. Capture the full page and displace the background based on the y-scroll axis:

   The theme API does not support any custom values for alignment and is only limited to top, bottom, etc.

2. Migrate it into a "chrome profile plugin" (like CustomJSforFx):

   The main focus of this extension is allowing non-power-users to enjoy the visuals with a simple click.

Known issues

• Bottom search bar inherits the background.

• User theme's original background image will be replaced.

• Scrolling too slowly will cause sticky/fixed elements to display.

• Only the main scrollbar will be registered to scroll events (eg. will not work properly in The “Basics”)

• CPU intensive extension:

  This extension is currently processing images on CPU-accelerated canvas (2d context). Aside from that, is also encoding and decoding a base64 screenshot, resizing and blurring it, and worse, encoding it again to base64 only to be decoded again by the browser.

• Background is not aligned properly:

  To remove the artifacts of the blurred background at the edges (example here), the image needs to be upscaled to hide these hard edges. Also, when taking a screenshot of the page, the width of the page scrollbars is subtracted from the final image.

• Background does not sync properly with the page scroll:

  The other issues need to be solved before this one can be fixed. But the idea to is:

  • On first load of the page, the extension will have two options based on the user preferences on how to stylize the top of the page:
    1. Capture a tiny height of the top of the page and repeat in all the background.
    2. Set a solid color, based on the theme-color metadata of the page (similar to Adaptive Tab Bar Colour)
  • Static mode: Create a static buffer of the page (up to 25% as is the maximum distance the user can travel on a quick scroll) and keep repeating this behavior. Cut the full static buffer into small chunks so we can match them when the user scrolls.
  • Dynamic mode: Listen to page mutations to verify if the page contains dynamic content. Re-create the buffer on demand.
  • Cache the buffers (up to 25%) for quick access in case the user scroll ups.
  • The rest of the cache will be compressed down and decoded when needed.
  • On page unload, compress down all buffers using a worker.
  • On page load, use the behavior of step 1 while decompressing the cache.
  • On page close, clear the cache.

  Note: compressed cache will probably use BlurHash Algorithm or One-byte Granularity and the most expensive calculations should be migrated to WebAssembly and accessed through a shared worker.

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Notes:

• Maximum width/height of a PNG screenshot: 2147483647 pixels per specification

• Maximum width/height of a JPEG screenshot: 65535 pixels per specification

A screen of higher resolution (physical/virtual points per pixel of which is 1.5, 2, 2.5, 3, etc.) costs more computer memory (points converted to pixels) i.e. costs more pixels to save a screenshot unless you want to sacrifice the image quality by resizing and resampling. For example, with 2x resolution, a 50x50 region will be saved as a screenshot of size 100x100, resulting in an image not only 4 times larger in display size but also likely in file size.

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This browser extension was forked from jakwings's firefox-screenshot fork of M-Reimer/savescreenshot that was modified to make it work on Firefox version 57 and onward.