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https://github.com/ssb22/css-generator

Low-vision stylesheet generator
https://github.com/ssb22/css-generator

dark-mode high-contrast low-vision web-accessibility

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Low-vision stylesheet generator

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README 

        
# css-generator

Low-vision stylesheet generator from http://ssb22.user.srcf.net/css/



(also mirrored at http://ssb22.gitlab.io/css/ just in case)



Many modern Web browsers allow users to set their own CSS

stylesheets for accessibility purposes. It can be difficult to write a comprehensive

accessibility stylesheet by hand, especially if you

want to work around browser bugs and the

difficulties posed by complex websites. So I made this program to

generate long CSS files with workarounds for many problems.



You can adjust [the Python code](css-generate.py) to your needs

(it works in both Python 2 and Python 3).

Alternatively, you can try one of the presets on the

[web page](http://ssb22.user.srcf.net/css/)

(which, if you have Javascript, has an interactive chooser: the code

for this is also generated by the script).



Size "unchanged" lacks size-related layout changes; this can be useful

if you do not need large print, or your monitor is big enough for the

browser's built-in zoom controls to be enough, but you still need to

change the colours (see

[advantages of dark backgrounds](http://ssb22.user.srcf.net/css/dark.html)).



What is the best pixel size?

----------------------------



You could just experiment, but if you frequently change between

different setups and/or have variable sight then it might help to know

how to choose a size without constantly re-experimenting:



1. You need to know the best size in points (36, 48 or whatever) for

   text you read **at the distance of the screen**.



    - First you need to know your normal distance to the screen. You

      can move the screen nearer, but the limits will vary with the

      type of mounting and the size of your keyboard, desk, chair,

      etc; you need to be aware of this variation if you use different

      computers. Also, if you have variable sight, remember to allow

      yourself room to get even nearer when your sight is worse (and

      without hurting your posture too much), which is usually easier

      than temporary size changes.



    - Divide the screen's distance by your normal reading distance for

      printed text (both measured from your eyes to the text itself,

      ignoring any magnifying device in between), and multiply by the

      size in points of the printed text you prefer to read.



    - If you normally use a magnifier for printed text but cannot use

      it for the screen, multiply your answer by the scale factor of

      this magnifier.



    - If you have a full-screen magnifier (fresnel lens) permanently

      mounted to the screen, then **divide** your answer by the scale

      factor of this magnifier.



    - Do **not** try to work out your size by setting the "point

      size" on the screen of a wordprocessor or similar, because that

      might not be calibrated correctly.



2. Let `P` be your on-screen point size, `H` and `V` be the horizontal and

   vertical resolution of your monitor, and `D` be its size in inches

   (measure across the diagonal if you don't know, and if you're on an

   old CRT monitor then you should subtract about an inch from the

   rated figure whereas TFT monitors' figures are OK as they are).

   Your pixel size is the square root of `(H*H + V*V)`, divided by `D`,

   multiplied by `P` and divided by 72.  (If your monitor has the old

   standard 4x3 aspect ratio then this simplifies to `P*V/D * 5/216`.)



3. With some browsers, you'll need to divide this by the browser's

   value of `window.devicePixelRatio`



How to install a stylesheet

---------------------------



Save the stylesheet to a file on your disk, and do what is appropriate

for your browser:



**Firefox:** On the desktop version, locate your profile directory

[as described on mozilla.org](http://support.mozilla.org/en-US/kb/profiles-where-firefox-stores-user-data#w_how-do-i-find-my-profile),

and save the file as `userContent.css` in the `chrome` subdirectory of

your profile directory (if no `chrome` subdirectory exists, create it).



  * On Firefox 69+, you also have to go to `about:config` and turn on

    `toolkit.legacyUserProfileCustomizations.stylesheets`

  

  * You have to restart Firefox when changing userContent.css; on

    GNU/Linux you might want the provided [togglecss

    script](togglecss.sh) to toggle the presence of userContent.css

    and restart Firefox.

  

  * On Firefox 51, you'll also need to go into about:config, set

    browser.tabs.remote.autostart.2 to false and restart. This was

    fixed in Firefox 52 (bug 1333157).

  

  * Not always possible on mobile Firefox: for example in Android

    you'll need to "root" your device before you can see the profile

    directory (and that's not always feasible). You might try the

    "Stylish" plugin, but it doesn't always work as well as installing

    a local stylesheet (colours are occasionally overridden by the

    site; black-on-white might work better).

  

  * Some versions of Firefox scale their pixels at high DPI settings,

    so the stylesheet size needs to be reduced to

    compensate. (E.g. Firefox 3+ on Windows, and more recent versions

    of Firefox on GNOME 3 with text-scaling-factor set.)

  

  * If you use dark backgrounds, some versions of Firefox 2 on Windows

    display a white background around the page (so any overspill text

    that is not dark will become unreadable) unless you go into high

    contrast mode. However if you then come out of high contrast mode,

    the fix will persist. (High contrast mode is a nice idea but it

    does break a lot of applications.)



**Internet Explorer:** Go to Tools / Internet Options / Accessibility

and set that file as a user-supplied stylesheet.



  * If you are using a low resolution or a high DPI setting as a means

    of getting Windows to magnify consistently, and if as a result of

    this the dialogue boxes won't entirely fit on your screen, you

    _may_ be able to reach Accessibility by clicking on General in

    Tools/Internet Options, pressing Tab 13 times (in IE6) or 12 times

    (in IE7), and pressing Enter.  But this is likely to change in

    different versions of IE.

  

  * If you also set text and background colours, _do not_ check

    "always use these colours" because it will override the

    stylesheet.



  * Some versions of **Windows XP** will override this stylesheet when

    in high contrast mode, and the result is not always readable. You

    may have to come out of high contrast mode when browsing.



**Safari:** Go to Safari / Preferences / Advanced / Style sheet,

select Other, and select the file



**Google Chrome:** Create a directory with the

stylesheet saved as `userContent.css` and a file called

`manifest.json` with the following content:



    {"manifest_version": 3,

    "name": "Low-vision stylesheet",

    "version": "1",

    "content_scripts": [{

       "matches": [""],

       "css": ["userContent.css"]}]}



then go to `chrome://extensions` and with Developer Mode

turned on "load unpacked extension" and point to this directory.



  * On recent Chrome versions you can also try

    `chrome://flags/#enable-force-dark` instead of using

    this CSS for dark mode

    

    * Or you could try running Chrome with

      [Web Adjuster](http://ssb22.user.srcf.net/adjuster/)

    

      * e.g. on GNU/Linux set up a `/usr/local/bin/x-www-browser`

        script to do `python` (full path to adjuster.py)

        `--browser="google-chrome --proxy-server=localhost:28080 $*"`

        `--real_proxy --delete_doctype --address=localhost`

        `--headAppendCSS=http://` (URL of stylesheet goes here),

        although SSL sites will need domain-rewriting

      

      * A white background will still show in Chrome's blank page and

        new tab screen etc (so you might want to set a homepage); when

        navigating _within_ sites it should happen rarely if ever. (If

        reloading already-visited pages, clear the cache.)

        At any rate, Chrome is likely to cope less well

        than other browsers with some sites' use of CSS

        priorities, because the CSS we insert does not

        have the extra privileges given it by other browsers.



**Midori:** Before version 0.0.20, use Edit / Preferences / Behaviour /

User Stylesheet. In later versions, go to Tools / Extensions (or

Preferences / Extensions), enable ‘User Addons’, and save the .css

file in `.local/share/midori/styles/`.

Some versions of Midori do not have this functionality.



**KDE browsers:** In Rekonq, use Configure / Appearance / Stylesheets.

In the older Konqueror browser, go to "Settings", "Configure

Konqueror", "Stylesheets" (in some versions it's a tab of

"Appearance"), "user-defined stylesheet" and set the filename; you may

have to restart Konqueror. Some Konqueror versions have a bug that

causes it to completely fail to apply the stylesheet; if you have an

affected version then you might need to switch to another browser.



**Opera 12 or below:** (these instructions do _not_ apply to the new

Opera 15 which is basically Chromium see above)

Opera menu / Settings / Preferences / Advanced / Content / Style options / My style sheet



  * Some versions (e.g. 12) will not style "textarea" edit controls

    unless you apply the stylesheet from a bookmarklet. Even then the

    borders may be missing.

  

  * Opera 12 **can crash** on some sites. You might be able to make it

    more stable by disabling the `:first-letter`, `:first-line` and

    `:hover` rules (e.g. replace `:first` with `:girst` and `:hover`

    with `:gover` throughout), but this is not a complete solution.

  

  * You might also want to set a background colour in the "Web pages"

    tab: this will be shown when new tabs etc are taking a while to

    load



**Otter:** Go to Tools / Preferences / Advanced / Content / User style sheet

and type in the full path or Browse to it.

Not yet working if you're using the newer QtWebEngine instead of QtWebKit.



**OLPC browser:**

Save the file as `~/.sugar/default/gecko/user-stylesheet.css` and

restart. (When calculating the best stylesheet size, remember the

OLPC's screen is 1200x900 and 7.5 inches.)



For other setups (including some mobiles) you can try

[Web Adjuster](http://ssb22.user.srcf.net/adjuster/);

for demonstration purposes there is an installation of Web Adjuster

with these stylesheets at `large-print-websites.appspot.com/`



All material (c) Silas S. Brown unless otherwise stated.

Android is a trademark of Google LLC.

Firefox is a registered trademark of The Mozilla Foundation.

Google is a trademark of Google LLC.

Javascript is a trademark of Oracle Corporation in the US.

Linux is the registered trademark of Linus Torvalds in the U.S. and other countries.

Python is a trademark of the Python Software Foundation.

Safari is a registered trademark of Apple Inc.

Windows is a registered trademark of Microsoft Corp.

Any other trademarks I mentioned without realising are trademarks of their respective holders.