Enhance

Enlarge all p-Tags on a page with AltGr+p, reduce with AltGr+l, reset with AltGr-o. ALtGr+b sets all p-Tags to have black text and a white background. AltGr+m tries to apply some styles that should make any page look better.

You will need to install an extension such as Tampermonkey, Greasemonkey or Violentmonkey to install this script.

You will need to install an extension such as Tampermonkey or Violentmonkey to install this script.

You will need to install an extension such as Tampermonkey or Violentmonkey to install this script.

You will need to install an extension such as Tampermonkey or Userscripts to install this script.

You will need to install an extension such as Tampermonkey to install this script.

You will need to install a user script manager extension to install this script.

(I already have a user script manager, let me install it!)

You will need to install an extension such as Stylus to install this style.

You will need to install an extension such as Stylus to install this style.

You will need to install an extension such as Stylus to install this style.

You will need to install a user style manager extension to install this style.

You will need to install a user style manager extension to install this style.

You will need to install a user style manager extension to install this style.

(I already have a user style manager, let me install it!)

// ==UserScript==
// @name        Enhance
// @namespace   meyerk.com
// @match       *://*/*
// @grant       none
// @version     1.6
// @author      MeyerK
// @description Enlarge all p-Tags on a page with AltGr+p, reduce with AltGr+l, reset with AltGr-o. ALtGr+b sets all p-Tags to have black text and a white background. AltGr+m tries to apply some styles that should make any page look better.
// ==/UserScript==

class enhance
{
  constructor()
  {
    this.rightAltKeyIsOn = false;
    this.zoomInc = 3;
    this.currentZoomStep = 0;
    this.maxZoomSteps = 7;
  }

  toggleAltGr(ev)
  {
    if (ev.code == 'AltRight')
    {
      this.rightAltKeyIsOn = (ev.type == 'keydown') ? true : false;
    }
  }

  do(ev)
  {
    if (this.rightAltKeyIsOn)
    {
      if (ev.code == 'KeyP')
      {
        if (this.currentZoomStep < this.maxZoomSteps)
        {
          this.currentZoomStep = this.currentZoomStep + 1;
          this.setFontSize('inc');
        }
        else
        {
          this.currentZoomStep = this.maxZoomSteps;
        }
      }

      if (ev.code == 'KeyL')
      {
        if (this.currentZoomStep > 0)
        {
          this.currentZoomStep = this.currentZoomStep - 1;
          this.setFontSize('dec');
        }
        else
        {
          this.currentZoomStep = 0;
        }
      }

      if (ev.code == 'KeyO')
      {
        this.currentZoomStep = 0;
        this.resetFontSize();
      }

      if (ev.code == 'KeyB')
      {
        this.setPropertyOfPs('color', 'black');
        this.setPropertyOfPs('backgroundColor', 'white');
      }

      if (ev.code == 'KeyM')
      {
        let htmlEl = document.getElementsByTagName('html')[0];
        if (htmlEl.style.maxWidth != "70ch")
        {
          htmlEl.style.maxWidth = "70ch";
          htmlEl.style.padding = "3em 1em";
          htmlEl.style.margin = "auto";
          htmlEl.style.lineHeight = "1.75";
          htmlEl.style.fontSize = "1.25em";
        }
        else
        {
          htmlEl.style.maxWidth = "";
          htmlEl.style.padding = "";
          htmlEl.style.margin = "";
          htmlEl.style.lineHeight = "";
          htmlEl.style.fontSize = "";
        }
      }
    }
  }

  setFontSize(act)
  {
    let newSize = null;
    let currentSize = null;
    let pElems = document.querySelectorAll('p');

    pElems.forEach((pElem) =>
    {
      currentSize = parseInt(window.getComputedStyle(pElem).fontSize, 10);

      if (this.currentZoomStep == 0)
      {
        newSize = '';
      }
      else
      {
        if (act == 'inc')
        {
          newSize = (currentSize + this.zoomInc) + 'px';
        }
        else if (act == 'dec')
        {
          newSize = (currentSize - this.zoomInc) + 'px';
        }
      }

      pElem.style.fontSize = newSize;

    });
  }

  resetFontSize()
  {
    this.setPropertyOfPs('fontSize', '');
  }

  setPropertyOfPs(propName, val)
  {
    var i = 0;
    var pElems = null;

    pElems = document.querySelectorAll('p');
    pElems.forEach((pElem) =>
    {
      pElem.style[propName] = val;
    });
  }
}

var e = new enhance();
document.addEventListener('keydown', e.toggleAltGr.bind(e));
document.addEventListener('keyup',   e.toggleAltGr.bind(e));
document.addEventListener('keyup',   e.do.bind(e));