Corrupted settings can crash doq on launch

[juarezr]

bug: doq stopped working with previously corrupted settings

Suddenly the doq stopped working for me in Firefox. However, it still worked on Chromium.

After some debugging, I've found that the cause was a previously stored setting scheme that not matched the colorSchemes anymore.

Steps to Reproduce

I've compared the following pages:

1. Example viewer linked from the doqment repository front page.
2. Showing the same PDF of the example viewer in another Firefox tab using plain pdf.js without doqment extension installed.

Debugger Output

viewer.html
Uncaught (in promise) TypeError: scheme is undefined
    updateColorScheme https://shivaprsd.github.io/doq-demo/addon/doq.js:283
    updateReaderState https://shivaprsd.github.io/doq-demo/addon/doq.js:277
    load https://shivaprsd.github.io/doq-demo/addon/doq.js:83
    doqInit https://shivaprsd.github.io/doq-demo/addon/doq.js:16
doq.js:283:9
PDF 110dd61fd57444010b1ab5ff38782f0f [1.4 pdfeTeX-1.21a / TeX] (PDF.js: 2.13.216) app.js:1530:12

Call Stack

  updateColorScheme(index) {                   // index == 3
    const scheme = this.colorSchemes[index];   // this.colorSchemes == [{"Safari"}, {"Solarized"}] == 2 items
    if (!scheme.tones || !scheme.tones.length) // scheme === undefined --> Exception above
      return;
    ...
  },

Property Values

I've got these value inspecting variables inside the DevTools.

this.preferences

{
    flags: {
      ​​imagesOn: true,
      ​​shapesOn: true
    },
    ​​scheme: 3,  // <- does'nt matches this.colorSchemes
    ​tone: "2",
    theme: "dark"
}

localStorage.getItem('doq.preferences.dark')

{"scheme":3,"tone":"2","flags":{"shapesOn":true,"imagesOn":true}}

this.colorSchemes

Array [ {…}, {…} ]
    0: Object { name: "Safari", tones: (4) […], colors: [] }
        colors: Array []
        name: "Safari"
        tones: Array(4) [ {…}, {…}, {…}, … ]
            ​​0: Object { name: "White", background: "#FFFFFF", foreground: "#1B1B1B", … }
            ​​​1: Object { name: "Sepia", background: "#F8F1E3", foreground: "#4F321C", … }
            ​​​2: Object { name: "Gray", background: "#4A4A4D", foreground: "#D7D7D8", … }
            ​​​3: Object { name: "Night", background: "#121212", foreground: "#B0B0B0", … }
            ​​​length: 4
    ​​​1: Object { name: "Solarized", tones: (2) […], accents: (8) […], … }
        accents: Array(8) [ "#B58900", "#CB4B16", "#DC322F", … ]
        colors: Array(8) [ {…}, {…}, {…}, … ]
        name: "Solarized"
        tones: Array [ {…}, {…} ]
            ​​​0: Object { name: "Light", background: "#FDF6E3", foreground: "#657B83", … }
            ​​​1: Object { name: "Dark", background: "#002B36", foreground: "#839496", … }
            ​​​length: 2
    ​​​length: 2

Patch to fix the issue

This makes the code more reliable on bad/corrupted settings:

  updateColorScheme(index) {
    const scheme = this.colorSchemes[index];
--    if (!scheme.tones || !scheme.tones.length)
++    if (!scheme || !scheme.tones || !scheme.tones.length)
      return;
    ...
  },

[shivaprsd]

@juarezr Thanks for the detailed investigation and bug report! And for the patch too! 🔥

This is something I encounter occasionally while developing. But that is when I randomly add/delete color schemes or tinker with the localStorage in Dev Tools. So I was intrigued by your report because the normal user should never come across this as a bug. You cannot corrupt the settings via the UI.

Upon investigation I noted a few things. Firstly, the Example viewer you linked above is an outdated demo from 2022; the updated viewer is here. I had changed the link on the repo front page a long time ago.

Second, the new viewer uses slightly different settings and has 4 color schemes. Since both demos are hosted on the same domain (github.io) they share the localStorage entry. So if you have ever opened the new demo, changed the theme, and then visited the old demo, the later is likely to break.

Can you check the updated demo and/or the browser extension and see if this bug occurs? I am pulling down the old demo to avoid the confusion.

[juarezr]

I couldn't test the updated viewer because the page froze, but:

• The schema: 3 may have been injected into local storage and crashed the old viewer.
• It looks like the patch can prevent further crashes on future changes.

[shivaprsd]

Can you please explain how "the page froze"? Did you investigate further?

The patch indeed prevents the crash, but unfortunately we then end up with a blank toolbar:

Then selecting a scheme from the dropdown resets it and "un-corrupts" the settings also. Still it is poor UX. We would need a more comprehensive patch, especially if we consider the possibility that other corrupt settings can crash doq in different ways.

[juarezr]

Can you please explain how "the page froze"? Did you investigate further?

It was a side effect caused by the Dark Mode.

Then selecting a scheme from the dropdown resets it and "un-corrupts" the settings also. Still it is poor UX. We would need a more comprehensive patch, especially if we consider the possibility that other corrupt settings can crash doq in different ways.

Yep! I didn't spend a lot of time looking for improvement.

[shivaprsd]

As this is not very high priority, I shall look in to it during the next code cleanup.