bugfix/15921-fillcolor-hcm

[goransle]

Fixed #15921 by applying fillColor to series from highContrastTheme.colors if set.

Also introduced highContrastMode option to allow disabling/forcing of high contrast mode.

WIP Fiddles:

• HCM disabled https://jsfiddle.net/goransle/vk6dLtqm/
• HCM explicitly enabled https://jsfiddle.net/goransle/7ckbvurx/

TODO:

• Internal review
• Add sample
• Add integration test

---

• To see the specific tasks where the Asana app for GitHub is being used, see below:
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[highsoft-bot]

File size comparison

Sizes for compiled+gzipped (bold) and compiled files.

	master	candidate	difference
modules/accessibility.js	37.3 kB 135.8 kB	37.4 kB 136.0 kB	76 B 224 B

[highsoft-bot]

Visual test results - No difference found

[KacperMadej]

• initial rendering of any Stock demo is wrongly styled and gets correct after a redraw - throws an error in the console
• color axis also throws an error (e.g. basic map)
• some paths with fill:'none' get one ('window') - e.g. flight-routes
  

[goransle]

• some paths with fill:'none' get one ('window') - e.g. flight-routes

Something interesting going on with series.setOptions here. Adding

        mappoint: {
            fillColor: 'none'
        },
        mapline: {
            fillColor: 'none'
        },
        map: {
            fillColor: 'none'
        }

to HighContrastTheme.ts produces this (map + mappoint added, but no mapline):

[goransle]

⬆️ added as issue #20716

[marvin19]

Looks good to me! I think (if possible) to remove pattern fills and find colors with enough contrast for the demos. You can use white as the color in the top triangle e.g

[oysteinmoseng]

Nice, just nitpick!

[oysteinmoseng]

a11yOptions.highContrastMode !== false? (save 1 byte 🥳)

[goransle]

🥳 / 😕

[goransle]

wait a minute...

[oysteinmoseng]

Gzip works in mysterious ways.. (But code is easier to read anyway)

[oysteinmoseng]

🥳

[TorsteinHonsi]

Thanks!