Fix inverted cells, make sure inverted cells are cleared correctly

[mofux]

Fixes #995

Addresses two issues:

1. Previously, the foreground was not correctly swapped, getting the same color as the background when inversed.

2. Removes a render optimisation that caused the white top bar in nano not to render and also caused an issue when redrawing color inverted cells that contained a space.

[Tyriar]

Oppsy 😄

[Tyriar]

I think this optimization actually saves heaps of time, especially when the viewport is very wide as we ignore space cells very early in the process. Should this instead be:

if space char AND is default bg AND is not inverted?

[mofux]

I've tried that first, and it restores the white top bar in nano, but it fails when nano is closed:

const isInverted = flags & FLAGS.INVERSE;
if (!code || (code === 32 /*' '*/ && isDefaultBackground && !isInverted) || isInvisible) {
    continue;
}

[Tyriar]

Oh, you need to pull this off the _state, ie. was it inverted. Similar to what's happening above with (state[CHAR_DATA_ATTR_INDEX] & 0x1ff) >= 256, this means "was default background color". I think you need to add it to the condition above:

// Clear the old character was not a space with the default background
if (state && !(state[CHAR_DATA_CODE_INDEX] === 32 /*' '*/ && (state[CHAR_DATA_ATTR_INDEX] & 0x1ff) >= 256) && <!wasInverted>) 

Pulling state[CHAR_DATA_ATTR_INDEX] out into an oldAttr var will help.

[mofux]

I think I've managed to fix it 😅

[coveralls]

Coverage remained the same at 70.123% when pulling cce440c on mofux:995 into 1f49879 on sourcelair:v3.

[Tyriar]

It should actually be:

const wasInverted = state && ((state[CHAR_DATA_ATTR_INDEX] >> 18) & FLAGS.INVERSE);

CHAR_DATA_ATTR_INDEX & FLAGS.INVERSE is equivalent to 0 & 8 which equals 0, so currently it will return the character code.

Broken down this is:

const attr = state[CHAR_DATA_ATTR_INDEX];
const flags = attr >> 18; // Bit shift right 18 bits
const wasInverted = !!(flags & FLAGS.INVERSE); // true if flags contains the bit for 8 (0b1000)

[coveralls]

Coverage decreased (-0.02%) to 70.102% when pulling 4e88979 on mofux:995 into 1f49879 on sourcelair:v3.

[coveralls]

Coverage decreased (-0.02%) to 70.102% when pulling 642cdf0 on mofux:995 into 1f49879 on sourcelair:v3.

[coveralls]

Coverage decreased (-0.02%) to 70.102% when pulling 642cdf0 on mofux:995 into 1f49879 on sourcelair:v3.