Add pen pressure to annotations + various fixes

[frankrousseau]

Problem

• The drawing tool doesn't support pen pressure
• Sequence stats loading doesn't occur when shots are already loaded

Solution

• Use PSBrush library to handle pen pressure and fake mouse pressure based on distance (or time) when using a mouse or a touch device. Solution implemented by @tetsuoanimation
• Reload sequences if some data are missing

[NicoPennec]

@tetsuoanimation I'm not sure to understand this one.
It doesn't look like a classic distance calculation (Euclidean or Manhattan distance formula).

[frankrousseau]

It's a Pythagore formula. With two coordinates and their projections, you can make a triangle rectangle.

[frankrousseau]

But you're right, it seems that squares are missing.

[frankrousseau]

I will let it as it is because it works better than real distance and add some comments.

[NicoPennec]

ok, notice that current usage of pow(..., 1) is useless.

Else, for the real distance you can use the Math.hypot() operator:
return Math.hypot(p1_rel.x - p2_rel.x, p1_rel.y - p2_rel.y)

and remove this weird line:
delta_dist *= 50 // magic number to scale to nicer values

[tetsuoanimation]

But you're right, it seems that squares are missing.

I think in this case, I always ended up with squaring a 1 which does nothing - but I might be wrong?

I found a note that Math.hypot is very slow - since this is basically running every frame I preferred the faster sqrt way. It's totally ok if you'd prefer it.

The delta_dist scaling is weird indeed and I don't like using a magic number there. It just makes the resulting line and pressure values look prettier on screen and I couldn't find another way to make it look as nice.

Totally happy to adjust.

[NicoPennec]

I found a note that Math.hypot is very slow - since this is basically running every frame I preferred the faster sqrt way. It's totally ok if you'd prefer it.

Your point about performance is relevant, see benchmark.