[MU4 Issue] [Engraving] Note stems don't take the SMuFL anchors "stemUpNW" and "stemDownSW" into account

[cbjeukendrup]

Describe the bug
The stems of notes and chords don't take the stemUpNW and stemDownSW SMuFL anchors of the flag into account. This causes that the stem has an incorrect length.
For normal flags, this is not very visible (but if you look closely, you might see an edge at some zoom levels when anti-aliasing is turned on). The problem becomes very obvious with straight flags*:

* Not yet possible, but I will implement this as soon as this issue is fixed and PR #8867 gets merged.

Additional context
For the Shadow Note, it already works correctly because I implemented this in PR #7316.

[cbjeukendrup]

I would like to fix this issue.

[oktophonie]

Be my guest ;)

If you're in that bit of the code, is it worth investigating a fix for stemUpSE and stemDownNW on certain noteheads like the cross and triangle? They seem almost right, but not quite:

[Jojo-Schmitz]

That 'edge' on normal flags:

[DmitryArefiev]

Hi @cbjeukendrup , can you help with creating straight flags please? I'm new to MU and don't find a way how to create straight flags..

[cbjeukendrup]

The problem is that there is no way to enable straight flags yet. I can implement that when PR #8867 is merged. (The screenshot at the top of this issue was taken from a development build that was made on top of that PR.)

For testing PR #9237, you could also look at the position of the grip box to make the stem longer or shorter; that one always appears at the end of the stem line.

[Jojo-Schmitz]

Make a 2nd PR on top of that one? Maybe as Draft, until the underlying one got merged?

[DmitryArefiev]

The problem is that there is no way to enable straight flags yet. I can implement that when PR #8867 is merged. (The screenshot at the top of this issue was taken from a development build that was made on top of that PR.)

For testing PR #9237, you could also look at the position of the grip box to make the stem longer or shorter; that one always appears at the end of the stem line.

Thanks for the advice! That helped

[DmitryArefiev]

Checked #8952 on Win10, Mac11.13.1, Linux Mint 20.2 - FIXED