Build Surge with a fork of VSTGUI

[baconpaul]

This diff begins building Surge with a fork of VSTGUI rather than the
VSTGUI which ships with the vst3sdk pointer. The rationale is described
in #515 and elsewhere.

It accomplishes it by the following:

1. there is a fork of vstgui called surge-synthesizer/vstgui with a branch
   called surge which is master + diffs
2. There is a submodule in surge called vstgui.surge which points at that
   branch
3. There are changes to premake to point our vstgui implementation

This first version points to a branch which has one and only one
vstgui fix in it; which is submenu checkmarks on windows. But
by building this way we address that problem.

[baconpaul]

@falkTX @jsakkine @kzantow this is mostly a git change; would very much appreciate your once over to make sure I have done it correctly. I will certainly not merge this without some consensus building.

[baconpaul]

OK @falkTX I pushed cleaner documentation. Clearly I was too close to it when I wrote it.

https://github.com/surge-synthesizer/surge/blob/cbe193d05e67b1277424120852e97a48d957fa9f/doc/vstgui-dev.md

thanks for looking. Sorry it was so sloppy. Again this was fiddly to do and tricky to describe.

[baconpaul]

OK thanks for the looks @falkTX - all updated.

This is a big change so I'm going to leave this open until the end of the weekend so others can offer comments. @jsakkine @kzantow especially want to make sure you get an opportunity to weigh in.

Best.

[jarkkojs]

You should document the reasoning. We should have an architecture document that should evolve over time. Now it can just have this documented. Otherwise, sounds good.

[baconpaul]

Yeah will copy some of the text I. #515 into the document before I push good idea

[esaruoho]

@baconpaul did you see the conversation on the surge-irc chat where rgh had switched all Arials to Lato and there were less crashes on the gui?

Files in question:

vst3sdk/vstgui4/vstgui/lib/cfont.cpp
src/common/gui/SurgeGUIEditor.cpp:SharedPointer<CFontDesc> patchfont = new CFontDesc("Arial", 14);

[baconpaul]

Not yet; but the problem with using Lato isn't changing the code (tho that's good to know it helps) but is getting the font file loadable on the users machine. That's the work in #214. I'll say the same in slack!

[kzantow]

LGTM and makes sense to take this approach 👍 ; hope Steinberg moves reasonably quickly to get fixes merged though

[baconpaul]

Thanks. As discussed on slack, as well as @jsakkine comment on adding a motivation section to the doc, I'll also add a comment on the steinberg branch strategy

[baconpaul]

OK after review from each of you I"m going to merge this.