Godot: Godot 3 Custom Drawing unusable Framerates on Android

[Skyfish1]

Godot version:
3.0.6-stable

OS/device including version:
Android 8.0.0/ Samsung Galaxy S7

Issue description:
_Edited_
2D Game has as stable 60 FPS (with Sprites, large Textures, a lot of Stuff ) until I add just the simplest custom drawing script e.g. for drawing the outline of a Node2D. Now the framerate on my Android S7 drops dramatically to about 6 FPS with just a few instances of that Node2D + custom drawing. A custom _draw() kills fps more than anything.

Update: I'm not refering to the Polygon2D issue but to the slow Custom drawing on any Node2D. Therefore I attached a second project with only Node2D instead of Polygon2D and edited the description to be more precise.

Steps to reproduce:
Example Project attached. Just hit the buttons to add Node2Ds with and without outline (custom draw) and watch the framerate drop on Android device.

Minimal reproduction project:
CustomDrawingSlowOnAndroid.zip
CustomDrawingSlowOnAndroid_Node2D.zip

[volzhs]

I gues it's duplicated or related of #19943

[Skyfish1]

@volzhs the Poly2D part yes, but the custom drawing part which is my main issue I didn't find any open issue. I have the same problem if I use just a Node2D with custom drawing instead of Polygon2D. Here is the same project without Poly2D and it has the same issues.
CustomDrawingSlowOnAndroid_Node2D.zip

[volzhs]

I didn't test it recently but I had a same problem with draw_line while ago.
I guess it's also 3.1 issue. cc @akien-mga @reduz

[jabcross]

Having the same issue here. It was very difficult to find the cause, because id been testing on PC, and my test device was high-end (which masks the problem a little bit). Always test often on a low-end device if you can.

[Markaroninoranor]

If someone is looking for a workaround(like I did for days) for this issue try changing the buffer sizes in Project Settings > Rendering > Limits. Lowering all of them to 4kb in official Godot 3.1.1 build drastically improved FPS in my game when rendering custom shapes.

Also this issue is probably related to #25400, that's where I've found this workaround.

[ZodmanPerth]

Workaround didn't work for me. I don't think this is a driver issue anymore, but a legit issue with Godot.

https://github.com/godotengine/godot/issues/25400#issuecomment-530345891

I'll reiterate here; I'm happy to work with someone to do what it takes to get this fixed. At the moment it could kill my entire project.

[ZodmanPerth]

Fortunately I've been able to switch to drawing with 2D meshes and cleared myself a way to progress forward.