Enabled text wrapping on TextEdit node causes low perfomance

[grotar00]

Godot version: 3.2.stable.official

OS/device including version: Windows 10 x64

Issue description: I suppose everything is just the way it is, but this was quite unexpected source of lag for my text processing app. Perfomance decrease depends on (string length / node width) ratio and gets worse if text is selected.
Gif below demonstrates CPU (left column) and GPU (rightmost column) usage (RAM is middle).

Can it be because line splits of entire string are calculated every frame? Is it possible to freeze the node unless it has focus or text is changed?

Steps to reproduce: Paste text (>10k symbols) to TextEdit node with true wrap_enabled.

Minimal reproduction project: Text Wrap Test.zip

[Calinou]

I wonder if the high CPU usage is just due to the amount of draw calls. Support for 2D batching is being worked in #35957.

[lawnjelly]

As well as the need for batching in the renderer as Calinou says, there may also be a problem in the way the text boxes calculate layout and cull (or don't cull) characters that are off screen.

Before it even gets to the renderer the text boxes should be:

1. Caching the layout (as you say)
2. Culling out lines / characters that are outside the view area of the window

I've not looked at any of the text widgets but I'm pretty sure (2) is not working correctly for some of the nodes.

[Nolkaloid]

@grotar00 for now you can use the application/run/low_processor_mode in the project settings to improve performance.

[lawnjelly]

I had another little test with this, it is approx 9x faster with batching in debug (should be faster in release) but I can't see any obvious option in the node to cull out the text that is not on screen, either with this or with label. There is a 'clip' option in label but it doesn't speed things up, it probably just activates glScissor.

So although the batching will hide it, it really should be solved within the nodes themselves imo.

[KoBeWi]

Seems still valid in 3.2.4 beta4
Not sure about FPS, but CPU usage skyrockets when the text is filled.