[TRACKER] Improving editor startup time

[toger5]

The editor startup time is not too bad, but there is (of course) play for improvement:

Pls comment below if you have ideas which is slowing down the editor startup and how it can be improved.

Possible Improvements:

• Icon svg to png conversion on every startup could be cached Improve theming: Add scale factor to Theme + scale factor, modulate to Texture #19887

Ideas that could slow down startup:

• Is there any font preparing done on startup?
• build with target=release_debug use_lto=yes might increase startup time.
• editor is slower to start on Windows with nVidia cards (driver issue with power mode) The editor is less responsive when set to "update only changes" #11030

[Calinou]

In my experience, the editor starts up faster if you build with target=release_debug use_lto=yes.

[Zylann]

I know that probably due to #11030, the editor is slower to start on Windows with nVidia cards due to an issue on driver level (it slows everything that relies on yielding frames for example). On my laptop if I launch it using the less-powerful Intel graphics I can get it open a lot faster (within seconds).

[toger5]

It would also be really cool, when we could add some debug prints during startup to see what parts take how long to launch?

[Calinou]

Slightly off-topic, but I believe we could improve perceived performance when loading the editor by adapting the splash screen's background color to match the editor background color. This makes the transition between the splash screen and the editor window more subtle.
Edit: Done in #47119.

This should be done dynamically, so that it can match both dark and light editor themes (including gray or solarized variants). When using a light theme, the logo should use dark text as to be readable, and sponsors should be put on a dark background somehow.

Icon svg to png conversion on every startup could be cached

I like the idea, but couldn't this end up being slower on a HDD? While most Godot users are probably using a SSD by now, people on old machines shouldn't be penalized (as this is where Godot is the slowest to start).

[lawnjelly]

Just throwing these in here rather than starting a new issue, these are some profiles for master (4.x) I made today for starting the project manager, and the editor. These are release builds on Linux.

Project Manager

Editor with simple project (GLES3)

Notable it seems to spend a good amount of time in the font code.
#60781 and #60463 may be relevant here (thanks to @Calinou for pointing these out).

[bruvzg]

#60781 is not intended to make the editor start faster, but to avoid stutters when visual scripts/shaders are used (MSDF fonts are slow to rasterize).