Should use raw string literal in particle_process_material instead of adding statements line by line

[jsjtxietian]

Godot version

Godot v4.2.beta (5ee9831)

System information

Windows 10.0.19045 - Vulkan (Forward+) - dedicated NVIDIA GeForce RTX 3060 (NVIDIA; 31.0.15.3619) - 11th Gen Intel(R) Core(TM) i7-11700K @ 3.60GHz (16 Threads)

Issue description

As @akien-mga mentioned in #83881 (comment), we can probably do some clean up in particle_process_material.cpp in 4.3

For example, change the code from :

code += "uniform vec3 direction;\n";
code += "uniform float spread;\n";
code += "uniform float flatness;\n";
code += "uniform float inherit_emitter_velocity_ratio = 0;\n";
code += "uniform float initial_linear_velocity_min;\n";
code += "uniform float initial_linear_velocity_max;\n";
code += "uniform float directional_velocity_min;\n";
code += "uniform float directional_velocity_max;\n";

to something like:

code += R"
uniform vec3 direction;
uniform float spread;
uniform float flatness;
uniform float inherit_emitter_velocity_ratio = 0;
uniform float initial_linear_velocity_min;
uniform float initial_linear_velocity_max;
uniform float directional_velocity_min;
uniform float directional_velocity_max;"

Not only it will improve code style, but also more importantly, it can reduce string operation times which can help reduce the shuttering when ParticleProcessMaterial::_update_shader is called.

But while changing this requires all other related pr to rebase on this one, so there is a question about when to do this.

Steps to reproduce

Check particle_process_material.cpp

Minimal reproduction project

N/A

[akien-mga]

CC @QbieShay

I think this would be a nice change, but indeed we should see when is the right time. This change will make it difficult to cherry-pick changes to 4.2, so would require making dedicated PRs for bugfixes in the particles material for both 4.2 and master. If Qbie is OK with that process, I think we can do the raw string conversion ASAP.

But we can also give it a few weeks first to see if some regressions are reported against 4.2 that need a quick fix. Basically, I would do this change before starting to do more feature work on particles for 4.3.

[QbieShay]

Yes I think it'd be nice to wait 2 weeks or so to fix immediate bugs ( i don't think theres any outstanding bug rn though), then this can be done. I'm willing to coordinate but in this period I don't have time to refactor the whole class. Lmk if there's someome willing to do it

[jsjtxietian]

Lmk if there's someome willing to do it

IMHO it won't have a huge impact as we just compress the code, so maybe I can help resolve this at the appropriate time.

[QbieShay]

ok thank you!

[Calinou]

This would be a good opportunity to make this code follow the Godot shader language style guide too, as the current code has many formatting issues (such as not having spaces between function parameters).