Added editor dialog for easily creating shaders.

[Chaosus]

Added a dialog similar to GDScript but for the shaders instead.

Language options is to select between Shader and VisualShader.

Mode options are Spatial,CanvasItem,Particles and Sky.

Template options may be Default (which adds some code for functions) and Empty (shader_mode is defined only).

Demo GIF

This will helps new users to better engage with the shaders + it speeds up the creation of shaders by allowing adding some template code afterward.

Bugsquad edit: Closes #20152

[KoBeWi]

There should be an option for built-in shaders.

[Calinou]

In the long run, we may want to rename the Shader resource to TextShader to distinguish it from VisualShader. Right now, it's not obvious from the name alone that Shader is for text-based shaders.

[Chaosus]

There should be an option for built-in shaders.

@KoBeWi Done

In the long run, we may want to rename the Shader resource to TextShader to distinguish it from VisualShader. Right now, it's not obvious from the name alone that Shader is for text-based shaders.

Yeah, but it's not a subject for this PR...

[KoBeWi]

This warning seems to be permanently in the dialog:

It's irrelevant to shaders.

[Chaosus]

This warning seems to be permanently in the dialog:
It's irrelevant to shaders.

I've removed it in the last commit. Check again.

[Chaosus]

Removed almost all comments outside the constructor. ^^

[KoBeWi]

Looks great now!

The last thing to fix is the file path in the dialog:

	if (path == "") {
		String root_path = editor_data->get_edited_scene_root()->get_filename();
		if (root_path == "") {
			path = String("res://").plus_file(selected_shader_material->get_name());
		} else {
			path = root_path.get_base_dir().plus_file(selected_shader_material->get_name());
		}
	}

Using selected_shader_material->get_name() exclusively is not a good idea, because the material is unnamed in most cases. If the name doesn't exist, it should fallback to scene name.

Also editor_data->get_edited_scene_root() might return null if the resource was created in the inspector and no scene is open. It's rare, but leads to editor crash, so you should check first if a scene exists before getting filename.

[Chaosus]

@KoBeWi Well, I think I'm done with it, check again.

[Chaosus]

Ok, let this be, hope users would like it as I did 😃