Add support in Visual Shader (Shader Graph) for Instance Parameter preview

[galberola]

Godot version: v4.4.1.stable.official

Situation

When using the Visual Shader Editor, if a Parameter is defined as Instance (Qualifier: Instance), all previews connected to the chain will stop working, and present the message "The 2D preview cannot correctly show the result retrieved from instance parameter.".

Expected behavior

When the Qualifier is set to None then the preview utilizes the default parameter (if set).
I was expecting for this behavior to not change, even when selecting a different Qualifier

Current workaround

I'm manually switching properties to Qualifier: None while I'm working on the Shader, and then changing it back to Qualifier: Instance when I run the program.

Depending on the Shader, and the amount of properties, this can range from "a minor nuance" to "doubting my life decisions" situation 😓

Notes

The behavior in code is working properly.

I.e. Using set_instance_shader_parameter is applying the effect to each individual element.

Source

The code for the Visual Shader (.tres) used in the test:

[gd_resource type="VisualShader" load_steps=6 format=3 uid="uid://qwa7w2k8upon"]

[sub_resource type="VisualShaderNodeFloatParameter" id="VisualShaderNodeFloatParameter_ekskg"]
parameter_name = "ProgressPct"
qualifier = 2
hint = 1
default_value = 0.56

[sub_resource type="VisualShaderNodeInput" id="VisualShaderNodeInput_mv64t"]
output_port_for_preview = 0
input_name = "uv"

[sub_resource type="VisualShaderNodeVectorDecompose" id="VisualShaderNodeVectorDecompose_57cj2"]
default_input_values = [0, Vector2(0, 0)]
op_type = 0

[sub_resource type="VisualShaderNodeFloatFunc" id="VisualShaderNodeFloatFunc_ekskg"]
output_port_for_preview = 0
function = 31

[sub_resource type="VisualShaderNodeStep" id="VisualShaderNodeStep_4scda"]
output_port_for_preview = 0

[resource]
code = "shader_type canvas_item;
render_mode blend_mix;

instance uniform float ProgressPct : hint_range(0.0, 1.0);



void fragment() {
// Input:35
	vec2 n_out35p0 = UV;


// VectorDecompose:36
	float n_out36p0 = n_out35p0.x;
	float n_out36p1 = n_out35p0.y;


// FloatFunc:37
	float n_out37p0 = 1.0 - n_out36p1;


// FloatParameter:30
	float n_out30p0 = ProgressPct;


// Step:38
	float n_out38p0 = step(n_out37p0, n_out30p0);


// Output:0
	COLOR.rgb = vec3(n_out38p0);


}
"
graph_offset = Vector2(-20.0218, 440.632)
mode = 1
flags/light_only = false
nodes/fragment/0/position = Vector2(1560, 1560)
nodes/fragment/30/node = SubResource("VisualShaderNodeFloatParameter_ekskg")
nodes/fragment/30/position = Vector2(700, 2000)
nodes/fragment/35/node = SubResource("VisualShaderNodeInput_mv64t")
nodes/fragment/35/position = Vector2(0, 1520)
nodes/fragment/36/node = SubResource("VisualShaderNodeVectorDecompose_57cj2")
nodes/fragment/36/position = Vector2(500, 1480)
nodes/fragment/37/node = SubResource("VisualShaderNodeFloatFunc_ekskg")
nodes/fragment/37/position = Vector2(820, 1580)
nodes/fragment/38/node = SubResource("VisualShaderNodeStep_4scda")
nodes/fragment/38/position = Vector2(1200, 1520)
nodes/fragment/connections = PackedInt32Array(35, 0, 36, 0, 36, 1, 37, 0, 37, 0, 38, 0, 30, 0, 38, 1, 38, 0, 0, 0)