material-maker/addons/material_maker/preview/preview_2d.tscn

[gd_scene load_steps=4 format=2]

[ext_resource path="res://addons/material_maker/preview/preview_2d.gd" type="Script" id=1]

[sub_resource type="Shader" id=1]
code = "shader_type canvas_item;

uniform sampler2D tex;
uniform vec2 size;

void fragment() {
	float ms = max(size.x, size.y);
	vec2 uv = fract(0.5+1.2*(UV-vec2(0.5))*ms/size.yx);
	vec2 m2 = min(fract(uv), 1.0-fract(uv));
	COLOR = mix(texture(tex, uv), vec4(0.0, 1.0, 0.0, 1.0), step(min(m2.x, m2.y), 1.0/min(size.x, size.y)));
}"

[sub_resource type="ShaderMaterial" id=2]
shader = SubResource( 1 )
shader_param/size = Vector2( 64, 64 )

[node name="Preview2D" type="ColorRect"]
material = SubResource( 2 )
anchor_right = 1.0
anchor_bottom = 1.0
margin_right = -1216.0
margin_bottom = -656.0
rect_min_size = Vector2( 64, 64 )
mouse_filter = 1
size_flags_horizontal = 0
size_flags_vertical = 8
script = ExtResource( 1 )
[connection signal="resized" from="." to="." method="on_resized"]