Simple Faster Blur for Godot Shader

gistfile1.txt

// VERTEX SHADER
uniform vec2 screen_size = vec2(1280,800);

VAR1 = vec4(1.0/screen_size.x,1.0/screen_size.y,0.0,0.0);

// FRAGMENT SHADER

vec3 sc =
	texscreen( vec2(SCREEN_UV.x-VAR1.x*4.0, SCREEN_UV.y-VAR1.y*4.0) )	* 0.0162162162 +
	texscreen( vec2(SCREEN_UV.x-VAR1.x*3.0, SCREEN_UV.y-VAR1.y*3.0) )	* 0.0540540541 +
	texscreen( vec2(SCREEN_UV.x-VAR1.x*2.0, SCREEN_UV.y-VAR1.y*2.0) )	* 0.1216216216 +
	texscreen( vec2(SCREEN_UV.x-VAR1.x, SCREEN_UV.y-VAR1.y) )			* 0.1945945946 +
	
	texscreen(SCREEN_UV)												* 0.2270270270 +

	texscreen( vec2(SCREEN_UV.x+VAR1.x, SCREEN_UV.y+VAR1.y) )			* 0.1945945946 +
	texscreen( vec2(SCREEN_UV.x+VAR1.x*2.0, SCREEN_UV.y+VAR1.y*2.0) )	* 0.1216216216 +
	texscreen( vec2(SCREEN_UV.x+VAR1.x*3.0, SCREEN_UV.y+VAR1.y*3.0) )	* 0.0540540541 +
	texscreen( vec2(SCREEN_UV.x+VAR1.x*4.0, SCREEN_UV.y+VAR1.y*4.0) )	* 0.0162162162
	;

COLOR = color(sc.r,sc.g,sc.b,1.0);

how do you use this, but using vec4 instead of vec3?