fix: correct blur shader not working anymore in Godot 4.X

DemoPage/Assets/BlurShader.gdshader

@@ -1,26 +1,40 @@
 shader_type canvas_item;
 
-uniform vec2 blur_scale = vec2(1, 0);
-uniform vec4 color_modulate: source_color;
-uniform sampler2D SCREEN_TEXTURE : hint_screen_texture, filter_linear_mipmap;
-
-const int SAMPLES = 8;
-const float WEIGHTS[70] = {0.000008, 0.000014, 0.000022, 0.000035, 0.000054, 0.000084, 0.000127, 0.000189, 0.000279, 0.000405, 0.00058, 0.00082, 0.001141, 0.001567, 0.002121, 0.002831, 0.003726, 0.004835, 0.006186, 0.007804, 0.009708, 0.011908, 0.014402, 0.017174, 0.020194, 0.023412, 0.026764, 0.030168, 0.033529, 0.036743, 0.039703, 0.042301, 0.044438, 0.046031, 0.047013, 0.047346, 0.047013, 0.046031, 0.044438, 0.042301, 0.039703, 0.036743, 0.033529, 0.030168, 0.026764, 0.023412, 0.020194, 0.017174, 0.014402, 0.011908, 0.009708, 0.007804, 0.006186, 0.004835, 0.003726, 0.002831, 0.002121, 0.001567, 0.001141, 0.00082, 0.00058, 0.000405, 0.000279, 0.000189, 0.000127, 0.000084, 0.000054, 0.000035, 0.000022, 0.000014};
+uniform sampler2D screen_texture : hint_screen_texture, repeat_disable, filter_nearest;
+uniform float blur_size = 1.0;
+uniform vec3 color_modulate: source_color = vec3(1.0);
 
 void fragment() {
-	vec2 scale = SCREEN_PIXEL_SIZE * blur_scale;
+	const int SAMPLES = 9;
+	const int SAMPLES_HALF = SAMPLES / 2;
+	const float TOTAL_WEIGHT = 1.627038;
+	const float WEIGHTS[8] = {
+		0.05467,
+		0.080657,
+		0.106483,
+		0.125794,
+		0.132981,
+		0.125794,
+		0.106483,
+		0.080657
+	};
+
+	vec2 scale = SCREEN_PIXEL_SIZE * blur_size;
+
+	COLOR = vec4(0.0);
 
-	float total_weight = 0.0;
-	vec4 color = vec4(0.0);
+	vec2 blur_direction_1 = TEXTURE_PIXEL_SIZE * vec2(blur_size);
+	vec2 blur_direction_2 = TEXTURE_PIXEL_SIZE * vec2(blur_size, -blur_size);
 
-	for (int i = -SAMPLES / 2; i < SAMPLES / 2; ++i) {
-		for (int j = -SAMPLES / 2; j < SAMPLES / 2; ++j) {
-			int weight_index = ((i + SAMPLES/2) * SAMPLES) + j;
-			float weight = WEIGHTS[weight_index];
-			color.rgb += texture(SCREEN_TEXTURE, UV + scale * vec2(float(i), float(j))).rgb * weight;
-			total_weight += weight;
-		}
+	for(int i = -SAMPLES_HALF; i < SAMPLES_HALF; ++i) {
+		int w = i + SAMPLES_HALF;
+		COLOR += texture(screen_texture, SCREEN_UV + blur_direction_1 * float(i) * scale) * WEIGHTS[w];
+	}
+	for(int i = -SAMPLES_HALF; i < SAMPLES_HALF; ++i) {
+		int w = i + SAMPLES_HALF;
+		COLOR += texture(screen_texture, SCREEN_UV + blur_direction_2 * float(i) * scale) * WEIGHTS[w];
 	}
 
-	COLOR.rgb = (color.rgb / total_weight) * color_modulate.rgb;
+	COLOR /= TOTAL_WEIGHT;
+	COLOR.rgb *= color_modulate;
 }

DemoPage/DemoPage.tscn

@@ -30,8 +30,8 @@
 
 [sub_resource type="ShaderMaterial" id="ShaderMaterial_oq2x4"]
 shader = ExtResource("2_07raf")
-shader_parameter/blur_scale = Vector2(4, 4)
-shader_parameter/color_modulate = Color(0.780392, 0.717647, 0.968627, 1)
+shader_parameter/blur_size = 2.0
+shader_parameter/color_modulate = Color(0.522997, 0.612903, 0.846875, 1)
 
 [sub_resource type="LabelSettings" id="LabelSettings_swl1q"]
 font_size = 20