carpet: add dual scroll animation effect

metadata/extra-animations.xml

@@ -135,7 +135,7 @@
 			</option>
 			<option name="carpet_roll_direction" type="int">
 				<_short>Roll Direction</_short>
-				<_long>From which side to unroll the carpet for the open animation. The opposite direction will be used on close animation.</_long>
+				<_long>Choose from where the window unrolls for open animation. Left, right, top and bottom unroll from the selected edge. Horizontal and vertical scroll unrolls from the middle, much like an ancient scroll.</_long>
 				<default>0</default>
 				<desc>
 					<value>0</value>
@@ -153,6 +153,14 @@
 					<value>3</value>
 					<_name>Bottom</_name>
 				</desc>
+				<desc>
+					<value>4</value>
+					<_name>Horizontal Scroll</_name>
+				</desc>
+				<desc>
+					<value>5</value>
+					<_name>Vertical Scroll</_name>
+				</desc>
 			</option>
 		</group>
 		<group>

src/extra-animations/carpet.hpp

@@ -2,6 +2,7 @@
  * The MIT License (MIT)
  *
  * Copyright (c) 2025 Scott Moreau <oreaus@gmail.com>
+ * Copyright (c) 2025 Andrew Pliatsikas <futurebytestore@gmail.com>
  *
  * Permission is hereby granted, free of charge, to any person obtaining a copy
  * of this software and associated documentation files (the "Software"), to deal
@@ -60,7 +61,8 @@ uniform int direction;
 
 #define M_PI 3.1415926535897932384626433832795
 
-void main()
+// Original single roll effect
+vec4 single_roll(vec2 uvpos_var, float progress, int direction)
 {
     vec4 wfrag;
     vec2 uv;
@@ -180,6 +182,154 @@ void main()
         wfrag = mix(wfrag, pfrag, pfrag.a);
     }
 
+    return wfrag;
+}
+
+// Dual scroll effect (both sides rolling toward/from middle) by Phodius
+vec4 dual_scroll(vec2 uvpos_var, float progress, int dir)
+{
+    vec4 wfrag = vec4(0.0);
+    vec2 uv;
+
+    float coord;
+    float other_coord;
+
+    // dir 5 = vertical, dir 4 = horizontal
+    if (dir == 5)
+    {
+        coord = uvpos_var.y;
+        other_coord = uvpos_var.x;
+    }
+    else
+    {
+        coord = uvpos_var.x;
+        other_coord = uvpos_var.y;
+    }
+
+    // Determine which half we're on
+    bool second_half = (coord > 0.5);
+
+    // Map to local coordinate: 0 at middle, 1 at edge
+    float local_coord;
+    if (second_half)
+    {
+        local_coord = (coord - 0.5) * 2.0;
+    }
+    else
+    {
+        local_coord = (0.5 - coord) * 2.0;
+    }
+
+    float offset = 0.1;
+    float p = progress * 1.2 - 0.2;
+
+    // Get pixel from default position if before peel line
+    if (local_coord < p + offset + 0.05)
+    {
+        if (uvpos_var.x >= 0.0 && uvpos_var.x <= 1.0 &&
+            uvpos_var.y >= 0.0 && uvpos_var.y <= 1.0)
+        {
+            wfrag = get_pixel(uvpos_var);
+        }
+    }
+
+    // Back of roll
+    if (local_coord > p + offset + 0.05 && local_coord < p + offset + 0.1)
+    {
+        float tsin = (local_coord - (p + offset + 0.05)) * 20.0;
+        float angle = asin(tsin);
+
+        float local_sample = (angle / M_PI) * 0.15 + p + offset + 0.05;
+
+        float global_sample;
+        if (second_half)
+        {
+            global_sample = 0.5 + local_sample * 0.5;
+        }
+        else
+        {
+            global_sample = 0.5 - local_sample * 0.5;
+        }
+
+        float perp_sample = (other_coord - 0.5) * pow(cos(angle), 0.02) + 0.5;
+
+        if (dir == 5)
+        {
+            uv.y = global_sample;
+            uv.x = perp_sample;
+        }
+        else
+        {
+            uv.x = global_sample;
+            uv.y = perp_sample;
+        }
+
+        vec4 pfrag = vec4(0.0);
+        if (uv.x >= 0.0 && uv.x <= 1.0 && uv.y >= 0.0 && uv.y <= 1.0)
+        {
+            pfrag = get_pixel(uv);
+        }
+        wfrag = mix(pfrag, wfrag, wfrag.a);
+    }
+
+    // Front of roll
+    if (local_coord > p + offset && local_coord < p + offset + 0.1)
+    {
+        float tsin = (local_coord - (p + offset + 0.1)) * 20.0 + 1.0;
+        float angle = asin(tsin);
+
+        float local_sample = (angle / (-M_PI)) * 0.1 + p + offset + 0.2;
+
+        float global_sample;
+        if (second_half)
+        {
+            global_sample = 0.5 + local_sample * 0.5;
+        }
+        else
+        {
+            global_sample = 0.5 - local_sample * 0.5;
+        }
+
+        float perp_sample = (other_coord - 0.5) * 0.9 * pow(cos(angle), -0.04) + 0.5;
+
+        if (dir == 5)
+        {
+            uv.y = global_sample;
+            uv.x = perp_sample;
+        }
+        else
+        {
+            uv.x = global_sample;
+            uv.y = perp_sample;
+        }
+
+        vec4 pfrag = vec4(0.0);
+        if (uv.x >= 0.0 && uv.x <= 1.0 && uv.y >= 0.0 && uv.y <= 1.0)
+        {
+            pfrag = get_pixel(uv);
+        }
+        pfrag = vec4(clamp(pfrag.rgb + (angle / -M_PI), 0.0, 1.0), pfrag.a);
+        wfrag = mix(wfrag, pfrag, pfrag.a);
+    }
+
+    return wfrag;
+}
+
+void main()
+{
+    vec4 wfrag;
+
+    if (direction <= 3)
+    {
+        // single roll: left, right, top, bottom
+        wfrag = single_roll(uvpos_var, progress, direction);
+    }
+    else
+    {
+        // dual scroll: horizontal or vertical from middle
+        wfrag = dual_scroll(uvpos_var, progress, direction);
+    }
+
     gl_FragColor = wfrag;
 }
 )";