MultiRenderTarget Texture rendering with jit.gl.slab

Hi

I am looking for an elegant way to process a list of textures - like the result from a MRT render pass - through one [jit.gl.slab] object.

currently I am using this akward contraption in order to keep the shader short and uncluttered:

<jittershader name="blur">
    <description>
    baking border extender
    </description>
    <param name="width" type="float" default="2">
        <description>Width of filter</description>
    </param>
    <language name="glsl" version="1.0">
        <bind param="width" program="vp" />
        <program name="vp" type="vertex">
<![CDATA[
uniform float width;

varying vec2 texcoord11;
varying vec2 texcoord00;
varying vec2 texcoord02;
varying vec2 texcoord20;
varying vec2 texcoord22;

void main()
{
    // perform standard transform on vertex
    gl_Position = ftransform();

    // transform texcoord
    vec2 texcoord = vec2(gl_TextureMatrix[0] * gl_MultiTexCoord0);

    // get texcoords
    texcoord11 = texcoord;
    texcoord00 = texcoord + vec2(-width, -width);
    texcoord02 = texcoord + vec2( width, -width);
    texcoord20 = texcoord + vec2( width,  width);
    texcoord22 = texcoord + vec2(-width,  width);
}
]]>
        </program>
        <program name="fp" type="fragment">
<![CDATA[
/*
 * GLSL fragment program baking border extender.
 */

uniform sampler2DRect image;

varying vec2 texcoord11;
varying vec2 texcoord00;
varying vec2 texcoord02;
varying vec2 texcoord20;
varying vec2 texcoord22;

void main()
{
    vec4 blur;

    vec4 seed = texture2DRect(image, texcoord11);

    vec4 s1 = texture2DRect(image, texcoord00);
    vec4 s2 = texture2DRect(image, texcoord02);
    vec4 s3 = texture2DRect(image, texcoord20);
    vec4 s4 = texture2DRect(image, texcoord22);


    blur = (s1.r == 0.)?(s2.r == 0.)?(s3.r == 0.)?(s4.r == 0.)?seed:s4:s3:s2:s1;
    
    gl_FragColor = (seed.r == 0.)?blur:seed;
}
]]>
        </program>
    </language>
</jittershader>

But I wonder if there is more elegant solution. I know, [jit.gl.slab] can handle the input and output of multiple textures - my problem with the inlet-outlet approach is I have a varying number of textures I need to process - sometime its only one, sometime its up to 6. And the shader would get very cluttered. The provided max example can handle this.

In short: I am looking for an elegant solution that can process a varying number of textures with the same simple texture shader without the need of a cluttered patch.

cheers