Q:

GLSL - make effect only on one texture

I wish to blur my background, with the following fragment shader:
varying vec4 vColor;
varying vec2 vTexCoord;

uniform vec2 screenSize;

uniform sampler2D u_texture;
uniform vec4 v_time;

const float RADIUS = 0.75;

const float SOFTNESS = 0.6;

const float blurSize = 1.0/1000.0;

void main() {

    vec4 texColor = vec4(0.0); // texture2D(u_texture, vTexCoord)
    texColor += texture2D(u_texture, vTexCoord - 4.0*blurSize) * 0.05;
    texColor += texture2D(u_texture, vTexCoord - 3.0*blurSize) * 0.09;
    texColor += texture2D(u_texture, vTexCoord - 2.0*blurSize) * 0.12;
    texColor += texture2D(u_texture, vTexCoord - blurSize) * 0.15;
    texColor += texture2D(u_texture, vTexCoord) * 0.16;
    texColor += texture2D(u_texture, vTexCoord + blurSize) * 0.15;
    texColor += texture2D(u_texture, vTexCoord + 2.0*blurSize) * 0.12;
    texColor += texture2D(u_texture, vTexCoord + 3.0*blurSize) * 0.09;
    texColor += texture2D(u_texture, vTexCoord + 4.0*blurSize) * 0.05;

    vec4 timedColor = (vColor + v_time);

    vec2 position = (gl_FragCoord.xy / screenSize.xy) - vec2(0.5);
    float len = length(position);

    float vignette = smoothstep(RADIUS, RADIUS-SOFTNESS, len);

    texColor.rgb = mix(texColor.rgb, texColor.rgb * vignette, 0.5);

    gl_FragColor = vec4(texColor.rgb * timedColor.rgb, texColor.a);
}

But the problem being is that the shader blurs all screen.. what should i write to make it focus on my background texture instead of all the screen?

A:

OK, I gonna answer my question.
I wanted my shader program to blur only the background texture instead of all the screen.
so I created two shader programs, one for the background and one for the rest.
when the program draws the background it switches to the background shader, and after that is switches to the default shader.
Simple is that.

