shaders/rounded_rectangle.glsl


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uniform float radius;
uniform vec2 band_pos;
uniform vec2 band_size;
uniform vec4 band_color;
uniform vec2 resolution;

float rounded_rect(vec2 coord, vec2 size, float r) {
	return length(max(abs(coord) - size, 0.0)) - r;
}

void main() {
    vec2 uv = gl_TexCoord[0].xy * resolution;
    vec2 center = resolution * 0.5;
    vec2 size = resolution * 0.5;

	float a = clamp(rounded_rect(uv - center, size - radius, radius), 0.0, 1.0);
    // same as: if(uv.x >= band_pos.x && uv.x <= band_pos.x + band_size.x && uv.y >= band_pos.y && uv.y <= band_pos.y + band_size.y)
    vec2 band_blend = step(band_pos, uv) - step(band_pos + band_size, uv);
    vec4 front_color = mix(gl_Color, band_color, band_blend.x*band_blend.y);
    front_color.a *= (1.0 - a);
    gl_FragColor = front_color;
}