// windowslice — generated from https://github.com/gl-transitions/gl-transitions/blob/master/transitions/windowslice.glsl
// Author: gre
// License: MIT
// Description: The incoming image appears through vertical slices that widen

uniform shader _from;
uniform shader _to;
uniform float2 _resolution;
uniform float progress;
uniform float ratio;

vec4 getFromColor(vec2 uv) { return vec4(unpremul(_from.eval(vec2(uv.x, 1.0 - uv.y) * _resolution))); }
vec4 getToColor(vec2 uv) { return vec4(unpremul(_to.eval(vec2(uv.x, 1.0 - uv.y) * _resolution))); }

uniform float count; 

uniform float smoothness; 

vec4 transition (vec2 p) {
  float pr = smoothstep(-smoothness, 0.0, p.x - progress * (1.0 + smoothness));
  float s = step(pr, fract(count * p.x));
  return mix(getFromColor(p), getToColor(p), s);
}

half4 main(float2 _coord) {
  vec2 _uv = _coord / _resolution;
  vec4 _c = clamp(transition(vec2(_uv.x, 1.0 - _uv.y)), 0.0, 1.0);
  return half4(_c.rgb * _c.a, _c.a);
}