// Hard-edged wipe from top to bottom, from gl-transitions.com
// Author: Jake Nelson (MIT)
//
// Ported to ZShell's GLSL ABI (see wallpaper_trans_bowtie.frag).

uniform sampler2D from;
uniform sampler2D to;
uniform vec2 size;
uniform vec4 fromCrop;
uniform vec4 toCrop;
uniform float progress;
uniform float fromFlip;
uniform float toFlip;

out vec4 outColor;

vec4 getFromColor(vec2 uv) {
	vec2 s = vec2(uv.x, fromFlip > 0.5 ? 1.0 - uv.y : uv.y);
	return texture(from, fromCrop.xy + s * fromCrop.zw);
}

vec4 getToColor(vec2 uv) {
	vec2 s = vec2(uv.x, toFlip > 0.5 ? 1.0 - uv.y : uv.y);
	return texture(to, toCrop.xy + s * toCrop.zw);
}

vec4 transition(vec2 uv) {
	return mix(getFromColor(uv), getToColor(uv), step(1.0 - uv.y, progress));
}

void main() {
	vec2 uv = gl_FragCoord.xy / size;
	outColor = transition(uv);
}