// enve - 2D animations software
// Copyright (C) 2016-2020 Maurycy Liebner

// This program is free software: you can redistribute it and/or modify
// it under the terms of the GNU General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.

// This program is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU General Public License for more details.

// You should have received a copy of the GNU General Public License
// along with this program.  If not, see <http://www.gnu.org/licenses/>.

#version 330 core
layout(location = 0) out vec4 fragColor;

in vec2 texCoord;

uniform sampler2D texture;

uniform float sharpness;
uniform float time;

void main(void) {
    float width = 2 - sharpness;
    float margin = 0.5*(width - 1);
    float x0 = width * (1 - time) - margin;
    float x1 = x0 + 1 - sharpness;
    float alpha;
    float fragX = texCoord.x + 0.5*(1 - sharpness);
    if(fragX < x0) {
        alpha = 1;
    } else if(fragX > x1) {
        alpha = 0;
    } else {
        alpha = 0.5*(cos(3.14159*(fragX - x0)/(1 - sharpness)) + 1);
    }
    fragColor = texture2D(texture, texCoord) * alpha;
}