'''
Plasma Shader
=============

This shader example have been taken from
http://www.iquilezles.org/apps/shadertoy/ with some adaptation.

This might become a Kivy widget when experimentation will be done.
'''


from kivy.clock import Clock
from kivy.app import App
from kivy.uix.floatlayout import FloatLayout
from kivy.core.window import Window
from kivy.graphics import RenderContext
from kivy.properties import StringProperty

# This header must be not changed, it contain the minimum information from Kivy.
header = '''
#ifdef GL_ES
precision highp float;
#endif

/* Outputs from the vertex shader */
varying vec4 frag_color;
varying vec2 tex_coord0;

/* uniform texture samplers */
uniform sampler2D texture0;
'''

# Plasma shader
plasma_shader = header + '''
uniform vec2 resolution;
uniform float time;

void main(void)
{
   float x = gl_FragCoord.x;
   float y = gl_FragCoord.y;
   float mov0 = x+y+cos(sin(time)*2.)*100.+sin(x/100.)*1000.;
   float mov1 = y / resolution.y / 0.2 + time;
   float mov2 = x / resolution.x / 0.2;
   float c1 = abs(sin(mov1+time)/2.+mov2/2.-mov1-mov2+time);
   float c2 = abs(sin(c1+sin(mov0/1000.+time)
              +sin(y/40.+time)+sin((x+y)/100.)*3.));
   float c3 = abs(sin(c2+cos(mov1+mov2+c2)+cos(mov2)+sin(x/1000.)));
   gl_FragColor = vec4( c1,c2,c3,1.0);
}
'''


class ShaderWidget(FloatLayout):

    # property to set the source code for fragment shader
    fs = StringProperty(None)

    def __init__(self, **kwargs):
        # Instead of using Canvas, we will use a RenderContext,
        # and change the default shader used.
        self.canvas = RenderContext()

        # call the constructor of parent
        # if they are any graphics object, they will be added on our new canvas
        super(ShaderWidget, self).__init__(**kwargs)

        # We'll update our glsl variables in a clock
        Clock.schedule_interval(self.update_glsl, 1 / 60.)

    def on_fs(self, instance, value):
        # set the fragment shader to our source code
        shader = self.canvas.shader
        old_value = shader.fs
        shader.fs = value
        if not shader.success:
            shader.fs = old_value
            raise Exception('failed')

    def update_glsl(self, *largs):
        self.canvas['time'] = Clock.get_boottime()
        self.canvas['resolution'] = list(map(float, self.size))
        # This is needed for the default vertex shader.
        self.canvas['projection_mat'] = Window.render_context['projection_mat']


class PlasmaApp(App):
    def build(self):
        return ShaderWidget(fs=plasma_shader)

if __name__ == '__main__':
    PlasmaApp().run()
