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#ifdef GL_ES
	#ifdef GL_FRAGMENT_PRECISION_HIGH   
		precision highp float;
	#else
		precision mediump float;
	#endif
#endif

uniform sampler2D texture0;
varying vec2 uvVarying;

uniform vec2 screenSize;
uniform float noise;

float rand(vec2 n)
{
  return 0.5 + 0.5 * 
     fract(sin(dot(n.xy, vec2(12.9898, 78.233)))* 43758.5453);
}

void main()
{
	float y = floor(uvVarying.y * screenSize.y);
	float ran = (rand(uvVarying.xy) - 1.0) * 0.5;
	if (noise < 0.1)
	{
		ran = 0.0;
	}
	float delta = mod(y, 4.0) * 0.5;
	gl_FragColor = texture2D(texture0, uvVarying.xy) * (delta + ran);
}

// Project: scanline 
// Created: 2016-10-04

// show all errors
SetErrorMode(2)

// set display properties
SetWindowTitle( "scanline" )
SetWindowSize( 1024, 768, 0 )
SetVirtualResolution( 1024, 768 )
SetSyncRate( 60, 0 )
SetPrintSize(16)

// load media
img = LoadImage("scanline.png")

// load shader
shader = LoadFullScreenShader("scanline.ps")
SetShaderConstantByName(shader, "screenSize", 1024, 768, 0, 0)
// set 1 to 0 to remove noise
SetShaderConstantByName(shader, "noise", 1, 0, 0, 0)

// create quad object
renderImage = CreateRenderImage(1024, 768, 0, 0)
quad = CreateObjectQuad()
SetObjectShader(quad, shader)

// create sprite
SetImageMagFilter(img, 0)
spr = CreateSprite(img)
SetSpriteScale(spr, 2, 2)
SetSpritePositionByOffset(spr, 512, 384)

do
    
    // do actions on mouse button pressed
    // reset state
	MODE = 0
	change = 0
	
	// set state based on mouse pressed
    if GetPointerState()>0
		if MODE=0 then change = 1
		MODE = 1
	else
		if MODE=1 then change = 2
		MODE = 0
	endif
	
	// set shader visible as needed
	select change
		case 1
			SetObjectShader(quad, shader)
		endcase
		case 2
			SetObjectShader(quad, 0)
		endcase
	endselect
	
	select MODE
		case 0
			Print("Press mouse button to see shader")
			Sync()
		endcase
		case 1
			// render to the render image
			SetRenderToImage(renderImage, -1)
			ClearScreen()
			Update(GetFrameTime())
			print("Showing shader")
			Render2DBack()
			Render2DFront()
			SetObjectImage(quad, renderImage, 0)
			
			// render to the screen
			SetRenderToScreen()
			ClearScreen()
			DrawObject(quad)
			Swap()
		endcase
	endselect
loop

#ifdef GL_ES
    #ifdef GL_FRAGMENT_PRECISION_HIGH   
        precision highp float;
    #else
        precision mediump float;
    #endif
#endif
 
uniform sampler2D texture0;
varying vec2 uvVarying;
 
uniform vec2 screenSize;
 
void main()
{
    float y = floor(uvVarying.y * screenSize.y);
    float delta = mod(y, 4.0) * 0.5;
    gl_FragColor = texture2D(texture0, uvVarying.xy) * delta;
}