io.stdout:setvbuf("no")
local texture_shader_source = [[
#VERTEX_SHADER
Vertex vert(Vertex v)
{
    return v; 
}
#END_VERTEX_SHADER

#FRAGMENT_SHADER
Color frag(Color c, Texture tex, Vertex v)
{
    return c * texel(tex, v.uv);
}
#END_FRAGMENT_SHADER
]] 
local texture_shader = nil
local JGUI = require("JGUI")

local panel = JGUI.newPanel("Panel")
panel:setSize(300, 300)
local button = JGUI.newButton("test")
button:setSize(200, 50)
button:setPosition(0, 0)
panel:add(button)
local b1 = jin.graphics.newBitmap("a.png")
local b2 = jin.graphics.newBitmap("b.png")
local bt1 = jin.graphics.newTexture(b1)
local bt2 = jin.graphics.newTexture(b2)
b1 = nil 
b2 = nil
local bt = bt1
button.onClick = function() 
    print("click")
        bt = bt2
end 
button.onRelease = function()
    bt = bt1
end
function jin.core.onLoad() 
    texture_shader = jin.graphics.newShader(texture_shader_source)
end

function jin.core.onEvent(e)
    if e.type == "Quit" then 
        jin.core.stop()
    end
    if e.type == "KeyDown" and e.key == "Escape" then 
        jin.core.stop()
    end
    panel:onEvent(e)
end
local t = 0
local f = 0
function jin.core.onUpdate(dt)
    panel:onUpdate(dt)
    f = f + 1 
    t = t + dt 
    if t >= 1 then 
        print(f)
        t = t - 1
        f = 0
    end
end

function jin.core.onDraw()
    jin.graphics.setColor(255 * math.sin(t), 255 * math.cos(t), 255 * math.tan(t), 255)
    jin.graphics.useShader(texture_shader)
    -- jin.graphics.unbindCanvas()
    jin.graphics.draw(bt, 0, button.y)
    jin.graphics.unuseShader()
end