// key events are a way to get input from GLFW.
// here we check for the escape key being pressed. if it is pressed,
// request that the window be closed
func keyCallback(w *glfw.Window, key glfw.Key, scancode int, action glfw.Action, mods glfw.ModifierKey) {
if key == glfw.KeyEscape && action == glfw.Press {
w.SetShouldClose(true)
} else if key == glfw.KeyZ && action == glfw.Press {
gZoom = 1
gOffX = 0
gOffY = 0
gBlend = 1
} else if key == glfw.KeyUp && (action == glfw.Press || action == glfw.Repeat) {
gBlend += 0.05
if gBlend > 1 {
gBlend = 1
}
} else if key == glfw.KeyDown && (action == glfw.Press || action == glfw.Repeat) {
gBlend -= 0.05
if gBlend < 0 {
gBlend = 0
}
} else if key == glfw.KeyLeftBracket && (action == glfw.Press || action == glfw.Repeat) {
gZoom /= 2
} else if key == glfw.KeyRightBracket && (action == glfw.Press || action == glfw.Repeat) {
gZoom *= 2
} else if key == glfw.Key1 && (action == glfw.Press || action == glfw.Repeat) {
gBlend = 0
} else if key == glfw.Key2 && (action == glfw.Press || action == glfw.Repeat) {
gBlend = 1
} else if key == glfw.Key3 && (action == glfw.Press || action == glfw.Repeat) {
gBlend = 0.5
} else if key == glfw.KeyH && (action == glfw.Press || action == glfw.Repeat) {
gHelp = !gHelp
}
}
