如何设置自定义滑块的值

Question

I am creating a slider control, I have problems setting the value though

_x = 512;
_y = 256;
_width = 128;
_height = 12;
_min = 0;
_max = 10;

I do something like,

// set the value
_input = 5;
_value = median(_x-(_width/2)+(_input/_max),_x-((_width/2)),_x+((_width/2)))

Setting the _input to 5 should put the slider in the middle, but it doesn't, I think I have the calculation wrong in some way.

_x-(_width/2) will give you 0 in percent, 0 in value

_x+(_width/2) will give you 100 in percent, 10 in value. The max.

Answer 1

Mapping x0 € [_x-_width/2 .. _x+_width/2] to sl € [0..10] linearly and vica versa is not a big deal.

If having x0 : offset of -(_x-_width/2) transforms it to 0.._width , so a scale of 10/_width is needed for 0..10 :

sl == ( x0 - (_x-_width/2) ) * 10 / _width    // float div unless 10 | _width

Reversed:

x0 == (_x-_width/2) + sl * _width / 10

Take care of int vs. float divisions and rounding ( +.5 ).