private static void NormalizeCoordinates(ref int x, ref int y)
{
int vScreenWidth = MySendKeys.GetSystemMetrics(MySendKeys.SMCxvirtualscreen);
int vScreenHeight = MySendKeys.GetSystemMetrics(MySendKeys.SMCyvirtualscreen);
int vScreenLeft = MySendKeys.GetSystemMetrics(MySendKeys.SMXvirtualscreen);
int vScreenTop = MySendKeys.GetSystemMetrics(MySendKeys.SMYvirtualscreen);
// Absolute input requires that input is in 'normalized' coords - with the entire
// desktop being (0,0)...(65536,65536). Need to convert input x,y coords to this
// first.
//
// In this normalized world, any pixel on the screen corresponds to a block of values
// of normalized coords - eg. on a 1024x768 screen,
// y pixel 0 corresponds to range 0 to 85.333,
// y pixel 1 corresponds to range 85.333 to 170.666,
// y pixel 2 correpsonds to range 170.666 to 256 - and so on.
// Doing basic scaling math - (x-top)*65536/Width - gets us the start of the range.
// However, because int math is used, this can end up being rounded into the wrong
// pixel. For example, if we wanted pixel 1, we'd get 85.333, but that comes out as
// 85 as an int, which falls into pixel 0's range - and that's where the pointer goes.
// To avoid this, we add on half-a-"screen pixel"'s worth of normalized coords - to
// push us into the middle of any given pixel's range - that's the 65536/(Width*2)
// part of the formula. So now pixel 1 maps to 85+42 = 127 - which is comfortably
// in the middle of that pixel's block.
// The key ting here is that unlike points in coordinate geometry, pixels take up
// space, so are often better treated like rectangles - and if you want to target
// a particular pixel, target its rectangle's midpoint, not its edge.
x = ((x - vScreenLeft) * 65536) / vScreenWidth + 65536 / (vScreenWidth * 2);
y = ((y - vScreenTop) * 65536) / vScreenHeight + 65536 / (vScreenHeight * 2);
}
