--- xinput_calibrator.orig/src/calibrator.cpp	2021-01-21 05:52:42.096387477 +0300
+++ xinput_calibrator/src/calibrator.cpp	2021-01-21 11:11:20.368336089 +0300
@@ -144,6 +144,58 @@
         return false;
     }
 
+// Transformation matrix
+// from http://support.fccps.cz/download/adv/frr/matrix_calibrator/matrix_calibrator.htm
+
+    // get the average left/right X and upper/lower Y
+    float x0x = ( clicked.x[UL] + clicked.x[LL] ) / 2.0 / width;
+    float x0y = ( clicked.y[UL] + clicked.y[LL] ) / 2.0 / height;
+    float x1x = ( clicked.x[UR] + clicked.x[LR] ) / 2.0 / width;
+    float x1y = ( clicked.y[UR] + clicked.y[LR] ) / 2.0 / height;
+    float y0x = ( clicked.x[UL] + clicked.x[UR] ) / 2.0 / width;
+    float y0y = ( clicked.y[UL] + clicked.y[UR] ) / 2.0 / height;
+    float y1x = ( clicked.x[LL] + clicked.x[LR] ) / 2.0 / width;
+    float y1y = ( clicked.y[LL] + clicked.y[LR] ) / 2.0 / height;
+//printf ("ZZ: %f %f    %f %f   %f %f    %f %f\n", x0x,x0y, x1x,x1y, y0x,y0y, y1x,y1y);
+
+    //get the difference right-left X and lower-upper Y
+    float dxx=x1x-x0x;
+    float dxy=x1y-x0y;
+    float dyx=y1x-y0x;
+    float dyy=y1y-y0y;
+//printf ("ZZ: Ds %f %f %f %f\n",dxx,dxy,dyx,dyy);
+
+/* Calculation equations:
+    1.	x0x * a + x0y * b + c = 1/8	(the left point equation)
+    2.	x1x * a + x1y * b + c = 7/8	(the right point equation)
+    3.	a / b = dxx / dxy		(tg alfa)
+    Subtract 1. from 2.:
+    4.	(x1x - x0x) * a + (x1y - x0y) * b = 6/8
+    5.	dxx * a + dxy * b = 6/8
+    Isolate (b) from 3.:
+    6.	b = a * dxy / dxx
+    Substitute (b) in 5.:
+    7.	dxx * a + dxy * a * dxy / dxx = 6/8
+    Isolate (a) from 7.:
+    8.	a * (dxx + dxy^2 / dxx) = 6/8
+    9.	a * (dxx^2 + dxy^2) / dxx = 6/8
+    10.	a = 6/8 * dxx / (dxx^2 + dxy^2)	!RESULT!
+    Analogically for (b):
+    11.	b = 6/8 * dxy / (dxx^2 + dxy^2) !RESULT!
+    We will get (c) substituting (a) and (b) in 1.
+    For (d), (e) and (f) we use the same solution analogically.
+*/
+
+    //calculate the special sauce coefficients
+    float a = 6.0/8 *  (dxx / (dxx*dxx + dxy*dxy));
+    float b = 6.0/8 *  (dxy / (dxx*dxx + dxy*dxy));
+    float c = 1.0/8 - a*x0x - b*x0y;
+    float d = 6.0/8 *  (dyx / (dyx*dyx + dyy*dyy));
+    float e = 6.0/8 *  (dyy / (dyx*dyx + dyy*dyy));
+    float f = 1.0/8 - d*y0x - e*y0y;
+
+    printf ("ZZ: TransformationMatrix %f %f %f %f %f %f 0 0 1\n", a, b, c, d, e, f);
+
     // new axis origin and scaling
     // based on old_axys: inversion/swapping is relative to the old axis
     XYinfo new_axis(old_axys);