Just add the vector (y * cos(x * pi / 180), y * sin(x * pi / 180)).
It would be something like
from math import pi, cos, sin
cursor.x += y * cos(x * pi / 180)
cursor.y += y * sin(x * pi / 180)
The * pi / 180 is because you probably want to input degrees, not radians. The cosine gives you the x displacement on a unit circle, the sine gives you the y displacement. This way you point in the right direction. You multiply by the length to go the desired amount of units in that direction. It is just really basic trigonometry.
The main problem I see with this is you’d need some special magic because blender works in a 3d workspace while the mockup only deals with a 2d space.
Is the cursor supposed to move on the X axis or Y axis? Follow the plane of the view like left click placing of the cursor currently does? How about if you wanted to move the cursor on the Z axis? What about rotating on more than one axis?
Lots of non-obvious corner cases to be worked out.
There are easier ways this could be done without no cursor.
When extruding, you should be able to write in the angle, not just the lenght.
When a length is specificated with the numpad, it should lock the length and let you freely select the direction (or type it in)
Or, you could choose to specific the direction and then select the length.
Actually If you have active element set for pivot point(next to viewport shading drop-down) then you don’t need to mess with the cursor. The last element selected is the active element and will be the pivot point.
I would like the ability to set the angle while extruding (and all transformations) too.
But I think it should be implemented differently:
E, G, R, or S
Click and hold MMB+Type angle
The two axis lines(R,G,B/X,Y,Z) that the white line(appears while holding MMB) is between will be the plane that the angle will be on
[maybe have the ability to enter an angle followed by a comma and then another angle so the vector will be 3D]
Then after releasing MMB enter scalar(length,scale,etc.)
This way everything stays the same except you now have the option to enter an angle