>> >> The largest distance that wx can support is INT_MAX, since it represents >> distance often in a wxCoord or wxSize. As a scalar, a distance is always >> positive. On most machines which run KiCad, int is 32 bits and INT_MAX is >> 2147483647. The most difficult distance for a virtual (world) cartesian >> space is the hypotenuse, or diagonal measurement at a 45 degree angle. This >> puts the most stress on the distance magnitude within the bounded virtual >> space. So if we allow this distance to be our constraint of <= INT_MAX, this >> constraint then propagates to the maximum distance in X and in Y that can be >> supported on each axis. Remember that the hypotenuse of a 1x1 square is >> sqrt( 1x1 + 1x1 ) = sqrt(2) = 1.41421356. >> >> hypotenuse of any square = sqrt(2) * deltaX; >> >> Let maximum supported hypotenuse be INT_MAX, then: >> >> MAX_AXIS = INT_MAX / sqrt(2) = 2147483647 / 1.41421356 = 1518500251 >> >> This maximum distance is imposed by wxWidgets, not by KiCad. The imposition >> comes in the form of the data structures used in the graphics API at the >> wxDC level. Obviously when we are not interacting with wx we can use double >> to compute distances larger than this. For example the computation of the >> total length of a net, can and should be done in double, since it might >> actually be longer than a single diagonal line. >> >> The next choice is what to use for internal units (IU), sometimes called >> world units. If nanometers, then the virtual space must be limited to >> about 1.5 x 1.5 meters square. This is 1518500251 divided by 1e9 nm/meter. >> >> The maximum zoom factor then depends on the client window size. If we ask >> wx to handle something outside INT_MIN to INT_MAX, there are unreported >> problems in the non-Debug build because wxRound() goes silent. >> >> Let: >> const double MAX_AXIS = 1518500251; >> >> Then a maximum zoom factor for a screen of 1920 pixels wide is >> 1518500251 / 1920 = 790885. >> >> The largest ZOOM_FACTOR in above table is ZOOM_FACTOR( 300 ), which computes >> out to 762000 just below 790885.
If we don't drop the bucket on our toes, proceed carefully, watch where we are going, it looks like it will hold water using a virtual world sized at 2.14 meters x 2.14 meters. So far so good. Dick _______________________________________________ Mailing list: https://launchpad.net/~kicad-developers Post to : [email protected] Unsubscribe : https://launchpad.net/~kicad-developers More help : https://help.launchpad.net/ListHelp
