75 lines
3.3 KiB
C
75 lines
3.3 KiB
C
/*
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* This program source code file is part of KiCad, a free EDA CAD application.
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*
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* Copyright (C) 2012-2016 Jean-Pierre Charras, jp.charras at wanadoo.fr
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* Copyright (C) 1992-2020 KiCad Developers, see AUTHORS.txt for contributors.
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*
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* This program is free software; you can redistribute it and/or
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* modify it under the terms of the GNU General Public License
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* as published by the Free Software Foundation; either version 2
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* of the License, or (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program; if not, you may find one here:
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* http://www.gnu.org/licenses/old-licenses/gpl-2.0.html
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* or you may search the http://www.gnu.org website for the version 2 license,
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* or you may write to the Free Software Foundation, Inc.,
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* 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA
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*/
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#pragma once
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/* ZOOM LIMITS
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The largest distance that we (and Kicad) can support is INT_MAX, since it represents
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distance often in a wxCoord or wxSize. As a scalar, a distance is always
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positive. Because int is 32 bits and INT_MAX is
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2147483647. The most difficult distance for a virtual (world) cartesian
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space is the hypotenuse, or diagonal measurement at a 45 degree angle. This
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puts the most stress on the distance magnitude within the bounded virtual
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space. So if we allow this distance to be our constraint of <= INT_MAX, this
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constraint then propagates to the maximum distance in X and in Y that can be
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supported on each axis. Remember that the hypotenuse of a 1x1 square is
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sqrt( 1x1 + 1x1 ) = sqrt(2) = 1.41421356.
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hypotenuse of any square = sqrt(2) * deltaX;
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Let maximum supported hypotenuse be INT_MAX, then:
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MAX_AXIS = INT_MAX / sqrt(2) = 2147483647 / 1.41421356 = 1518500251
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This maximum distance is imposed by wxWidgets, not by KiCad. The imposition
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comes in the form of the data structures used in the graphics API at the
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wxDC level. Obviously when we are not interacting with wx we can use double
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to compute distances larger than this. For example the computation of the
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total length of a net, can and should be done in double, since it might
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actually be longer than a single diagonal line.
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The next choice is what to use for internal units (IU), sometimes called
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world units. If nanometers, then the virtual space must be limited to
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about 1.5 x 1.5 meters square. This is 1518500251 divided by 1e9 nm/meter.
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The maximum zoom factor then depends on the client window size. If we ask
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wx to handle something outside INT_MIN to INT_MAX, there are unreported
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problems in the non-Debug build because wxRound() goes silent.
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Let:
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const double MAX_AXIS = 1518500251;
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Then a maximum zoom factor for a screen of 1920 pixels wide is
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1518500251 / 1920 = 790885.
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The largest zoom factor allowed is therefore ~ 300 (which computes to 762000).
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*/
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#define MAX_ZOOM_FACTOR 300.0
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// Adjusted to display zoom level ~ 1 when the screen shows a 1:1 image.
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// Obviously depends on the monitor, but this is an acceptable value.
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#define ZOOM_COEFF 1.1
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