51 lines
1.3 KiB
C
51 lines
1.3 KiB
C
// 11 october 2015
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#include <math.h>
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#include "../ui.h"
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#include "uipriv.h"
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void uiDrawMatrixSetIdentity(uiDrawMatrix *m)
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{
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m->M11 = 1;
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m->M12 = 0;
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m->M21 = 0;
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m->M22 = 1;
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m->M31 = 0;
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m->M32 = 0;
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}
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// The rest of this file provides basic utilities in case the platform doesn't provide any of its own for these tasks.
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// Keep these as minimal as possible. They should generally not call other fallbacks.
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// see https://msdn.microsoft.com/en-us/library/windows/desktop/ff684171%28v=vs.85%29.aspx#skew_transform
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// TODO see if there's a way we can avoid the multiplication
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void uiprivFallbackSkew(uiDrawMatrix *m, double x, double y, double xamount, double yamount)
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{
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uiDrawMatrix n;
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uiDrawMatrixSetIdentity(&n);
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// TODO explain this
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n.M12 = tan(yamount);
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n.M21 = tan(xamount);
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n.M31 = -y * tan(xamount);
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n.M32 = -x * tan(yamount);
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uiDrawMatrixMultiply(m, &n);
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}
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void uiprivScaleCenter(double xCenter, double yCenter, double *x, double *y)
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{
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*x = xCenter - (*x * xCenter);
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*y = yCenter - (*y * yCenter);
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}
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// the basic algorithm is from cairo
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// but it's the same algorithm as the transform point, just without M31 and M32 taken into account, so let's just do that instead
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void uiprivFallbackTransformSize(uiDrawMatrix *m, double *x, double *y)
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{
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uiDrawMatrix m2;
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m2 = *m;
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m2.M31 = 0;
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m2.M32 = 0;
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uiDrawMatrixTransformPoint(&m2, x, y);
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}
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