/* Helper function that, given a set of angles, constructs the appropriate
* skew matrix.
*/
static void ProcessSkewHelper(double aXAngle, double aYAngle, float aMain[4])
{
/* We want our matrix to look like this:
* | 1 tan(ThetaX) 0|
* | tan(ThetaY) 1 0|
* | 0 0 1|
* However, to avoid infinite values, we'll use the SafeTangent function
* instead of the C standard tan function.
*/
aMain[2] = SafeTangent(aXAngle);
aMain[1] = SafeTangent(aYAngle);
}
/* Helper function that, given a set of angles, constructs the appropriate
* skew matrix.
*/
/* static */ gfx3DMatrix
nsStyleTransformMatrix::ProcessSkewHelper(double aXAngle, double aYAngle)
{
/* We want our matrix to look like this:
* | 1 tan(ThetaY) 0 0 |
* | tan(ThetaX) 1 0 0 |
* | 0 0 1 0 |
* | 0 0 0 1 |
* However, to avoid infinite values, we'll use the SafeTangent function
* instead of the C standard tan function.
*/
gfx3DMatrix temp;
temp._12 = SafeTangent(aYAngle);
temp._21 = SafeTangent(aXAngle);
return temp;
}
void
Matrix4x4::SkewXY(double aXSkew, double aYSkew)
{
// XXX Is double precision really necessary here
float tanX = SafeTangent(aXSkew);
float tanY = SafeTangent(aYSkew);
float temp;
temp = _11;
_11 += tanY * _21;
_21 += tanX * temp;
temp = _12;
_12 += tanY * _22;
_22 += tanX * temp;
temp = _13;
_13 += tanY * _23;
_23 += tanX * temp;
temp = _14;
_14 += tanY * _24;
_24 += tanX * temp;
}
