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Bug 734953 - Remove skew() transformation function; r=dbaron

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This commit is contained in:
Aryeh Gregor
2012-03-20 13:39:57 -04:00
parent 1963b26419
commit cde53b9a3d
17 changed files with 33 additions and 180 deletions
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84
layout/style/nsStyleAnimation.cpp
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@@ -1011,7 +1011,6 @@ AppendTransformFunction(nsCSSKeyword aTransformFunction,
nargs = 3;
break;
case eCSSKeyword_translate:
case eCSSKeyword_skew:
case eCSSKeyword_scale:
nargs = 2;
break;
@@ -1114,59 +1113,6 @@ AppendTransformFunction(nsCSSKeyword aTransformFunction,
* Thus, after step 5, C = -sin(φ), D = cos(φ), and the XY shear is tan(φ).
* Thus, in step 6, A * D - B * C = cos²(φ) + sin²(φ) = 1.
* In step 7, the rotation is thus φ.
*
* skew(θ, φ), which is matrix(1, tan(φ), tan(θ), 1, 0, 0), which decomposes
* to 'rotate(φ) skewX(θ + φ) scale(sec(φ), cos(φ))' since (ignoring
* the alternate sign possibilities that would get fixed in step 6):
* In step 3, the X scale factor is sqrt(1+tan²(φ)) = sqrt(sec²(φ)) = sec(φ).
* Thus, after step 3, A = 1/sec(φ) = cos(φ) and B = tan(φ) / sec(φ) = sin(φ).
* In step 4, the XY shear is cos(φ)tan(θ) + sin(φ).
* Thus, after step 4,
* C = tan(θ) - cos(φ)(cos(φ)tan(θ) + sin(φ)) = tan(θ)sin²(φ) - cos(φ)sin(φ)
* D = 1 - sin(φ)(cos(φ)tan(θ) + sin(φ)) = cos²(φ) - sin(φ)cos(φ)tan(θ)
* Thus, in step 5, the Y scale is sqrt(C² + D²) =
* sqrt(tan²(θ)(sin⁴(φ) + sin²(φ)cos²(φ)) -
* 2 tan(θ)(sin³(φ)cos(φ) + sin(φ)cos³(φ)) +
* (sin²(φ)cos²(φ) + cos⁴(φ))) =
* sqrt(tan²(θ)sin²(φ) - 2 tan(θ)sin(φ)cos(φ) + cos²(φ)) =
* cos(φ) - tan(θ)sin(φ) (taking the negative of the obvious solution so
* we avoid flipping in step 6).
* After step 5, C = -sin(φ) and D = cos(φ), and the XY shear is
* (cos(φ)tan(θ) + sin(φ)) / (cos(φ) - tan(θ)sin(φ)) =
* (dividing both numerator and denominator by cos(φ))
* (tan(θ) + tan(φ)) / (1 - tan(θ)tan(φ)) = tan(θ + φ).
* (See http://en.wikipedia.org/wiki/List_of_trigonometric_identities .)
* Thus, in step 6, A * D - B * C = cos²(φ) + sin²(φ) = 1.
* In step 7, the rotation is thus φ.
*
* To check this result, we can multiply things back together:
*
* [ cos(φ) -sin(φ) ] [ 1 tan(θ + φ) ] [ sec(φ) 0 ]
* [ sin(φ) cos(φ) ] [ 0 1 ] [ 0 cos(φ) ]
*
* [ cos(φ) cos(φ)tan(θ + φ) - sin(φ) ] [ sec(φ) 0 ]
* [ sin(φ) sin(φ)tan(θ + φ) + cos(φ) ] [ 0 cos(φ) ]
*
* but since tan(θ + φ) = (tan(θ) + tan(φ)) / (1 - tan(θ)tan(φ)),
* cos(φ)tan(θ + φ) - sin(φ)
* = cos(φ)(tan(θ) + tan(φ)) - sin(φ) + sin(φ)tan(θ)tan(φ)
* = cos(φ)tan(θ) + sin(φ) - sin(φ) + sin(φ)tan(θ)tan(φ)
* = cos(φ)tan(θ) + sin(φ)tan(θ)tan(φ)
* = tan(θ) (cos(φ) + sin(φ)tan(φ))
* = tan(θ) sec(φ) (cos²(φ) + sin²(φ))
* = tan(θ) sec(φ)
* and
* sin(φ)tan(θ + φ) + cos(φ)
* = sin(φ)(tan(θ) + tan(φ)) + cos(φ) - cos(φ)tan(θ)tan(φ)
* = tan(θ) (sin(φ) - sin(φ)) + sin(φ)tan(φ) + cos(φ)
* = sec(φ) (sin²(φ) + cos²(φ))
* = sec(φ)
* so the above is:
* [ cos(φ) tan(θ) sec(φ) ] [ sec(φ) 0 ]
* [ sin(φ) sec(φ) ] [ 0 cos(φ) ]
*
* [ 1 tan(θ) ]
* [ tan(φ) 1 ]
*/
/*
@@ -1529,9 +1475,8 @@ AddTransformLists(const nsCSSValueList* aList1, double aCoeff1,
NS_ABORT_IF_FALSE(a2->Count() == 2 || a2->Count() == 3,
"unexpected count");
// This is different from skew() and translate(), since an
// omitted second parameter repeats the first rather than being
// zero.
// This is different from translate(), since an omitted second
// parameter repeats the first rather than being zero.
// Add Y component of scale.
AddTransformScale(a1->Count() == 3 ? a1->Item(2) : a1->Item(1),
aCoeff1,
@@ -1575,27 +1520,6 @@ AddTransformLists(const nsCSSValueList* aList1, double aCoeff1,
// skews with infinite tangents, and behavior changes pretty
// drastically when crossing such skews (since the direction of
// animation flips), so interop is probably more important here.
case eCSSKeyword_skew: {
NS_ABORT_IF_FALSE(a1->Count() == 2 || a1->Count() == 3,
"unexpected count");
NS_ABORT_IF_FALSE(a2->Count() == 2 || a2->Count() == 3,
"unexpected count");
nsCSSValue zero(0.0f, eCSSUnit_Radian);
// Add Y component of skew.
AddCSSValueAngle(a1->Count() == 3 ? a1->Item(2) : zero,
aCoeff1,
a2->Count() == 3 ? a2->Item(2) : zero,
aCoeff2,
arr->Item(2));
// Add X component of skew (which can be merged with case below
// in non-DEBUG).
AddCSSValueAngle(a1->Item(1), aCoeff1, a2->Item(1), aCoeff2,
arr->Item(1));
break;
}
case eCSSKeyword_skewx:
case eCSSKeyword_skewy:
case eCSSKeyword_rotate:
@@ -2030,8 +1954,8 @@ nsStyleAnimation::AddWeighted(nsCSSProperty aProperty,
// We want to avoid the matrix decomposition when we can, since
// avoiding it can produce better results both for compound
// transforms and for skew and skewY (see below). We can do this
// in two cases:
// transforms and for skewY (see below). We can do this in two
// cases:
// (1) if one of the transforms is 'none'
// (2) if the lists have the same length and the transform
// functions match