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gecko-dev/layout/style/nsStyleTransformMatrix.cpp

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/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/* ***** BEGIN LICENSE BLOCK *****
* Version: MPL 1.1/GPL 2.0/LGPL 2.1
*
* The contents of this file are subject to the Mozilla Public License Version
* 1.1 (the "License"); you may not use this file except in compliance with
* the License. You may obtain a copy of the License at
* http://www.mozilla.org/MPL/
*
* Software distributed under the License is distributed on an "AS IS" basis,
* WITHOUT WARRANTY OF ANY KIND, either express or implied. See the License
* for the specific language governing rights and limitations under the
* License.
*
* The Original Code is mozilla.org code.
*
* The Initial Developer of the Original Code is
* Mozilla Corporation
*
* Contributor(s):
* Keith Schwarz <kschwarz@mozilla.com> (original author)
*
* Alternatively, the contents of this file may be used under the terms of
* either of the GNU General Public License Version 2 or later (the "GPL"),
* or the GNU Lesser General Public License Version 2.1 or later (the "LGPL"),
* in which case the provisions of the GPL or the LGPL are applicable instead
* of those above. If you wish to allow use of your version of this file only
* under the terms of either the GPL or the LGPL, and not to allow others to
* use your version of this file under the terms of the MPL, indicate your
* decision by deleting the provisions above and replace them with the notice
* and other provisions required by the GPL or the LGPL. If you do not delete
* the provisions above, a recipient may use your version of this file under
* the terms of any one of the MPL, the GPL or the LGPL.
*
* ***** END LICENSE BLOCK ***** */
/*
* A class used for intermediate representations of the -moz-transform property.
*/
#include "nsStyleTransformMatrix.h"
#include "nsAutoPtr.h"
#include "nsCSSValue.h"
#include "nsStyleContext.h"
#include "nsPresContext.h"
#include "nsRuleNode.h"
#include "nsCSSKeywords.h"
#include <math.h>
/* Arguably, this loses precision, but it doesn't hurt! */
const float kPi = 3.1415926535897932384626433832795f;
const float kTwoPi = 6.283185307179586476925286766559f;
const float kEpsilon = 0.0001f;
/* Computes tan(theta). For values of theta such that
* tan(theta) is undefined or arbitrarily large, SafeTangent
* returns a managably large or small value of the correct sign.
*/
static float SafeTangent(float aTheta)
{
/* We'll do this by computing sin and cos theta. If cos(theta) is
* is too close to zero, we'll set it to some arbitrary epsilon value
* that avoid float overflow or undefined result.
*/
float sinTheta = sin(aTheta);
float cosTheta = cos(aTheta);
/* Bound cos(theta) to be in the range [-1, -epsilon) U (epsilon, 1] */
if (cosTheta >= 0 && cosTheta < kEpsilon)
cosTheta = kEpsilon;
else if (cosTheta < 0 && cosTheta >= -kEpsilon)
cosTheta = -kEpsilon;
return sinTheta / cosTheta;
}
/* Helper function to constrain an angle to a value in the range [-pi, pi),
* which reduces accumulated floating point errors from trigonometric functions
* by keeping the error terms small.
*/
static inline float ConstrainFloatValue(float aValue)
{
/* Get in range [0, 2pi) */
aValue = fmod(aValue, kTwoPi);
return aValue >= kPi ? aValue - kTwoPi : aValue;
}
/* Converts an nsCSSValue containing an angle into an equivalent measure
* of radians. The value is guaranteed to be in the range (-pi, pi) to
* minimize error.
*/
static float CSSToRadians(const nsCSSValue &aValue)
{
NS_PRECONDITION(aValue.IsAngularUnit(),
"Expected an angle, but didn't find one!");
switch (aValue.GetUnit()) {
case eCSSUnit_Degree:
/* 360deg = 2pi rad, so deg = pi / 180 rad */
return
ConstrainFloatValue(aValue.GetFloatValue() * kPi / 180.0f);
case eCSSUnit_Grad:
/* 400grad = 2pi rad, so grad = pi / 200 rad */
return
ConstrainFloatValue(aValue.GetFloatValue() * kPi / 200.0f);
case eCSSUnit_Radian:
/* Yay identity transforms! */
return ConstrainFloatValue(aValue.GetFloatValue());
default:
NS_NOTREACHED("Unexpected angular unit!");
return 0.0f;
}
}
/* Constructor sets the data to the identity matrix. */
nsStyleTransformMatrix::nsStyleTransformMatrix()
{
SetToIdentity();
}
/* SetToIdentity just fills in the appropriate values. */
void nsStyleTransformMatrix::SetToIdentity()
{
/* Set the main matrix to the identity. */
mMain[0] = 1.0f;
mMain[1] = 0.0f;
mMain[2] = 0.0f;
mMain[3] = 1.0f;
mDelta[0] = 0;
mDelta[1] = 0;
/* Both translation matrices are zero. */
mX[0] = 0.0f;
mX[1] = 0.0f;
mY[0] = 0.0f;
mY[1] = 0.0f;
}
/* Adds the constant translation to the scale factor translation components. */
nscoord nsStyleTransformMatrix::GetXTranslation(const nsRect& aBounds) const
{
return NSToCoordRound(aBounds.width * mX[0] + aBounds.height * mY[0]) +
mDelta[0];
}
nscoord nsStyleTransformMatrix::GetYTranslation(const nsRect& aBounds) const
{
return NSToCoordRound(aBounds.width * mX[1] + aBounds.height * mY[1]) +
mDelta[1];
}
/* GetThebesMatrix converts the stored matrix in a few steps. */
gfxMatrix nsStyleTransformMatrix::GetThebesMatrix(const nsRect& aBounds,
float aScale) const
{
/* Compute the graphics matrix. We take the stored main elements, along with
* the delta, and add in the matrices:
*
* | 0 0 dx1|
* | 0 0 dx2| * width
* | 0 0 0|
*
* | 0 0 dy1|
* | 0 0 dy2| * height
* | 0 0 0|
*/
return gfxMatrix(mMain[0], mMain[1], mMain[2], mMain[3],
NSAppUnitsToFloatPixels(GetXTranslation(aBounds), aScale),
NSAppUnitsToFloatPixels(GetYTranslation(aBounds), aScale));
}
/* Performs the matrix multiplication necessary to multiply the two matrices,
* then hands back a reference to ourself.
*/
nsStyleTransformMatrix&
nsStyleTransformMatrix::operator *= (const nsStyleTransformMatrix &aOther)
{
/* We'll buffer all of our results into a temporary storage location
* during this operation since we don't want to overwrite the values of
* the old matrix with the values of the new.
*/
float newMatrix[4];
nscoord newDelta[2];
float newX[2];
float newY[2];
/* [this] [aOther]
* |a1 c1 e1| |a0 c0 e0| |a0a1 + b0c1 c0a1 + d0c1 e0a1 + f0c1 + e1|
* |b1 d1 f1|x|b0 d0 f0| = |a0b1 + b0d1 c0b1 + d0d1 e0b1 + f0d1 + f1|
* |0 0 1 | | 0 0 1| | 0 0 1|
*/
newMatrix[0] = aOther.mMain[0] * mMain[0] + aOther.mMain[1] * mMain[2];
newMatrix[1] = aOther.mMain[0] * mMain[1] + aOther.mMain[1] * mMain[3];
newMatrix[2] = aOther.mMain[2] * mMain[0] + aOther.mMain[3] * mMain[2];
newMatrix[3] = aOther.mMain[2] * mMain[1] + aOther.mMain[3] * mMain[3];
newDelta[0] = NSToCoordRound(aOther.mDelta[0] * mMain[0] +
aOther.mDelta[1] * mMain[2]) + mDelta[0];
newDelta[1] = NSToCoordRound(aOther.mDelta[0] * mMain[1] +
aOther.mDelta[1] * mMain[3]) + mDelta[1];
/* For consistent terminology, let u0, u1, v0, and v1 be the four transform
* coordinates from our matrix, and let x0, x1, y0, and y1 be the four
* transform coordinates from the other matrix. Then the new transform
* coordinates are:
*
* u0' = a1u0 + c1u1 + x0
* u1' = b1u0 + d1u1 + x1
* v0' = a1v0 + c1v1 + y0
* v1' = b1v0 + d1v1 + y1
*/
newX[0] = mMain[0] * aOther.mX[0] + mMain[2] * aOther.mX[1] + mX[0];
newX[1] = mMain[1] * aOther.mX[0] + mMain[3] * aOther.mX[1] + mX[1];
newY[0] = mMain[0] * aOther.mY[0] + mMain[2] * aOther.mY[1] + mY[0];
newY[1] = mMain[1] * aOther.mY[0] + mMain[3] * aOther.mY[1] + mY[1];
/* Now, write everything back in. */
for (PRInt32 index = 0; index < 4; ++index)
mMain[index] = newMatrix[index];
for (PRInt32 index = 0; index < 2; ++index) {
mDelta[index] = newDelta[index];
mX[index] = newX[index];
mY[index] = newY[index];
}
/* As promised, return a reference to ourselves. */
return *this;
}
/* op* is implemented in terms of op*=. */
const nsStyleTransformMatrix
nsStyleTransformMatrix::operator *(const nsStyleTransformMatrix &aOther) const
{
return nsStyleTransformMatrix(*this) *= aOther;
}
/* Helper function to fill in an nscoord with the specified nsCSSValue. */
static void SetCoordToValue(const nsCSSValue &aValue,
nsStyleContext* aContext,
nsPresContext* aPresContext,
PRBool &aCanStoreInRuleTree, nscoord &aOut)
{
aOut = nsRuleNode::CalcLength(aValue, aContext, aPresContext,
aCanStoreInRuleTree);
}
/* Helper function to process a matrix entry. */
static void ProcessMatrix(float aMain[4], nscoord aDelta[2],
float aX[2], float aY[2],
const nsCSSValue::Array* aData,
nsStyleContext* aContext,
nsPresContext* aPresContext,
PRBool& aCanStoreInRuleTree)
{
NS_PRECONDITION(aData->Count() == 7, "Invalid array!");
/* Take the first four elements out of the array as floats and store
* them in aMain.
*/
for (PRUint16 index = 1; index <= 4; ++index)
aMain[index - 1] = aData->Item(index).GetFloatValue();
/* For the fifth element, if it's a percentage, store it in aX[0].
* Otherwise, it's a length that needs to go in aDelta[0]
*/
if (aData->Item(5).GetUnit() == eCSSUnit_Percent)
aX[0] = aData->Item(5).GetPercentValue();
else
SetCoordToValue(aData->Item(5), aContext, aPresContext, aCanStoreInRuleTree,
aDelta[0]);
/* For the final element, if it's a percentage, store it in aY[1].
* Otherwise, it's a length that needs to go in aDelta[1].
*/
if (aData->Item(6).GetUnit() == eCSSUnit_Percent)
aY[1] = aData->Item(6).GetPercentValue();
else
SetCoordToValue(aData->Item(6), aContext, aPresContext, aCanStoreInRuleTree,
aDelta[1]);
}
/* Helper function to process a translatex function. */
static void ProcessTranslateX(nscoord aDelta[2], float aX[2],
const nsCSSValue::Array* aData,
nsStyleContext* aContext,
nsPresContext* aPresContext,
PRBool& aCanStoreInRuleTree)
{
NS_PRECONDITION(aData->Count() == 2, "Invalid array!");
/* There are two cases. If we have a number, we want our matrix to look
* like this:
*
* | 1 0 dx|
* | 0 1 0|
* | 0 0 1|
* So E = value
*
* Otherwise, we might have a percentage, so we want to set the dX component
* to the percent.
*/
if (aData->Item(1).GetUnit() != eCSSUnit_Percent)
SetCoordToValue(aData->Item(1), aContext, aPresContext, aCanStoreInRuleTree,
aDelta[0]);
else
aX[0] = aData->Item(1).GetPercentValue();
}
/* Helper function to process a translatey function. */
static void ProcessTranslateY(nscoord aDelta[2], float aY[2],
const nsCSSValue::Array* aData,
nsStyleContext* aContext,
nsPresContext* aPresContext,
PRBool& aCanStoreInRuleTree)
{
NS_PRECONDITION(aData->Count() == 2, "Invalid array!");
/* There are two cases. If we have a number, we want our matrix to look
* like this:
*
* | 1 0 0|
* | 0 1 dy|
* | 0 0 1|
* So E = value
*
* Otherwise, we might have a percentage, so we want to set the dY component
* to the percent.
*/
if (aData->Item(1).GetUnit() != eCSSUnit_Percent)
SetCoordToValue(aData->Item(1), aContext, aPresContext, aCanStoreInRuleTree,
aDelta[1]);
else
aY[1] = aData->Item(1).GetPercentValue();
}
/* Helper function to process a translate function. */
static void ProcessTranslate(nscoord aDelta[2], float aX[2], float aY[2],
const nsCSSValue::Array* aData,
nsStyleContext* aContext,
nsPresContext* aPresContext,
PRBool& aCanStoreInRuleTree)
{
NS_PRECONDITION(aData->Count() == 2 || aData->Count() == 3, "Invalid array!");
/* There are several cases to consider.
* First, we might have one value, or we might have two. If we have
* two, we need to consider both dX and dY components.
* Next, the values might be lengths, or they might be percents. If they're
* percents, store them in the dX and dY components. Otherwise, store them in
* the main matrix.
*/
const nsCSSValue &dx = aData->Item(1);
if (dx.GetUnit() == eCSSUnit_Percent)
aX[0] = dx.GetPercentValue();
else
SetCoordToValue(dx, aContext, aPresContext, aCanStoreInRuleTree, aDelta[0]);
/* If we read in a Y component, set it appropriately */
if (aData->Count() == 3) {
const nsCSSValue &dy = aData->Item(2);
if (dy.GetUnit() == eCSSUnit_Percent)
aY[1] = dy.GetPercentValue();
else
SetCoordToValue(dy, aContext, aPresContext, aCanStoreInRuleTree,
aDelta[1]);
}
}
/* Helper function to set up a scale matrix. */
static void ProcessScaleHelper(float aXScale, float aYScale, float aMain[4])
{
/* We want our matrix to look like this:
* | dx 0 0|
* | 0 dy 0|
* | 0 0 1|
* So A = value
*/
aMain[0] = aXScale;
aMain[3] = aYScale;
}
/* Process a scalex function. */
static void ProcessScaleX(float aMain[4], const nsCSSValue::Array* aData)
{
NS_PRECONDITION(aData->Count() == 2, "Bad array!");
ProcessScaleHelper(aData->Item(1).GetFloatValue(), 1.0f, aMain);
}
/* Process a scaley function. */
static void ProcessScaleY(float aMain[4], const nsCSSValue::Array* aData)
{
NS_PRECONDITION(aData->Count() == 2, "Bad array!");
ProcessScaleHelper(1.0f, aData->Item(1).GetFloatValue(), aMain);
}
/* Process a scale function. */
static void ProcessScale(float aMain[4], const nsCSSValue::Array* aData)
{
NS_PRECONDITION(aData->Count() == 2 || aData->Count() == 3, "Bad array!");
/* We either have one element or two. If we have one, it's for both X and Y.
* Otherwise it's one for each.
*/
const nsCSSValue& scaleX = aData->Item(1);
const nsCSSValue& scaleY = (aData->Count() == 2 ? scaleX :
aData->Item(2));
ProcessScaleHelper(scaleX.GetFloatValue(),
scaleY.GetFloatValue(), aMain);
}
/* Helper function that, given a set of angles, constructs the appropriate
* skew matrix.
*/
static void ProcessSkewHelper(float aXAngle, float 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 infinte values, we'll use the SafeTangent function
* instead of the C standard tan function.
*/
aMain[2] = SafeTangent(aXAngle);
aMain[1] = SafeTangent(aYAngle);
}
/* Function that converts a skewx transform into a matrix. */
static void ProcessSkewX(float aMain[4], const nsCSSValue::Array* aData)
{
NS_ASSERTION(aData->Count() == 2, "Bad array!");
ProcessSkewHelper(CSSToRadians(aData->Item(1)), 0.0f, aMain);
}
/* Function that converts a skewy transform into a matrix. */
static void ProcessSkewY(float aMain[4], const nsCSSValue::Array* aData)
{
NS_ASSERTION(aData->Count() == 2, "Bad array!");
ProcessSkewHelper(0.0f, CSSToRadians(aData->Item(1)), aMain);
}
/* Function that converts a skew transform into a matrix. */
static void ProcessSkew(float aMain[4], const nsCSSValue::Array* aData)
{
NS_ASSERTION(aData->Count() == 2 || aData->Count() == 3, "Bad array!");
float xSkew = CSSToRadians(aData->Item(1));
float ySkew = (aData->Count() == 2 ? 0.0f : CSSToRadians(aData->Item(2)));
ProcessSkewHelper(xSkew, ySkew, aMain);
}
/* Function that converts a rotate transform into a matrix. */
static void ProcessRotate(float aMain[4], const nsCSSValue::Array* aData)
{
NS_PRECONDITION(aData->Count() == 2, "Invalid array!");
/* We want our matrix to look like this:
* | cos(theta) -sin(theta) 0|
* | sin(theta) cos(theta) 0|
* | 0 0 1|
* (see http://www.w3.org/TR/SVG/coords.html#RotationDefined)
*/
float theta = CSSToRadians(aData->Item(1));
float cosTheta = cos(theta);
float sinTheta = sin(theta);
aMain[0] = cosTheta;
aMain[1] = sinTheta;
aMain[2] = -sinTheta;
aMain[3] = cosTheta;
}
/**
* SetToTransformFunction is essentially a giant switch statement that fans
* out to many smaller helper functions.
*/
void
nsStyleTransformMatrix::SetToTransformFunction(const nsCSSValue::Array * aData,
nsStyleContext* aContext,
nsPresContext* aPresContext,
PRBool& aCanStoreInRuleTree)
{
NS_PRECONDITION(aData, "Why did you want to get data from a null array?");
NS_PRECONDITION(aContext, "Need a context for unit conversion!");
NS_PRECONDITION(aPresContext, "Need a context for unit conversion!");
/* Reset the matrix to the identity so that each subfunction can just
* worry about its own components.
*/
SetToIdentity();
/* Get the keyword for the transform. */
nsAutoString keyword;
aData->Item(0).GetStringValue(keyword);
switch (nsCSSKeywords::LookupKeyword(keyword)) {
case eCSSKeyword_translatex:
ProcessTranslateX(mDelta, mX, aData, aContext, aPresContext,
aCanStoreInRuleTree);
break;
case eCSSKeyword_translatey:
ProcessTranslateY(mDelta, mY, aData, aContext, aPresContext,
aCanStoreInRuleTree);
break;
case eCSSKeyword_translate:
ProcessTranslate(mDelta, mX, mY, aData, aContext, aPresContext,
aCanStoreInRuleTree);
break;
case eCSSKeyword_scalex:
ProcessScaleX(mMain, aData);
break;
case eCSSKeyword_scaley:
ProcessScaleY(mMain, aData);
break;
case eCSSKeyword_scale:
ProcessScale(mMain, aData);
break;
case eCSSKeyword_skewx:
ProcessSkewX(mMain, aData);
break;
case eCSSKeyword_skewy:
ProcessSkewY(mMain, aData);
break;
case eCSSKeyword_skew:
ProcessSkew(mMain, aData);
break;
case eCSSKeyword_rotate:
ProcessRotate(mMain, aData);
break;
case eCSSKeyword_matrix:
ProcessMatrix(mMain, mDelta, mX, mY, aData, aContext, aPresContext,
aCanStoreInRuleTree);
break;
default:
NS_NOTREACHED("Unknown transform function!");
}
}
/* Does an element-by-element comparison and returns whether or not the
* matrices are equal.
*/
PRBool
nsStyleTransformMatrix::operator ==(const nsStyleTransformMatrix &aOther) const
{
for (PRInt32 index = 0; index < 4; ++index)
if (mMain[index] != aOther.mMain[index])
return PR_FALSE;
for (PRInt32 index = 0; index < 2; ++index)
if (mDelta[index] != aOther.mDelta[index] ||
mX[index] != aOther.mX[index] ||
mY[index] != aOther.mY[index])
return PR_FALSE;
return PR_TRUE;
}
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