Commit 6d4b6c15 authored by Timothy Nikkel's avatar Timothy Nikkel
Browse files

Bug 1737722. esr91. r=botond, a=dmeehan 

Differential Revision: https://phabricator.services.mozilla.com/D151886
parent b2fe222f

gfx/layers/apz/src/APZCTreeManager.cpp

+54 −0
Original line number Diff line number Diff line
@@ -25,6 +25,7 @@ 
#include "mozilla/gfx/GPUParent.h"          // for GPUParent

#include "mozilla/gfx/Logging.h"            // for gfx::TreeLog

#include "mozilla/gfx/Point.h"              // for Point

#include "mozilla/gfx/Matrix.h"

#include "mozilla/layers/APZSampler.h"      // for APZSampler

#include "mozilla/layers/APZThreadUtils.h"  // for AssertOnControllerThread, etc

#include "mozilla/layers/APZUpdater.h"      // for APZUpdater
@@ -2842,6 +2843,53 @@ APZCTreeManager::HitTestResult APZCTreeManager::GetTargetAPZC( 
  return GetAPZCAtPoint(aPoint, lock);

}



static bool CheckCloseToIdentity(const gfx::Matrix4x4& aMatrix) {

  // We allow a factor of 1/2048 in the multiply part of the matrix, so that if

  // we multiply by a point on a screen of size 2048 we would be off by at most

  // 1 pixel approximately.

  const float multiplyEps = 1 / 2048.f;

  // We allow 1 pixel in the translate part of the matrix.

  const float translateEps = 1.f;



  if (!FuzzyEqualsAdditive(aMatrix._11, 1.f, multiplyEps) ||

      !FuzzyEqualsAdditive(aMatrix._12, 0.f, multiplyEps) ||

      !FuzzyEqualsAdditive(aMatrix._13, 0.f, multiplyEps) ||

      !FuzzyEqualsAdditive(aMatrix._14, 0.f, multiplyEps) ||

      !FuzzyEqualsAdditive(aMatrix._21, 0.f, multiplyEps) ||

      !FuzzyEqualsAdditive(aMatrix._22, 1.f, multiplyEps) ||

      !FuzzyEqualsAdditive(aMatrix._23, 0.f, multiplyEps) ||

      !FuzzyEqualsAdditive(aMatrix._24, 0.f, multiplyEps) ||

      !FuzzyEqualsAdditive(aMatrix._31, 0.f, multiplyEps) ||

      !FuzzyEqualsAdditive(aMatrix._32, 0.f, multiplyEps) ||

      !FuzzyEqualsAdditive(aMatrix._33, 1.f, multiplyEps) ||

      !FuzzyEqualsAdditive(aMatrix._34, 0.f, multiplyEps) ||

      !FuzzyEqualsAdditive(aMatrix._41, 0.f, translateEps) ||

      !FuzzyEqualsAdditive(aMatrix._42, 0.f, translateEps) ||

      !FuzzyEqualsAdditive(aMatrix._43, 0.f, translateEps) ||

      !FuzzyEqualsAdditive(aMatrix._44, 1.f, multiplyEps)) {

    return false;

  }

  return true;

}



// Checks that within the constraints of floating point math we can invert it

// reasonably enough that multiplying by the computed inverse is close to the

// identity.

static bool CheckInvertibleWithFinitePrecision(const gfx::Matrix4x4& aMatrix) {

  auto inverse = aMatrix.MaybeInverse();

  if (inverse.isNothing()) {

    // Should we return false?

    return true;

  }

  if (!CheckCloseToIdentity(aMatrix * *inverse)) {

    return false;

  }

  if (!CheckCloseToIdentity(*inverse * aMatrix)) {

    return false;

  }

  return true;

}



APZCTreeManager::HitTestResult APZCTreeManager::GetAPZCAtPointWR(

    const ScreenPoint& aHitTestPoint,

    const RecursiveMutexAutoLock& aProofOfTreeLock) {
@@ -2903,6 +2951,12 @@ APZCTreeManager::HitTestResult APZCTreeManager::GetAPZCAtPointWR( 
      continue;

    }



    if (!CheckInvertibleWithFinitePrecision(

            GetScreenToApzcTransform(node->GetApzc()).ToUnknownMatrix())) {

      APZCTM_LOG("skipping due to check inverse accuracy\n");

      continue;

    }



    APZCTM_LOG("selecting as chosen result.\n");

    chosenResult = Some(result);

    hit.mTargetApzc = node->GetApzc();