item-view-orientation-constraint.h
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#ifndef ITEM_VIEW_ORIENTATION_CONSTRAINT_H
#define ITEM_VIEW_ORIENTATION_CONSTRAINT_H
/*
* Copyright (c) 2020 Samsung Electronics Co., Ltd.
*
* Licensed under the Apache License, Version 2.0 (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.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*
*/
// EXTERNAL INCLUDES
#include <dali/public-api/animation/constraint.h>
#include <dali/public-api/math/degree.h>
#include <dali/public-api/math/math-utils.h>
#include <dali/public-api/math/quaternion.h>
#include <dali/public-api/math/radian.h>
#include <dali/public-api/math/vector3.h>
/**
* @brief Constraint used to constrain the orientation of the item-view depending on the position within the layout.
*/
class ItemViewOrientationConstraint
{
public:
/**
* @brief Constructor.
* @param[in] maximumRotationInDegrees The maximum rotation (in degrees) that we should rotate the item-view by.
* @param[in] layoutPositionChangeMultiplier This value is used to multiply the change in layout position
* (in order to exaggerate the amount moved so it's more visible).
*/
ItemViewOrientationConstraint(float maximumRotationInDegrees, float layoutPositionChangeMultiplier)
: mMaximumRotationInDegrees(maximumRotationInDegrees),
mLayoutPositionChangeMultiplier(layoutPositionChangeMultiplier),
mStartingLayoutPosition(0.0f),
mStartingAngle(0.0f),
mFirstCall(true)
{
}
/**
* @brief Will be called by the Constraint.
*
* The first time this operator is called, it uses the values as it's base reference.
* Thereafter, the position in the layout is used to determine the rotation around the X-Axis.
*
* @param[in] rotation The rotation of the item-view.
* @param[in] inputs The constraint inputs:
* [0] ItemView::Property::LAYOUT_POSITION, float
*/
void operator()(Dali::Quaternion& rotation, const Dali::PropertyInputContainer& inputs)
{
const float& layoutPosition = inputs[0]->GetFloat();
// Store values for base reference when called the first call.
if(mFirstCall)
{
mStartingLayoutPosition = layoutPosition;
Dali::Vector3 axis;
Dali::Radian angleInRadians;
rotation.ToAxisAngle(axis, angleInRadians);
Dali::Degree angleInDegrees(angleInRadians); // Convert to Degrees
mStartingAngle = angleInDegrees.degree;
if(axis.x < 0.0f) // We only rotate round the X-Axis. So if the X-Axis is negative, then the angle is also a negative angle.
{
mStartingAngle = -mStartingAngle;
}
mFirstCall = false;
}
else
{
// All subsequent calls should tilt the orientation of the item-view around the X-Axis depending on how much our position has changed in the layout.
Dali::Degree angle(mStartingAngle + mLayoutPositionChangeMultiplier * (mStartingLayoutPosition - layoutPosition));
Dali::ClampInPlace(angle.degree, -mMaximumRotationInDegrees, mMaximumRotationInDegrees); // Ensure the angle does not exceed maximum specified (in both directions).
rotation = Dali::Quaternion(angle, Dali::Vector3::XAXIS);
}
}
private:
const float mMaximumRotationInDegrees; ///< The maximum allowable rotation of the item-view.
const float mLayoutPositionChangeMultiplier; ///< This value is used to multiply the change in layout position.
float mStartingLayoutPosition; ///< The starting layout position.
float mStartingAngle; ///< The starting angle (in degrees) of the item-view.
bool mFirstCall; ///< A boolean to state whether this is the first time the operator() is called. Allows us to set the starting values.
};
#endif // ITEM_VIEW_ORIENTATION_CONSTRAINT_H