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// Copyright 2018 The Fuchsia Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#include <fuchsia/ui/input/cpp/fidl.h>
#include <map>
#include "src/ui/lib/glm_workaround/glm_workaround.h"
namespace input {
// Tracks an individual gesture, defined as an ensemble of time-overlapping touch points in an
// interaction with a particular input device. Changes are transformed into a |Gesture::Delta| with
// aggregate 2D relative translation, rotation, and scale as suggested by touch point updates.
// This class does not handle tapping or threshold-based classification of gestures, which can be
// handled by the caller. |GestureDetector| is an implementation of such a higher level facility.
class Gesture {
using PointerId = decltype(fuchsia::ui::input::PointerEvent::pointer_id);
// Represents a change from the previous |UpdatePointer| state.
struct Delta {
Delta& operator+=(const Delta& other);
bool operator==(const Delta& other) const;
// Delta translation is expressed in the coordinate system determined by the input source. For
// most use cases, this is the view space, which is x-right y-down and scaled according to view
// properties.
glm::vec2 translation;
// Delta rotation is expressed in radians about the right-hand z of the coordinate system of the
// input source. For most use cases, this is clockwise.
float rotation = 0;
float scale = 1;
bool has_pointers() const { return !pointers_.empty(); }
size_t pointer_count() const { return pointers_.size(); }
const glm::vec2& centroid() const { return centroid_; }
void AddPointer(PointerId pointer_id, const glm::vec2& position);
Delta UpdatePointer(PointerId pointer_id, const glm::vec2& position);
void RemovePointer(PointerId pointer_id);
struct PointerInfo {
glm::vec2 absolute; // input coordinates
glm::vec2 relative; // centroid coordinates
float distance; // centroid-relative
void UpdateCentroid();
void UpdateRelative();
glm::vec2 centroid_;
std::map<PointerId, PointerInfo> pointers_;
} // namespace input