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[Impeller] Make PathComponent POD, allow querying specific component type counts #40605

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Mar 24, 2023
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[Impeller] Make PathComponent POD, allow querying specific component type counts #40605

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a566357
Make PathComponent POD, allow querying specific component type counts
dnfield Mar 24, 2023
fcf45c8
Merge branch 'main' into path
dnfield Mar 24, 2023
cb0c79b
Merge branch 'main' into path
dnfield Mar 24, 2023
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4 changes: 4 additions & 0 deletions impeller/geometry/geometry_unittests.cc
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Original file line number Diff line number Diff line change
Expand Up @@ -589,6 +589,10 @@ TEST(GeometryTest, SimplePath) {
.AddCubicComponent({300, 300}, {400, 400}, {500, 500}, {600, 600});

ASSERT_EQ(path.GetComponentCount(), 4u);
ASSERT_EQ(path.GetComponentCount(Path::ComponentType::kLinear), 1u);
ASSERT_EQ(path.GetComponentCount(Path::ComponentType::kQuadratic), 1u);
ASSERT_EQ(path.GetComponentCount(Path::ComponentType::kCubic), 1u);
ASSERT_EQ(path.GetComponentCount(Path::ComponentType::kContour), 1u);

path.EnumerateComponents(
[](size_t index, const LinearPathComponent& linear) {
Expand Down
47 changes: 31 additions & 16 deletions impeller/geometry/path.cc
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Original file line number Diff line number Diff line change
Expand Up @@ -5,9 +5,9 @@
#include "impeller/geometry/path.h"

#include <optional>
#include <variant>

#include "impeller/geometry/path_component.h"
#include "path_component.h"

namespace impeller {

Expand All @@ -29,7 +29,19 @@ std::tuple<size_t, size_t> Path::Polyline::GetContourPointBounds(
return std::make_tuple(start_index, end_index);
}

size_t Path::GetComponentCount() const {
size_t Path::GetComponentCount(std::optional<ComponentType> type) const {
if (type.has_value()) {
switch (type.value()) {
case ComponentType::kLinear:
return linears_.size();
case ComponentType::kQuadratic:
return quads_.size();
case ComponentType::kCubic:
return cubics_.size();
case ComponentType::kContour:
return contours_.size();
}
}
return components_.size();
}

Expand Down Expand Up @@ -243,10 +255,9 @@ Path::Polyline Path::CreatePolyline(Scalar scale) const {
}
};

auto get_path_component =
[this](size_t component_i) -> std::optional<const PathComponent*> {
auto get_path_component = [this](size_t component_i) -> PathComponentVariant {
if (component_i >= components_.size()) {
return std::nullopt;
return std::monostate{};
}
const auto& component = components_[component_i];
switch (component.type) {
Expand All @@ -257,18 +268,20 @@ Path::Polyline Path::CreatePolyline(Scalar scale) const {
case ComponentType::kCubic:
return &cubics_[component.index];
case ComponentType::kContour:
return std::nullopt;
return std::monostate{};
}
};

auto compute_contour_start_direction =
[&get_path_component](size_t current_path_component_index) {
size_t next_component_index = current_path_component_index + 1;
while (get_path_component(next_component_index).has_value()) {
auto next_component =
get_path_component(next_component_index).value();
if (next_component->GetStartDirection().has_value()) {
return next_component->GetStartDirection().value();
while (!std::holds_alternative<std::monostate>(
get_path_component(next_component_index))) {
auto next_component = get_path_component(next_component_index);
auto maybe_vector =
std::visit(PathComponentStartDirectionVisitor(), next_component);
if (maybe_vector.has_value()) {
return maybe_vector.value();
} else {
next_component_index++;
}
Expand All @@ -293,11 +306,13 @@ Path::Polyline Path::CreatePolyline(Scalar scale) const {
contour.end_direction = Vector2(0, 1);

size_t previous_index = previous_path_component_index.value();
while (get_path_component(previous_index).has_value()) {
auto previous_path_component = get_path_component(previous_index).value();
if (previous_path_component->GetEndDirection().has_value()) {
contour.end_direction =
previous_path_component->GetEndDirection().value();
while (!std::holds_alternative<std::monostate>(
get_path_component(previous_index))) {
auto previous_component = get_path_component(previous_index);
auto maybe_vector =
std::visit(PathComponentEndDirectionVisitor(), previous_component);
if (maybe_vector.has_value()) {
contour.end_direction = maybe_vector.value();
break;
} else {
if (previous_index == 0) {
Expand Down
2 changes: 1 addition & 1 deletion impeller/geometry/path.h
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Expand Up @@ -77,7 +77,7 @@ class Path {

~Path();

size_t GetComponentCount() const;
size_t GetComponentCount(std::optional<ComponentType> type = {}) const;

void SetFillType(FillType fill);

Expand Down
50 changes: 48 additions & 2 deletions impeller/geometry/path_component.cc
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Original file line number Diff line number Diff line change
Expand Up @@ -8,8 +8,6 @@

namespace impeller {

PathComponent::~PathComponent() = default;

/*
* Based on: https://en.wikipedia.org/wiki/B%C3%A9zier_curve#Specific_cases
*/
Expand Down Expand Up @@ -345,4 +343,52 @@ std::optional<Vector2> CubicPathComponent::GetEndDirection() const {
return std::nullopt;
}

std::optional<Vector2> PathComponentStartDirectionVisitor::operator()(
const LinearPathComponent* component) {
if (!component) {
return std::nullopt;
}
return component->GetStartDirection();
}

std::optional<Vector2> PathComponentStartDirectionVisitor::operator()(
const QuadraticPathComponent* component) {
if (!component) {
return std::nullopt;
}
return component->GetStartDirection();
}

std::optional<Vector2> PathComponentStartDirectionVisitor::operator()(
const CubicPathComponent* component) {
if (!component) {
return std::nullopt;
}
return component->GetStartDirection();
}

std::optional<Vector2> PathComponentEndDirectionVisitor::operator()(
const LinearPathComponent* component) {
if (!component) {
return std::nullopt;
}
return component->GetEndDirection();
}

std::optional<Vector2> PathComponentEndDirectionVisitor::operator()(
const QuadraticPathComponent* component) {
if (!component) {
return std::nullopt;
}
return component->GetEndDirection();
}

std::optional<Vector2> PathComponentEndDirectionVisitor::operator()(
const CubicPathComponent* component) {
if (!component) {
return std::nullopt;
}
return component->GetEndDirection();
}

} // namespace impeller
54 changes: 38 additions & 16 deletions impeller/geometry/path_component.h
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Original file line number Diff line number Diff line change
Expand Up @@ -4,6 +4,8 @@

#pragma once

#include <type_traits>
#include <variant>
#include <vector>

#include "impeller/geometry/point.h"
Expand All @@ -22,14 +24,7 @@ namespace impeller {
// points for the given scale.
static constexpr Scalar kDefaultCurveTolerance = .1f;

struct PathComponent {
virtual ~PathComponent();

virtual std::optional<Vector2> GetStartDirection() const = 0;
virtual std::optional<Vector2> GetEndDirection() const = 0;
};

struct LinearPathComponent : public PathComponent {
struct LinearPathComponent {
Point p1;
Point p2;

Expand All @@ -47,12 +42,12 @@ struct LinearPathComponent : public PathComponent {
return p1 == other.p1 && p2 == other.p2;
}

std::optional<Vector2> GetStartDirection() const override;
std::optional<Vector2> GetStartDirection() const;

std::optional<Vector2> GetEndDirection() const override;
std::optional<Vector2> GetEndDirection() const;
};

struct QuadraticPathComponent : public PathComponent {
struct QuadraticPathComponent {
Point p1;
Point cp;
Point p2;
Expand Down Expand Up @@ -87,12 +82,12 @@ struct QuadraticPathComponent : public PathComponent {
return p1 == other.p1 && cp == other.cp && p2 == other.p2;
}

std::optional<Vector2> GetStartDirection() const override;
std::optional<Vector2> GetStartDirection() const;

std::optional<Vector2> GetEndDirection() const override;
std::optional<Vector2> GetEndDirection() const;
};

struct CubicPathComponent : public PathComponent {
struct CubicPathComponent {
Point p1;
Point cp1;
Point cp2;
Expand Down Expand Up @@ -131,9 +126,9 @@ struct CubicPathComponent : public PathComponent {
p2 == other.p2;
}

std::optional<Vector2> GetStartDirection() const override;
std::optional<Vector2> GetStartDirection() const;

std::optional<Vector2> GetEndDirection() const override;
std::optional<Vector2> GetEndDirection() const;

private:
QuadraticPathComponent Lower() const;
Expand All @@ -153,4 +148,31 @@ struct ContourComponent {
}
};

using PathComponentVariant = std::variant<std::monostate,
const LinearPathComponent*,
const QuadraticPathComponent*,
const CubicPathComponent*>;

struct PathComponentStartDirectionVisitor {
std::optional<Vector2> operator()(const LinearPathComponent* component);
std::optional<Vector2> operator()(const QuadraticPathComponent* component);
std::optional<Vector2> operator()(const CubicPathComponent* component);
std::optional<Vector2> operator()(std::monostate monostate) {
return std::nullopt;
}
};

struct PathComponentEndDirectionVisitor {
std::optional<Vector2> operator()(const LinearPathComponent* component);
std::optional<Vector2> operator()(const QuadraticPathComponent* component);
std::optional<Vector2> operator()(const CubicPathComponent* component);
std::optional<Vector2> operator()(std::monostate monostate) {
return std::nullopt;
}
};

static_assert(!std::is_polymorphic<LinearPathComponent>::value);
static_assert(!std::is_polymorphic<QuadraticPathComponent>::value);
static_assert(!std::is_polymorphic<CubicPathComponent>::value);
Comment on lines +174 to +176
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@dnfield dnfield Mar 24, 2023

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This is my "test" that these stay POD.

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@bdero bdero Mar 24, 2023

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Ooh nice, I didn't know this was a thing.

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@dnfield dnfield Mar 24, 2023

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I was going to add some asserts about the sizes but this is better


} // namespace impeller