generator/templates/dawn/utils/ComboLimits.h

//* Copyright 2025 The Dawn & Tint Authors
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#ifndef SRC_DAWN_UTILS_COMBOLIMITS_H_
#define SRC_DAWN_UTILS_COMBOLIMITS_H_

#include <webgpu/webgpu_cpp.h>

#include <concepts>

#include "dawn/common/NonMovable.h"

namespace dawn::utils {

{% set limits_and_extensions = [types['limits']] + types['limits'].extensions %}
{% set ns = namespace(member_count=0) %}
{% for type in limits_and_extensions %}
    {% set ns.member_count = ns.member_count + (type.members | length) %}
{% endfor %}
class ComboLimits : public NonMovable
    {% for type in limits_and_extensions %}
            , private wgpu::{{as_cppType(type.name)}}
    {% endfor %}
    {
  public:
    static constexpr size_t kMemberCount = {{ ns.member_count }};

    ComboLimits();

    // This is not copyable or movable to avoid surprises with nextInChain pointers becoming stale
    // (or getting replaced with nullptr). This explicit copy makes it clear what happens.
    void UnlinkedCopyTo(ComboLimits*) const;

    // Modify the ComboLimits in-place to link the extension structs correctly, and return the base
    // struct. Optionally accepts any number of additional structs to add to the
    // end of the chain, e.g.: `comboLimits.GetLinked(&extension1, &extension2)`.
    // Always use GetLinked (rather than `&comboLimits`) whenever passing a ComboLimits to the API.
    template <typename... Extension>
        requires (std::convertible_to<Extension, wgpu::ChainedStructOut*> && ...)
    wgpu::Limits* GetLinked(Extension... extension) {
        wgpu::ChainedStructOut* lastExtension = nullptr;
        // Link all of the standard extensions.
        {% for type in types['limits'].extensions %}
            {% if loop.first %}
                lastExtension = this->wgpu::Limits::nextInChain =
            {% else %}
                lastExtension = lastExtension->nextInChain =
            {% endif %}
                static_cast<wgpu::{{as_cppType(type.name)}}*>(this);
        {% endfor %}
        // Link any extensions passed by the caller.
        ((lastExtension = lastExtension->nextInChain = extension), ...);
        lastExtension->nextInChain = nullptr;
        return this;
    }

    {% for type in limits_and_extensions %}
        {% for member in type.members %}
            using wgpu::{{as_cppType(type.name)}}::{{as_varName(member.name)}};
        {% endfor %}
    {% endfor %}
};

}  // namespace dawn::utils

#endif  // SRC_DAWN_UTILS_COMBOLIMITS_H_