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It's a bit involved as we need to ensure that gl.Context.current doesn't outline the Application instance, so we need to: - remember the Application object when it gets constructed (and clear it again when it gets destructed) - in gl.Context.current check if there's an active Application (which means sharing data across two different Python modules, and even though pybind11 docs suggest to "simply export a symbol", this *cannot* possibly work in practice; instead we share data using a Python capsule), and increase its refcount when returning the Context instance - decrease the Application refcount again when the Context gets destructedpull/11/head
Vladimír Vondruš
5 years ago
11 changed files with 250 additions and 7 deletions
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#ifndef magnum_platform_holder_h |
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#define magnum_platform_holder_h |
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/*
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This file is part of Magnum. |
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Copyright © 2010, 2011, 2012, 2013, 2014, 2015, 2016, 2017, 2018, 2019, |
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2020, 2021 Vladimír Vondruš <mosra@centrum.cz> |
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Permission is hereby granted, free of charge, to any person obtaining a |
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copy of this software and associated documentation files (the "Software"), |
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to deal in the Software without restriction, including without limitation |
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the rights to use, copy, modify, merge, publish, distribute, sublicense, |
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and/or sell copies of the Software, and to permit persons to whom the |
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Software is furnished to do so, subject to the following conditions: |
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The above copyright notice and this permission notice shall be included |
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in all copies or substantial portions of the Software. |
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THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR |
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IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, |
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FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL |
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THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER |
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LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING |
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FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER |
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DEALINGS IN THE SOFTWARE. |
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*/ |
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#include <pybind11/pybind11.h> |
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namespace magnum { namespace platform { namespace { |
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/* Takes care of updating magnum::glContextOwner so it doesn't need to be
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duplicated in every application implementation */ |
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template<class T> struct ApplicationHolder: std::unique_ptr<T> { |
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explicit ApplicationHolder(T* object): std::unique_ptr<T>{object} { |
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/* There's no real possibility to export a symbol from magnum.gl and
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access it from here (because there's no real possibility for a |
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module to ensure another module is loaded before it in order to make |
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the symbols resolve correctly; Corrade's PluginManager does that by |
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having dependency info *external* to the module, that's the only |
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way), so we're sharing the data using a bunch of very ugly |
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allocations instead. Fortunately construction/destruction of an |
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application happens *very seldom*, and gl.Context.current() |
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hopefully also not that often. Yes, the parameter is a std::string. |
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JOY. */ |
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auto* glContextOwner = static_cast<std::pair<const void*, const std::type_info*>*>(py::get_shared_data("magnumGLContextOwner")); |
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if(!glContextOwner) |
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py::set_shared_data("magnumGLContextOwner", glContextOwner = new std::pair<const void*, const std::type_info*>{}); |
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CORRADE_ASSERT(!glContextOwner->first, "Sorry, just one magnum.*.Application instance can exist at a time", ); |
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*glContextOwner = {object, &typeid(T)}; |
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} |
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ApplicationHolder(ApplicationHolder<T>&&) noexcept = default; |
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ApplicationHolder(const ApplicationHolder<T>&) = delete; |
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~ApplicationHolder() { |
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auto* glContextOwner = static_cast<std::pair<const void*, const std::type_info*>*>(py::get_shared_data("magnumGLContextOwner")); |
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CORRADE_INTERNAL_ASSERT(glContextOwner && glContextOwner->first == this->get()); |
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delete glContextOwner; |
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py::set_shared_data("magnumGLContextOwner", nullptr); |
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} |
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ApplicationHolder<T>& operator=(ApplicationHolder<T>&&) noexcept = default; |
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ApplicationHolder<T>& operator=(const ApplicationHolder<T>&) = default; |
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}; |
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}}} |
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PYBIND11_DECLARE_HOLDER_TYPE(T, magnum::platform::ApplicationHolder<T>) |
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#endif |
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