733661948c
- Guards against duplicate activations by checking wether the backend of the prior scope is the same as the current ones - Makes sure that only the most outer backend scope deactivates by tracking activation state
89 lines
2.9 KiB
C++
89 lines
2.9 KiB
C++
#pragma once
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#include <mbgl/map/map_observer.hpp>
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#include <mbgl/util/image.hpp>
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#include <mbgl/util/size.hpp>
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#include <mbgl/util/util.hpp>
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#include <memory>
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#include <mutex>
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namespace mbgl {
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namespace gl {
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class Context;
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using ProcAddress = void (*)();
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using FramebufferID = uint32_t;
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} // namespace gl
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class BackendScope;
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class Backend : public MapObserver {
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public:
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Backend();
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virtual ~Backend();
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// Returns the backend's context which manages OpenGL state.
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gl::Context& getContext();
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// Called prior to rendering to update the internally assumed OpenGL state.
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virtual void updateAssumedState() = 0;
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// Called when the map needs to be rendered; the backend should call Map::render() at some point
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// in the near future. (Not called for Map::renderStill() mode.)
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virtual void invalidate() = 0;
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protected:
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// Called with the name of an OpenGL extension that should be loaded. Backend implementations
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// must call the API-specific version that obtains the function pointer for this function,
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// or a null pointer if unsupported/unavailable.
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virtual gl::ProcAddress initializeExtension(const char*) = 0;
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// Called when the backend's GL context needs to be made active or inactive. These are called,
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// as a matched pair, in four situations:
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//
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// 1. When releasing GL resources during Map destruction
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// 2. When calling a CustomLayerInitializeFunction, during Map::addLayer
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// 3. When calling a CustomLayerDeinitializeFunction, during Map::removeLayer
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// 4. When rendering for Map::renderStill
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//
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// They are *not* called for Map::render; it is assumed that the correct context is already
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// activated prior to calling Map::render.
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virtual void activate() = 0;
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virtual void deactivate() = 0;
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// Reads the color pixel data from the currently bound framebuffer.
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PremultipliedImage readFramebuffer(const Size&) const;
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// A constant to signal that a framebuffer is bound, but with an unknown ID.
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static constexpr const gl::FramebufferID ImplicitFramebufferBinding =
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std::numeric_limits<gl::FramebufferID>::max();
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// Tells the renderer that OpenGL state has already been set by the windowing toolkit.
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// It sets the internal assumed state to the supplied values.
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void assumeFramebufferBinding(gl::FramebufferID fbo);
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void assumeViewportSize(const Size&);
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// Returns true when assumed framebuffer binding hasn't changed from the implicit binding.
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bool implicitFramebufferBound();
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// Triggers an OpenGL state update if the internal assumed state doesn't match the
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// supplied values.
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void setFramebufferBinding(gl::FramebufferID fbo);
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void setViewportSize(const Size&);
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protected:
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std::unique_ptr<gl::Context> context;
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private:
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std::once_flag initialized;
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friend class BackendScope;
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};
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constexpr bool operator==(const Backend& a, const Backend& b) {
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return &a == &b;
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}
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} // namespace mbgl
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