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Diffstat (limited to 'include/mbgl/renderer/renderer_backend.hpp')
-rw-r--r-- | include/mbgl/renderer/renderer_backend.hpp | 92 |
1 files changed, 92 insertions, 0 deletions
diff --git a/include/mbgl/renderer/renderer_backend.hpp b/include/mbgl/renderer/renderer_backend.hpp new file mode 100644 index 0000000000..295838c71b --- /dev/null +++ b/include/mbgl/renderer/renderer_backend.hpp @@ -0,0 +1,92 @@ +#pragma once + +#include <mbgl/renderer/backend_scope.hpp> +#include <mbgl/util/image.hpp> +#include <mbgl/util/size.hpp> +#include <mbgl/util/util.hpp> + +#include <memory> +#include <mutex> + +namespace mbgl { + +namespace gl { +class Context; +using ProcAddress = void (*)(); +using FramebufferID = uint32_t; +} // namespace gl + +// The RendererBackend is used by the Renderer to facilitate +// the actual rendering. +class RendererBackend { +public: + RendererBackend(); + virtual ~RendererBackend(); + + // Returns the backend's context which manages OpenGL state. + gl::Context& getContext(); + + // Called prior to rendering to update the internally assumed OpenGL state. + virtual void updateAssumedState() = 0; + + // Called when this backend is used for rendering. Implementations should ensure that a renderable + // object is bound and glClear/glDraw* calls can be done. They should also make sure that + // calling .bind() repeatedly is a no-op and that the appropriate gl::Context values are + // set to the current state. + virtual void bind() = 0; + + virtual Size getFramebufferSize() const = 0; + +protected: + // Called with the name of an OpenGL extension that should be loaded. RendererBackend implementations + // must call the API-specific version that obtains the function pointer for this function, + // or a null pointer if unsupported/unavailable. + virtual gl::ProcAddress initializeExtension(const char*) = 0; + + // Called when the backend's GL context needs to be made active or inactive. These are called, + // as a matched pair, exclusively through BackendScope, in two situations: + // + // 1. When releasing GL resources during Renderer destruction + // (Including calling CustomLayerDeinitializeFunction during RenderCustomLayer destruction) + // 2. When renderering through Renderer::render() + // (Including calling CustomLayerDeinitializeFunction for newly added custom layers and + // CustomLayerDeinitializeFunction on layer removal) + virtual void activate() = 0; + virtual void deactivate() = 0; + + // Reads the color pixel data from the currently bound framebuffer. + PremultipliedImage readFramebuffer(const Size&) const; + + // A constant to signal that a framebuffer is bound, but with an unknown ID. + static constexpr const gl::FramebufferID ImplicitFramebufferBinding = + std::numeric_limits<gl::FramebufferID>::max(); + + // Tells the renderer that OpenGL state has already been set by the windowing toolkit. + // It sets the internal assumed state to the supplied values. + void assumeFramebufferBinding(gl::FramebufferID fbo); + void assumeViewport(int32_t x, int32_t y, const Size&); + void assumeScissorTest(bool); + + // Returns true when assumed framebuffer binding hasn't changed from the implicit binding. + bool implicitFramebufferBound(); + + // Triggers an OpenGL state update if the internal assumed state doesn't match the + // supplied values. + void setFramebufferBinding(gl::FramebufferID fbo); + void setViewport(int32_t x, int32_t y, const Size&); + void setScissorTest(bool); + +protected: + std::unique_ptr<gl::Context> context; + +private: + std::once_flag initialized; + + friend class BackendScope; +}; + +MBGL_CONSTEXPR bool operator==(const RendererBackend& a, const RendererBackend& b) { + return &a == &b; +} + +} // namespace mbgl |