1 #pragma once
2
3 #include <mbgl/renderer/backend_scope.hpp>
4 #include <mbgl/util/image.hpp>
5 #include <mbgl/util/size.hpp>
6 #include <mbgl/util/util.hpp>
7
8 #include <memory>
9 #include <mutex>
10
11 namespace mbgl {
12
13 namespace gl {
14 class Context;
15 using ProcAddress = void (*)();
16 using FramebufferID = uint32_t;
17 } // namespace gl
18
19 // The RendererBackend is used by the Renderer to facilitate
20 // the actual rendering.
21 class RendererBackend {
22 public:
23 RendererBackend();
24 virtual ~RendererBackend();
25
26 // Returns the backend's context which manages OpenGL state.
27 gl::Context& getContext();
28
29 // Called prior to rendering to update the internally assumed OpenGL state.
30 virtual void updateAssumedState() = 0;
31
32 // Called when this backend is used for rendering. Implementations should ensure that a renderable
33 // object is bound and glClear/glDraw* calls can be done. They should also make sure that
34 // calling .bind() repeatedly is a no-op and that the appropriate gl::Context values are
35 // set to the current state.
36 virtual void bind() = 0;
37
38 virtual Size getFramebufferSize() const = 0;
39
40 protected:
41 // Called with the name of an OpenGL extension that should be loaded. RendererBackend implementations
42 // must call the API-specific version that obtains the function pointer for this function,
43 // or a null pointer if unsupported/unavailable.
44 virtual gl::ProcAddress getExtensionFunctionPointer(const char*) = 0;
45
46 // Called when the backend's GL context needs to be made active or inactive. These are called,
47 // as a matched pair, exclusively through BackendScope, in two situations:
48 //
49 // 1. When releasing GL resources during Renderer destruction
50 // (Including calling CustomLayerHost::deinitialize during RenderCustomLayer destruction)
51 // 2. When renderering through Renderer::render()
52 // (Including calling CustomLayerHost::initialize for newly added custom layers and
53 // CustomLayerHost::deinitialize on layer removal)
54 virtual void activate() = 0;
55 virtual void deactivate() = 0;
56
57 // Reads the color pixel data from the currently bound framebuffer.
58 PremultipliedImage readFramebuffer(const Size&) const;
59
60 // A constant to signal that a framebuffer is bound, but with an unknown ID.
61 static constexpr const gl::FramebufferID ImplicitFramebufferBinding =
62 std::numeric_limits<gl::FramebufferID>::max();
63
64 // Tells the renderer that OpenGL state has already been set by the windowing toolkit.
65 // It sets the internal assumed state to the supplied values.
66 void assumeFramebufferBinding(gl::FramebufferID fbo);
67 void assumeViewport(int32_t x, int32_t y, const Size&);
68 void assumeScissorTest(bool);
69
70 // Returns true when assumed framebuffer binding hasn't changed from the implicit binding.
71 bool implicitFramebufferBound();
72
73 // Triggers an OpenGL state update if the internal assumed state doesn't match the
74 // supplied values.
75 void setFramebufferBinding(gl::FramebufferID fbo);
76 void setViewport(int32_t x, int32_t y, const Size&);
77 void setScissorTest(bool);
78
79 protected:
80 std::unique_ptr<gl::Context> context;
81
82 private:
83 std::once_flag initialized;
84
85 friend class BackendScope;
86 };
87
operator ==(const RendererBackend & a,const RendererBackend & b)88 MBGL_CONSTEXPR bool operator==(const RendererBackend& a, const RendererBackend& b) {
89 return &a == &b;
90 }
91
92 } // namespace mbgl
93