easy-gl › Device

Device

easygl::Device is the central object for initialisation, render-state management, and draw calls. You typically create one per OpenGL context and use it throughout your application.

Construction & initialization

// Default config
easygl::Device device;

// Custom config
easygl::Config cfg;
cfg.enable_debug_logging = true;
easygl::Device device(cfg);

// Must be called after the GL context is current
device.initialize(reinterpret_cast<easygl::GLGetProcAddressFn>(SDL_GL_GetProcAddress));

Capabilities & features

const auto& caps = device.capabilities();
const auto& info = caps.context_info();
std::cout << info.vendor << ' ' << info.version_string << '\n';

if (device.supports(easygl::Feature::ComputeShader))
    std::cout << "Compute shaders available\n";

device.require(easygl::Feature::FramebufferObject); // throws if missing

ClearFlags

ClearFlags is a bitmask enum defined in Device.hpp:

Value	Clears
`ClearFlags::None`	Nothing
`ClearFlags::Color`	Color buffer
`ClearFlags::Depth`	Depth buffer
`ClearFlags::Stencil`	Stencil buffer

device.set_clear_color(0.0f, 0.0f, 0.0f, 1.0f);
device.set_clear_depth(1.0f);
device.set_clear_stencil(0);
device.clear(easygl::ClearFlags::Color | easygl::ClearFlags::Depth);

Viewport & scissor

device.set_viewport(0, 0, width, height);

int x, y, w, h;
device.get_viewport(x, y, w, h);

device.set_scissor_test_enabled(true);
device.set_scissor(10, 10, 200, 200);

Blending

device.set_blend_enabled(true);
device.set_blend_func(
    easygl::BlendFactor::SrcAlpha,
    easygl::BlendFactor::OneMinusSrcAlpha);
device.set_blend_equation(easygl::BlendEquation::Add);

// Separate RGB / alpha factors:
device.set_blend_func_separate(
    easygl::BlendFactor::SrcAlpha,
    easygl::BlendFactor::OneMinusSrcAlpha,
    easygl::BlendFactor::One,
    easygl::BlendFactor::Zero);

Depth test

device.set_depth_test_enabled(true);
device.set_depth_mask(true);
device.set_depth_func(easygl::CompareFunc::Less);
device.set_depth_range(0.0f, 1.0f);

Stencil test

device.set_stencil_test_enabled(true);
device.set_stencil_func(easygl::CompareFunc::Always, 1, 0xFF);
device.set_stencil_op(
    easygl::StencilOp::Keep,
    easygl::StencilOp::Keep,
    easygl::StencilOp::Replace);
device.set_stencil_mask(0xFF);

Cull face

device.set_cull_face_enabled(true);
device.set_cull_face(easygl::CullFace::Back);
device.set_front_face(easygl::FrontFace::CounterClockwise);

Draw calls

// Non-indexed
device.draw_arrays(easygl::PrimitiveType::Triangles, 0, vertexCount);

// Indexed
device.draw_elements(easygl::PrimitiveType::Triangles,
                     indexCount, easygl::DataType::UnsignedInt, nullptr);

// Instanced
device.draw_arrays_instanced(easygl::PrimitiveType::Triangles, 0, vertexCount, instanceCount);
device.draw_elements_instanced(easygl::PrimitiveType::Triangles,
                               indexCount, easygl::DataType::UnsignedInt,
                               nullptr, instanceCount);

Compute dispatch

device.dispatch_compute(64, 64, 1);
device.memory_barrier(easygl::MemoryBarrierMask::ShaderStorage);

Debug

device.set_debug_output_enabled(true);
device.set_debug_output_synchronous_enabled(true);
device.push_debug_group(easygl::DebugSource::Application, 1, "Shadow pass");
// ... render shadow pass ...
device.pop_debug_group();
device.object_label(easygl::DebugObjectLabel::Buffer, vbo.native_handle(), "Vertex buffer");

Misc

device.flush();
device.finish();
easygl::ErrorCode err = device.get_error();
easygl::GraphicsResetStatus rs = device.get_graphics_reset_status();

Full method reference

Method	Description
`initialize(loader)`	Load all GL function pointers via the provided loader.
`is_initialized()`	Returns true after successful initialize().
`config()`	Returns the Config used at construction.
`capabilities()`	Returns Capabilities containing ContextInfo and feature flags.
`supports(Feature)`	Returns true if the feature is available.
`require(Feature)`	Throws Exception if the feature is not available.
`clear(ClearFlags)`	Clear color/depth/stencil buffers by bitmask.
`set_clear_color(r,g,b,a)`	Set the clear color value.
`set_clear_depth(d)`	Set the clear depth value (0–1).
`set_clear_stencil(v)`	Set the clear stencil value.
`set_viewport(x,y,w,h)`	Set the rendering viewport.
`get_viewport(x,y,w,h)`	Query the current viewport.
`set_blend_enabled(bool)`	Enable/disable blending.
`set_blend_func(src,dst)`	Set blend source/destination factors.
`set_depth_test_enabled(bool)`	Enable/disable depth testing.
`set_depth_func(func)`	Set depth comparison function.
`set_cull_face_enabled(bool)`	Enable/disable back-face culling.
`draw_arrays(prim,first,count)`	Non-indexed draw call.
`draw_elements(prim,count,type,offset)`	Indexed draw call.
`draw_arrays_instanced(...)`	Instanced non-indexed draw.
`draw_elements_instanced(...)`	Instanced indexed draw.
`dispatch_compute(x,y,z)`	Launch a compute shader.
`memory_barrier(mask)`	Insert a memory barrier.
`get_error()`	Poll for a pending GL error.
`get_graphics_reset_status()`	Check for GPU context reset.
`flush() / finish()`	Flush or synchronously finish all pending commands.