easy-gl › Program

Program

Manages a linked OpenGL shader program. Handles shader compilation, linking, uniform setting and attribute binding. Non-copyable, movable, RAII.

One-line construction (recommended)

Compile and link a vertex + fragment program in a single constructor call:

easygl::Program prog(vertexShaderSource, fragmentShaderSource);
// Throws easygl::Exception if compilation or link fails
prog.use();

Step-by-step construction

easygl::Program prog;
prog.create();

easygl::Shader vert(easygl::ShaderType::Vertex);
vert.create();
vert.compile_from_source(vertSrc);

easygl::Shader frag(easygl::ShaderType::Fragment);
frag.create();
frag.compile_from_source(fragSrc);

prog.attach_owned(vert);   // ownership transferred
prog.attach_owned(frag);
prog.link();               // throws on failure
// vert and frag are now empty; prog owns them internally

compile_from_sources

Resets and recompiles/relinks an existing program object:

prog.compile_from_sources(newVertSrc, newFragSrc);

Uniforms — scalar and vector

int loc = prog.uniform_location("uColor");
if (loc < 0) { /* uniform not found or optimised away */ }

prog.set_uniform(loc, 1.0f);                        // float
prog.set_uniform(loc, 1.0f, 0.5f);                   // vec2
prog.set_uniform(loc, 1.0f, 0.5f, 0.2f);              // vec3
prog.set_uniform(loc, 1.0f, 0.5f, 0.2f, 1.0f);        // vec4

prog.set_uniform(loc, 42);                             // int
prog.set_uniform(loc, 42u);                            // uint

Uniforms — arrays

std::vector<float> pts = { 0.0f, 1.0f, 2.0f, 3.0f };
prog.set_uniform_fv(loc, pts, 2);  // 2 components per element → 2 × vec2

Uniforms — matrices

float model[16] = { /* column-major 4×4 */ };
float mvp[16]   = { /* ... */ };

prog.set_uniform_matrix4(prog.uniform_location("uModel"), model);
prog.set_uniform_matrix4(prog.uniform_location("uMVP"), mvp);

// Non-square matrices:
prog.set_uniform_matrix3x4(prog.uniform_location("uBones"), boneData);

// Transpose flag (false = column-major, the OpenGL default):
prog.set_uniform_matrix4(loc, data, false);

Uniform blocks (UBOs)

unsigned int blockIdx = prog.uniform_block_index("Matrices");
prog.set_uniform_block_binding(blockIdx, 0); // bind block to point 0

// Then bind the Buffer to the same point:
ubo.bind_base(easygl::BufferTarget::Uniform, 0);

Attribute binding

// Must be done BEFORE linking:
prog.bind_attrib_location(0, "aPos");
prog.bind_attrib_location(1, "aTexCoord");
prog.link();

// Or query after linking:
int posIdx = prog.attrib_location("aPos");

Validation

prog.validate(); // Calls glValidateProgram — useful in debug builds
std::cout << prog.info_log() << '\n';

Method reference

Method	Description
`Program()`	Default construction — empty, no GL handle yet.
`Program(vertSrc, fragSrc)`	Compile & link in one step. Throws on failure.
`create()`	Allocate GL program handle.
`destroy()`	Free handle. Noexcept.
`attach(shader)`	Attach shader (const ref, no ownership transfer).
`attach_owned(shader)`	Attach shader and transfer ownership to program.
`detach(shader)`	Detach shader from program.
`link()`	Link attached shaders. Throws on failure.
`compile_from_sources(v,f)`	Recompile/relink entire program from sources.
`use()`	Make this program current (`glUseProgram`).
`validate()`	Validate program state for current GL state.
`info_log()`	Link or validation log string.
`attrib_location(name)`	Get attribute location by name.
`bind_attrib_location(idx, name)`	Bind attribute to index before linking.
`uniform_location(name)`	Get uniform location by name.
`set_uniform(loc, ...)`	Overloaded: float/int/uint scalars and vectors.
`set_uniform_fv(loc, span, components)`	Float array uniform.
`set_uniform_matrix2..4(loc, data, transpose)`	Square matrix uniforms.
`set_uniform_matrix2x3..4x3(loc, data, transpose)`	Non-square matrix uniforms.
`uniform_block_index(name)`	Get UBO block index by name.
`set_uniform_block_binding(idx, point)`	Bind UBO block to binding point.
`is_linked()`	True after successful link.
`is_created()`	True if GL handle allocated.
`native_handle()`	Raw GL integer ID.
`reset_handle_no_gl()`	Context-loss recovery.