dusk/src/duskgl/display/mesh/meshgl.c

/**
 * Copyright (c) 2026 Dominic Masters
 * 
 * This software is released under the MIT License.
 * https://opensource.org/licenses/MIT
 */

#include "display/mesh/mesh.h"
#include "assert/assertgl.h"
#include "error/errorgl.h"

errorret_t meshInitGL(
  meshgl_t *mesh,
  const meshprimitivetypegl_t primitiveType,
  const int32_t vertexCount,
  const meshvertex_t *vertices
) {
  assertNotNull(mesh, "Mesh cannot be NULL");
  assertNotNull(vertices, "Vertices cannot be NULL");
  assertTrue(vertexCount > 0, "Vertex count must be greater than 0");

  mesh->primitiveType = primitiveType;
  mesh->vertexCount = vertexCount;
  mesh->vertices = vertices;

  #ifdef DUSK_OPENGL_LEGACY
    // Nothing needed.
  #else
    // Generate Vertex Buffer Object
    glGenBuffers(1, &mesh->vboId);
    errorChain(errorGLCheck());
    glBindBuffer(GL_ARRAY_BUFFER, mesh->vboId);
    errorChain(errorGLCheck());
    glBufferData(
      GL_ARRAY_BUFFER,
      vertexCount * sizeof(meshvertex_t),
      vertices,
      GL_DYNAMIC_DRAW
    );
    errorChain(errorGLCheck());

    // Generate Vertex Array Object
    glGenVertexArrays(1, &mesh->vaoId);
    errorChain(errorGLCheck());
    glBindVertexArray(mesh->vaoId);
    errorChain(errorGLCheck());
    glBindBuffer(GL_ARRAY_BUFFER, mesh->vboId);
    errorChain(errorGLCheck());

    // Set up vertex attribute pointers
    glVertexAttribPointer(
      0,
      MESH_VERTEX_POS_SIZE,
      GL_FLOAT,
      GL_FALSE,
      sizeof(meshvertex_t),
      (const GLvoid*)offsetof(meshvertex_t, pos)
    );
    errorChain(errorGLCheck());
    glEnableVertexAttribArray(0);
    errorChain(errorGLCheck());

    glVertexAttribPointer(
      1,
      MESH_VERTEX_UV_SIZE,
      GL_FLOAT,
      GL_FALSE,
      sizeof(meshvertex_t),
      (const GLvoid*)offsetof(meshvertex_t, uv)
    );
    errorChain(errorGLCheck());
    glEnableVertexAttribArray(1);
    errorChain(errorGLCheck());

    glVertexAttribPointer(
      2,
      sizeof(color_t) / sizeof(GLubyte),
      GL_UNSIGNED_BYTE,
      GL_TRUE,
      sizeof(meshvertex_t),
      (const GLvoid*)offsetof(meshvertex_t, color)
    );
    errorChain(errorGLCheck());
    glEnableVertexAttribArray(2);
    errorChain(errorGLCheck());

    // Unbind VAO and VBO to prevent accidental modification
    glBindBuffer(GL_ARRAY_BUFFER, 0);
    errorChain(errorGLCheck());
    glBindVertexArray(0);
    errorChain(errorGLCheck());
  #endif

  errorOk();
}

errorret_t meshFlushGL(
  meshgl_t *mesh,
  const int32_t vertOffset,
  const int32_t vertCount
) {
  #ifdef DUSK_OPENGL_LEGACY
    // Nothing doing, we use the glClientState stuff.
  #else
    glBindBuffer(GL_ARRAY_BUFFER, mesh->vboId);
    errorChain(errorGLCheck());
    glBufferData(
      GL_ARRAY_BUFFER,
      vertCount * sizeof(meshvertex_t),
      &mesh->vertices[vertOffset],
      GL_DYNAMIC_DRAW
    );
    errorChain(errorGLCheck());
  #endif
  errorOk();
}

errorret_t meshDrawGL(
  const meshgl_t *mesh,
  const int32_t offset,
  const int32_t count
) {
  #ifdef DUSK_OPENGL_LEGACY
    // Legacy pointer style rendering
    const GLsizei stride = sizeof(meshvertex_t);

    glColorPointer(
      sizeof(color4b_t),
      GL_UNSIGNED_BYTE,
      stride,
      (const GLvoid*)&mesh->vertices[offset].color
    );
    glTexCoordPointer(
      MESH_VERTEX_UV_SIZE,
      GL_FLOAT,
      stride,
      (const GLvoid*)&mesh->vertices[offset].uv
    );
    glVertexPointer(
      MESH_VERTEX_POS_SIZE,
      GL_FLOAT,
      stride,
      (const GLvoid*)&mesh->vertices[offset].pos
    );

    glDrawArrays(mesh->primitiveType, offset, count);
    errorChain(errorGLCheck());
  #else
    // Modern VAO/VBO rendering
    glBindVertexArray(mesh->vaoId);
    errorChain(errorGLCheck());
    glDrawArrays(mesh->primitiveType, offset, count);
    errorChain(errorGLCheck());
    glBindVertexArray(0);
    errorChain(errorGLCheck());
  #endif

  errorOk();
}

int32_t meshGetVertexCountGL(const meshgl_t *mesh) {
  return mesh->vertexCount;
}

errorret_t meshDisposeGL(meshgl_t *mesh) {
  #ifdef DUSK_OPENGL_LEGACY
    // No dynamic resources to free for this mesh implementation
  #else
    glDeleteBuffers(1, &mesh->vboId);
    errorChain(errorGLCheck());
    glDeleteVertexArrays(1, &mesh->vaoId);
    errorChain(errorGLCheck());
  #endif
  errorOk();
}