/// <summary>
/// Tries to find an <see cref="ActiveVertexAttrib"/> in this <see cref="ShaderProgram"/> with
/// the specified location.
/// </summary>
/// <param name="location">The location to look for an <see cref="ActiveVertexAttrib"/> at.</param>
/// <param name="attrib">The <see cref="ActiveVertexAttrib"/> that was found, if one was found.</param>
/// <returns>Whether an attribute was found in said location.</returns>
public bool TryFindAttributeByLocation(int location, out ActiveVertexAttrib attrib)
{
for (int i = 0; i < activeAttribs.Length; i++)
{
if (activeAttribs[i].Location == location)
{
attrib = activeAttribs[i];
return(true);
}
}
attrib = default;
return(false);
}
/// <summary>
/// Queries vertex attribute data from a compiled shader program and returns an
/// array with all the resulting <see cref="ActiveVertexAttrib"/>-s.
/// </summary>
/// <param name="graphicsDevice">The <see cref="GraphicsDevice"/> to use for gl calls.</param>
/// <param name="programHandle">The gl handle of the shader program to query attribs for.</param>
private static ActiveVertexAttrib[] CreateActiveAttribArray(GraphicsDevice graphicsDevice, uint programHandle)
{
// We query the total amount of attributes we'll be reading from OpenGL
graphicsDevice.GL.GetProgram(programHandle, ProgramPropertyARB.ActiveAttributes, out int attribCount);
// We'll be storing the attributes in this list and then turning it into an array, because we can't
// know for sure how many attributes we'll have at the end, we just know it's be <= than attribCount
ActiveVertexAttrib[] attribList = new ActiveVertexAttrib[attribCount];
int attribListIndex = 0;
// We query all the ShaderProgram's attributes one by one and add them to attribList
for (uint i = 0; i < attribCount; i++)
{
ActiveVertexAttrib a = new ActiveVertexAttrib(graphicsDevice, programHandle, i);
if (a.Location >= 0) // Sometimes other stuff shows up, such as gl_InstanceID with location -1.
{
attribList[attribListIndex++] = a; // We should, of course, filter these out.
}
}
// If, for any reason, we didn't write the whole attribList array, we trim it down before saving it in attributes
ActiveVertexAttrib[] attributes;
if (attribListIndex == attribList.Length)
{
attributes = attribList;
}
else
{
attributes = new ActiveVertexAttrib[attribListIndex];
Array.Copy(attribList, attributes, attribListIndex);
attributes = attribList;
}
// The attributes don't always appear ordered by location, so let's sort them now
Array.Sort(attributes, (x, y) => x.Location.CompareTo(y.Location));
return(attributes);
}
