On Mon, 10 Mar 2003 22:23:07 +0000 José Fonseca <[EMAIL PROTECTED]> wrote: [snip]
As I said above this can be done in C++, and without damage to efficiency.
Imagine you have a TnL abstract class:
class TNL {
// A OpenGL function
virtual void Coord3f(GLfloat x, GLfloat y, GLfloat z) = 0;
// Activate
virtual void activate() = 0;
protected: struct dispatch_table *my_dispatch_table; } ;
and then you have two inherited classes for software and hardware rendering:
class SoftwareTNL : public TNL { // The software version. Note the _inline_ inline void Coord3f(x, y, z) { _mesa_swrast_deal_with_this_vertex(x, y, z); } };
class HardwareTNL : public TNL { // The hardware version. Note the _inline_ inline void Coord3f(x, y, z) { _add_vertex_to_DMA_buffer(x, y, z); } };
and then the C-callable versions for the glapi disptach table:
void softwareCoord3f(GLcontext *ctx, GLfloat x, GLfloat y, GLfloat z) { Driver::Context *context = ctx; Driver::SoftwareTNL &tnl = ctx->tnl;
// There will be no call as the function will be expanded inline tnl.Coord3F(x, y, z); }
Here you're converting a GLcontext * to a Driver::Context *. Can you do that because Mesa::Context has GLcontext as first member? Anyway, if that didn't work you could always do some fancy pointer arithmetics with the offset of the GLcontext in Driver::Context.
There's a slight misconception happening here -- the 'ctx' argument doesn't exist. The function should read something like:
void swv3f( GLfloat x, GLfloat y, GLfloat z )
{
GET_CONTEXT_FROM_THREAD_LOCAL_STORE( ctx )
// get tnl somehow
tnl->v3f( x, y, z )
}But why bother? tnl->v3f isn't virtual, so what's the point of having the implementation somewhere else? Why not just do it here?
Keith
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