In moving src/glx/apple over to glapi this past week, I used our dispatch table
code from xserver/hw/xquartz/GL/indirect.c as the model for creating our
_glapi_table. Our table should contain pointers into OSX's OpenGL
implementation, so the call is just passed along to that implementation.
Currently, the table is created by calling SET_* for every possibly entry and
uses dlsym() with an appropriate handle to get the function pointer:
SET_Accum(__ogl_framework_api, dlsym(handle, "glAccum"));
SET_AlphaFunc(__ogl_framework_api, dlsym(handle, "glAlphaFunc"));
...
This works well enough, but it is not very robust, especially in cases where
there are multiple aliases for a particular function. If OpenGL.framework
provides an implementation as one of the other aliases, we don't end up picking
it up. I've special cased some, but this is just something that should be
easily generated rather than hand edited.
It would be nice to have an api in glapi to handle this. Someone familiar with
the specs parsing / code generation bits should be able to do it fairly easily.
I'm envisioning something like this:
struct _glapi_table *
_glapi_create_table_from_handle(void *handle, const char *symbol_prefix);
Which I would call like:
void *handle = dlopen(opengl_framework_path, RTLD_LOCAL);
__ogl_framework_api = _glapi_create_table_from_handle(handle, "gl");
The implementation would be something like:
struct _glapi_table *
_glapi_create_table_from_handle(void *handle, const char *symbol_prefix) {
struct _glapi_table *disp = calloc(1, sizeof(struct _glapi_table));
char symboln[512];
if(!disp)
return NULL;
// Simple cases
snprintf(symboln, sizeof(symboln), "%sAccum", symbol_prefix);
SET_Accum(disp, dlsym(handle, symboln));
snprintf(symboln, sizeof(symboln), "%sAlphaFunc", symbol_prefix);
SET_AlphaFunc(disp, dlsym(handle, symboln));
...
// More complex aliasing example
snprintf(symboln, sizeof(symboln), "%sFramebufferTextureLayerEXT",
symbol_prefix);
SET_FramebufferTextureLayerEXT(disp, dlsym(handle, symboln));
if(!disp->FramebufferTextureLayerEXT) {
snprintf(symboln, sizeof(symboln), "%sFramebufferTextureLayerARB",
symbol_prefix);
SET_FramebufferTextureLayerEXT(disp, dlsym(handle, symboln));
}
if(!disp->FramebufferTextureLayerEXT) {
snprintf(symboln, sizeof(symboln), "%sFramebufferTextureLayer",
symbol_prefix);
SET_FramebufferTextureLayerEXT(disp, dlsym(handle, symboln));
}
...
return disp;
}
This seems like something that would be useful outside of just the darwin case.
Hopefully someone with more experience in the specs code generation code would
be able to do this (or at least point me in the right direction if nobody is
willing to tackle it themselves ... I'm guessing gen/gl_table.py is a good
place to start ...).
And before I go down this road, is this the right approach for implementing
this API, or is there another way that you'd recommend?
Thanks,
Jeremy
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