cogl_pipeline_get_front_face_winding() is supposed to return a CoglWinding. It
takes a CoglPipeline as argument and does the following input validation:
g_return_val_if_fail (cogl_is_pipeline (pipeline),
COGL_PIPELINE_CULL_FACE_MODE_NONE);
The returned COGL_PIPELINE_CULL_FACE_MODE_NONE is not a winding.
The function was added with this check 8 years ago in
5369b3c601fc537db6712c27a5453fa11236c66b
I do not see any of the two options in the CoglWinding as particularly good
choice for a return value on bad input, but let's go with
COGL_WINDING_CLOCKWISE as that is equivalent with the behavior for all
these years.
Definitions of the two enums:
typedef enum
{
COGL_WINDING_CLOCKWISE,
COGL_WINDING_COUNTER_CLOCKWISE
} CoglWinding;
typedef enum
{
COGL_PIPELINE_CULL_FACE_MODE_NONE,
COGL_PIPELINE_CULL_FACE_MODE_FRONT,
COGL_PIPELINE_CULL_FACE_MODE_BACK,
COGL_PIPELINE_CULL_FACE_MODE_BOTH
} CoglPipelineCullFaceMode;
https://gitlab.gnome.org/GNOME/mutter/merge_requests/934
81bb4f0051