Exception handling changes

In preparation for work on progressive loading, update the exception
handling scheme slightly.

Until now, exceptions (as thrown with fz_throw, and caught with
fz_try/fz_catch) have merely had an informative string. They have
never had anything that can be compared to see if an error is of
a particular type.

We now introduce error codes; when we fz_throw, we now always
give an error code, and can optionally (using fz_throw_message)
give both an error code and an informative string.

When we fz_rethrow from within a fz_catch, both the error code and
the error message is maintained. Using fz_rethrow_message we can
'improve' the error message, but the code is maintained.

The error message can be read out using fz_caught_message() and the
error code can be read as fz_caught().

Currently we only define a 'generic' error. This will expand in future
versions to include other error types that may be tested for.

1 files changed, 2 insertions, 2 deletions

diff --git a/fitz/res_shade.c b/fitz/res_shade.c
index 676f375c..b13dc215 100644
--- a/fitz/res_shade.c
+++ b/fitz/res_shade.c
@@ -914,7 +914,7 @@ fz_process_mesh(fz_context *ctx, fz_shade *shade, const fz_matrix *ctm,
 	else if (shade->type == FZ_MESH_TYPE7)
 		fz_process_mesh_type7(ctx, shade, ctm, &painter);
 	else
-		fz_throw(ctx, "Unexpected mesh type %d\n", shade->type);
+		fz_throw(ctx, FZ_ERROR_GENERIC, "Unexpected mesh type %d\n", shade->type);
 }
 
 static fz_rect *
@@ -1006,7 +1006,7 @@ fz_bound_mesh(fz_context *ctx, fz_shade *shade, fz_rect *bbox)
 		shade->type == FZ_MESH_TYPE7)
 		fz_bound_mesh_type4567(ctx, shade, bbox);
 	else
-		fz_throw(ctx, "Unexpected mesh type %d\n", shade->type);
+		fz_throw(ctx, FZ_ERROR_GENERIC, "Unexpected mesh type %d\n", shade->type);
 
 	return bbox;
 }