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, 1 insertions, 1 deletions

diff --git a/draw/draw_edge.c b/draw/draw_edge.c
index 41647b0e..5f2f45d3 100644
--- a/draw/draw_edge.c
+++ b/draw/draw_edge.c
@@ -702,7 +702,7 @@ fz_scan_convert_aa(fz_gel *gel, int eofill, const fz_irect *clip,
 	{
 		fz_free(ctx, alphas);
 		fz_free(ctx, deltas);
-		fz_throw(ctx, "scan conversion failed (malloc failure)");
+		fz_throw(ctx, FZ_ERROR_GENERIC, "scan conversion failed (malloc failure)");
 	}
 	memset(deltas, 0, (xmax - xmin + 1) * sizeof(int));
 	gel->alen = 0;