Bug 7049

Summary:	cairo_*_destroy() lack status return
Product:	cairo	Reporter:	Steve Chaplin <d74n5pohf9>
Component:	general	Assignee:	Carl Worth <cworth>
Status:	RESOLVED MOVED	QA Contact:	cairo-bugs mailing list <cairo-bugs>
Severity:	normal
Priority:	high	CC:	tiwari.shekhar13
Version:	1.1.7
Hardware:	x86 (IA32)
OS:	Linux (All)
Whiteboard:
i915 platform:		i915 features:
Attachments:	demonstrate that error status is not reported Updated test case with explicit cairo_surface_finish()

Description Steve Chaplin 2006-05-27 15:28:50 UTC

I'm trying to add PS/PDF/SVG stream support to pycairo and want to make sure
that exceptions are raised when a stream write error occurs. The stream write
function returns CAIRO_STATUS_WRITE_ERROR on a write error but the surface and
cairo context ignore this and are not given an error status. So what is the
purpose of returning CAIRO_STATUS_WRITE_ERROR?

The attached program demonstrates stream errors, for me it outputs:
status (CAIRO_STATUS_SUCCESS is 0)
libpng error: Write Error
PNG 1
PS  0, 0
PS  0, 0
PS  0, 0
I/O error : flush error

I would expect all the status numbers to be non-zero (like PNG).

Comment 1 Steve Chaplin 2006-05-27 15:31:18 UTC

Created attachment 5747 [details]
demonstrate that error status is not reported

Comment 2 Chris Wilson 2007-09-25 16:54:51 UTC

The problem with the test case is that the surfaces do not attempt to write to the stream until cairo_surface_finish() (in this case called implicitly from cairo_surface_destroy) at which point the error status has been silently lost.

After adding cairo_surface_finish() before the cairo_surface_status(), the test output becomes:
status (CAIRO_STATUS_SUCCESS is 0)
PNG 11 (error while writing to output stream)
PS   0 (success), 11 (error while writing to output stream)
PDF  0 (success), 11 (error while writing to output stream)
SVG  0 (success), 11 (error while writing to output stream)

Comment 3 Chris Wilson 2007-09-25 16:55:33 UTC

Created attachment 11755 [details]
Updated test case with explicit cairo_surface_finish()

Comment 4 Chris Wilson 2008-09-29 03:36:45 UTC

Stephen, I've added test cases to ensure that a write error is propagated back to the application - but given the API constraints the application must call cairo_surface_finish() explicitly to ensure that the surface is written out (which requires fiddling with cairo_surface_get_refererence_count() in its surface_destroy function for PyCairo to support throwing exceptions from write-out). Retitling to reflect issue with current cairo_*_destroy() API.

Comment 5 Behdad Esfahbod 2008-09-29 04:58:17 UTC

We've discussed changing _destroy() functions to return cairo_status before.  Not sure how nicely that maps to language bindings though.

Comment 6 GitLab Migration User 2018-08-25 13:57:13 UTC

-- GitLab Migration Automatic Message --

This bug has been migrated to freedesktop.org's GitLab instance and has been closed from further activity.

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