[cairo-bugs] [Bug 86200] New: cairo-matrix: invalid matrix created in _cairo_matrix_to_pixman_matrix_offset()

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=86200

            Bug ID: 86200
           Summary: cairo-matrix: invalid matrix created in
                    _cairo_matrix_to_pixman_matrix_offset()
           Product: cairo
           Version: 1.12.16
          Hardware: Other
                OS: All
            Status: NEW
          Severity: normal
          Priority: medium
         Component: general
          Assignee: chris at chris-wilson.co.uk
          Reporter: bfo at andred.net
        QA Contact: cairo-bugs at cairographics.org

Created attachment 109340
  --> https://bugs.freedesktop.org/attachment.cgi?id=109340&action=edit
test case

The attached test is a copy of the code in
_cairo_matrix_to_pixman_matrix_offset()

Using the embedded values for the matrix, the cairo code converts this into a
pixman_transform_t which can not be handled by pixman, due to 16 bit overflow.

I believe this particular matrix doesn't need any translation, as all values
fit nicely into 16 bit from the start for pixman. The end-result is that the
drawing operation fails, although it need not.


Not sure what the correct fix is, it could either check whether the matrix as
passed in needs any modification for pixman, or it could check whether a
smallest maximum norm was found before applying the matrix tranlation.

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