This function is supposed to describe the backend in use. The describe
function is optional - and therefore initialized as NULL everywhere.
Note:
It is well known that the xlib backend uses X. What is not known is what
version the server supports or what graphics card it is running on. That
is the information the describe vfunc is supposed to provide.
Text with size 0 has a singular scale matrix, thus requires special
handling to avoid invalidating the context where it is used.
Fixes pthread-show-text and text-zero-len (they failed with assertion
when ran using the user font backend).
Currently the translation component of the scaled_font scale matrix
is applied by gstate and only linear components should be applied in
font backends.
Fixes font-matrix-translation (when using user-font as font backend).
glyph_path was taking into account the translation (which currently
is already applied in gstate) and the sign of the elements of the
matrices was not explained.
Use scale instead of manually compositing font_matrix and ctm and
composite it with the context ctm, so that no workaround for clipping
is needed anymore.
I don't know why _cairo_boilerplate_xlib_window_create_surface()
is in the Render-only section of the code, but since it is, this
patch makes the boilerplate at least compile if we don't have
Render support built in.
On error, surface creation functions should always return a surface
created with _cairo_surface_create_in_error() instead of a new surface
in an error state. This simplifies internal code as no refcounting has
to be done.
Under the restrictive conditions where we are doing an untransformed
contained upload of an image into a matching surface, perform it in
place. The drivers will attempt to stream such uploads efficiently, far
more so than our code.
Previously, the code returned a status and required the caller to mangle
this status with his own status. Now, the function takes the previous
status ass an argument and does the mangling itself.
Also contains fixes for all the callers to actually check the return
value - which is now rather trivial as it just requires passing through
the status variable.
When acquiring the GL context, do not assert that the GL context is not
in an error state. Do not even call _cairo_error(). Handling GL errors
in other code is not Cairo's responsibility.
Instead just clear all previous errors so we don't accidentally set
surfaces into error states to unrelated errors.
Now that we probably call _cairo_error() on every GL error, there is no
need to use custom methods to catch those errors. The usual breakpoint
is enough.
