46c71f04c9
It was introduced in
commit 9090dc1f3b27195f5defd35586ac79357992be21
Date: Mon Jan 18 18:27:19 2021 +0200
split OutputDevice from Window
and caused my GCC 10 '--enable-werror' build to fail with
In file included from /usr/include/c++/10/cassert:44,
from .../include/tools/ref.hxx:23,
from .../include/vcl/outdev.hxx:24,
from .../canvas/source/vcl/impltools.hxx:25,
from .../canvas/source/vcl/canvas.hxx:39,
from .../canvas/source/vcl/canvas.cxx:22:
.../canvas/source/vcl/outdevholder.hxx: In constructor ‘vclcanvas::OutDevHolder::OutDevHolder(OutputDevice&)’:
.../canvas/source/vcl/outdevholder.hxx:38:16: error: the compiler can assume that the address of ‘rOutDev’ will never be NULL [-Werror=address]
38 | assert(&rOutDev);
| ^~~~~~~~
cc1plus: all warnings being treated as errors
make[1]: *** [.../solenv/gbuild/LinkTarget.mk:301: /home/michi/development/git/libreoffice/workdir/CxxObject/canvas/source/vcl/canvas.o] Error 1
make[1]: *** Waiting for unfinished jobs....
In file included from .../include/comphelper/solarmutex.hxx:25,
from .../include/vcl/svapp.hxx:29,
from .../canvas/source/vcl/impltools.hxx:24,
from .../canvas/source/vcl/spritecanvas.hxx:44,
from .../canvas/source/vcl/spritecanvas.cxx:28:
.../canvas/source/vcl/outdevholder.hxx: In constructor ‘vclcanvas::OutDevHolder::OutDevHolder(OutputDevice&)’:
.../canvas/source/vcl/outdevholder.hxx:38:16: error: the compiler can assume that the address of ‘rOutDev’ will never be NULL [-Werror=address]
38 | assert(&rOutDev);
Change-Id: I9e8ef7e91dba847f4894124348f13755fc620fac
Reviewed-on: https://gerrit.libreoffice.org/c/core/+/115737
Tested-by: Jenkins
Reviewed-by: Michael Weghorn <m.weghorn@posteo.de>
UNO-based Graphics Backend
UNO-based graphics backend, lesser impedance to modern graphics APIs than vcl.
The canvas Framework
The canvas framework is the successor of the system GUI and graphics
backend VCL. Basic functionality is available, supplying just as much
features as necessary to provide a VCL-equivalent feature set (except
proper BiDi/CTL support).
The canvas framework consists of the following two modules, canvas and
cppcanvas. Additionally, a new generic graphics tooling is used (but
not exclusively by the canvas, Armin's drawinglayer module also make
use of it), which resides in basegfx.
The UNO API used by the canvas is primarily under
css::rendering, with css::rendering::XCanvas
being the central interface.
The slideshow Engine
The slideshow engine has replaced the former Impress-embedded
presentation framework with a fully independent UNO component, and it
is based on the canvas. Some features used there are only available
from canvas, like double-buffering, and hardware-accelerated
alpha-blending (currently not on all platforms).
Cairo canvas
Cairo canvas is one of backends of canvas component. canvas is mostly
used for slideshow rendering and also for emf+ rendering. we hoped it
will even be used by drawing layer, but it didn't happen (yet?) for
API look at offapi/com/sun/star/rendering/, the implementation is in
canvas and cppcanvas modules.
Cairo canvas backend uses Cairo library for rendering. Main advantage
is support of alpha transparency and in some cases accelerated
rendering.
The backend itself is quite old and stable, not many changes in that area lately, mostly changes for emf+ rendering, communication with vcl and bugfixes
Future Works
Look at Cairo canvas and situation when it is used
(mostly slideshow).
TODO
There still might be more cases when we can save some roundtrips when exchanging data with vcl.