This renames cogl_offscreen_new_to_texture to
cogl_offscreen_new_with_texture. The intention is to then cherry-pick
this back to the cogl-1.16 branch so we can maintain a parallel
cogl_offscreen_new_to_texture() function which keeps the synchronous
allocation semantics that some clutter applications are currently
relying on.
Reviewed-by: Neil Roberts <neil@linux.intel.com>
(cherry picked from commit ecc6d2f64481626992b2fe6cdfa7b999270b28f5)
Note: Since we can't break the 1.x api on this branch this keeps a
thin shim around cogl_offscreen_new_with_texture to implement
cogl_offscreen_new_to_texture with its synchronous allocation
semantics.
This splits out the cogl_path_ api into a separate cogl-path sub-library
like cogl-pango and cogl-gst. This enables developers to build Cogl with
this sub-library disabled if they don't need it which can be useful when
its important to keep the size of an application and its dependencies
down to a minimum. The functions cogl_framebuffer_{fill,stroke}_path
have been renamed to cogl_path_{fill,stroke}.
There were a few places in core cogl and cogl-gst that referenced the
CoglPath api and these have been decoupled by using the CoglPrimitive
api instead. In the case of cogl_framebuffer_push_path_clip() the core
clip stack no longer accepts path clips directly but it's now possible
to get a CoglPrimitive for the fill of a path and so the implementation
of cogl_framebuffer_push_path_clip() now lives in cogl-path and works as
a shim that first gets a CoglPrimitive and uses
cogl_framebuffer_push_primitive_clip instead.
We may want to consider renaming cogl_framebuffer_push_path_clip to
put it in the cogl_path_ namespace.
Reviewed-by: Neil Roberts <neil@linux.intel.com>
(cherry picked from commit 8aadfd829239534fb4ec8255cdea813d698c5a3f)
So as to avoid breaking the 1.x API or even the ABI since we are quite
late in the 1.16 development cycle the patch was modified to build
cogl-path as a noinst_LTLIBRARY before building cogl and link the code
directly into libcogl.so as it was previously. This way we can wait
until the start of the 1.18 cycle before splitting the code into a
separate libcogl-path.so.
This also adds shims for cogl_framebuffer_fill/stroke_path() to avoid
breaking the 1.x API/ABI.
Almost nothing draws attributes directly and for those things that do
it's trivial to adapt them to instead draw via the cogl_primitive api.
This simplifies the Cogl api a bit.
Reviewed-by: Neil Roberts <neil@linux.intel.com>
(cherry picked from commit 7395925bcc01aad6c695fd0d9af78b784b3c64d4)
Conflicts:
cogl/cogl-framebuffer.c
cogl/cogl-framebuffer.h
When splitting out the CoglPath api we saw that we would be left with
inconsistent drawing apis if the drawing apis in core Cogl were lumped
into the cogl_framebuffer_ api considering other Cogl sub-libraries or
that others will want to create higher level drawing apis outside of
Cogl but can't use the same namespace.
So that we can aim for a more consistent style this adds a
cogl_primitive_draw() api, comparable to cogl_path_fill() or
cogl_pango_show_layout() that's intended to replace
cogl_framebuffer_draw_primitive()
Note: the attribute and rectangle drawing apis are still in the
cogl_framebuffer_ namespace and this might potentially change but in
these cases there is no single object representing the thing being drawn
so it seems a more reasonable they they live in the framebuffer
namespace for now.
Note: the cogl_framebuffer_draw_primitive() api isn't removed by this
patch so it can more conveniently be cherry picked to the 1.16 branch so
we can mark it deprecated for a short while. Even though it's marked as
experimental api we know that there are people using the api so we'd
like to give them a chance to switch to the new api.
Reviewed-by: Neil Roberts <neil@linux.intel.com>
(cherry picked from commit 418912b93ff81a47f9b38114d05335ab76277c48)
Conflicts:
cogl-pango/cogl-pango-display-list.c
cogl/Makefile.am
cogl/cogl-framebuffer.c
cogl/cogl-pipeline-layer-state.h
cogl/cogl2-path.c
cogl/driver/gl/cogl-clip-stack-gl.c
Cogl publicly exposes the depth buffer state so we might as well have
a function to query the number of depth bits of a framebuffer.
Reviewed-by: Robert Bragg <robert@linux.intel.com>
(cherry picked from commit 853143eb10387f50f8d32cf09af31b8829dc1e01)
Symbols changed names, %1 makes gtk-doc sad and some referenced symbols
were missing in the -sections.txt file.
(cherry picked from commit c12919c321186ac7b223bc4f82c588ca2f199d67)
Argument names and @$arg suffered from various little mismatches, fix
them in a batch commit.
(cherry picked from commit d2ac3c5a88d980e7519c98bd261111b93cf73a6e)
We have found several times now when writing code using Cogl that it
would really help if Cogl's matrix stack api was public as a utility
api. In Rig for example we want to avoid redundant arithmetic when
deriving the matrices of entities used to render and we aren't able
to simply use the framebuffer's matrix stack to achieve this. Also when
implementing cairo-cogl we found that it would be really useful if we
could have a matrix stack utility api.
(cherry picked from commit d17a01fd935d88fab96fe6cc0b906c84026c0067)
This fixes some problems which were stopping --disable-glib from
working properly:
• A lot of the public headers were including glib.h. This shouldn't be
necessary because the API doesn't expose any glib types. Otherwise
any apps would require glib in order to get the header.
• The public headers were using G_BEGIN_DECLS. There is now a
replacement macro called COGL_BEGIN_DECLS which is defined in
cogl-types.h.
• A similar fix has been done for G_GNUC_NULL_TERMINATED and
G_GNUC_DEPRECATED.
• The CFLAGS were not including $(builddir)/deps/glib which was
preventing it finding the generated glibconfig.h when building out
of tree.
Reviewed-by: Robert Bragg <robert@linux.intel.com>
(cherry picked from commit 4138b3141c2f39cddaea3d72bfc04342ed5092d0)
Annotate that the float* is an out parameter that points to a caller
allocated array of 4 floats.
Reviewed-by: Robert Bragg <robert@linux.intel.com>
(cherry picked from commit f40b0d03d796c16c62f4937e99e16de084fc6b9a)
Although we use GLib internally in Cogl we would rather not leak GLib
api through Cogl's own api, except through explicitly namespaced
cogl_glib_ / cogl_gtype_ feature apis.
One of the benefits we see to not leaking GLib through Cogl's public API
is that documentation for Cogl won't need to first introduce the Glib
API to newcomers, thus hopefully lowering the barrier to learning Cogl.
This patch provides a Cogl specific typedef for reporting runtime errors
which by no coincidence matches the typedef for GError exactly. If Cogl
is built with --enable-glib (default) then developers can even safely
assume that a CoglError is a GError under the hood.
This patch also enforces a consistent policy for when NULL is passed as
an error argument and an error is thrown. In this case we log the error
and abort the application, instead of silently ignoring it. In common
cases where nothing has been implemented to handle a particular error
and/or where applications are just printing the error and aborting
themselves then this saves some typing. This also seems more consistent
with language based exceptions which usually cause a program to abort if
they are not explicitly caught (which passing a non-NULL error signifies
in this case)
Since this policy for NULL error pointers is stricter than the standard
GError convention, there is a clear note in the documentation to warn
developers that are used to using the GError api.
Reviewed-by: Neil Roberts <neil@linux.intel.com>
(cherry picked from commit b068d5ea09ab32c37e8c965fc8582c85d1b2db46)
Note: Since we can't change the Cogl 1.x api the patch was changed to
not rename _error_quark() functions to be _error_domain() functions and
although it's a bit ugly, instead of providing our own CoglError type
that's compatible with GError we simply #define CoglError to GError
unless Cogl is built with glib disabled.
Note: this patch does technically introduce an API break since it drops
the cogl_error_get_type() symbol generated by glib-mkenum (Since the
CoglError enum was replaced by a CoglSystemError enum) but for now we
are assuming that this will not affect anyone currently using the Cogl
API. If this does turn out to be a problem in practice then we would be
able to fix this my manually copying an implementation of
cogl_error_get_type() generated by glib-mkenum into a compatibility
source file and we could also define the original COGL_ERROR_ enums for
compatibility too.
Note: another minor concern with cherry-picking this patch to the 1.14
branch is that an api scanner would be lead to believe that some APIs
have changed, and for example the gobject-introspection parser which
understands the semantics of GError will not understand the semantics of
CoglError. We expect most people that have tried to use
gobject-introspection with Cogl already understand though that it is not
well suited to generating bindings of the Cogl api anyway and we aren't
aware or anyone depending on such bindings for apis involving GErrors.
(GnomeShell only makes very-very minimal use of Cogl via the gjs
bindings for the cogl_rectangle and cogl_color apis.)
The main reason we have cherry-picked this patch to the 1.14 branch
even given the above concerns is that without it it would become very
awkward for us to cherry-pick other beneficial patches from master.
This commit introduces some new framebuffer api to be able to
enable texture based depth buffers for a framebuffer (currently
only supported for offscreen framebuffers) and once allocated
to be able to retrieve the depth buffer as a texture for further
usage, say, to implement shadow mapping.
The API works as follow:
* Before the framebuffer is allocated, you can request that a depth
texture is created with
cogl_framebuffer_set_depth_texture_enabled()
* cogl_framebuffer_get_depth_texture() can then be used to grab a
CoglTexture once the framebuffer has been allocated.
cogl_framebuffer_set_{projection,modelview}_matrix don't need to read
from the matrix argument so they should probably take a const pointer.
Reviewed-by: Robert Bragg <robert@linux.intel.com>
(cherry picked from commit 710d6af053aca97935b54f9ff68858ef51f4482b)
This adds the following new functions to apply a rotation described by
a euler or a quaternion to either a CoglMatrix or directly to the
modelview stack of a framebuffer:
cogl_matrix_rotate_quaternion
cogl_matrix_rotate_euler
cogl_framebuffer_rotate_quaternion
cogl_framebuffer_rotate_euler
The direct framebuffer functions have corresponding functions in the
CoglMatrixStack to store an entry describing the rotation.
Reviewed-by: Robert Bragg <robert@linux.intel.com>
(cherry picked from commit 5064315678b496395e1d01f266f322d73e55e324)
The existing functions for stroking and filling a path depend on the
global framebuffer and source stacks. These are now replaced with
cogl_framebuffer_{stroke,fill}_path which get explicitly passed the
framebuffer and pipeline.
Reviewed-by: Robert Bragg <robert@linux.intel.com>
(cherry picked from commit 713a8f8160bc5884b091c69eb7a84b069e0950e6)
The coding style has for a long time said to avoid using redundant glib
data types such as gint or gchar etc because we feel that they make the
code look unnecessarily foreign to developers coming from outside of the
Gnome developer community.
Note: When we tried to find the historical rationale for the types we
just found that they were apparently only added for consistent syntax
highlighting which didn't seem that compelling.
Up until now we have been continuing to use some of the platform
specific type such as gint{8,16,32,64} and gsize but this patch switches
us over to using the standard c99 equivalents instead so we can further
ensure that our code looks familiar to the widest range of C developers
who might potentially contribute to Cogl.
So instead of using the gint{8,16,32,64} and guint{8,16,32,64} types this
switches all Cogl code to instead use the int{8,16,32,64}_t and
uint{8,16,32,64}_t c99 types instead.
Instead of gsize we now use size_t
For now we are not going to use the c99 _Bool type and instead we have
introduced a new CoglBool type to use instead of gboolean.
Reviewed-by: Neil Roberts <neil@linux.intel.com>
(cherry picked from commit 5967dad2400d32ca6319cef6cb572e81bf2c15f0)
Because the wayland-client-protocol.h header defines symbols that
collide with the wayland-server-protocol.h header we allow applications
to explicitly ensure that they are only including one at a time by
exposing corresponding <cogl/cogl-wayland-client.h> and
<cogl/cogl-wayland-server.h> headers. This also adds a missing guard to
cogl-texture-2d.h that it isn't included directly.
Reviewed-by: Neil Roberts <neil@linux.intel.com>
• The documentation for the framebuffer and texture interfaces had a
mis-matching open and close <note> tag so DocBook got upset and the
whole documentation disappeared.
• A lot of symbols from the cogl_framebuffer_* interface were missing
from the cogl-2.0-experimental-sections.txt file.
• cogl_framebuffer_frustum had the wrong version in its Since tag:
Reviewed-by: Robert Bragg <robert@linux.intel.com>
This adds experimental 2.0 api replacements for the cogl_rectangle[_*]
functions that don't depend on having a current pipeline set on the
context via cogl_{set,push}_source() or having a current framebuffer set
on the context via cogl_push_framebuffer(). The aim for 2.0 is to switch
away from having a statefull context that affects drawing to having
framebuffer drawing apis that are explicitly passed a framebuffer and
pipeline.
To test this change several of the conformance tests were updated to use
this api instead of cogl_rectangle and
cogl_rectangle_with_texture_coords. Since it's quite laborious going
through all of the conformance tests the opportunity was taken to make
other clean ups in the conformance tests to replace other uses of
1.x api with experimental 2.0 api so long as that didn't affect what was
being tested.
This was causing the DocBook for the documentation to be invalid so
all of the framebuffer documentation disappeared.
Reviewed-by: Robert Bragg <robert@linux.intel.com>
This adds a public convenience wrapper around
cogl_framebuffer_read_pixels_into_bitmap which allocates a temporary
CoglBitmap to read into the application's own buffer. This can only be
used for the 99% common case where the rowstride is exactly the
bpp*width and the source is the color buffer.
Reviewed-by: Robert Bragg <robert@linux.intel.com>
This option to GCC makes it give a warning whenever a global function
is defined without a declaration. This should catch cases were we've
defined a function but forgot to put it in a header. In that case it
is either only used within one file so we should make it static or we
should declare it in a header.
The following changes where made to fix problems:
• Some functions were made static
• cogl-path.h (the one containing the 1.0 API) was split into two
files, one defining the functions and one defining the enums so that
cogl-path.c can include the enum and function declarations from the
2.0 API as well as the function declarations from the 1.0 API.
• cogl2-clip-state has been removed. This only had one experimental
function called cogl_clip_push_from_path but as this is unstable we
might as well remove it favour of the equivalent cogl_framebuffer_*
API.
• The GLX, SDL and WGL winsys's now have a private header to define
their get_vtable function instead of directly declaring in the C
file where it is called.
• All places that were calling COGL_OBJECT_DEFINE need to have the
cogl_is_whatever function declared so these have been added either
as a public function or in a private header.
• Some files that were not including the header containing their
function declarations have been fixed to do so.
• Any unused error quark functions have been removed. If we later want
them we should add them back one by one and add a declaration for
them in a header.
• _cogl_is_framebuffer has been renamed to cogl_is_framebuffer and
made a public function with a declaration in cogl-framebuffer.h
• Similarly for CoglOnscreen.
• cogl_vdraw_indexed_attributes is called
cogl_framebuffer_vdraw_indexed_attributes in the header. The
definition has been changed to match the header.
• cogl_index_buffer_allocate has been removed. This had no declaration
and I'm not sure what it's supposed to do.
• CoglJournal has been changed to use the internal CoglObject macro so
that it won't define an exported cogl_is_journal symbol.
• The _cogl_blah_pointer_from_handle functions have been removed.
CoglHandle isn't used much anymore anyway and in the few places
where it is used I think it's safe to just use the implicit cast
from void* to the right type.
• The test-utils.h header for the conformance tests explicitly
disables the -Wmissing-declaration option using a pragma because all
of the tests declare their main function without a header. Any
mistakes relating to missing declarations aren't really important
for the tests.
• cogl_quaternion_init_from_quaternion and init_from_matrix have been
given declarations in cogl-quaternion.h
Reviewed-by: Robert Bragg <robert@linux.intel.com>
This adds a public function to read pixels from a framebuffer into a
CoglBitmap. This replaces the internal function
_cogl_read_pixels_with_rowstride because a CoglBitmap contains a
rowstride so it can be used for the same purpose. A CoglBitmap already
has public API to make one that points to a CoglPixelBuffer so this
function can be used to read pixels into a PBO. It also avoids the
need to push the framebuffer on to the context's stack so it provides
a function which can be used in the 2.0 API after the stack is
removed.
Reviewed-by: Robert Bragg <robert@linux.intel.com>
So we can get to the point where cogl.h is merely an aggregation of
header includes for the 1.x api this moves all the function prototypes
and type definitions into a cogl-context.h and a new cogl1-context.h.
Ideally no code internally should ever need to include cogl.h as it just
represents the public facing header for accessing the 1.x api which
should only be used by Clutter.
Reviewed-by: Neil Roberts <neil@linux.intel.com>
This adds cogl_framebuffer_ apis for drawing attributes and primitives
that replace corresponding apis that depend on the default CoglContext.
This is part of the on going effort to adapt the Cogl api so it no
longer depends on a global context variable.
All the new drawing functions also take an explicit pipeline argument
since we are also aiming to avoid being a stateful api like Cairo and
OpenGL. Being stateless makes it easier for orthogonal components to
share access to the GPU. Being stateless should also minimize any
impedance miss-match for those wanting to build higher level stateless
apis on top of Cogl.
Note: none of the legacy, global state options such as
cogl_set_depth_test_enabled(), cogl_set_backface_culling_enabled() or
cogl_program_use() are supported by these new drawing apis and if set
will simply be silently ignored.
Reviewed-by: Neil Roberts <neil@linux.intel.com>
We are in the process of removing all _EXP suffix mangling for
experimental APIs (Ref: c6528c4b6c) and adding missing gtk-doc
comments so that we can instead rely on the "Stability: unstable"
markers in the gtk-doc comments. This patch tackles the cogl framebuffer
symbols.
This adds CoglFramebuffer methods for accessing the clip stack. We plan
on making some optimizations to how framebuffer state is flushed which
will require us to track when a framebuffer's clip state has changed.
This api also ties in to the longer term goal of removing the need for a
default global CoglContext since these methods are all implicitly
related to a specific context via their framebuffer argument.
Reviewed-by: Neil Roberts <neil@linux.intel.com>
This adds a cogl_framebuffer_identity_matrix() method that can be used
to reset the current modelview matrix to the identity matrix.
Reviewed-by: Neil Roberts <neil@linux.intel.com>
This adds cogl_framebuffer_ methods to update the modelview and
projection matrix stacks to replace functions like cogl_translate(),
cogl_rotate() and cogl_scale() etc.
This is part of the on-going effort to get rid of the global CoglContext
pointer since the existing methods don't take an explicit pointer to a
CoglContext. All the methods are now related to a context via the
framebuffer.
We added framebuffer methods instead of direct context methods because
the matrix stacks are per-framebuffer and as well as removing the global
CoglContext we would rather aim for a more direct state access API
design than, say, cairo or OpenGL, so we'd like to avoid needing the
cogl_push/pop_framebuffer(). We anticipate that Cogl will mostly be
consumed by middleware graphics layers such as toolkits or game engines
and feel that a more stateless model will avoid impedance mismatches if
higher levels want to expose a stateless model to their developers and
statefullness can still be added by higher levels if really desired.
Reviewed-by: Neil Roberts <neil@linux.intel.com>
It's useful to be able to query back the number of
point_samples_per_pixel that may have previously be chosen using
cogl_framebuffer_set_samples_per_pixel().
Reviewed-by: Neil Roberts <neil@linux.intel.com>
This factors out the CoglOnscreen code from cogl-framebuffer.c so we now
have cogl-onscreen.c, cogl-onscreen.h and cogl-onscreen-private.h.
Notably some of the functions pulled out are currently namespaced as
cogl_framebuffer but we know we are planning on renaming them to be in
the cogl_onscreen namespace; such as cogl_framebuffer_swap_buffers().
Reviewed-by: Neil Roberts <neil@linux.intel.com>
This adds a new experimental function, cogl_framebuffer_finish(), which
can be used to explicitly synchronize the CPU with the GPU. It's rare
that this level of explicit synchronization is desirable but for example
it can be useful during performance analysys to make sure measurements
reflect the working time of the GPU not just the time to queue commands.
Reviewed-by: Neil Roberts <neil@linux.intel.com>
This adds support for multisample rendering to offscreen framebuffers.
After an offscreen framebuffer is first instantiated using
cogl_offscreen_new_to_texture() it is then possible to use
cogl_framebuffer_set_samples_per_pixel() to request multisampling before
the framebuffer is allocated. This also adds
cogl_framebuffer_resolve_samples() for explicitly resolving point
samples into pixels. Even though we currently only support the
IMG_multisampled_render_to_texture extension which doesn't require an
explicit resolve, the plan is to also support the
EXT_framebuffer_multisample extension which uses the framebuffer_blit
extension to issue an explicit resolve.
Reviewed-by: Neil Roberts <neil@linux.intel.com>
This adds cogl_framebuffer_discard_buffers API that allows applications
to explicitly discard depth and stencil buffers which really helps when
using a tile based GPU architexture by potentially avoiding the need to
save the results of depth and stencil buffer changes to system memory
between frames since these can usually be handled directly with on-chip
memory instead.
The semantics for cogl_framebuffer_swap_buffers and
cogl_framebuffer_swap_region are now documented to include an implicit
discard of all buffers, including the color buffer.
We now recommend that all rendering to a CoglOffscreen framebuffer
should be followed by a call like:
cogl_framebuffer_discard_buffers (fb,
COGL_BUFFER_BIT_DEPTH|
COGL_BUFFER_BIT_STENCIL);
Reviewed-by: Neil Roberts <neil@linux.intel.com>
This adds a new function, cogl_framebuffer_get_color_format() to be able
to query the common pixel format for any color buffers attached to a
given CoglFramebuffer. For example an offscreen framebuffer created
using cogl_offscreen_new_to_texture() would have a format matching the
texture.
Reviewed-by: Neil Roberts <neil@linux.intel.com>
Cogl aims to consistently put the origin of 2D objects at the top-left
instead of the bottom left as OpenGL does, but there was an oversight
and the experimental cogl_framebuffer_swap_region API was accepting
coordinates relative to the bottom left. Cogl will now flip the user's
given rectangles to be relative to the bottom of the framebufffer before
sending them to APIs like glXCopySubBuffer and glBlitFramebuffer.
Reviewed-by: Neil Roberts <neil@linux.intel.com>
This makes cogl_framebuffer_clear and cogl_framebuffer_clear4f public as
experimental API. Since these functions take explicit framebuffer
pointers you don't need to push/pop a framebuffer just to clear it. Also
these functions are implicitly tied to a specific CoglContext via the
framebuffer pointer unlike cogl_clear.
Reviewed-by: Neil Roberts <neil@linux.intel.com>
This adds a function to query what CoglContext a given framebuffer
belongs too. This can be useful if you pass framebuffer pointers around
and at some point you want to create another framebuffer as part of the
same context as a given framebuffer without assuming there is a single
default context.
Reviewed-by: Neil Roberts <neil@linux.intel.com>
The cogl_framebuffer_get_blue_bits was defined 2 times-fix to use the
correct define for cogl_framebuffer_get_alpha_bits
Reviewed-by: Neil Roberts <neil@linux.intel.com>
This adds CoglPipeline and CoglFramebuffer support for setting a color
mask which is a bit mask defining which color channels should be written
to the current framebuffer.
The final color mask is the intersection of the framebuffer color mask
and the pipeline color mask. The framebuffer mask affects all rendering
to the framebuffer while the pipeline masks can be used to affect
individual primitives.
Reviewed-by: Neil Roberts <neil@linux.intel.com>
This adds a getter and setter for requesting dithering to be enabled.
Dithering is a hardware dependent technique to increase the visible
color resolution beyond what the underlying hardware supports by playing
tricks with the colors placed into the framebuffer to give the illusion
of other colors. (For example this can be compared to half-toning used
by some news papers to show varying levels of grey even though their may
only be black and white are available).
The results of enabling dithering are platform dependent and may have no
effect.
Signed-off-by: Neil Roberts <neil@linux.intel.com>
There were several CoglOnscreen functions named like:
cogl_onscreen_<platform>_blah instead of cogl_<platform>_onscreen_blah
so this patch updates those to be consistent with other platform
specific apis we have in cogl.
Signed-off-by: Neil Roberts <neil@linux.intel.com>
This adds a description for the cogl-framebuffer section and adds lots
of missing symbols to the 2.0 reference manual.
Signed-off-by: Neil Roberts <neil@linux.intel.com>
This exposes the previously internal only
_cogl_framebuffer_get_red/green/blue/alpha_bits() functions as 2.0
experimental API.
Signed-off-by: Neil Roberts <neil@linux.intel.com>
This exposes experimental cogl_framebuffer APIs for getting and setting
a viewport without having to refer to the implicit CoglContext. It adds
the following experimental API:
cogl_framebuffer_set_viewport
cogl_framebuffer_get_viewport4fv
cogl_framebuffer_get_viewport_x
cogl_framebuffer_get_viewport_y
cogl_framebuffer_get_viewport_width
cogl_framebuffer_get_viewport_height
Signed-off-by: Neil Roberts <neil@linux.intel.com>
