* BView::TranslateBy(), BView::ScaleBy() and BView::RotateBy()
allow to conveniently modify the current affine transformation.
This makes it unnecessary to first read the current transform,
modify it, and then set it again.
Uses the new Pre...() methods of BAffineTransform.
* Also, remove setting the transform "through" to the BView even
while recording a BPicture, as this now results in transforms
being applied more than once.
* Add new clipping API for rectangles (ClipToRect, ClipToInverseRect)
and shapes (ClipToShape, ClipToInverseShape)
* Works with affine transforms and automatically switches from fast
region-based clipping to alpha-mask based clipping as necessary.
* Always self-intersecting, i.e. no state push required to further
narrow down the clipping region. All of the 4 new methods can be
mixed in any order.
* Add new methods
BView::BeginLayer(uint8 opacity)
BView::EndLayer()
* All drawing between begin and end of a layer is redirected onto an
intermediate bitmap. When ending the layer, this bitmap is
composited onto the view with the opacity given when the layer was
started.
* Layers can be nested arbitrarily and will be blended onto each
other in order. There can also be any arbitrary interleaving of
layer begin/end and drawing operations.
* Internally, drawing commands are redirected into a BPicture between
BeginLayer and EndLayer (but client code need not know or care
about this). Client code can also start/end other BPictures while
inside a layer.
* Uses the PictureBoundingBoxPlayer to determine the size of the
layer bitmap before allocating and drawing into it, so it does not
allocate more memory than necessary and -- more importantly -- it
will not alpha-composite more pixels than necessary.
* Drawing mode is always set to B_OP_ALPHA, blend mode to
(B_PIXEL_ALPHA, B_ALPHA_COMPOSITE) while inside layers. This is
necessary for (a) correct compositing output and (b) for
redirection of drawing into the intermediate bitmap, which uses the
renderer_region offset (in B_OP_COPY, the Painter does not use the
AGG renderer methods, it directly accesses the pixel data. This
would access out-of-bounds without the offset, so B_OP_COPY cannot
be allowed.)
To ensure these modes aren't changed, BView::SetDrawingMode()
and BView::SetBlendingMode() are ignored while inside a layer.
* The main motivation behind this new API is WebKit, which internally
expects such a layers functionality to be present. A performant and
reusable implementation of this functionality can only be done
server-side in app_server.
Everything untested, but compiles, so it must work. The idea is to introduce
BAffineTransform additionally to the existing Origin and Scale properties of
BViews. One may use it in parallel or as an alternative. Painter in app_server
is not yet aware of the additional transformation. It is however already used
to transform drawing coordinates. It probably needs to work differently,
perhaps only in Painter and AGGTextRenderer.
