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[CGD2D] Draw primitives with Porter-Duff blend modes #1389

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DHowett-MSFT opened this issue Nov 15, 2016 · 1 comment · Fixed by #2222
Closed

[CGD2D] Draw primitives with Porter-Duff blend modes #1389

DHowett-MSFT opened this issue Nov 15, 2016 · 1 comment · Fixed by #2222
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Area-Foundation SubArea-CoreGraphics Task
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1703

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@DHowett-MSFT
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DHowett-MSFT commented Nov 15, 2016 •
edited by rajsesh
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Direct2D supports a subset of CG's blend modes as direct composition modes, and a subset of CG's porter-duff blend modes with its blend effect.

The blend effect, however, requires a full target readback and recompose.

The scope of this issue is to support only the basic non-blend-effect composition modes for 1611.

kCGBlendModeNormal = kCGBlendModeSourceOver
kCGBlendModeSourceOver
kCGBlendModeDestinationOver
kCGBlendModeSourceIn
kCGBlendModeDestinationIn
kCGBlendModeSourceOut
kCGBlendModeDestinationOut
kCGBlendModeSourceAtop
kCGBlendModeDestinationAtop
kCGBlendModeXOR
kCGBlendModePlusLighter
kCGBlendModeCopy
kCGBlendModePlusDarker // Not supported
@DHowett-MSFT DHowett-MSFT added this to the 1611 milestone Nov 15, 2016
@DHowett-MSFT DHowett-MSFT self-assigned this Nov 15, 2016
@rajsesh rajsesh modified the milestones: 1612, 1611 Nov 18, 2016
@rajsesh rajsesh changed the title [CGD2D] Draw primitives with blend modes (composite only). [CGD2D] Draw primitives with blend modes (composite only, porter-def and clear). Nov 18, 2016
@rajsesh rajsesh modified the milestones: 1701, 1612 Dec 16, 2016
@rajsesh
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rajsesh commented Dec 16, 2016

Still have some open issues here that need to be sorted out. May not be required for merge back to develop.

@rajsesh rajsesh modified the milestones: 1702, 1701 Jan 6, 2017
@rajsesh rajsesh modified the milestones: 1703, 1702, 1704 Jan 27, 2017
@DHowett-MSFT DHowett-MSFT mentioned this issue Feb 1, 2017
Merged
@rajsesh rajsesh modified the milestones: 1703, 1704 Feb 23, 2017
@DHowett-MSFT DHowett-MSFT changed the title [CGD2D] Draw primitives with blend modes (composite only, porter-def and clear). [CGD2D] Draw primitives with Porter-Duff blend modes Mar 2, 2017
@DHowett-MSFT DHowett-MSFT mentioned this issue Mar 14, 2017
Merged
DHowett-MSFT pushed a commit that referenced this issue Mar 15, 2017
@DHowett
Add support for blending operations to CGContext (#2222)
13999bd 
This pull request adds support for blending to CGContext. There are a number of
caveats.

* `kCGBlendModeClear` is not supported.
* The *Source In*, *Destination In*, *Source Out*, *Destination Atop*, and
  *Source Copy* blend modes cannot be used properly without transparency layers.
  Their use per-primitive will result in unusual artifacts.
* `kCGBlendModePlusDarker` is not supported (and was not supported in the
original Cairo implementation).

Some blend modes (the ones without Source/Destination) in the name require a
full buffer read-back and compose operation. This is unavoidable.

This change unfortunately _does_ include a rewrite of the CGD2D rendering
stack. Instead of adding yet another nesting level of command lists and layers,
I switched it to a scaffold/commit stack. Depending on various conditions,
operations will be queued up, started in order, and committed in reverse order.
A great many of those operations involve creating command lists and layers and
blending them or otherwise composing them.

There is a not-insignificant performance penalty in certain cases:

|                                    before             after   delta
| CoreText__CTLineDrawComplete       742.51            716.11   -3.5546% faster |
| CoreText__CTLineDrawGroup         292,909           307,828    5.0934% slower |
| CoreText__CTLineDrawSingle         233.43            280.05   19.9746% slower |

times in μs.

While 19% seems like a lot, it's only 47μs/operation; an application running at
60fps requires its rendering operations complete in ~16000μs. It's not
_significant_, but it is a cost taken per operation.

I believe there is opportunity for improvement; specifically, I had to
compromise on allocations to achieve the desired effects of polymorphism in the
new render operation stack.

Fixes #1389.
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Add support for blending operations to CGContext DHowett-MSFT/WinObjC
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