sky/sdk/lib/rendering/README.md - Issue 1190123003: Decouple Canvas from DisplayList and map Picture and PictureRecorder more directly to their Skia co…

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Issue 1190123003: Decouple Canvas from DisplayList and map Picture and PictureRecorder more directly to their Skia co… (Closed) Base URL: git@github.com:domokit/mojo.git@master

Patch Set: j/k -- this one should actually be fully merged and testable Created 5 years, 5 months ago

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« sky/examples/raw/spinning_square.dart ('K') | « sky/examples/rendering/touch_demo.dart ('k') | sky/sdk/lib/rendering/block.dart » ('j') | sky/sdk/lib/rendering/box.dart » ('J')

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1 Sky Rendering	1 Sky Rendering

2 =============	2 =============

3	3

4 The Sky render tree is a low-level layout and painting system based on a	4 The Sky render tree is a low-level layout and painting system based on a

5 retained tree of objects that inherit from [`RenderObject`](object.dart). Most	5 retained tree of objects that inherit from [`RenderObject`](object.dart). Most

6 developers using Sky will not need to interact directly with the rendering tree.	6 developers using Sky will not need to interact directly with the rendering tree.

7 Instead, most developers should use [Sky widgets](../widgets/README.md), which	7 Instead, most developers should use [Sky widgets](../widgets/README.md), which

8 are built using the render tree.	8 are built using the render tree.

9	9

10 Base Model	10 Base Model

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35	35

36 * Implementations of `performLayout` are expected to call `layout` on their	36 * Implementations of `performLayout` are expected to call `layout` on their

37 children. When calling `layout`, a `RenderObject` must use the	37 children. When calling `layout`, a `RenderObject` must use the

38 `parentUsesSize` parameter to declare whether its `performLayout` function	38 `parentUsesSize` parameter to declare whether its `performLayout` function

39 depends on information read from the child. If the parent doesn't declare	39 depends on information read from the child. If the parent doesn't declare

40 that it uses the child's size, the edge from the parent to the child becomes	40 that it uses the child's size, the edge from the parent to the child becomes

41 a _relayout boundary_, which means the child (and its subtree) might undergo	41 a _relayout boundary_, which means the child (and its subtree) might undergo

42 layout without the parent undergoing layout.	42 layout without the parent undergoing layout.

43	43

44 * Subclasses of `RenderObject` must implement a `paint` function that draws a	44 * Subclasses of `RenderObject` must implement a `paint` function that draws a

45 visual representation of the object onto an `RenderObjectDisplayList`. If	45 visual representation of the object onto a `RenderCanvas`. If

46 the `RenderObject` has children, the `RenderObject` is responsible for	46 the `RenderObject` has children, the `RenderObject` is responsible for

47 painting its children using the `paintChild` function.	47 painting its children using the `paintChild` function on the `RenderCanvas`.

48	48

49 * Subclasses of `RenderObject` must call `adoptChild` whenever they add a	49 * Subclasses of `RenderObject` must call `adoptChild` whenever they add a

50 child. Similarly, they must call `dropChild` whenever they remove a child.	50 child. Similarly, they must call `dropChild` whenever they remove a child.

51	51

52 * Most subclasses of `RenderObject` will implement a `hitTest` function that	52 * Most subclasses of `RenderObject` will implement a `hitTest` function that

53 lets clients query the render tree for objects that intersect with a given	53 lets clients query the render tree for objects that intersect with a given

54 user input location. `RenderObject` itself does not impose a particular	54 user input location. `RenderObject` itself does not impose a particular

55 type signature on `hitTest`, but most implementations will take an argument	55 type signature on `hitTest`, but most implementations will take an argument

56 of type `HitTestResult` (or, more likely, a model-specific subclass of	56 of type `HitTestResult` (or, more likely, a model-specific subclass of

57 `HitTestResult`) as well as an object that describes the location at which	57 `HitTestResult`) as well as an object that describes the location at which

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84 Bespoke Models	84 Bespoke Models

85 --------------	85 --------------

86	86

87	87

88 Dependencies	88 Dependencies

89 ------------	89 ------------

90	90

91 * [`package:sky/base`](../base)	91 * [`package:sky/base`](../base)

92 * [`package:sky/mojo`](../mojo)	92 * [`package:sky/mojo`](../mojo)

93 * [`package:sky/animation`](../mojo)	93 * [`package:sky/animation`](../mojo)

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