fix(📏): substancial improvements on getting canvas sizes (#3256)

See https://shopify.github.io/react-native-skia/docs/canvas/overview

Author: wcandillon

apps/docs/docs/animations/hooks.md

@@ -108,25 +108,6 @@ export default function App() {
 }
 ```
 
-## Canvas Size
-
-The Canvas element has an `onSize` property that can receive a shared value, which will be updated whenever the canvas size changes.
-
-```tsx twoslash
-import {useSharedValue} from "react-native-reanimated";
-import {Fill, Canvas} from "@shopify/react-native-skia";
-
-const Demo = () => {
-  // size will be updated as the canvas size changes
-  const size = useSharedValue({ width: 0, height: 0 });
-  return (
-    <Canvas style={{ flex: 1 }} onSize={size}>
-      <Fill color="white" />
-    </Canvas>
-  );
-};
-```
-
 ## useRectBuffer
 
 Creates an array for rectangle to be animated.

apps/docs/docs/canvas/canvas.md

@@ -14,13 +14,75 @@ Behind the scenes, it is using its own React renderer.
 | style?   | `ViewStyle` | View style |
 | ref?   | `Ref<SkiaView>` | Reference to the `SkiaView` object |
 | onSize? | `SharedValue<Size>` | Reanimated value to which the canvas size will be assigned  (see [canvas size](/docs/animations/hooks#canvas-size)) |
-| onLayout? | `NativeEvent<LayoutEvent>` | Invoked on mount and on layout changes (see [onLayout](https://reactnative.dev/docs/view#onlayout)) |
 
-## Getting the Canvas size
+## Canvas size
+
+The size of the canvas is available on both the UI and JS thread.
+
+### UI thread
+
+The `onSize` property receives a shared value, which will be updated whenever the canvas size changes.
+You can see it in action in the example below.
+
+```tsx twoslash
+import {useSharedValue, useDerivedValue} from "react-native-reanimated";
+import {Fill, Canvas, Rect} from "@shopify/react-native-skia";
+
+const Demo = () => {
+  // size will be updated as the canvas size changes
+  const size = useSharedValue({ width: 0, height: 0 });
+  const rect = useDerivedValue(() => {
+    const {width, height} = size.value;
+    return { x: 0, y: 0, width, height };
+  });
+  return (
+    <Canvas style={{ flex: 1 }} onSize={size}>
+      <Rect color="cyan" rect={rect} />
+    </Canvas>
+  );
+};
+```
+
+### JS thread
+
+To get the canvas size on the JS thread, you can use `useLayoutEffect` and `measure()`.
+Since this is a very common pattern, we offer a `useCanvasSize` hook you can use for convenience.
+
+```tsx twoslash
+import {Fill, Canvas, Rect, useCanvasSize} from "@shopify/react-native-skia";
+
+const Demo = () => {
+  const {ref, size: {width, height}} = useCanvasSize();
+  return (
+    <Canvas style={{ flex: 1 }} ref={ref}>
+      <Rect color="cyan" rect={{ x: 0, y: 0, width, height }} />
+    </Canvas>
+  );
+};
+```
+
+This example is equivalent to the code below:
+
+```tsx twoslash
+import {useLayoutEffect, useState} from "react";
+import {Fill, Canvas, Rect, useCanvasRef} from "@shopify/react-native-skia";
+
+const Demo = () => {
+  const ref = useCanvasRef();
+  const [rect, setRect] = useState({ x: 0, y: 0, width: 0, height: 0 });
+  useLayoutEffect(() => {
+    ref.current?.measure((_x, _y, width, height) => {
+      setRect({ x: 0, y: 0, width, height });
+    });
+  }, []);
+  return (
+    <Canvas style={{ flex: 1 }} ref={ref}>
+      <Rect color="cyan" rect={rect} />
+    </Canvas>
+  );
+};
+```
 
-If the size of the Canvas is unknown, there are two ways to access it:
-  * **On the JS thread**, using the [`onLayout`](https://reactnative.dev/docs/view#onlayout) prop, like you would on any regular React Native View. 
-  * **On the UI thread**, using the [`onSize`](/docs/animations/hooks#canvas-size) prop with [Reanimated](/docs/animations/animations).
 
 ## Getting a Canvas Snapshot
 
@@ -58,8 +120,8 @@ export const Demo = () => {
 };
 ```
 
-## Accessibilty
+## Accessibility
 
 The Canvas component supports the same properties as a View component including its [accessibility properties](https://reactnative.dev/docs/accessibility#accessible).
 You can make elements inside the canvas accessible as well by overlayings views on top of your canvas.
-This is the same recipe used for [applying gestures on specific canvas elements](https://shopify.github.io/react-native-skia/docs/animations/gestures/#element-tracking).
+This is the same recipe used for [applying gestures on specific canvas elements](https://shopify.github.io/react-native-skia/docs/animations/gestures/#element-tracking).

apps/example/ios/Podfile.lock

@@ -1327,7 +1327,7 @@ PODS:
     - ReactCommon/turbomodule/bridging
     - ReactCommon/turbomodule/core
     - Yoga
-  - react-native-slider (4.5.7):
+  - react-native-slider (4.5.6):
     - DoubleConversion
     - glog
     - hermes-engine
@@ -1340,7 +1340,7 @@ PODS:
     - React-featureflags
     - React-graphics
     - React-ImageManager
-    - react-native-slider/common (= 4.5.7)
+    - react-native-slider/common (= 4.5.6)
     - React-NativeModulesApple
     - React-RCTFabric
     - React-rendererdebug
@@ -1349,7 +1349,7 @@ PODS:
     - ReactCommon/turbomodule/bridging
     - ReactCommon/turbomodule/core
     - Yoga
-  - react-native-slider/common (4.5.7):
+  - react-native-slider/common (4.5.6):
     - DoubleConversion
     - glog
     - hermes-engine
@@ -2162,77 +2162,77 @@ SPEC CHECKSUMS:
   fmt: a40bb5bd0294ea969aaaba240a927bd33d878cdd
   glog: eb93e2f488219332457c3c4eafd2738ddc7e80b8
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-  RCT-Folly: 36fe2295e44b10d831836cc0d1daec5f8abcf809
+  RCT-Folly: e78785aa9ba2ed998ea4151e314036f6c49e6d82
   RCTDeprecation: b2eecf2d60216df56bc5e6be5f063826d3c1ee35
   RCTRequired: 78522de7dc73b81f3ed7890d145fa341f5bb32ea
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   React: b229c49ed5898dab46d60f61ed5a0bfa2ee2fadb
   React-callinvoker: 2ac508e92c8bd9cf834cc7d7787d94352e4af58f
-  React-Core: 13cdd1558d0b3f6d9d5a22e14d89150280e79f02
-  React-CoreModules: b07a6744f48305405e67c845ebf481b6551b712a
-  React-cxxreact: 1055a86c66ac35b4e80bd5fb766aed5f494dfff4
+  React-Core: 325b4f6d9162ae8b9a6ff42fe78e260eb124180d
+  React-CoreModules: 558041e5258f70cd1092f82778d07b8b2ff01897
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   React-debug: 0a5fcdbacc6becba0521e910c1bcfdb20f32a3f6
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-  React-FabricImage: 37d8e8b672eda68a19d71143eb65148084efb325
+  React-defaultsnativemodule: 618dc50a0fad41b489997c3eb7aba3a74479fd14
+  React-domnativemodule: 7ba599afb6c2a7ec3eb6450153e2efe0b8747e9a
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   React-featureflags: 19682e02ef5861d96b992af16a19109c3dfc1200
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-  React-performancetimeline: bc2e48198ec814d578ac8401f65d78a574358203
+  React-featureflagsnativemodule: 23528c7e7d50782b7ef0804168ba40bbaf1e86ab
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+  React-ImageManager: e3300996ac2e2914bf821f71e2f2c92ae6e62ae2
+  React-jserrorhandler: fa75876c662e5d7e79d6efc763fc9f4c88e26986
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+  react-native-skia: d696b43cb1a6560ec3902856cdc8f0838cc25b64
+  react-native-slider: bb7eb4732940fab78217e1c096bb647d8b0d1cf3
+  React-NativeModulesApple: 88433b6946778bea9c153e27b671de15411bf225
+  React-perflogger: 9e8d3c0dc0194eb932162812a168aa5dc662f418
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   React-RCTActionSheet: 592674cf61142497e0e820688f5a696e41bf16dd
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   React-rendererconsistency: 64e897e00d2568fd8dfe31e2496f80e85c0aaad1
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+  React-rendererdebug: 41ce452460c44bba715d9e41d5493a96de277764
   React-rncore: 58748c2aa445f56b99e5118dad0aedb51c40ce9f
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   React-runtimeexecutor: a188df372373baf5066e6e229177836488799f80
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   React-timing: bb220a53a795ed57976a4855c521f3de2f298fe5
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-  ReactTestApp-DevSupport: 15d2ef4884e8f5fd30ded3dec59b010f76384f37
+  React-utils: 3b054aaebe658fc710a8d239d0e4b9fd3e0b78f9
+  ReactAppDependencyProvider: a1fb08dfdc7ebc387b2e54cfc9decd283ed821d8
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+  ReactCommon: 0c097b53f03d6bf166edbcd0915da32f3015dd90
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   ReactTestApp-Resources: 1bd9ff10e4c24f2ad87101a32023721ae923bccf
-  RNGestureHandler: 66e593addd8952725107cfaa4f5e3378e946b541
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-  RNSVG: 8588ee1ca9b2e6fd2c99466e35b3db0e9f81bb40
+  RNGestureHandler: dcb1b1db024f3744b03af56d132f4f72c4c27195
+  RNReanimated: 3b2312c84f8c747ab1e9d9c3ce879e93a5ba96f3
+  RNScreens: 790123c4a28783d80a342ce42e8c7381bed62db1
+  RNSVG: 8126581b369adf6a0004b6a6cab1a55e3002d5b0
   SocketRocket: d4aabe649be1e368d1318fdf28a022d714d65748
-  Yoga: 9b7fb56e7b08cde60e2153344fa6afbd88e5d99f
+  Yoga: afd04ff05ebe0121a00c468a8a3c8080221cb14c
 
 PODFILE CHECKSUM: 87506345285a0371afb28b9c3e6daaa999c214f3
 
-COCOAPODS: 1.15.2
+COCOAPODS: 1.16.2

apps/example/src/Examples/API/OnLayout.tsx

@@ -1,17 +1,13 @@
-import React, { useState } from "react";
-import type { LayoutRectangle } from "react-native";
+import React from "react";
 import { Text } from "react-native";
-import { Canvas, Fill } from "@shopify/react-native-skia";
+import { Canvas, Fill, useCanvasSize } from "@shopify/react-native-skia";
 
 export const OnLayoutDemo = () => {
-  const [layout, setLayout] = useState<LayoutRectangle>();
+  const { ref, size } = useCanvasSize();
   return (
     <>
-      <Text>{`OnLayout: ${layout?.width} / ${layout?.height}`}</Text>
-      <Canvas
-        style={{ flex: 1 }}
-        onLayout={(evt) => setLayout(evt.nativeEvent.layout)}
-      >
+      <Text>{`OnLayout: ${size?.width} / ${size?.height}`}</Text>
+      <Canvas style={{ flex: 1 }} ref={ref}>
         <Fill color="red" />
       </Canvas>
     </>

apps/example/src/Examples/LiquidGlass/components/Scene.tsx

@@ -12,8 +12,9 @@ import {
   processUniforms,
   Skia,
   TileMode,
+  useCanvasSize,
 } from "@shopify/react-native-skia";
-import React, { useState } from "react";
+import React from "react";
 import {
   ReduceMotion,
   useDerivedValue,
@@ -104,7 +105,8 @@ export const Scene = ({
   filter: filterCB,
   shader: shaderFilter,
 }: SceneProps) => {
-  const [{ width, height }, setSize] = useState({ width: 0, height: 0 });
+  const { ref, size } = useCanvasSize();
+  const { width, height } = size;
   const props = useButtonGroup({ width, height }, r);
   const { progress, c1, box, bounds } = props;
   const uniforms = useDerivedValue(() => {
@@ -165,15 +167,7 @@ export const Scene = ({
   return (
     <View style={{ flex: 1 }}>
       <GestureDetector gesture={gesture}>
-        <Canvas
-          style={{ flex: 1 }}
-          onLayout={({ nativeEvent: { layout } }) => {
-            setSize({
-              width: layout.width,
-              height: layout.height,
-            });
-          }}
-        >
+        <Canvas style={{ flex: 1 }} ref={ref}>
           <Pattern />
           <BackdropFilter filter={<ImageFilter filter={filter} />} />
           <ButtonGroup {...props} />

packages/skia/cpp/rnskia/RNSkJsiViewApi.h

@@ -232,10 +232,45 @@ class RNSkJsiViewApi : public RNJsi::JsiHostObject,
         });
   }
 
+  JSI_HOST_FUNCTION(size) {
+    if (count != 1) {
+      _platformContext->raiseError(
+          std::string("size: Expected 1 argument, got " +
+                      std::to_string(count) + "."));
+      return jsi::Value::undefined();
+    }
+
+    if (!arguments[0].isNumber()) {
+      _platformContext->raiseError(
+          "size: First argument must be a number");
+      return jsi::Value::undefined();
+    }
+
+    // find Skia View
+    int nativeId = arguments[0].asNumber();
+    std::shared_ptr<RNSkView> view = ViewRegistry::getInstance().withViewInfo(
+        nativeId,
+        [](std::shared_ptr<RNSkViewInfo> info) { return info->view; });
+    if (view != nullptr) {
+      auto pixelDensity = _platformContext->getPixelDensity();
+      auto sizeObj = jsi::Object(runtime);
+      sizeObj.setProperty(runtime, "width", view->getScaledWidth() / pixelDensity);
+      sizeObj.setProperty(runtime, "height", view->getScaledHeight() / pixelDensity);
+      return sizeObj;
+    }
+    
+    // Return default size if view not found
+    auto sizeObj = jsi::Object(runtime);
+    sizeObj.setProperty(runtime, "width", 0);
+    sizeObj.setProperty(runtime, "height", 0);
+    return sizeObj;
+  }
+
   JSI_EXPORT_FUNCTIONS(JSI_EXPORT_FUNC(RNSkJsiViewApi, setJsiProperty),
                        JSI_EXPORT_FUNC(RNSkJsiViewApi, requestRedraw),
                        JSI_EXPORT_FUNC(RNSkJsiViewApi, makeImageSnapshotAsync),
-                       JSI_EXPORT_FUNC(RNSkJsiViewApi, makeImageSnapshot))
+                       JSI_EXPORT_FUNC(RNSkJsiViewApi, makeImageSnapshot),
+                       JSI_EXPORT_FUNC(RNSkJsiViewApi, size))
 
   /**
    * Constructor