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useScaleCanvas performance improvements (#67496)
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* Rely on containerHeight resize listener instead of iframe.documentElement.clientHeight when setting the CSS variable
* Only add CSS variables if we need them (scaleValue < 1)
* Remove unmounting of CSS variables in useEffect return

---------

Co-authored-by: Ella <[email protected]>
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@jeryj @ellatrix
jeryj and ellatrix authored Dec 2, 2024
1 parent c54d810 commit ec756b0
Showing 1 changed file with 55 additions and 69 deletions.
124 changes: 55 additions & 69 deletions packages/block-editor/src/components/iframe/use-scale-canvas.js
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Original file line number Diff line number Diff line change
Expand Up @@ -6,11 +6,11 @@ import { useReducedMotion, useResizeObserver } from '@wordpress/compose';

/**
* @typedef {Object} TransitionState
* @property {number} scaleValue Scale of the canvas.
* @property {number} frameSize Size of the frame/offset around the canvas.
* @property {number} clientHeight ClientHeight of the iframe.
* @property {number} scrollTop ScrollTop of the iframe.
* @property {number} scrollHeight ScrollHeight of the iframe.
* @property {number} scaleValue Scale of the canvas.
* @property {number} frameSize Size of the frame/offset around the canvas.
* @property {number} containerHeight containerHeight of the iframe.
* @property {number} scrollTop ScrollTop of the iframe.
* @property {number} scrollHeight ScrollHeight of the iframe.
*/

/**
Expand Down Expand Up @@ -44,27 +44,28 @@ function calculateScale( {
*/
function computeScrollTopNext( transitionFrom, transitionTo ) {
const {
clientHeight: prevClientHeight,
containerHeight: prevContainerHeight,
frameSize: prevFrameSize,
scaleValue: prevScale,
scrollTop,
scrollHeight,
} = transitionFrom;
const { clientHeight, frameSize, scaleValue } = transitionTo;
const { containerHeight, frameSize, scaleValue } = transitionTo;
// Step 0: Start with the current scrollTop.
let scrollTopNext = scrollTop;
// Step 1: Undo the effects of the previous scale and frame around the
// midpoint of the visible area.
scrollTopNext =
( scrollTopNext + prevClientHeight / 2 - prevFrameSize ) / prevScale -
prevClientHeight / 2;
( scrollTopNext + prevContainerHeight / 2 - prevFrameSize ) /
prevScale -
prevContainerHeight / 2;

// Step 2: Apply the new scale and frame around the midpoint of the
// visible area.
scrollTopNext =
( scrollTopNext + clientHeight / 2 ) * scaleValue +
( scrollTopNext + containerHeight / 2 ) * scaleValue +
frameSize -
clientHeight / 2;
containerHeight / 2;

// Step 3: Handle an edge case so that you scroll to the top of the
// iframe if the top of the iframe content is visible in the container.
Expand All @@ -78,7 +79,7 @@ function computeScrollTopNext( transitionFrom, transitionTo ) {
const maxScrollTop =
scrollHeight * ( scaleValue / prevScale ) +
frameSize * 2 -
clientHeight;
containerHeight;

// Step 4: Clamp the scrollTopNext between the minimum and maximum
// possible scrollTop positions. Round the value to avoid subpixel
Expand Down Expand Up @@ -146,8 +147,10 @@ export function useScaleCanvas( {
} ) {
const [ contentResizeListener, { height: contentHeight } ] =
useResizeObserver();
const [ containerResizeListener, { width: containerWidth } ] =
useResizeObserver();
const [
containerResizeListener,
{ width: containerWidth, height: containerHeight },
] = useResizeObserver();

const initialContainerWidthRef = useRef( 0 );
const isZoomedOut = scale !== 1;
Expand Down Expand Up @@ -186,7 +189,7 @@ export function useScaleCanvas( {
const transitionFromRef = useRef( {
scaleValue,
frameSize,
clientHeight: 0,
containerHeight: 0,
scrollTop: 0,
scrollHeight: 0,
} );
Expand All @@ -198,7 +201,7 @@ export function useScaleCanvas( {
const transitionToRef = useRef( {
scaleValue,
frameSize,
clientHeight: 0,
containerHeight: 0,
scrollTop: 0,
scrollHeight: 0,
} );
Expand Down Expand Up @@ -333,40 +336,41 @@ export function useScaleCanvas( {
} );
}

// If we are not going to animate the transition, set the scale and frame size directly.
// If we are animating, these values will be set when the animation is finished.
// Example: Opening sidebars that reduce the scale of the canvas, but we don't want to
// animate the transition.
if ( ! startAnimationRef.current ) {
if ( scaleValue < 1 ) {
// If we are not going to animate the transition, set the scale and frame size directly.
// If we are animating, these values will be set when the animation is finished.
// Example: Opening sidebars that reduce the scale of the canvas, but we don't want to
// animate the transition.
if ( ! startAnimationRef.current ) {
iframeDocument.documentElement.style.setProperty(
'--wp-block-editor-iframe-zoom-out-scale',
scaleValue
);
iframeDocument.documentElement.style.setProperty(
'--wp-block-editor-iframe-zoom-out-frame-size',
`${ frameSize }px`
);
}

iframeDocument.documentElement.style.setProperty(
'--wp-block-editor-iframe-zoom-out-scale',
scaleValue
'--wp-block-editor-iframe-zoom-out-content-height',
`${ contentHeight }px`
);

iframeDocument.documentElement.style.setProperty(
'--wp-block-editor-iframe-zoom-out-frame-size',
`${ frameSize }px`
'--wp-block-editor-iframe-zoom-out-inner-height',
`${ containerHeight }px`
);
}

iframeDocument.documentElement.style.setProperty(
'--wp-block-editor-iframe-zoom-out-content-height',
`${ contentHeight }px`
);

const clientHeight = iframeDocument.documentElement.clientHeight;
iframeDocument.documentElement.style.setProperty(
'--wp-block-editor-iframe-zoom-out-inner-height',
`${ clientHeight }px`
);

iframeDocument.documentElement.style.setProperty(
'--wp-block-editor-iframe-zoom-out-container-width',
`${ containerWidth }px`
);
iframeDocument.documentElement.style.setProperty(
'--wp-block-editor-iframe-zoom-out-scale-container-width',
`${ scaleContainerWidth }px`
);
iframeDocument.documentElement.style.setProperty(
'--wp-block-editor-iframe-zoom-out-container-width',
`${ containerWidth }px`
);
iframeDocument.documentElement.style.setProperty(
'--wp-block-editor-iframe-zoom-out-scale-container-width',
`${ scaleContainerWidth }px`
);
}

/**
* Handle the zoom out animation:
Expand Down Expand Up @@ -405,8 +409,9 @@ export function useScaleCanvas( {
// the iframe at this point when we're about to animate the zoom out.
// The iframe scrollTop, scrollHeight, and clientHeight will all be
// the most accurate.
transitionFromRef.current.clientHeight =
transitionFromRef.current.clientHeight ?? clientHeight;
transitionFromRef.current.containerHeight =
transitionFromRef.current.containerHeight ??
containerHeight; // Use containerHeight, as it's the previous container height value if none was set.
transitionFromRef.current.scrollTop =
iframeDocument.documentElement.scrollTop;
transitionFromRef.current.scrollHeight =
Expand All @@ -415,7 +420,8 @@ export function useScaleCanvas( {
transitionToRef.current = {
scaleValue,
frameSize,
clientHeight,
containerHeight:
iframeDocument.documentElement.clientHeight, // use clientHeight to get the actual height of the new container, as it will be the most up-to-date.
};
transitionToRef.current.scrollTop = computeScrollTopNext(
transitionFromRef.current,
Expand All @@ -432,27 +438,6 @@ export function useScaleCanvas( {
}
}
}

return () => {
iframeDocument.documentElement.style.removeProperty(
'--wp-block-editor-iframe-zoom-out-scale'
);
iframeDocument.documentElement.style.removeProperty(
'--wp-block-editor-iframe-zoom-out-frame-size'
);
iframeDocument.documentElement.style.removeProperty(
'--wp-block-editor-iframe-zoom-out-content-height'
);
iframeDocument.documentElement.style.removeProperty(
'--wp-block-editor-iframe-zoom-out-inner-height'
);
iframeDocument.documentElement.style.removeProperty(
'--wp-block-editor-iframe-zoom-out-container-width'
);
iframeDocument.documentElement.style.removeProperty(
'--wp-block-editor-iframe-zoom-out-scale-container-width'
);
};
}, [
startZoomOutAnimation,
finishZoomOutAnimation,
Expand All @@ -463,6 +448,7 @@ export function useScaleCanvas( {
iframeDocument,
contentHeight,
containerWidth,
containerHeight,
maxContainerWidth,
scaleContainerWidth,
] );
Expand Down

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