fix: introduce baseline to fix the layout shift when switching to text editor (#6397)

* fix: introduce baseline to fix the layout shift when switching to text editor

* uncomment

* change offset to 8pixels

* [debug]

* introduce DOM baseline in canvas rendering instead

* introduce baseline in element making it backward compat

* fix

* lint

* fix

* update baseline when resizing text element

* fix safari backward compat

* fix for safari

* lint

* reduce safari LS

* floor line height and height when dom height increases than canvas height

* Revert "floor line height and height when dom height increases than canvas height"

This reverts commit 8de6516823.

* cleanup

* use DOM height only for safari to fix LS

* Revert "use DOM height only for safari to fix LS"

This reverts commit d75889238d.

* fix lint and test

* fix

* calculate line height by rounding off instead of DOM

* cleanup

---------

Co-authored-by: dwelle <luzar.david@gmail.com>

src/actions/actionBoundText.tsx

@@ -43,7 +43,7 @@ export const actionUnbindText = register({
     selectedElements.forEach((element) => {
       const boundTextElement = getBoundTextElement(element);
       if (boundTextElement) {
-        const { width, height } = measureText(
+        const { width, height, baseline } = measureText(
           boundTextElement.originalText,
           getFontString(boundTextElement),
           boundTextElement.lineHeight,
@@ -57,6 +57,7 @@ export const actionUnbindText = register({
           containerId: null,
           width,
           height,
+          baseline,
           text: boundTextElement.originalText,
         });
         mutateElement(element, {

src/data/restore.ts

@@ -31,11 +31,15 @@ import {
 import { getDefaultAppState } from "../appState";
 import { LinearElementEditor } from "../element/linearElementEditor";
 import { bumpVersion } from "../element/mutateElement";
-import { getUpdatedTimestamp, updateActiveTool } from "../utils";
+import { getFontString, getUpdatedTimestamp, updateActiveTool } from "../utils";
 import { arrayToMap } from "../utils";
 import oc from "open-color";
 import { MarkOptional, Mutable } from "../utility-types";
-import { detectLineHeight, getDefaultLineHeight } from "../element/textElement";
+import {
+  detectLineHeight,
+  getDefaultLineHeight,
+  measureBaseline,
+} from "../element/textElement";
 
 type RestoredAppState = Omit<
   AppState,
@@ -171,6 +175,24 @@ const restoreElement = (
       }
       const text = element.text ?? "";
 
+      // line-height might not be specified either when creating elements
+      // programmatically, or when importing old diagrams.
+      // For the latter we want to detect the original line height which
+      // will likely differ from our per-font fixed line height we now use,
+      // to maintain backward compatibility.
+      const lineHeight =
+        element.lineHeight ||
+        (element.height
+          ? // detect line-height from current element height and font-size
+            detectLineHeight(element)
+          : // no element height likely means programmatic use, so default
+            // to a fixed line height
+            getDefaultLineHeight(element.fontFamily));
+      const baseline = measureBaseline(
+        element.text,
+        getFontString(element),
+        lineHeight,
+      );
       element = restoreElementWithProperties(element, {
         fontSize,
         fontFamily,
@@ -179,19 +201,9 @@ const restoreElement = (
         verticalAlign: element.verticalAlign || DEFAULT_VERTICAL_ALIGN,
         containerId: element.containerId ?? null,
         originalText: element.originalText || text,
-        // line-height might not be specified either when creating elements
-        // programmatically, or when importing old diagrams.
-        // For the latter we want to detect the original line height which
-        // will likely differ from our per-font fixed line height we now use,
-        // to maintain backward compatibility.
-        lineHeight:
-          element.lineHeight ||
-          (element.height
-            ? // detect line-height from current element height and font-size
-              detectLineHeight(element)
-            : // no element height likely means programmatic use, so default
-              // to a fixed line height
-              getDefaultLineHeight(element.fontFamily)),
+
+        lineHeight,
+        baseline,
       });
 
       if (refreshDimensions) {

src/element/newElement.ts

@@ -145,6 +145,7 @@ export const newTextElement = (
   const text = normalizeText(opts.text);
   const metrics = measureText(text, getFontString(opts), lineHeight);
   const offsets = getTextElementPositionOffsets(opts, metrics);
+
   const textElement = newElementWith(
     {
       ..._newElementBase<ExcalidrawTextElement>("text", opts),
@@ -157,6 +158,7 @@ export const newTextElement = (
       y: opts.y - offsets.y,
       width: metrics.width,
       height: metrics.height,
+      baseline: metrics.baseline,
       containerId: opts.containerId || null,
       originalText: text,
       lineHeight,
@@ -174,14 +176,15 @@ const getAdjustedDimensions = (
   y: number;
   width: number;
   height: number;
+  baseline: number;
 } => {
   const container = getContainerElement(element);
 
-  const { width: nextWidth, height: nextHeight } = measureText(
-    nextText,
-    getFontString(element),
-    element.lineHeight,
-  );
+  const {
+    width: nextWidth,
+    height: nextHeight,
+    baseline: nextBaseline,
+  } = measureText(nextText, getFontString(element), element.lineHeight);
   const { textAlign, verticalAlign } = element;
   let x: number;
   let y: number;
@@ -256,6 +259,7 @@ const getAdjustedDimensions = (
   return {
     width: nextWidth,
     height: nextHeight,
+    baseline: nextBaseline,
     x: Number.isFinite(x) ? x : element.x,
     y: Number.isFinite(y) ? y : element.y,
   };

src/element/resizeElements.ts

@@ -46,6 +46,8 @@ import {
   handleBindTextResize,
   getMaxContainerWidth,
   getApproxMinLineHeight,
+  measureText,
+  getMaxContainerHeight,
 } from "./textElement";
 
 export const normalizeAngle = (angle: number): number => {
@@ -193,7 +195,8 @@ const MIN_FONT_SIZE = 1;
 const measureFontSizeFromWidth = (
   element: NonDeleted<ExcalidrawTextElement>,
   nextWidth: number,
-): number | null => {
+  nextHeight: number,
+): { size: number; baseline: number } | null => {
   // We only use width to scale font on resize
   let width = element.width;
 
@@ -208,8 +211,15 @@ const measureFontSizeFromWidth = (
   if (nextFontSize < MIN_FONT_SIZE) {
     return null;
   }
-
-  return nextFontSize;
+  const metrics = measureText(
+    element.text,
+    getFontString({ fontSize: nextFontSize, fontFamily: element.fontFamily }),
+    element.lineHeight,
+  );
+  return {
+    size: nextFontSize,
+    baseline: metrics.baseline + (nextHeight - metrics.height),
+  };
 };
 
 const getSidesForTransformHandle = (
@@ -280,8 +290,8 @@ const resizeSingleTextElement = (
   if (scale > 0) {
     const nextWidth = element.width * scale;
     const nextHeight = element.height * scale;
-    const nextFontSize = measureFontSizeFromWidth(element, nextWidth);
-    if (nextFontSize === null) {
+    const metrics = measureFontSizeFromWidth(element, nextWidth, nextHeight);
+    if (metrics === null) {
       return;
     }
     const [nextX1, nextY1, nextX2, nextY2] = getResizedElementAbsoluteCoords(
@@ -305,9 +315,10 @@ const resizeSingleTextElement = (
       deltaY2,
     );
     mutateElement(element, {
-      fontSize: nextFontSize,
+      fontSize: metrics.size,
       width: nextWidth,
       height: nextHeight,
+      baseline: metrics.baseline,
       x: nextElementX,
       y: nextElementY,
     });
@@ -360,7 +371,7 @@ export const resizeSingleElement = (
   let scaleX = atStartBoundsWidth / boundsCurrentWidth;
   let scaleY = atStartBoundsHeight / boundsCurrentHeight;
 
-  let boundTextFontSize: number | null = null;
+  let boundTextFont: { fontSize?: number; baseline?: number } = {};
   const boundTextElement = getBoundTextElement(element);
 
   if (transformHandleDirection.includes("e")) {
@@ -410,7 +421,10 @@ export const resizeSingleElement = (
       boundTextElement.id,
     ) as typeof boundTextElement | undefined;
     if (stateOfBoundTextElementAtResize) {
-      boundTextFontSize = stateOfBoundTextElementAtResize.fontSize;
+      boundTextFont = {
+        fontSize: stateOfBoundTextElementAtResize.fontSize,
+        baseline: stateOfBoundTextElementAtResize.baseline,
+      };
     }
     if (shouldMaintainAspectRatio) {
       const updatedElement = {
@@ -419,14 +433,18 @@ export const resizeSingleElement = (
         height: eleNewHeight,
       };
 
-      const nextFontSize = measureFontSizeFromWidth(
+      const nextFont = measureFontSizeFromWidth(
         boundTextElement,
         getMaxContainerWidth(updatedElement),
+        getMaxContainerHeight(updatedElement),
       );
-      if (nextFontSize === null) {
+      if (nextFont === null) {
         return;
       }
-      boundTextFontSize = nextFontSize;
+      boundTextFont = {
+        fontSize: nextFont.size,
+        baseline: nextFont.baseline,
+      };
     } else {
       const minWidth = getApproxMinLineWidth(
         getFontString(boundTextElement),
@@ -568,9 +586,10 @@ export const resizeSingleElement = (
     });
 
     mutateElement(element, resizedElement);
-    if (boundTextElement && boundTextFontSize != null) {
+    if (boundTextElement && boundTextFont != null) {
       mutateElement(boundTextElement, {
-        fontSize: boundTextFontSize,
+        fontSize: boundTextFont.fontSize,
+        baseline: boundTextFont.baseline,
       });
     }
     handleBindTextResize(element, transformHandleDirection);
@@ -677,6 +696,7 @@ const resizeMultipleElements = (
       y: number;
       points?: Point[];
       fontSize?: number;
+      baseline?: number;
     } = {
       width,
       height,
@@ -685,7 +705,7 @@ const resizeMultipleElements = (
       ...rescaledPoints,
     };
 
-    let boundTextUpdates: { fontSize: number } | null = null;
+    let boundTextUpdates: { fontSize: number; baseline: number } | null = null;
 
     const boundTextElement = getBoundTextElement(element.latest);
 
@@ -695,24 +715,29 @@ const resizeMultipleElements = (
         width,
         height,
       };
-      const fontSize = measureFontSizeFromWidth(
+      const metrics = measureFontSizeFromWidth(
         boundTextElement ?? (element.orig as ExcalidrawTextElement),
         boundTextElement
           ? getMaxContainerWidth(updatedElement)
           : updatedElement.width,
+        boundTextElement
+          ? getMaxContainerHeight(updatedElement)
+          : updatedElement.height,
       );
 
-      if (!fontSize) {
+      if (!metrics) {
         return;
       }
 
       if (isTextElement(element.orig)) {
-        update.fontSize = fontSize;
+        update.fontSize = metrics.size;
+        update.baseline = metrics.baseline;
       }
 
       if (boundTextElement) {
         boundTextUpdates = {
-          fontSize,
+          fontSize: metrics.size,
+          baseline: metrics.baseline,
         };
       }
     }

src/element/textElement.ts

@@ -14,6 +14,7 @@ import {
   DEFAULT_FONT_FAMILY,
   DEFAULT_FONT_SIZE,
   FONT_FAMILY,
+  isSafari,
   TEXT_ALIGN,
   VERTICAL_ALIGN,
 } from "../constants";
@@ -58,6 +59,7 @@ export const redrawTextBoundingBox = (
     text: textElement.text,
     width: textElement.width,
     height: textElement.height,
+    baseline: textElement.baseline,
   };
 
   boundTextUpdates.text = textElement.text;
@@ -78,6 +80,7 @@ export const redrawTextBoundingBox = (
 
   boundTextUpdates.width = metrics.width;
   boundTextUpdates.height = metrics.height;
+  boundTextUpdates.baseline = metrics.baseline;
 
   if (container) {
     if (isArrowElement(container)) {
@@ -183,6 +186,7 @@ export const handleBindTextResize = (
     const maxWidth = getMaxContainerWidth(container);
     const maxHeight = getMaxContainerHeight(container);
     let containerHeight = containerDims.height;
+    let nextBaseLine = textElement.baseline;
     if (transformHandleType !== "n" && transformHandleType !== "s") {
       if (text) {
         text = wrapText(
@@ -191,13 +195,14 @@ export const handleBindTextResize = (
           maxWidth,
         );
       }
-      const dimensions = measureText(
+      const metrics = measureText(
         text,
         getFontString(textElement),
         textElement.lineHeight,
       );
-      nextHeight = dimensions.height;
-      nextWidth = dimensions.width;
+      nextHeight = metrics.height;
+      nextWidth = metrics.width;
+      nextBaseLine = metrics.baseline;
     }
     // increase height in case text element height exceeds
     if (nextHeight > maxHeight) {
@@ -225,6 +230,7 @@ export const handleBindTextResize = (
       text,
       width: nextWidth,
       height: nextHeight,
+      baseline: nextBaseLine,
     });
 
     if (!isArrowElement(container)) {
@@ -285,8 +291,59 @@ export const measureText = (
   const fontSize = parseFloat(font);
   const height = getTextHeight(text, fontSize, lineHeight);
   const width = getTextWidth(text, font);
+  const baseline = measureBaseline(text, font, lineHeight);
+  return { width, height, baseline };
+};
 
-  return { width, height };
+export const measureBaseline = (
+  text: string,
+  font: FontString,
+  lineHeight: ExcalidrawTextElement["lineHeight"],
+  wrapInContainer?: boolean,
+) => {
+  const container = document.createElement("div");
+  container.style.position = "absolute";
+  container.style.whiteSpace = "pre";
+  container.style.font = font;
+  container.style.minHeight = "1em";
+  if (wrapInContainer) {
+    container.style.overflow = "hidden";
+    container.style.wordBreak = "break-word";
+    container.style.whiteSpace = "pre-wrap";
+  }
+
+  container.style.lineHeight = String(lineHeight);
+
+  container.innerText = text;
+
+  // Baseline is important for positioning text on canvas
+  document.body.appendChild(container);
+
+  const span = document.createElement("span");
+  span.style.display = "inline-block";
+  span.style.overflow = "hidden";
+  span.style.width = "1px";
+  span.style.height = "1px";
+  container.appendChild(span);
+  let baseline = span.offsetTop + span.offsetHeight;
+  const height = container.offsetHeight;
+
+  if (isSafari) {
+    const canvasHeight = getTextHeight(text, parseFloat(font), lineHeight);
+    const fontSize = parseFloat(font);
+    // In Safari the font size gets rounded off when rendering hence calculating the safari height and shifting the baseline if it differs
+    // from the actual canvas height
+    const domHeight = getTextHeight(text, Math.round(fontSize), lineHeight);
+    if (canvasHeight > height) {
+      baseline += canvasHeight - domHeight;
+    }
+
+    if (height > canvasHeight) {
+      baseline -= domHeight - canvasHeight;
+    }
+  }
+  document.body.removeChild(container);
+  return baseline;
 };
 
 /**

src/element/textWysiwyg.tsx

@@ -11,7 +11,7 @@ import {
   isBoundToContainer,
   isTextElement,
 } from "./typeChecks";
-import { CLASSES, VERTICAL_ALIGN } from "../constants";
+import { CLASSES, isSafari, VERTICAL_ALIGN } from "../constants";
 import {
   ExcalidrawElement,
   ExcalidrawLinearElement,
@@ -35,6 +35,7 @@ import {
   getMaxContainerHeight,
   getMaxContainerWidth,
   computeContainerDimensionForBoundText,
+  detectLineHeight,
 } from "./textElement";
 import {
   actionDecreaseFontSize,
@@ -271,13 +272,24 @@ export const textWysiwyg = ({
       } else {
         textElementWidth += 0.5;
       }
+
+      let lineHeight = updatedTextElement.lineHeight;
+
+      // In Safari the font size gets rounded off when rendering hence calculating the line height by rounding off font size
+      if (isSafari) {
+        lineHeight = detectLineHeight({
+          ...updatedTextElement,
+          fontSize: Math.round(updatedTextElement.fontSize),
+        });
+      }
+
       // Make sure text editor height doesn't go beyond viewport
       const editorMaxHeight =
         (appState.height - viewportY) / appState.zoom.value;
       Object.assign(editable.style, {
         font: getFontString(updatedTextElement),
         // must be defined *after* font ¯\_(ツ)_/¯
-        lineHeight: element.lineHeight,
+        lineHeight,
         width: `${textElementWidth}px`,
         height: `${textElementHeight}px`,
         left: `${viewportX}px`,

src/element/types.ts

@@ -131,6 +131,7 @@ export type ExcalidrawTextElement = _ExcalidrawElementBase &
     fontSize: number;
     fontFamily: FontFamilyValues;
     text: string;
+    baseline: number;
     textAlign: TextAlign;
     verticalAlign: VerticalAlign;
     containerId: ExcalidrawGenericElement["id"] | null;

src/renderer/renderElement.ts

@@ -245,7 +245,6 @@ const drawImagePlaceholder = (
     size,
   );
 };
-
 const drawElementOnCanvas = (
   element: NonDeletedExcalidrawElement,
   rc: RoughCanvas,
@@ -331,18 +330,16 @@ const drawElementOnCanvas = (
             : element.textAlign === "right"
             ? element.width
             : 0;
-        context.textBaseline = "bottom";
-
         const lineHeightPx = getLineHeightInPx(
           element.fontSize,
           element.lineHeight,
         );
-
+        const verticalOffset = element.height - element.baseline;
         for (let index = 0; index < lines.length; index++) {
           context.fillText(
             lines[index],
             horizontalOffset,
-            (index + 1) * lineHeightPx,
+            (index + 1) * lineHeightPx - verticalOffset,
           );
         }
         context.restore();

src/tests/data/__snapshots__/restore.test.ts.snap

@@ -282,6 +282,7 @@ exports[`restoreElements should restore text element correctly passing value for
 Object {
   "angle": 0,
   "backgroundColor": "transparent",
+  "baseline": 0,
   "boundElements": Array [],
   "containerId": null,
   "fillStyle": "hachure",
@@ -321,6 +322,7 @@ exports[`restoreElements should restore text element correctly with unknown font
 Object {
   "angle": 0,
   "backgroundColor": "transparent",
+  "baseline": 0,
   "boundElements": Array [],
   "containerId": null,
   "fillStyle": "hachure",