[EuiTextTruncate] Fix testenv mocks

scripts/jest/setup/mocks.js

@@ -15,10 +15,12 @@ jest.mock('./../../../src/components/icon', () => {
   return { EuiIcon };
 });
 
-jest.mock('./../../../src/components/text_truncate', () => {
-  const rest = jest.requireActual('./../../../src/components/text_truncate');
-  const utils = require('./../../../src/components/text_truncate/utils.testenv');
-  return { ...rest, ...utils };
+jest.mock('./../../../src/services/canvas', () => {
+  const rest = jest.requireActual('./../../../src/services/canvas');
+  const {
+    CanvasTextUtils,
+  } = require('./../../../src/services/canvas/canvas_text_utils.testenv');
+  return { ...rest, CanvasTextUtils };
 });
 
 jest.mock('./../../../src/services/accessibility', () => {

src/components/combo_box/combo_box_input/combo_box_input.tsx

@@ -16,8 +16,7 @@ import React, {
 import classNames from 'classnames';
 
 import { CommonProps } from '../../common';
-import { htmlIdGenerator, keys } from '../../../services';
-import { CanvasTextUtils } from '../../text_truncate';
+import { htmlIdGenerator, keys, CanvasTextUtils } from '../../../services';
 import { EuiScreenReaderOnly } from '../../accessibility';
 import {
   EuiFormControlLayout,

src/components/text_truncate/index.ts

@@ -12,4 +12,4 @@ export type {
 } from './text_truncate';
 export { EuiTextTruncate } from './text_truncate';
 
-export { CanvasTextUtils, TruncationUtils } from './utils';
+export { TruncationUtils } from './utils';

src/components/text_truncate/utils.test.ts

@@ -6,47 +6,7 @@
  * Side Public License, v 1.
  */
 
-import { CanvasTextUtils, TruncationUtils } from './utils';
-
-let mockCanvasWidth = 0;
-Object.defineProperty(HTMLCanvasElement.prototype, 'getContext', {
-  value: () => ({ measureText: () => ({ width: mockCanvasWidth }), font: '' }),
-});
-
-describe('CanvasTextUtils', () => {
-  describe('font calculations', () => {
-    it('computes the set font if passed a container element', () => {
-      const container = document.createElement('div');
-      container.style.font = '14px Inter';
-
-      const utils = new CanvasTextUtils({ container });
-      expect(utils.context.font).toEqual('14px Inter');
-    });
-
-    it('accepts a static font string', () => {
-      const utils = new CanvasTextUtils({ font: '14px Inter' });
-      expect(utils.context.font).toEqual('14px Inter');
-    });
-  });
-
-  describe('text width utils', () => {
-    const utils = new CanvasTextUtils({ font: '' });
-
-    describe('textWidth', () => {
-      it('returns the measured text width from the canvas', () => {
-        mockCanvasWidth = 200;
-        expect(utils.textWidth).toEqual(200);
-      });
-    });
-
-    describe('setTextToCheck', () => {
-      it('sets the internal currentText variable', () => {
-        utils.setTextToCheck('hello world');
-        expect(utils.currentText).toEqual('hello world');
-      });
-    });
-  });
-});
+import { TruncationUtils } from './utils';
 
 describe('TruncationUtils', () => {
   const params = {
@@ -56,6 +16,11 @@ describe('TruncationUtils', () => {
     font: '14px Inter',
   };
 
+  const setMockTextWidth = (width: number) => (utils: TruncationUtils) => {
+    // @ts-ignore - mocked canvas_text_utils.testenv allows setting this value
+    utils.textWidth = width;
+  };
+
   // A few utilities log errors - silence them and capture the messages
   const consoleErrorSpy = jest.spyOn(console, 'error').mockImplementation();
   beforeEach(() => consoleErrorSpy.mockClear());
@@ -69,23 +34,23 @@ describe('TruncationUtils', () => {
 
     describe('setTextWidthRatio', () => {
       it('sets the ratio of the available width to the full text width', () => {
-        mockCanvasWidth = 10000;
+        setMockTextWidth(10000)(utils);
         utils.setTextWidthRatio();
         expect(utils.widthRatio).toEqual(0.1);
       });
 
       it('allow measuring passed text and deducting an offset width', () => {
         // Note: there isn't a super great way to mock a real-world example of this
         // in Jest because mockCanvasWidth applies to both the measured text and excluded text
-        mockCanvasWidth = 500;
+        setMockTextWidth(500)(utils);
         utils.setTextWidthRatio('text to measure', 'some excluded text');
         expect(utils.widthRatio).toEqual(1);
       });
     });
 
     describe('getTextFromRatio', () => {
       it('splits the passed text string by the ratio determined by `setTextWidthRatio`', () => {
-        mockCanvasWidth = 3000;
+        setMockTextWidth(3000)(utils);
         utils.setTextWidthRatio(); // 0.33
         // Should split the strings by the last/first third
         expect(utils.getTextFromRatio('Lorem ipsum', 'start')).toEqual('psum');
@@ -99,36 +64,36 @@ describe('TruncationUtils', () => {
 
     describe('checkIfTruncationIsNeeded', () => {
       it('returns false if truncation is not needed', () => {
-        mockCanvasWidth = 100;
+        setMockTextWidth(100)(utils);
         expect(utils.checkIfTruncationIsNeeded()).toEqual(false);
 
-        mockCanvasWidth = 400;
+        setMockTextWidth(400)(utils);
         expect(utils.checkIfTruncationIsNeeded()).toBeUndefined();
       });
     });
 
     describe('checkSufficientEllipsisWidth', () => {
       it('returns false and errors if the container is not wide enough for the ellipsis', () => {
-        mockCanvasWidth = 201;
+        setMockTextWidth(201)(utils);
         expect(utils.checkSufficientEllipsisWidth('startEnd')).toEqual(false);
         expect(consoleErrorSpy).toHaveBeenCalledWith(
           'The truncation ellipsis is larger than the available width. No text can be rendered.'
         );
 
-        mockCanvasWidth = 10;
+        setMockTextWidth(10)(utils);
         expect(utils.checkSufficientEllipsisWidth('start')).toBeUndefined();
       });
     });
 
     describe('checkTruncationOffsetWidth', () => {
       it('returns false and errors if the container is not wide enough for the offset text', () => {
-        mockCanvasWidth = 201;
+        setMockTextWidth(201)(utils);
         expect(utils.checkTruncationOffsetWidth('hello')).toEqual(false);
         expect(consoleErrorSpy).toHaveBeenCalledWith(
           'The passed truncationOffset is too large for the available width. Truncating the offset instead.'
         );
 
-        mockCanvasWidth = 200;
+        setMockTextWidth(200)(utils);
         expect(utils.checkTruncationOffsetWidth('world')).toBeUndefined();
       });
     });

src/components/text_truncate/utils.ts

@@ -6,72 +6,14 @@
  * Side Public License, v 1.
  */
 
-import type { ExclusiveUnion } from '../common';
+import { CanvasTextParams, CanvasTextUtils } from '../../services/canvas';
 
-type CanvasTextParams = ExclusiveUnion<
-  { container: HTMLElement },
-  { font: CanvasTextDrawingStyles['font'] }
->;
 type TruncationParams = CanvasTextParams & {
   fullText: string;
   ellipsis: string;
   availableWidth: number;
 };
 
-/**
- * Under the hood, a temporary Canvas element is created for manipulating text
- * & determining text width.
- *
- * To accurately measure text, canvas rendering requires either a container to
- * compute/derive font styles from, or a static font string (useful for usage
- * outside the DOM). Particular care should be applied when fallback fonts are
- * used, as more fallback fonts can lead to less precision.
- *
- * Please note that while canvas is more significantly more performant than DOM
- * measurement, there are subpixel to single digit pixel differences between
- * DOM and canvas measurement due to the different rendering engines used.
- */
-export class CanvasTextUtils {
-  context: CanvasRenderingContext2D;
-  currentText = '';
-
-  constructor({ font, container }: CanvasTextParams) {
-    this.context = document.createElement('canvas').getContext('2d')!;
-
-    // Set the canvas font to ensure text width calculations are correct
-    if (font) {
-      this.context.font = font;
-    } else if (container) {
-      this.context.font = this.computeFontFromElement(container);
-    }
-  }
-
-  computeFontFromElement = (element: HTMLElement) => {
-    const computedStyles = window.getComputedStyle(element);
-    // TODO: font-stretch is not included even though it potentially should be
-    // @see https://developer.mozilla.org/en-US/docs/Web/CSS/font#constituent_properties
-    // It appears to be unsupported and/or breaks font computation in canvas
-    return [
-      'font-style',
-      'font-variant',
-      'font-weight',
-      'font-size',
-      'font-family',
-    ]
-      .map((prop) => computedStyles.getPropertyValue(prop))
-      .join(' ')
-      .trim();
-  };
-
-  get textWidth() {
-    return this.context.measureText(this.currentText).width;
-  }
-
-  setTextToCheck = (text: string) => {
-    this.currentText = text;
-  };
-}
-
 /**
  * Utilities for truncating types at various positions, as well as
  * determining whether truncation is possible or even necessary.

src/services/canvas/canvas_text_utils.test.ts

@@ -0,0 +1,49 @@
+/*
+ * Copyright Elasticsearch B.V. and/or licensed to Elasticsearch B.V. under one
+ * or more contributor license agreements. Licensed under the Elastic License
+ * 2.0 and the Server Side Public License, v 1; you may not use this file except
+ * in compliance with, at your election, the Elastic License 2.0 or the Server
+ * Side Public License, v 1.
+ */
+
+import { CanvasTextUtils } from './canvas_text_utils';
+
+let mockCanvasWidth = 0;
+Object.defineProperty(HTMLCanvasElement.prototype, 'getContext', {
+  value: () => ({ measureText: () => ({ width: mockCanvasWidth }), font: '' }),
+});
+
+describe('CanvasTextUtils', () => {
+  describe('font calculations', () => {
+    it('computes the set font if passed a container element', () => {
+      const container = document.createElement('div');
+      container.style.font = '14px Inter';
+
+      const utils = new CanvasTextUtils({ container });
+      expect(utils.context.font).toEqual('14px Inter');
+    });
+
+    it('accepts a static font string', () => {
+      const utils = new CanvasTextUtils({ font: '14px Inter' });
+      expect(utils.context.font).toEqual('14px Inter');
+    });
+  });
+
+  describe('text width utils', () => {
+    const utils = new CanvasTextUtils({ font: '' });
+
+    describe('textWidth', () => {
+      it('returns the measured text width from the canvas', () => {
+        mockCanvasWidth = 200;
+        expect(utils.textWidth).toEqual(200);
+      });
+    });
+
+    describe('setTextToCheck', () => {
+      it('sets the internal currentText variable', () => {
+        utils.setTextToCheck('hello world');
+        expect(utils.currentText).toEqual('hello world');
+      });
+    });
+  });
+});

src/services/canvas/canvas_text_utils.testenv.ts

@@ -0,0 +1,20 @@
+/*
+ * Copyright Elasticsearch B.V. and/or licensed to Elasticsearch B.V. under one
+ * or more contributor license agreements. Licensed under the Elastic License
+ * 2.0 and the Server Side Public License, v 1; you may not use this file except
+ * in compliance with, at your election, the Elastic License 2.0 or the Server
+ * Side Public License, v 1.
+ */
+
+export class CanvasTextUtils {
+  constructor(_: any) {}
+
+  computeFontFromElement = (_: HTMLElement) => '';
+
+  textWidth = 0;
+
+  currentText = '';
+  setTextToCheck = (text: string) => {
+    this.currentText = text;
+  };
+}