add string tags for HTMLCanvasElement, ImageData and `CanvasGradi…

…ent`

CHANGELOG.md

@@ -9,6 +9,7 @@ project adheres to [Semantic Versioning](http://semver.org/).
 ==================
 ### Changed
 ### Added
+* Added string tags for `ImageData` and `CanvasGradient` to support class detection
 ### Fixed
 * Add missing property `canvas` to the `CanvasRenderingContext2D` type
 * Fixed glyph positions getting rounded, resulting text having a slight `letter-spacing` effect

lib/bindings.js

@@ -4,10 +4,22 @@ const bindings = require('../build/Release/canvas.node')
 
 module.exports = bindings
 
+Object.defineProperty(bindings.Canvas.prototype, Symbol.toStringTag, {
+  value: 'HTMLCanvasElement'
+})
+
 bindings.ImageData.prototype.toString = function () {
 	return '[object ImageData]'
 }
 
+Object.defineProperty(bindings.ImageData.prototype, Symbol.toStringTag, {
+  value: 'ImageData'
+})
+
 bindings.CanvasGradient.prototype.toString = function () {
 	return '[object CanvasGradient]'
 }
+
+Object.defineProperty(bindings.CanvasGradient.prototype, Symbol.toStringTag, {
+  value: 'CanvasGradient'
+})

test/canvas.test.js

@@ -1439,6 +1439,11 @@ describe('Canvas', function () {
     assert.equal(0, imageData.data[i + 2])
     assert.equal(255, imageData.data[i + 3])
   })
+  it('Canvas has class string of `HTMLCanvasElement`', function () {
+    const canvas = createCanvas(20, 1)
+
+    assert.strictEqual(Object.prototype.toString.call(canvas), '[object HTMLCanvasElement]')
+  })
 
   it('CanvasGradient stringifies as [object CanvasGradient]', function () {
     const canvas = createCanvas(20, 1)
@@ -1447,6 +1452,13 @@ describe('Canvas', function () {
     assert.strictEqual(gradient.toString(), '[object CanvasGradient]')
   })
 
+  it('CanvasGradient has class string of `CanvasGradient`', function () {
+    const canvas = createCanvas(20, 1)
+    const ctx = canvas.getContext('2d')
+    const gradient = ctx.createLinearGradient(1, 1, 19, 1)
+    assert.strictEqual(Object.prototype.toString.call(gradient), '[object CanvasGradient]')
+  })
+
   describe('Context2d#putImageData()', function () {
     it('throws for invalid arguments', function () {
       const canvas = createCanvas(2, 1)
@@ -1943,7 +1955,7 @@ describe('Canvas', function () {
         ctx[k] = v
         ctx.restore()
         assert.strictEqual(ctx[k], old)
-  
+
         // save() doesn't modify the value:
         ctx[k] = v
         old = ctx[k]

test/imageData.test.js

@@ -17,6 +17,11 @@ describe('ImageData', function () {
     assert.strictEqual(imageData.toString(), '[object ImageData]')
   })
 
+  it('gives class string as `ImageData`', function () {
+    const imageData = createImageData(2, 3)
+    assert.strictEqual(Object.prototype.toString.call(imageData), '[object ImageData]')
+  })
+
   it('should throw with invalid numeric arguments', function () {
     assert.throws(() => { createImageData(0, 0) }, /width is zero/)
     assert.throws(() => { createImageData(1, 0) }, /height is zero/)