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Commit da33bbe

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mcfedrchearon
andcommitted
Add link tags for pdfs
Co-Authored-By: Caleb Hearon <caleb@chearon.net>
1 parent 728e76c commit da33bbe

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8 files changed

+141
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lines changed

8 files changed

+141
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lines changed

‎.gitignore

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@@ -4,6 +4,7 @@ build
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test/images/*.png
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examples/*.png
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examples/*.jpg
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examples/*.pdf
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testing
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out.png
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out.pdf

‎CHANGELOG.md

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@@ -12,6 +12,8 @@ project adheres to [Semantic Versioning](http://semver.org/).
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* `ctx.font` has a new C++ parser and is 2x-400x faster. Please file an issue if you experience different results, as caching has been removed.
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### Added
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* Support for accessibility and links in PDFs
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### Fixed
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3.0.1

‎Readme.md

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@@ -515,6 +515,26 @@ ctx.addPage(400, 800)
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ctx.fillText('Hello World 2', 50, 80)
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```
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It is possible to add hyperlinks using `.beginTag()` and `.endTag()`:
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```js
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ctx.beginTag('Link', "uri='https://google.com'")
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ctx.font = '22px Helvetica'
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ctx.fillText('Hello World', 50, 80)
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ctx.endTag('Link')
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```
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Or with a defined rectangle:
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```js
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ctx.beginTag('Link', "uri='https://google.com' rect=[50 80 100 20]")
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ctx.endTag('Link')
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```
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Note that the syntax for attributes is unique to Cairo. See [cairo_tag_begin](https://www.cairographics.org/manual/cairo-Tags-and-Links.html#cairo-tag-begin) for the full documentation.
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You can create areas on the canvas using the "cairo.dest" tag, and then link to them using the "Link" tag with the `dest=` attribute. You can also define PDF structure for accessibility by using tag names like "P", "H1", and "TABLE". The standard tags are defined in §14.8.4 of the [PDF 1.7](https://opensource.adobe.com/dc-acrobat-sdk-docs/pdfstandards/PDF32000_2008.pdf) specification.
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See also:
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* [Image#dataMode](#imagedatamode) for embedding JPEGs in PDFs

‎examples/pdf-link.js

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@@ -0,0 +1,20 @@
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const fs = require('fs')
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const path = require('path')
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const Canvas = require('..')
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const canvas = Canvas.createCanvas(400, 300, 'pdf')
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const ctx = canvas.getContext('2d')
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ctx.beginTag('Link', 'uri=\'https://google.com\'')
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ctx.font = '22px Helvetica'
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ctx.fillText('Text link to Google', 110, 50)
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ctx.endTag('Link')
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ctx.fillText('Rect link to node-canvas below!', 40, 180)
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ctx.beginTag('Link', 'uri=\'https://github.com/Automattic/node-canvas\' rect=[0 200 400 100]')
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ctx.endTag('Link')
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fs.writeFile(path.join(__dirname, 'pdf-link.pdf'), canvas.toBuffer(), function (err) {
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if (err) throw err
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})

‎index.d.ts

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@@ -232,6 +232,8 @@ export class CanvasRenderingContext2D {
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createPattern(image: Canvas|Image, repetition: 'repeat' | 'repeat-x' | 'repeat-y' | 'no-repeat' | '' | null): CanvasPattern
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createLinearGradient(x0: number, y0: number, x1: number, y1: number): CanvasGradient;
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createRadialGradient(x0: number, y0: number, r0: number, x1: number, y1: number, r1: number): CanvasGradient;
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beginTag(tagName: string, attributes?: string): void;
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endTag(tagName: string): void;
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/**
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* _Non-standard_. Defaults to 'good'. Affects pattern (gradient, image,
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* etc.) rendering quality.

‎src/CanvasRenderingContext2d.cc

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@@ -135,6 +135,10 @@ Context2d::Initialize(Napi::Env& env, Napi::Object& exports) {
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InstanceMethod<&Context2d::CreatePattern>("createPattern", napi_default_method),
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InstanceMethod<&Context2d::CreateLinearGradient>("createLinearGradient", napi_default_method),
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InstanceMethod<&Context2d::CreateRadialGradient>("createRadialGradient", napi_default_method),
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#if CAIRO_VERSION >= CAIRO_VERSION_ENCODE(1, 16, 0)
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InstanceMethod<&Context2d::BeginTag>("beginTag", napi_default_method),
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InstanceMethod<&Context2d::EndTag>("endTag", napi_default_method),
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#endif
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InstanceAccessor<&Context2d::GetFormat>("pixelFormat", napi_default_jsproperty),
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InstanceAccessor<&Context2d::GetPatternQuality, &Context2d::SetPatternQuality>("patternQuality", napi_default_jsproperty),
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InstanceAccessor<&Context2d::GetImageSmoothingEnabled, &Context2d::SetImageSmoothingEnabled>("imageSmoothingEnabled", napi_default_jsproperty),
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width = cairo_image_surface_get_width(patternSurface);
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height = y2 - y1;
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}
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cairo_new_path(_context);
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cairo_rectangle(_context, 0, 0, width, height);
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cairo_clip(_context);
@@ -3348,3 +3352,53 @@ Context2d::Ellipse(const Napi::CallbackInfo& info) {
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}
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cairo_set_matrix(ctx, &save_matrix);
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}
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#if CAIRO_VERSION >= CAIRO_VERSION_ENCODE(1, 16, 0)
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void
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Context2d::BeginTag(const Napi::CallbackInfo& info) {
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std::string tagName = "";
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std::string attributes = "";
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if (info.Length() == 0) {
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Napi::TypeError::New(env, "Tag name is required").ThrowAsJavaScriptException();
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return;
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} else {
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if (!info[0].IsString()) {
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Napi::TypeError::New(env, "Tag name must be a string.").ThrowAsJavaScriptException();
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return;
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} else {
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tagName = info[0].As<Napi::String>().Utf8Value();
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}
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if (info.Length() > 1) {
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if (!info[1].IsString()) {
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Napi::TypeError::New(env, "Attributes must be a string matching Cairo's attribute format").ThrowAsJavaScriptException();
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return;
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} else {
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attributes = info[1].As<Napi::String>().Utf8Value();
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}
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}
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}
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cairo_tag_begin(_context, tagName.c_str(), attributes.c_str());
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}
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void
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Context2d::EndTag(const Napi::CallbackInfo& info) {
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if (info.Length() == 0) {
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Napi::TypeError::New(env, "Tag name is required").ThrowAsJavaScriptException();
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return;
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}
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if (!info[0].IsString()) {
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Napi::TypeError::New(env, "Tag name must be a string.").ThrowAsJavaScriptException();
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return;
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}
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std::string tagName = info[0].As<Napi::String>().Utf8Value();
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cairo_tag_end(_context, tagName.c_str());
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}
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#endif

‎src/CanvasRenderingContext2d.h

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@@ -178,6 +178,10 @@ class Context2d : public Napi::ObjectWrap<Context2d> {
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void SetFont(const Napi::CallbackInfo& info, const Napi::Value& value);
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void SetTextBaseline(const Napi::CallbackInfo& info, const Napi::Value& value);
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void SetTextAlign(const Napi::CallbackInfo& info, const Napi::Value& value);
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#if CAIRO_VERSION >= CAIRO_VERSION_ENCODE(1, 16, 0)
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void BeginTag(const Napi::CallbackInfo& info);
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void EndTag(const Napi::CallbackInfo& info);
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#endif
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inline void setContext(cairo_t *ctx) { _context = ctx; }
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inline cairo_t *context(){ return _context; }
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inline Canvas *canvas(){ return _canvas; }

‎test/canvas.test.js

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@@ -755,6 +755,11 @@ describe('Canvas', function () {
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assertPixel(0xffff0000, 5, 0, 'first red pixel')
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})
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})
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it('Canvas#toBuffer("application/pdf")', function () {
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const buf = createCanvas(200, 200, 'pdf').toBuffer('application/pdf')
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assert.equal('PDF', buf.slice(1, 4).toString())
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})
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})
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describe('#toDataURL()', function () {
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})
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}
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})
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describe('Context2d#beingTag()/endTag()', function () {
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before(function () {
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const canvas = createCanvas(20, 20, 'pdf')
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const ctx = canvas.getContext('2d')
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if (!('beginTag' in ctx)) {
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this.skip()
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}
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})
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it('generates a pdf', function () {
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const canvas = createCanvas(20, 20, 'pdf')
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const ctx = canvas.getContext('2d')
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ctx.beginTag('Link', "uri='http://example.com'")
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ctx.strokeText('hello', 0, 0)
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ctx.endTag('Link')
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const buf = canvas.toBuffer('application/pdf')
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assert.equal('PDF', buf.slice(1, 4).toString())
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})
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it('requires tag argument', function () {
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const canvas = createCanvas(20, 20, 'pdf')
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const ctx = canvas.getContext('2d')
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assert.throws(() => { ctx.beginTag() })
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})
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it('requires attributes to be a string', function () {
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const canvas = createCanvas(20, 20, 'pdf')
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const ctx = canvas.getContext('2d')
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assert.throws(() => { ctx.beginTag('Link', {}) })
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})
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})
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})

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