Add link tags for pdfs

CHANGELOG.md

@@ -9,6 +9,7 @@ project adheres to [Semantic Versioning](http://semver.org/).
 ==================
 ### Changed
 ### Added
+* Support for links in PDFs
 ### Fixed
 
 

Readme.md

@@ -521,6 +521,15 @@ ctx.addPage(400, 800)
 ctx.fillText('Hello World 2', 50, 80)
 ```
 
+It is possible to add hyperlinks use `.beginTag()` and `.closeTag()`:
+
+```js
+ctx.beginTag({name: 'Link', uri: 'https://google.com'})
+ctx.font = '22px Helvetica'
+ctx.fillText('Hello World', 50, 80)
+ctx.closeTag()
+```
+
 See also:
 
 * [Image#dataMode](#imagedatamode) for embedding JPEGs in PDFs

examples/pdf-link.js

@@ -0,0 +1,19 @@
+const fs = require('fs')
+const Canvas = require('..')
+
+const canvas = Canvas.createCanvas(400, 200, 'pdf')
+const ctx = canvas.getContext('2d')
+
+let y = 80
+let x = 50
+
+ctx.beginTag({ name: 'Link', uri: 'https://google.com' })
+ctx.font = '22px Helvetica'
+ctx.fillText('node-canvas pdf', x, y)
+ctx.closeTag()
+
+fs.writeFile('out.pdf', canvas.toBuffer(), function (err) {
+  if (err) throw err
+
+  console.log('created out.pdf')
+})

index.d.ts

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

src/CanvasRenderingContext2d.cc

@@ -134,6 +134,10 @@ Context2d::Initialize(Napi::Env& env, Napi::Object& exports) {
     InstanceMethod<&Context2d::CreatePattern>("createPattern"),
     InstanceMethod<&Context2d::CreateLinearGradient>("createLinearGradient"),
     InstanceMethod<&Context2d::CreateRadialGradient>("createRadialGradient"),
+    #if CAIRO_VERSION >= CAIRO_VERSION_ENCODE(1, 16, 0)
+    InstanceMethod<&Context2d::BeginTag>("beginTag", napi_default_method),
+    InstanceMethod<&Context2d::CloseTag>("closeTag", napi_default_method),
+    #endif
     InstanceAccessor<&Context2d::GetFormat>("pixelFormat"),
     InstanceAccessor<&Context2d::GetPatternQuality, &Context2d::SetPatternQuality>("patternQuality"),
     InstanceAccessor<&Context2d::GetImageSmoothingEnabled, &Context2d::SetImageSmoothingEnabled>("imageSmoothingEnabled"),
@@ -3354,3 +3358,77 @@ Context2d::Ellipse(const Napi::CallbackInfo& info) {
   }
   cairo_set_matrix(ctx, &save_matrix);
 }
+
+#if CAIRO_VERSION >= CAIRO_VERSION_ENCODE(1, 16, 0)
+
+/*
+ * Open and close a link tag
+ */
+
+void
+replaceAll( std::string &s, const std::string &search, const std::string &replace ) {
+    for( size_t pos = 0; ; pos += replace.length() ) {
+        // Locate the substring to replace
+        pos = s.find( search, pos );
+        if( pos == std::string::npos ) break;
+        // Replace by erasing and inserting
+        s.erase( pos, search.length() );
+        s.insert( pos, replace );
+    }
+}
+
+bool
+containsOnlyASCII(const std::string& str) {
+  for (auto c: str) {
+    if (static_cast<unsigned char>(c) > 127) {
+      return false;
+    }
+  }
+  return true;
+}
+
+void
+Context2d::BeginTag(const Napi::CallbackInfo& info) {
+  if (info.Length() < 1 || !info[0].IsObject()) {
+    Napi::TypeError::New(env, "config must be an object").ThrowAsJavaScriptException();
+    return;
+  }
+
+  Napi::Object config = info[0].As<Napi::Object>();
+
+  Napi::String nameValue;
+  if (!config.Get("name").UnwrapTo(&nameValue)) {
+    Napi::TypeError::New(env, "config must have a name key").ThrowAsJavaScriptException();
+    return;
+  }
+  std::string name = nameValue.Utf8Value();
+  if (name != CAIRO_TAG_LINK) {
+    Napi::TypeError::New(env, "name must be 'Link'").ThrowAsJavaScriptException();
+    return;
+  }
+
+  Napi::String uriValue;
+  if (!config.Get("uri").UnwrapTo(&uriValue)) {
+    Napi::TypeError::New(env, "config must have a uri key").ThrowAsJavaScriptException();
+    return;
+  }
+  std::string uri = uriValue.Utf8Value();
+  if (!containsOnlyASCII(uri)) {
+    Napi::TypeError::New(env, "uri must be ascii only").ThrowAsJavaScriptException();
+    return;
+  }
+
+  replaceAll(uri, "'", "\\'");
+  std::string attrs = "uri='" + uri + "'";
+
+  cairo_t *ctx = context();
+  cairo_tag_begin(ctx, CAIRO_TAG_LINK, attrs.c_str());
+}
+
+void
+Context2d::CloseTag(const Napi::CallbackInfo& info) {
+  cairo_t *ctx = context();
+  cairo_tag_end(ctx, CAIRO_TAG_LINK);
+}
+
+#endif

src/CanvasRenderingContext2d.h

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

test/canvas.test.js

@@ -823,6 +823,11 @@ describe('Canvas', function () {
         assertPixel(0xffff0000, 5, 0, 'first red pixel')
       })
     })
+
+    it('Canvas#toBuffer("application/pdf")', function () {
+      const buf = createCanvas(200, 200, 'pdf').toBuffer('application/pdf')
+      assert.equal('PDF', buf.slice(1, 4).toString())
+    })
   })
 
   describe('#toDataURL()', function () {
@@ -2068,4 +2073,28 @@ describe('Canvas', function () {
       })
     }
   })
+
+  describe('Context2d#beingTag()/endTag()', function () {
+    it ("generates a pdf", function () {
+      const canvas = createCanvas(20, 20, 'pdf')
+      const ctx = canvas.getContext('2d')
+      ctx.beginTag({ name: 'Link', uri: 'tes\'t' })
+      ctx.strokeText('hello', 0, 0)
+      ctx.closeTag()
+      const buf = canvas.toBuffer('application/pdf')
+      assert.equal('PDF', buf.slice(1, 4).toString())
+    })
+
+    it("must be a link", function () {
+      const canvas = createCanvas(20, 20, 'pdf')
+      const ctx = canvas.getContext('2d')
+      assert.throws(() => { ctx.beginTag({ name: 'other', uri: 'test' }) })
+    })
+
+    it("must be a ascii", function () {
+      const canvas = createCanvas(20, 20, 'pdf')
+      const ctx = canvas.getContext('2d')
+      assert.throws(() => { ctx.beginTag({ name: 'Link', uri: 'має бути ascii' }) })
+    })
+  })
 })