implement internal links in PDF

ci/release/changelogs/next.md

@@ -1,10 +1,11 @@
 #### Features 🚀
 
+- PDF exports support external links [#891](https://github.com/terrastruct/d2/issues/891)
+- PDF exports support internal links [#891](https://github.com/terrastruct/d2/issues/966)
 - `border-radius` is now supported on connections (ELK and TALA only, since Dagre uses curves). [#913](https://github.com/terrastruct/d2/pull/913)
 
 #### Improvements 🧹
 
-- PDF exports now support external links on shapes [#891](https://github.com/terrastruct/d2/issues/891)
 - SVGs are fit to top left by default to avoid issues with zooming. [#954](https://github.com/terrastruct/d2/pull/954)
 - Person shapes now have labels below them and don't need to expand as much. [#960](https://github.com/terrastruct/d2/pull/960)
 

d2cli/main.go

@@ -29,6 +29,7 @@ import (
 	"oss.terrastruct.com/d2/d2themes/d2themescatalog"
 	"oss.terrastruct.com/d2/lib/imgbundler"
 	ctxlog "oss.terrastruct.com/d2/lib/log"
+	"oss.terrastruct.com/d2/lib/pdf"
 	pdflib "oss.terrastruct.com/d2/lib/pdf"
 	"oss.terrastruct.com/d2/lib/png"
 	"oss.terrastruct.com/d2/lib/textmeasure"
@@ -291,7 +292,8 @@ func compile(ctx context.Context, ms *xmain.State, plugin d2plugin.Plugin, sketc
 
 	var svg []byte
 	if filepath.Ext(outputPath) == ".pdf" {
-		svg, err = renderPDF(ctx, ms, plugin, sketch, pad, themeID, outputPath, page, ruler, diagram, nil, nil)
+		pageMap := pdf.BuildPDFPageMap(diagram, nil, nil)
+		svg, err = renderPDF(ctx, ms, plugin, sketch, pad, themeID, outputPath, page, ruler, diagram, nil, nil, pageMap)
 	} else {
 		compileDur := time.Since(start)
 		svg, err = render(ctx, ms, compileDur, plugin, sketch, pad, themeID, darkThemeID, inputPath, outputPath, bundle, forceAppendix, page, ruler, diagram)
@@ -443,7 +445,7 @@ func _render(ctx context.Context, ms *xmain.State, plugin d2plugin.Plugin, sketc
 	return svg, nil
 }
 
-func renderPDF(ctx context.Context, ms *xmain.State, plugin d2plugin.Plugin, sketch bool, pad, themeID int64, outputPath string, page playwright.Page, ruler *textmeasure.Ruler, diagram *d2target.Diagram, pdf *pdflib.GoFPDF, boardPath []string) (svg []byte, err error) {
+func renderPDF(ctx context.Context, ms *xmain.State, plugin d2plugin.Plugin, sketch bool, pad, themeID int64, outputPath string, page playwright.Page, ruler *textmeasure.Ruler, diagram *d2target.Diagram, pdf *pdflib.GoFPDF, boardPath []string, pageMap map[string]int) (svg []byte, err error) {
 	var isRoot bool
 	if pdf == nil {
 		pdf = pdflib.Init()
@@ -504,26 +506,26 @@ func renderPDF(ctx context.Context, ms *xmain.State, plugin d2plugin.Plugin, ske
 		if err != nil {
 			return svg, err
 		}
-		err = pdf.AddPDFPage(pngImg, currBoardPath, themeID, rootFill, diagram.Shapes, pad, viewboxX, viewboxY)
+		err = pdf.AddPDFPage(pngImg, currBoardPath, themeID, rootFill, diagram.Shapes, pad, viewboxX, viewboxY, pageMap)
 		if err != nil {
 			return svg, err
 		}
 	}
 
 	for _, dl := range diagram.Layers {
-		_, err := renderPDF(ctx, ms, plugin, sketch, pad, themeID, "", page, ruler, dl, pdf, currBoardPath)
+		_, err := renderPDF(ctx, ms, plugin, sketch, pad, themeID, "", page, ruler, dl, pdf, currBoardPath, pageMap)
 		if err != nil {
 			return nil, err
 		}
 	}
 	for _, dl := range diagram.Scenarios {
-		_, err := renderPDF(ctx, ms, plugin, sketch, pad, themeID, "", page, ruler, dl, pdf, currBoardPath)
+		_, err := renderPDF(ctx, ms, plugin, sketch, pad, themeID, "", page, ruler, dl, pdf, currBoardPath, pageMap)
 		if err != nil {
 			return nil, err
 		}
 	}
 	for _, dl := range diagram.Steps {
-		_, err := renderPDF(ctx, ms, plugin, sketch, pad, themeID, "", page, ruler, dl, pdf, currBoardPath)
+		_, err := renderPDF(ctx, ms, plugin, sketch, pad, themeID, "", page, ruler, dl, pdf, currBoardPath, pageMap)
 		if err != nil {
 			return nil, err
 		}

e2etests-cli/main_test.go

@@ -122,6 +122,28 @@ scenarios: {
 				assert.TestdataDir(t, filepath.Join(dir, "life"))
 			},
 		},
+		{
+			name: "internal_linked_pdf",
+			run: func(t *testing.T, ctx context.Context, dir string, env *xos.Env) {
+				writeFile(t, dir, "in.d2", `cat: how does the cat go? {
+  link: layers.cat
+}
+layers: {
+  cat: {
+    home: {
+      link: _
+    }
+    the cat -> meow: goes
+  }
+}
+`)
+				err := runTestMain(t, ctx, dir, env, "in.d2", "out.pdf")
+				assert.Success(t, err)
+
+				pdf := readFile(t, dir, "out.pdf")
+				testdataIgnoreDiff(t, ".pdf", pdf)
+			},
+		},
 	}
 
 	ctx := context.Background()

lib/pdf/pdf.go

@@ -7,6 +7,7 @@ import (
 
 	"github.com/jung-kurt/gofpdf"
 
+	"oss.terrastruct.com/d2/d2parser"
 	"oss.terrastruct.com/d2/d2renderers/d2fonts"
 	"oss.terrastruct.com/d2/d2target"
 	"oss.terrastruct.com/d2/d2themes"
@@ -58,7 +59,7 @@ func (g *GoFPDF) GetFillRGB(themeID int64, fill string) (color.RGB, error) {
 	return color.Hex2RGB(fill)
 }
 
-func (g *GoFPDF) AddPDFPage(png []byte, boardPath []string, themeID int64, fill string, shapes []d2target.Shape, pad int64, viewboxX, viewboxY float64) error {
+func (g *GoFPDF) AddPDFPage(png []byte, boardPath []string, themeID int64, fill string, shapes []d2target.Shape, pad int64, viewboxX, viewboxY float64, pageMap map[string]int) error {
 	var opt gofpdf.ImageOptions
 	opt.ImageType = "png"
 	imageInfo := g.pdf.RegisterImageOptionsReader(strings.Join(boardPath, "/"), opt, bytes.NewReader(png))
@@ -122,14 +123,28 @@ func (g *GoFPDF) AddPDFPage(png []byte, boardPath []string, themeID int64, fill
 	imageY := headerHeight + (pageHeight-imageHeight)/2
 	g.pdf.ImageOptions(strings.Join(boardPath, "/"), imageX, imageY, imageWidth, imageHeight, false, opt, 0, "")
 
-	// Draw external links
+	// Draw links
 	for _, shape := range shapes {
-		if shape.Link != "" {
-			linkX := imageX + float64(shape.Pos.X) - viewboxX - float64(shape.StrokeWidth)
-			linkY := imageY + float64(shape.Pos.Y) - viewboxY - float64(shape.StrokeWidth)
-			linkWidth := float64(shape.Width) + float64(shape.StrokeWidth*2)
-			linkHeight := float64(shape.Height) + float64(shape.StrokeWidth*2)
+		if shape.Link == "" {
+			continue
+		}
+
+		linkX := imageX + float64(shape.Pos.X) - viewboxX - float64(shape.StrokeWidth)
+		linkY := imageY + float64(shape.Pos.Y) - viewboxY - float64(shape.StrokeWidth)
+		linkWidth := float64(shape.Width) + float64(shape.StrokeWidth*2)
+		linkHeight := float64(shape.Height) + float64(shape.StrokeWidth*2)
+
+		key, err := d2parser.ParseKey(shape.Link)
+		if err != nil || key.Path[0].Unbox().ScalarString() != "root" {
+			// External link
 			g.pdf.LinkString(linkX, linkY, linkWidth, linkHeight, shape.Link)
+		} else {
+			// Internal link
+			if pageNum, ok := pageMap[shape.Link]; ok {
+				linkID := g.pdf.AddLink()
+				g.pdf.SetLink(linkID, 0, pageNum+1)
+				g.pdf.Link(linkX, linkY, linkWidth, linkHeight, linkID)
+			}
 		}
 	}
 
@@ -149,3 +164,28 @@ func (g *GoFPDF) AddPDFPage(png []byte, boardPath []string, themeID int64, fill
 func (g *GoFPDF) Export(outputPath string) error {
 	return g.pdf.OutputFileAndClose(outputPath)
 }
+
+// BuildPDFPageMap returns a map from board path to page int
+// To map correctly, it must follow the same traversal of PDF building
+func BuildPDFPageMap(diagram *d2target.Diagram, dictionary map[string]int, path []string) map[string]int {
+	newPath := append(path, diagram.Name)
+	if dictionary == nil {
+		dictionary = map[string]int{}
+		newPath[0] = "root"
+	}
+
+	key := strings.Join(newPath, ".")
+	dictionary[key] = len(dictionary)
+
+	for _, dl := range diagram.Layers {
+		BuildPDFPageMap(dl, dictionary, append(newPath, "layers"))
+	}
+	for _, dl := range diagram.Scenarios {
+		BuildPDFPageMap(dl, dictionary, append(newPath, "scenarios"))
+	}
+	for _, dl := range diagram.Steps {
+		BuildPDFPageMap(dl, dictionary, append(newPath, "steps"))
+	}
+
+	return dictionary
+}