Add ability to set custom stylesheets for SVG renderer (#105)
* Add ability to set custom stylesheets for SVG renderer This allow to set custom inline CSS and a optional CSP nonce. This solves the problem mentioned in #103 and is best used with it, as seen in the added examples. Without this one would have to write a custom renderer. * Add note with link to the custom_stylesheets example
This commit is contained in:
Justin Kromlinger
Will Charczuk
parent
96acfc6a9f
commit
3cb33d48d3
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@ -7,6 +7,8 @@ import (
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"net/http"
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)
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// Note: Additional examples on how to add Stylesheets are in the custom_stylesheets example
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func inlineSVGWithClasses(res http.ResponseWriter, req *http.Request) {
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res.Write([]byte(
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"<!DOCTYPE html><html><head>" +
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@ -0,0 +1,21 @@
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<svg xmlns="http://www.w3.org/2000/svg" xmlns:xlink="http://www.w3.org/1999/xlink" width="512" height="512">\n<style type="text/css"><![CDATA[svg .background { fill: white; }svg .canvas { fill: white; }svg path.blue { fill: blue; stroke: lightblue; }svg path.green { fill: green; stroke: lightgreen; }svg path.gray { fill: gray; stroke: lightgray; }svg text.blue { fill: white; }svg text.green { fill: white; }svg text.gray { fill: white; }]]></style><path d="M 0 0
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L 512 0
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L 512 512
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L 0 512
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L 0 0" class="background"/><path d="M 5 5
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L 507 5
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L 507 507
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L 5 507
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L 5 5" class="canvas"/><path d="M 256 256
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L 507 256
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A 251 251 128.56 0 1 100 452
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L 256 256
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Z" class="blue"/><path d="M 256 256
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L 100 452
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A 251 251 128.56 0 1 201 12
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L 256 256
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Z" class="green"/><path d="M 256 256
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L 201 12
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A 251 251 102.85 0 1 506 256
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L 256 256
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Z" class="gray"/><text x="313" y="413" class="blue">Blue</text><text x="73" y="226" class="green">Green</text><text x="344" y="133" class="gray">Gray</text></svg>
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After Width: | Height: | Size: 987 B |
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@ -0,0 +1,87 @@
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package main
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import (
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"fmt"
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"github.com/hashworks/go-chart"
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"log"
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"net/http"
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)
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const style = "svg .background { fill: white; }" +
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"svg .canvas { fill: white; }" +
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"svg path.blue { fill: blue; stroke: lightblue; }" +
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"svg path.green { fill: green; stroke: lightgreen; }" +
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"svg path.gray { fill: gray; stroke: lightgray; }" +
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"svg text.blue { fill: white; }" +
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"svg text.green { fill: white; }" +
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"svg text.gray { fill: white; }"
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func svgWithCustomInlineCSS(res http.ResponseWriter, _ *http.Request) {
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res.Header().Set("Content-Type", chart.ContentTypeSVG)
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// Render the CSS with custom css
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err := pieChart().Render(chart.SVGWithCSS(style, ""), res)
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if err != nil {
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fmt.Printf("Error rendering pie chart: %v\n", err)
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}
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}
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func svgWithCustomInlineCSSNonce(res http.ResponseWriter, _ *http.Request) {
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// https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/Content-Security-Policy/style-src
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// This should be randomly generated on every request!
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const nonce = "RAND0MBASE64"
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res.Header().Set("Content-Security-Policy", fmt.Sprintf("style-src 'nonce-%s'", nonce))
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res.Header().Set("Content-Type", chart.ContentTypeSVG)
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// Render the CSS with custom css and a nonce.
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// Try changing the nonce to a different string - your browser should block the CSS.
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err := pieChart().Render(chart.SVGWithCSS(style, nonce), res)
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if err != nil {
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fmt.Printf("Error rendering pie chart: %v\n", err)
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}
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}
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func svgWithCustomExternalCSS(res http.ResponseWriter, _ *http.Request) {
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// Add external CSS
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res.Write([]byte(
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`<?xml version="1.0" standalone="no"?>`+
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`<?xml-stylesheet href="/main.css" type="text/css"?>`+
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`<!DOCTYPE svg PUBLIC "-//W3C//DTD SVG 1.1//EN" "http://www.w3.org/Graphics/SVG/1.1/DTD/svg11.dtd">`))
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res.Header().Set("Content-Type", chart.ContentTypeSVG)
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err := pieChart().Render(chart.SVG, res)
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if err != nil {
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fmt.Printf("Error rendering pie chart: %v\n", err)
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}
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}
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func pieChart() chart.PieChart {
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return chart.PieChart{
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// Note that setting ClassName will cause all other inline styles to be dropped!
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Background: chart.Style{ClassName: "background"},
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Canvas: chart.Style{
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ClassName: "canvas",
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},
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Width: 512,
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Height: 512,
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Values: []chart.Value{
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{Value: 5, Label: "Blue", Style: chart.Style{ClassName: "blue"}},
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{Value: 5, Label: "Green", Style: chart.Style{ClassName: "green"}},
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{Value: 4, Label: "Gray", Style: chart.Style{ClassName: "gray"}},
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},
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}
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}
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func css(res http.ResponseWriter, req *http.Request) {
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res.Header().Set("Content-Type", "text/css")
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res.Write([]byte(style))
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}
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func main() {
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http.HandleFunc("/", svgWithCustomInlineCSS)
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http.HandleFunc("/nonce", svgWithCustomInlineCSSNonce)
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http.HandleFunc("/external", svgWithCustomExternalCSS)
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http.HandleFunc("/main.css", css)
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log.Fatal(http.ListenAndServe(":8080", nil))
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}
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@ -28,6 +28,25 @@ func SVG(width, height int) (Renderer, error) {
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}, nil
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}
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// SVGWithCSS returns a new png/raster renderer with attached custom CSS
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// The optional nonce argument sets a CSP nonce.
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func SVGWithCSS(css string, nonce string) (func(width, height int)(Renderer, error)) {
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return func(width, height int) (Renderer, error) {
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buffer := bytes.NewBuffer([]byte{})
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canvas := newCanvas(buffer)
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canvas.css = css
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canvas.nonce = nonce
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canvas.Start(width, height)
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return &vectorRenderer{
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b: buffer,
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c: canvas,
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s: &Style{},
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p: []string{},
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dpi: DefaultDPI,
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}, nil
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}
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}
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// vectorRenderer renders chart commands to a bitmap.
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type vectorRenderer struct {
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dpi float64
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@ -222,12 +241,23 @@ type canvas struct {
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textTheta *float64
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width int
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height int
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css string
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nonce string
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}
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func (c *canvas) Start(width, height int) {
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c.width = width
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c.height = height
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c.w.Write([]byte(fmt.Sprintf(`<svg xmlns="http://www.w3.org/2000/svg" xmlns:xlink="http://www.w3.org/1999/xlink" width="%d" height="%d">\n`, c.width, c.height)))
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if c.css != "" {
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c.w.Write([]byte(`<style type="text/css"`))
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if c.nonce != "" {
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// https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/Content-Security-Policy
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c.w.Write([]byte(fmt.Sprintf(` nonce="%s"`, c.nonce)))
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}
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// To avoid compatibility issues between XML and CSS (f.e. with child selectors) we should encapsulate the CSS with CDATA.
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c.w.Write([]byte(fmt.Sprintf(`><![CDATA[%s]]></style>`, c.css)))
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}
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}
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func (c *canvas) Path(d string, style Style) {
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@ -2,6 +2,7 @@ package chart
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import (
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"bytes"
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"fmt"
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"strings"
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"testing"
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@ -89,3 +90,30 @@ func TestCanvasClassSVG(t *testing.T) {
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as.Equal("class=\"test-class\"", canvas.styleAsSVG(set))
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}
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func TestCanvasCustomInlineStylesheet(t *testing.T) {
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b := strings.Builder{}
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canvas := &canvas{
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w: &b,
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css: ".background { fill: red }",
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}
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canvas.Start(200, 200)
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assert.New(t).Contains(b.String(), fmt.Sprintf(`<style type="text/css"><![CDATA[%s]]></style>`, canvas.css))
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}
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func TestCanvasCustomInlineStylesheetWithNonce(t *testing.T) {
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b := strings.Builder{}
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canvas := &canvas{
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w: &b,
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css: ".background { fill: red }",
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nonce: "RAND0MSTRING",
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}
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canvas.Start(200, 200)
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assert.New(t).Contains(b.String(), fmt.Sprintf(`<style type="text/css" nonce="%s"><![CDATA[%s]]></style>`, canvas.nonce, canvas.css))
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}
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