go-chart/_examples/custom_stylesheets/main.go
Justin Kromlinger 3cb33d48d3 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
2018-10-12 09:43:30 -07:00

88 lines
2.8 KiB
Go

package main
import (
"fmt"
"github.com/hashworks/go-chart"
"log"
"net/http"
)
const style = "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; }"
func svgWithCustomInlineCSS(res http.ResponseWriter, _ *http.Request) {
res.Header().Set("Content-Type", chart.ContentTypeSVG)
// Render the CSS with custom css
err := pieChart().Render(chart.SVGWithCSS(style, ""), res)
if err != nil {
fmt.Printf("Error rendering pie chart: %v\n", err)
}
}
func svgWithCustomInlineCSSNonce(res http.ResponseWriter, _ *http.Request) {
// https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/Content-Security-Policy/style-src
// This should be randomly generated on every request!
const nonce = "RAND0MBASE64"
res.Header().Set("Content-Security-Policy", fmt.Sprintf("style-src 'nonce-%s'", nonce))
res.Header().Set("Content-Type", chart.ContentTypeSVG)
// Render the CSS with custom css and a nonce.
// Try changing the nonce to a different string - your browser should block the CSS.
err := pieChart().Render(chart.SVGWithCSS(style, nonce), res)
if err != nil {
fmt.Printf("Error rendering pie chart: %v\n", err)
}
}
func svgWithCustomExternalCSS(res http.ResponseWriter, _ *http.Request) {
// Add external CSS
res.Write([]byte(
`<?xml version="1.0" standalone="no"?>`+
`<?xml-stylesheet href="/main.css" type="text/css"?>`+
`<!DOCTYPE svg PUBLIC "-//W3C//DTD SVG 1.1//EN" "http://www.w3.org/Graphics/SVG/1.1/DTD/svg11.dtd">`))
res.Header().Set("Content-Type", chart.ContentTypeSVG)
err := pieChart().Render(chart.SVG, res)
if err != nil {
fmt.Printf("Error rendering pie chart: %v\n", err)
}
}
func pieChart() chart.PieChart {
return chart.PieChart{
// Note that setting ClassName will cause all other inline styles to be dropped!
Background: chart.Style{ClassName: "background"},
Canvas: chart.Style{
ClassName: "canvas",
},
Width: 512,
Height: 512,
Values: []chart.Value{
{Value: 5, Label: "Blue", Style: chart.Style{ClassName: "blue"}},
{Value: 5, Label: "Green", Style: chart.Style{ClassName: "green"}},
{Value: 4, Label: "Gray", Style: chart.Style{ClassName: "gray"}},
},
}
}
func css(res http.ResponseWriter, req *http.Request) {
res.Header().Set("Content-Type", "text/css")
res.Write([]byte(style))
}
func main() {
http.HandleFunc("/", svgWithCustomInlineCSS)
http.HandleFunc("/nonce", svgWithCustomInlineCSSNonce)
http.HandleFunc("/external", svgWithCustomExternalCSS)
http.HandleFunc("/main.css", css)
log.Fatal(http.ListenAndServe(":8080", nil))
}