appview: serve ico favicons on /favicon.ico

this is recognized by safari. the only size this image is served at is
48x48. the dolly silhouette is used. cache/etag headers are identical to
the svg output.

Signed-off-by: oppiliappan <[e-mail]>

appview/pages/templates/layouts/base.html

···
             <script defer src="/static/htmx-ext-ws.min.js"></script>
             <script defer src="/static/actor-typeahead.js" type="module"></script>
 
+            <link rel="icon" href="/favicon.ico" sizes="48x48"/>
+            <link rel="icon" href="/favicon.svg" sizes="any" type="image/svg+xml"/>
+
             <!-- preconnect to image cdn -->
             <link rel="preconnect" href="https://avatar.tangled.sh" />
             <link rel="preconnect" href="https://camo.tangled.sh" />

appview/state/favicon.go

···
+package state
+
+import (
+	"bytes"
+	"fmt"
+	"html/template"
+	"image"
+	"image/color"
+	"net/http"
+
+	"github.com/srwiley/oksvg"
+	"github.com/srwiley/rasterx"
+	"golang.org/x/image/draw"
+	"tangled.org/core/appview/pages"
+	"tangled.org/core/ico"
+)
+
+func (s *State) FaviconSvg(w http.ResponseWriter, r *http.Request) {
+	w.Header().Set("Content-Type", "image/svg+xml")
+	w.Header().Set("Cache-Control", "public, max-age=31536000") // one year
+	w.Header().Set("ETag", `"favicon-svg-v1"`)
+
+	if match := r.Header.Get("If-None-Match"); match == `"favicon-svg-v1"` {
+		w.WriteHeader(http.StatusNotModified)
+		return
+	}
+
+	s.pages.Favicon(w)
+}
+
+func (s *State) FaviconIco(w http.ResponseWriter, r *http.Request) {
+	w.Header().Set("Content-Type", "image/x-icon")
+	w.Header().Set("Cache-Control", "public, max-age=31536000") // one year
+	w.Header().Set("ETag", `"favicon-ico-v1"`)
+
+	if match := r.Header.Get("If-None-Match"); match == `"favicon-ico-v1"` {
+		w.WriteHeader(http.StatusNotModified)
+		return
+	}
+
+	ico, err := dollyIco()
+	if err != nil {
+		s.logger.Error("failed to render ico", "err", err)
+		w.WriteHeader(http.StatusNotFound)
+		return
+	}
+
+	w.Write(ico)
+}
+
+func dollyIco() ([]byte, error) {
+	// first, get the bytes from the svg
+	tpl, err := template.New("dolly").
+		ParseFS(pages.Files, "templates/fragments/dolly/silhouette.html")
+	if err != nil {
+		return nil, err
+	}
+
+	var svgData bytes.Buffer
+	if err := tpl.ExecuteTemplate(&svgData, "fragments/dolly/silhouette", "#000000"); err != nil {
+		return nil, err
+	}
+
+	img, err := svgToImage(svgData.Bytes(), 48, 48)
+	if err != nil {
+		return nil, err
+	}
+
+	ico, err := ico.ImageToIco(img)
+	if err != nil {
+		return nil, err
+	}
+
+	return ico, nil
+}
+
+func svgToImage(svgData []byte, w, h int) (image.Image, error) {
+	icon, err := oksvg.ReadIconStream(bytes.NewReader(svgData))
+	if err != nil {
+		return nil, fmt.Errorf("error parsing SVG: %v", err)
+	}
+
+	icon.SetTarget(0, 0, float64(w), float64(h))
+	rgba := image.NewRGBA(image.Rect(0, 0, w, h))
+	draw.Draw(rgba, rgba.Bounds(), &image.Uniform{color.Transparent}, image.Point{}, draw.Src)
+	scanner := rasterx.NewScannerGV(w, h, rgba, rgba.Bounds())
+	raster := rasterx.NewDasher(w, h, scanner)
+	icon.Draw(raster, 1.0)
+
+	return rgba, nil
+}

appview/state/router.go

···
 		s.pages,
 	)
 
-	router.Get("/favicon.svg", s.Favicon)
-	router.Get("/favicon.ico", s.Favicon)
+	router.Get("/favicon.svg", s.FaviconSvg)
+	router.Get("/favicon.ico", s.FaviconIco)
 	router.Get("/pwa-manifest.json", s.PWAManifest)
 	router.Get("/robots.txt", s.RobotsTxt)
 

appview/state/state.go

···
 	return s.db.Close()
 }
 
-func (s *State) Favicon(w http.ResponseWriter, r *http.Request) {
-	w.Header().Set("Content-Type", "image/svg+xml")
-	w.Header().Set("Cache-Control", "public, max-age=31536000") // one year
-	w.Header().Set("ETag", `"favicon-svg-v1"`)
-
-	if match := r.Header.Get("If-None-Match"); match == `"favicon-svg-v1"` {
-		w.WriteHeader(http.StatusNotModified)
-		return
-	}
-
-	s.pages.Favicon(w)
-}
-
 func (s *State) RobotsTxt(w http.ResponseWriter, r *http.Request) {
 	w.Header().Set("Content-Type", "text/plain")
 	w.Header().Set("Cache-Control", "public, max-age=86400") // one day