run sass in development mode;

document how to install sass better

README.md

@@ -33,20 +33,20 @@ To deploy PixivFE using Docker or the compiled binary, see the [Hosting PixivFE]
 
 **Requirements:**
 
-- [pnpm](https://pnpm.io/installation) (to install Sass)
-- [go](https://go.dev/doc/install) (to build PixivFE from source)
+- [Go](https://go.dev/doc/install) (to build PixivFE from source)
+- [Sass](https://github.com/sass/dart-sass/) (will be run by PixivFE in development mode)
+
+To install Dart Sass, you can choose any of the following methods.
+
+- use system package manager (usually called `dart-sass`)
+- download executable from [the official release page](https://github.com/sass/dart-sass/releases)
+- `pnpm i -g sass`
 
 ```bash
 # Clone the PixivFE repository
 git clone https://codeberg.org/VnPower/PixivFE.git && cd PixivFE
 
-# Install Sass globally using pnpm
-pnpm i -g sass
-
-# Compile styles using Sass and watch for changes
-sass --watch ./views/css
-
-# Run in PixivFE in development mode (templates reload automatically)
+# Run in PixivFE in development mode (styles and templates reload automatically)
 PIXIVFE_DEV=1 <other_environment_variables> go run .
 ```
 

main.go

@@ -6,7 +6,11 @@ import (
 	"log"
 	"net"
 	"net/http"
+	"os"
+	"os/exec"
+	"runtime"
 	"strings"
+	"syscall"
 	"time"
 
 	config "codeberg.org/vnpower/pixivfe/v2/core/config"
@@ -205,6 +209,21 @@ func main() {
 	proxy.Get("/s.pximg.net/*", pages.SPximgProxy)
 	proxy.Get("/ugoira.com/*", pages.UgoiraProxy)
 
+	// run sass when in development mode
+	if config.GlobalServerConfig.InDevelopment {
+		go func() {
+			cmd := exec.Command("sass", "--watch", "views/css")
+			cmd.Stdout = os.Stderr // heh. (sass quirk)
+			cmd.Stderr = os.Stderr
+			cmd.SysProcAttr = &syscall.SysProcAttr{Setpgid: true, Pdeathsig: syscall.SIGHUP}
+			runtime.LockOSThread() // O.O https://github.com/golang/go/issues/27505
+			err := cmd.Run()
+			if err != nil {
+				log.Println(fmt.Errorf("when running sass: %w", err))
+			}
+		}()
+	}
+
 	// Listen
 	if config.GlobalServerConfig.UnixSocket != "" {
 		ln, err := net.Listen("unix", config.GlobalServerConfig.UnixSocket)