[feature] Add global instance CSS customization setting (#3352)

Allow instance admins to add custom CSS that will affect
every page of their instance.

This is done with a new CustomCSS instance setting that
works pretty much exactly like the Users CustomCSS property.
This custom CSS is then requested for every page load.
User styles/themes take precedence over this CSS.

Co-authored-by: tobi <tobi.smethurst@protonmail.com>

internal/web/about.go

@@ -54,7 +54,7 @@ func (m *Module) aboutGETHandler(c *gin.Context) {
 		Template:    "about.tmpl",
 		Instance:    instance,
 		OGMeta:      apiutil.OGBase(instance),
-		Stylesheets: []string{cssAbout},
+		Stylesheets: []string{cssAbout, instanceCustomCSSPath},
 		Extra: map[string]any{
 			"showStrap":        true,
 			"blocklistExposed": config.GetInstanceExposeSuspendedWeb(),

internal/web/confirmemail.go

@@ -127,8 +127,9 @@ func (m *Module) confirmEmailPOSTHandler(c *gin.Context) {
 	// Serve page informing user that their
 	// email address is now confirmed.
 	page := apiutil.WebPage{
-		Template: "confirmed_email.tmpl",
-		Instance: instance,
+		Template:    "confirmed_email.tmpl",
+		Instance:    instance,
+		Stylesheets: []string{instanceCustomCSSPath},
 		Extra: map[string]any{
 			"email":    user.Email,
 			"username": user.Account.Username,

internal/web/customcss.go

@@ -55,3 +55,22 @@ func (m *Module) customCSSGETHandler(c *gin.Context) {
 	c.Header(cacheControlHeader, cacheControlNoCache)
 	c.Data(http.StatusOK, textCSSUTF8, []byte(customCSS))
 }
+
+func (m *Module) instanceCustomCSSGETHandler(c *gin.Context) {
+
+	if _, err := apiutil.NegotiateAccept(c, apiutil.TextCSS); err != nil {
+		apiutil.WebErrorHandler(c, gtserror.NewErrorNotAcceptable(err, err.Error()), m.processor.InstanceGetV1)
+		return
+	}
+
+	instanceV1, errWithCode := m.processor.InstanceGetV1(c.Request.Context())
+	if errWithCode != nil {
+		apiutil.WebErrorHandler(c, errWithCode, m.processor.InstanceGetV1)
+		return
+	}
+
+	instanceCustomCSS := instanceV1.CustomCSS
+
+	c.Header(cacheControlHeader, cacheControlNoCache)
+	c.Data(http.StatusOK, textCSSUTF8, []byte(instanceCustomCSS))
+}

internal/web/domain-blocklist.go

@@ -67,7 +67,7 @@ func (m *Module) domainBlockListGETHandler(c *gin.Context) {
 		Template:    "domain-blocklist.tmpl",
 		Instance:    instance,
 		OGMeta:      apiutil.OGBase(instance),
-		Stylesheets: []string{cssFA},
+		Stylesheets: []string{cssFA, instanceCustomCSSPath},
 		Javascript:  []string{jsFrontend},
 		Extra:       map[string]any{"blocklist": domainBlocks},
 	}

internal/web/index.go

@@ -59,7 +59,7 @@ func (m *Module) indexHandler(c *gin.Context) {
 		Template:    "index.tmpl",
 		Instance:    instance,
 		OGMeta:      apiutil.OGBase(instance),
-		Stylesheets: []string{cssAbout, cssIndex},
+		Stylesheets: []string{cssAbout, cssIndex, instanceCustomCSSPath},
 		Extra:       map[string]any{"showStrap": true},
 	}
 

internal/web/profile.go

@@ -132,7 +132,7 @@ func (m *Module) profileGETHandler(c *gin.Context) {
 	}
 
 	// Prepare stylesheets for profile.
-	stylesheets := make([]string, 0, 6)
+	stylesheets := make([]string, 0, 7)
 
 	// Basic profile stylesheets.
 	stylesheets = append(
@@ -142,6 +142,7 @@ func (m *Module) profileGETHandler(c *gin.Context) {
 			cssStatus,
 			cssThread,
 			cssProfile,
+			instanceCustomCSSPath,
 		}...,
 	)
 

internal/web/settings-panel.go

@@ -53,6 +53,7 @@ func (m *Module) SettingsPanelHandler(c *gin.Context) {
 			cssProfile, // Used for rendering stub/fake profiles.
 			cssStatus,  // Used for rendering stub/fake statuses.
 			cssSettings,
+			instanceCustomCSSPath,
 		},
 		Javascript: []string{jsSettings},
 	}

internal/web/signup.go

@@ -126,9 +126,10 @@ func (m *Module) signupPOSTHandler(c *gin.Context) {
 	// Serve a page informing the
 	// user that they've signed up.
 	page := apiutil.WebPage{
-		Template: "signed-up.tmpl",
-		Instance: instance,
-		OGMeta:   apiutil.OGBase(instance),
+		Template:    "signed-up.tmpl",
+		Instance:    instance,
+		Stylesheets: []string{instanceCustomCSSPath},
+		OGMeta:      apiutil.OGBase(instance),
 		Extra: map[string]any{
 			"email":    user.UnconfirmedEmail,
 			"username": user.Account.Username,

internal/web/tag.go

@@ -59,7 +59,7 @@ func (m *Module) tagGETHandler(c *gin.Context) {
 		Template:    "tag.tmpl",
 		Instance:    instance,
 		OGMeta:      apiutil.OGBase(instance),
-		Stylesheets: []string{cssFA, cssThread, cssTag},
+		Stylesheets: []string{cssFA, cssThread, cssTag, instanceCustomCSSPath},
 		Extra:       map[string]any{"tagName": tagName},
 	}
 

internal/web/thread.go

@@ -115,7 +115,7 @@ func (m *Module) threadGETHandler(c *gin.Context) {
 	}
 
 	// Prepare stylesheets for thread.
-	stylesheets := make([]string, 0, 5)
+	stylesheets := make([]string, 0, 6)
 
 	// Basic thread stylesheets.
 	stylesheets = append(
@@ -131,6 +131,7 @@ func (m *Module) threadGETHandler(c *gin.Context) {
 	if theme := targetAccount.Theme; theme != "" {
 		stylesheets = append(
 			stylesheets,
+			instanceCustomCSSPath,
 			themesPathPrefix+"/"+theme,
 		)
 	}

internal/web/web.go

@@ -36,20 +36,21 @@ import (
 )
 
 const (
-	confirmEmailPath   = "/" + uris.ConfirmEmailPath
-	profileGroupPath   = "/@:username"
-	statusPath         = "/statuses/:" + apiutil.WebStatusIDKey // leave out the '/@:username' prefix as this will be served within the profile group
-	tagsPath           = "/tags/:" + apiutil.TagNameKey
-	customCSSPath      = profileGroupPath + "/custom.css"
-	rssFeedPath        = profileGroupPath + "/feed.rss"
-	assetsPathPrefix   = "/assets"
-	distPathPrefix     = assetsPathPrefix + "/dist"
-	themesPathPrefix   = assetsPathPrefix + "/themes"
-	settingsPathPrefix = "/settings"
-	settingsPanelGlob  = settingsPathPrefix + "/*panel"
-	userPanelPath      = settingsPathPrefix + "/user"
-	adminPanelPath     = settingsPathPrefix + "/admin"
-	signupPath         = "/signup"
+	confirmEmailPath      = "/" + uris.ConfirmEmailPath
+	profileGroupPath      = "/@:username"
+	statusPath            = "/statuses/:" + apiutil.WebStatusIDKey // leave out the '/@:username' prefix as this will be served within the profile group
+	tagsPath              = "/tags/:" + apiutil.TagNameKey
+	customCSSPath         = profileGroupPath + "/custom.css"
+	instanceCustomCSSPath = "/custom.css"
+	rssFeedPath           = profileGroupPath + "/feed.rss"
+	assetsPathPrefix      = "/assets"
+	distPathPrefix        = assetsPathPrefix + "/dist"
+	themesPathPrefix      = assetsPathPrefix + "/themes"
+	settingsPathPrefix    = "/settings"
+	settingsPanelGlob     = settingsPathPrefix + "/*panel"
+	userPanelPath         = settingsPathPrefix + "/user"
+	adminPanelPath        = settingsPathPrefix + "/admin"
+	signupPath            = "/signup"
 
 	cacheControlHeader    = "Cache-Control"     // https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/Cache-Control
 	cacheControlNoCache   = "no-cache"          // https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/Cache-Control#response_directives
@@ -114,6 +115,7 @@ func (m *Module) Route(r *router.Router, mi ...gin.HandlerFunc) {
 	r.AttachHandler(http.MethodGet, settingsPathPrefix, m.SettingsPanelHandler)
 	r.AttachHandler(http.MethodGet, settingsPanelGlob, m.SettingsPanelHandler)
 	r.AttachHandler(http.MethodGet, customCSSPath, m.customCSSGETHandler)
+	r.AttachHandler(http.MethodGet, instanceCustomCSSPath, m.instanceCustomCSSGETHandler)
 	r.AttachHandler(http.MethodGet, rssFeedPath, m.rssFeedGETHandler)
 	r.AttachHandler(http.MethodGet, confirmEmailPath, m.confirmEmailGETHandler)
 	r.AttachHandler(http.MethodPost, confirmEmailPath, m.confirmEmailPOSTHandler)