Feat: Add global instance CSS customization setting

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.

docs/admin/settings.md

@@ -167,3 +167,11 @@ Links to the set contact account and/or email address will appear on the footer
 The selected **contact user** must be an active (not suspended) admin and/or moderator on the instance.
 
 If you're on a single-user instance and you give admin privileges to your main account, you can just fill in your own username here; you don't need to make a separate admin account just for this.
+
+### Instance Custom CSS
+
+custom CSS allows you to further customize the way your instance looks when visited through a browser.
+
+This custom CSS will be applied to all pages of your instance. Users themes and CSS still take precedence over this customization.
+
+See the [Custom CSS](./custom_css.md) page for some tips on writing custom CSS for your instance.

docs/api/swagger.yaml

@@ -1545,6 +1545,10 @@ definitions:
                 $ref: '#/definitions/instanceV1Configuration'
             contact_account:
                 $ref: '#/definitions/account'
+            custom_css:
+                description: Custom CSS for the instance.
+                type: string
+                x-go-name: CustomCSS
             debug:
                 description: Whether or not instance is running in DEBUG mode. Omitted if false.
                 type: boolean
@@ -1725,6 +1729,10 @@ definitions:
                 $ref: '#/definitions/instanceV2Configuration'
             contact:
                 $ref: '#/definitions/instanceV2Contact'
+            custom_css:
+                description: Instance Custom Css
+                type: string
+                x-go-name: CustomCSS
             debug:
                 description: Whether or not instance is running in DEBUG mode. Omitted if false.
                 type: boolean

internal/api/client/instance/instancepatch.go

@@ -175,6 +175,7 @@ func validateInstanceUpdate(form *apimodel.InstanceSettingsUpdateRequest) error
 		form.ContactEmail == nil &&
 		form.ShortDescription == nil &&
 		form.Description == nil &&
+		form.CustomCSS == nil &&
 		form.Terms == nil &&
 		form.Avatar == nil &&
 		form.AvatarDescription == nil &&

internal/api/model/instance.go

@@ -33,6 +33,8 @@ type InstanceSettingsUpdateRequest struct {
 	ShortDescription *string `form:"short_description" json:"short_description" xml:"short_description"`
 	// Longer description of the instance, max 5,000 chars. HTML formatting accepted.
 	Description *string `form:"description" json:"description" xml:"description"`
+	// Custom CSS for the instance.
+	CustomCSS *string `form:"custom_css" json:"custom_css,omitempty" xml:"custom_css"`
 	// Terms and conditions of the instance, max 5,000 chars. HTML formatting accepted.
 	Terms *string `form:"terms" json:"terms" xml:"terms"`
 	// Image to use as the instance thumbnail.

internal/api/model/instancev1.go

@@ -38,6 +38,8 @@ type InstanceV1 struct {
 	//
 	// This should be displayed on the 'about' page for an instance.
 	Description string `json:"description"`
+	// Custom CSS for the instance.
+	CustomCSS string `json:"custom_css,omitempty"`
 	// Raw (unparsed) version of description.
 	DescriptionText string `json:"description_text,omitempty"`
 	// A shorter description of the instance.

internal/api/model/instancev2.go

@@ -53,6 +53,8 @@ type InstanceV2 struct {
 	Description string `json:"description"`
 	// Raw (unparsed) version of description.
 	DescriptionText string `json:"description_text,omitempty"`
+	// Instance Custom Css
+	CustomCSS string `json:"custom_css,omitempty"`
 	// Basic anonymous usage data for this instance.
 	Usage InstanceV2Usage `json:"usage"`
 	// An image used to represent this instance.

internal/db/bundb/migrations/20240924222938_add_instance_custom_css.go

@@ -0,0 +1,44 @@
+// GoToSocial
+// Copyright (C) GoToSocial Authors admin@gotosocial.org
+// SPDX-License-Identifier: AGPL-3.0-or-later
+//
+// This program is free software: you can redistribute it and/or modify
+// it under the terms of the GNU Affero General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// This program is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU Affero General Public License for more details.
+//
+// You should have received a copy of the GNU Affero General Public License
+// along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+package migrations
+
+import (
+	"context"
+	"strings"
+
+	"github.com/uptrace/bun"
+)
+
+func init() {
+	up := func(ctx context.Context, db *bun.DB) error {
+		_, err := db.ExecContext(ctx, "ALTER TABLE ? ADD COLUMN ? TEXT", bun.Ident("instances"), bun.Ident("custom_css"))
+		if err != nil && !(strings.Contains(err.Error(), "already exists") || strings.Contains(err.Error(), "duplicate column name") || strings.Contains(err.Error(), "SQLSTATE 42701")) {
+			return err
+		}
+		return nil
+	}
+
+	down := func(ctx context.Context, db *bun.DB) error {
+		_, err := db.ExecContext(ctx, "ALTER TABLE ? DROP COLUMN ?", bun.Ident("instances"), bun.Ident("custom_css"))
+		return err
+	}
+
+	if err := Migrations.Register(up, down); err != nil {
+		panic(err)
+	}
+}

internal/gtsmodel/instance.go

@@ -34,6 +34,7 @@ type Instance struct {
 	ShortDescriptionText   string       `bun:""`                                                            // Raw text version of short description (before parsing).
 	Description            string       `bun:""`                                                            // Longer description of this instance.
 	DescriptionText        string       `bun:""`                                                            // Raw text version of long description (before parsing).
+	CustomCSS              string       `bun:",nullzero"`                                                   // Custom CSS for the instance.
 	Terms                  string       `bun:""`                                                            // Terms and conditions of this instance.
 	TermsText              string       `bun:""`                                                            // Raw text version of terms (before parsing).
 	ContactEmail           string       `bun:""`                                                            // Contact email address for this instance

internal/processing/instance.go

@@ -227,6 +227,17 @@ func (p *Processor) InstancePatch(ctx context.Context, form *apimodel.InstanceSe
 		columns = append(columns, []string{"description", "description_text"}...)
 	}
 
+	// validate & update site custom css if it's set on the form
+	if form.CustomCSS != nil {
+		customCSS := *form.CustomCSS
+		if err := validate.InstanceCustomCSS(customCSS); err != nil {
+			return nil, gtserror.NewErrorBadRequest(err, err.Error())
+		}
+
+		instance.CustomCSS = text.SanitizeToPlaintext(customCSS)
+		columns = append(columns, []string{"custom_css"}...)
+	}
+
 	// Validate & update site
 	// terms if set on the form.
 	if form.Terms != nil {

internal/typeutils/internaltofrontend.go

@@ -1523,6 +1523,7 @@ func (c *Converter) InstanceToAPIV1Instance(ctx context.Context, i *gtsmodel.Ins
 		Title:                i.Title,
 		Description:          i.Description,
 		DescriptionText:      i.DescriptionText,
+		CustomCSS:            i.CustomCSS,
 		ShortDescription:     i.ShortDescription,
 		ShortDescriptionText: i.ShortDescriptionText,
 		Email:                i.ContactEmail,
@@ -1644,6 +1645,7 @@ func (c *Converter) InstanceToAPIV2Instance(ctx context.Context, i *gtsmodel.Ins
 		SourceURL:       instanceSourceURL,
 		Description:     i.Description,
 		DescriptionText: i.DescriptionText,
+		CustomCSS:       i.CustomCSS,
 		Usage:           apimodel.InstanceV2Usage{}, // todo: not implemented
 		Languages:       config.GetInstanceLanguages().TagStrs(),
 		Rules:           c.InstanceRulesToAPIRules(i.Rules),

internal/validate/formvalidation.go

@@ -189,6 +189,16 @@ func CustomCSS(customCSS string) error {
 	return nil
 }
 
+func InstanceCustomCSS(customCSS string) error {
+
+	maximumCustomCSSLength := config.GetAccountsCustomCSSLength()
+	if length := len([]rune(customCSS)); length > maximumCustomCSSLength {
+		return fmt.Errorf("custom_css must be less than %d characters, but submitted custom_css was %d characters", maximumCustomCSSLength, length)
+	}
+
+	return nil
+}
+
 // EmojiShortcode just runs the given shortcode through the regular expression
 // for emoji shortcodes, to figure out whether it's a valid shortcode, ie., 2-30 characters,
 // a-zA-Z, numbers, and underscores.

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

@@ -129,6 +129,7 @@ func (m *Module) confirmEmailPOSTHandler(c *gin.Context) {
 	page := apiutil.WebPage{
 		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

@@ -128,6 +128,7 @@ func (m *Module) signupPOSTHandler(c *gin.Context) {
 	page := apiutil.WebPage{
 		Template:    "signed-up.tmpl",
 		Instance:    instance,
+		Stylesheets: []string{instanceCustomCSSPath},
 		OGMeta:      apiutil.OGBase(instance),
 		Extra: map[string]any{
 			"email":    user.UnconfirmedEmail,

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

@@ -41,6 +41,7 @@
 	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"
@@ -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)

web/source/settings/lib/types/instance.ts

@@ -25,6 +25,7 @@ export interface InstanceV1 {
     description_text?:       string;
     short_description:      string;
     short_description_text?: string;
+    custom_css:             string;
     email:                  string;
     version:                string;
     debug?:                 boolean;

web/source/settings/views/admin/instance/settings.tsx

@@ -66,6 +66,10 @@ function InstanceSettingsForm({ data: instance }: InstanceSettingsFormProps) {
 			valueSelector: (s: InstanceV1) => s.description_text,
 			validator: (val: string) => val.length <= descLimit ? "" : `Instance description is ${val.length} characters; must be ${descLimit} characters or less`
 		}),
+		customCSS: useTextInput("custom_css", {
+			source: instance,
+			valueSelector: (s: InstanceV1) => s.custom_css
+		}),
 		terms: useTextInput("terms", {
 			source: instance,
 			// Select "raw" text version of parsed field for editing.
@@ -191,6 +195,15 @@ function InstanceSettingsForm({ data: instance }: InstanceSettingsFormProps) {
 				type="email"
 			/>
 
+			<TextArea
+				field={form.customCSS}
+				label={"Custom CSS"}
+				className="monospace"
+				rows={8}
+				autoCapitalize="none"
+				spellCheck="false"
+			/>
+
 			<MutationButton label="Save" result={result} disabled={false} />
 		</form>
 	);