Support selecting theme on the footer (#35741)

Fixes: https://github.com/go-gitea/gitea/pull/27576

routers/common/errpage.go

@@ -35,7 +35,7 @@ func RenderPanicErrorPage(w http.ResponseWriter, req *http.Request, err any) {
 	httpcache.SetCacheControlInHeader(w.Header(), &httpcache.CacheControlOptions{NoTransform: true})
 	w.Header().Set(`X-Frame-Options`, setting.CORSConfig.XFrameOptions)
 
-	tmplCtx := context.TemplateContext{}
+	tmplCtx := context.NewTemplateContext(req.Context(), req)
 	tmplCtx["Locale"] = middleware.Locale(w, req)
 	ctxData := middleware.GetContextData(req.Context())
 

routers/common/qos.go

@@ -133,7 +133,7 @@ func renderServiceUnavailable(w http.ResponseWriter, req *http.Request) {
 		return
 	}
 
-	tmplCtx := giteacontext.TemplateContext{}
+	tmplCtx := giteacontext.NewTemplateContext(req.Context(), req)
 	tmplCtx["Locale"] = middleware.Locale(w, req)
 	ctxData := middleware.GetContextData(req.Context())
 	err := templates.HTMLRenderer().HTML(w, http.StatusServiceUnavailable, tplStatus503, ctxData, tmplCtx)

routers/install/routes.go

@@ -14,6 +14,7 @@ import (
 	"code.gitea.io/gitea/modules/web"
 	"code.gitea.io/gitea/routers/common"
 	"code.gitea.io/gitea/routers/web/healthcheck"
+	"code.gitea.io/gitea/routers/web/misc"
 	"code.gitea.io/gitea/services/forms"
 )
 
@@ -32,7 +33,11 @@ func Routes() *web.Router {
 	r.Get("/", Install) // it must be on the root, because the "install.js" use the window.location to replace the "localhost" AppURL
 	r.Post("/", web.Bind(forms.InstallForm{}), SubmitInstall)
 	r.Get("/post-install", InstallDone)
+
+	r.Get("/-/web-theme/list", misc.WebThemeList)
+	r.Post("/-/web-theme/apply", misc.WebThemeApply)
 	r.Get("/api/healthz", healthcheck.Check)
+
 	r.NotFound(installNotFound)
 
 	base.Mount("", r)

routers/web/misc/webtheme.go

@@ -0,0 +1,42 @@
+// Copyright 2025 The Gitea Authors. All rights reserved.
+// SPDX-License-Identifier: MIT
+
+package misc
+
+import (
+	"net/http"
+
+	"code.gitea.io/gitea/modules/optional"
+	"code.gitea.io/gitea/modules/templates"
+	"code.gitea.io/gitea/modules/util"
+	"code.gitea.io/gitea/modules/web/middleware"
+	"code.gitea.io/gitea/services/context"
+	user_service "code.gitea.io/gitea/services/user"
+	"code.gitea.io/gitea/services/webtheme"
+)
+
+func WebThemeList(ctx *context.Context) {
+	curWebTheme := ctx.TemplateContext.CurrentWebTheme()
+	renderUtils := templates.NewRenderUtils(ctx)
+	allThemes := webtheme.GetAvailableThemes()
+
+	var results []map[string]any
+	for _, theme := range allThemes {
+		results = append(results, map[string]any{
+			"name":  renderUtils.RenderThemeItem(theme, 14),
+			"value": theme.InternalName,
+			"class": "item js-aria-clickable" + util.Iif(theme.InternalName == curWebTheme.InternalName, " selected", ""),
+		})
+	}
+	ctx.JSON(http.StatusOK, map[string]any{"results": results})
+}
+
+func WebThemeApply(ctx *context.Context) {
+	themeName := ctx.FormString("theme")
+	if ctx.Doer != nil {
+		opts := &user_service.UpdateOptions{Theme: optional.Some(themeName)}
+		_ = user_service.UpdateUser(ctx, ctx.Doer, opts)
+	} else {
+		middleware.SetSiteCookie(ctx.Resp, "gitea_theme", themeName, 0)
+	}
+}

routers/web/user/setting/profile.go

@@ -369,7 +369,7 @@ func UpdateUIThemePost(ctx *context.Context) {
 		return
 	}
 
-	if !webtheme.IsThemeAvailable(form.Theme) {
+	if webtheme.GetThemeMetaInfo(form.Theme) == nil {
 		ctx.Flash.Error(ctx.Tr("settings.theme_update_error"))
 		ctx.Redirect(setting.AppSubURL + "/user/settings/appearance")
 		return

routers/web/web.go

@@ -490,6 +490,9 @@ func registerWebRoutes(m *web.Router) {
 
 	m.Post("/-/markup", reqSignIn, web.Bind(structs.MarkupOption{}), misc.Markup)
 
+	m.Get("/-/web-theme/list", misc.WebThemeList)
+	m.Post("/-/web-theme/apply", optSignInIgnoreCsrf, misc.WebThemeApply)
+
 	m.Group("/explore", func() {
 		m.Get("", func(ctx *context.Context) {
 			ctx.Redirect(setting.AppSubURL + "/explore/repos")