站点背景功能优化、页脚上边距调整

backend/service/bg.go

@@ -17,14 +17,11 @@ const (
 	BgSurfaceSite  = "site"
 	BgSurfaceAdmin = "admin"
 
-	BgModeCover    = "cover"
+	BgModeCover   = "cover"
-	BgModeContain  = "contain"
+	BgModeContain = "contain"
-	BgModeRepeat   = "repeat"
+	BgModeRepeat  = "repeat"
-	BgModeRepeatX  = "repeat-x"
+	BgModeStretch = "stretch"
-	BgModeRepeatY  = "repeat-y"
+	DefaultBgMode = BgModeCover
-	BgModeStretch  = "stretch"
-	BgModeCenter   = "center"
-	DefaultBgMode  = BgModeCover
 )
 
 // ErrBgFileMissing 设置了合法 URL 但磁盘上没有对应文件
@@ -37,10 +34,7 @@ var bgModes = map[string]struct{}{
 	BgModeCover:   {},
 	BgModeContain: {},
 	BgModeRepeat:  {},
-	BgModeRepeatX: {},
-	BgModeRepeatY: {},
 	BgModeStretch: {},
-	BgModeCenter:  {},
 }
 
 // NormalizeBgMode 校验铺放模式；空串视为默认 cover

backend/service/bg_test.go

@@ -36,8 +36,13 @@ func TestNormalizeBgMode(t *testing.T) {
 	if _, ok := NormalizeBgMode("zoom"); ok {
 		t.Fatal("unknown mode should fail")
 	}
+	for _, legacy := range []string{"repeat-x", "repeat-y", "center"} {
+		if _, ok := NormalizeBgMode(legacy); ok {
+			t.Fatalf("legacy mode %s should fail", legacy)
+		}
+	}
 	for _, want := range []string{
-		BgModeCover, BgModeContain, BgModeRepeat, BgModeRepeatX, BgModeRepeatY, BgModeStretch, BgModeCenter,
+		BgModeCover, BgModeContain, BgModeRepeat, BgModeStretch,
 	} {
 		got, ok := NormalizeBgMode(" " + want + " ")
 		if !ok || got != want {

frontend/app/admin/appearance/AppearanceAdmin.tsx

@@ -24,8 +24,8 @@ import {
   AdminSettingRow,
   AdminStepper,
   AdminSwitch,
-  AdminSegmented,
 } from "@/components/admin";
+import BgModePicker from "./BgModePicker";
 import {
   apiUpdateSiteSettings,
   apiUploadSiteBackground,
@@ -41,10 +41,9 @@ import {
   normalizeHex,
 } from "@/lib/theme";
 import {
-  BG_MODE_OPTIONS,
+  BG_PREVIEW_ASPECT,
   applySiteBackground,
   bgConfigFromSettings,
-  normalizeBgMode,
   previewBoxStyle,
   type BgMode,
   type BgSurface,
@@ -239,7 +238,7 @@ export default function AppearanceAdmin({ initial }: { initial: PublicSettings }
     try {
       await saveBgPatch(
         { [key]: mode },
-        surface === "site" ? "前台铺放模式已保存" : "后台铺放模式已保存"
+        surface === "site" ? "前台铺放方式已保存" : "后台铺放方式已保存"
       );
     } catch (e) {
       toast(e instanceof Error ? e.message : "保存失败", "error");
@@ -285,11 +284,15 @@ export default function AppearanceAdmin({ initial }: { initial: PublicSettings }
           </div>
         </div>
         <div
-          className="relative h-36 rounded-[var(--r-sm)] border overflow-hidden"
+          className="relative w-full max-w-[480px] rounded-[var(--r-sm)] border overflow-hidden"
           style={{
+            aspectRatio: BG_PREVIEW_ASPECT,
             borderColor: "var(--line)",
             ...previewBoxStyle(url, mode),
           }}
+          role="img"
+          aria-label={`${title}背景预览，按 16:9 常见显示器比例`}
+          title="按 16:9（1920×1080）显示器比例预览"
         >
           {!url && (
             <span
@@ -299,6 +302,17 @@ export default function AppearanceAdmin({ initial }: { initial: PublicSettings }
               默认纹饰画布
             </span>
           )}
+          <span
+            className="absolute bottom-1.5 right-1.5 text-[10.5px] leading-none px-1.5 py-1 rounded-[4px] pointer-events-none"
+            aria-hidden
+            style={{
+              background: "color-mix(in srgb, var(--panel) 88%, transparent)",
+              color: "var(--ink-3)",
+              border: "1px solid var(--line)",
+            }}
+          >
+            16:9
+          </span>
         </div>
         <input
           ref={fileRef}
@@ -333,22 +347,13 @@ export default function AppearanceAdmin({ initial }: { initial: PublicSettings }
           ) : null}
         </div>
         <div>
-          <p className="field-label mb-2">铺放模式</p>
+          <p className="field-label mb-2">铺放方式</p>
-          <AdminSegmented
+          <BgModePicker
-            size="sm"
-            role="group"
-            ariaLabel={`${title}铺放模式`}
             value={mode}
-            onChange={(key) => void onChangeBgMode(surface, normalizeBgMode(key))}
+            disabled={busy}
-            options={BG_MODE_OPTIONS.map((o) => ({
+            ariaLabel={`${title}铺放方式`}
-              key: o.key,
+            onChange={(next) => void onChangeBgMode(surface, next)}
-              label: o.label,
-              disabled: busy,
-            }))}
           />
-          <p className="meta text-[12px] mt-1.5">
-            {BG_MODE_OPTIONS.find((o) => o.key === mode)?.hint}
-          </p>
         </div>
       </div>
     );
@@ -675,7 +680,7 @@ export default function AppearanceAdmin({ initial }: { initial: PublicSettings }
             <ImageIcon size={15} /> 站点背景图
           </span>
         }
-        description="前台与后台可分别上传 JPEG / PNG / WebP（≤8MB）。未配置时使用默认纹饰画布。"
+        description="前台与后台可分别上传 JPEG / PNG / WebP（≤8MB）。预览按 16:9 常见显示器比例。未配置时使用默认纹饰画布。"
       >
         <div className="grid grid-cols-1 lg:grid-cols-2 gap-6">
           {renderBgRail(

frontend/app/admin/appearance/BgModePicker.tsx

@@ -0,0 +1,107 @@
+"use client";
+
+import { BG_MODE_OPTIONS, type BgMode } from "@/lib/bg";
+
+/** 铺放示意：16:9 小窗里用色块表达裁切 / 完整 / 平铺 / 拉伸。 */
+function ModeGlyph({ mode }: { mode: BgMode }) {
+  const photo = "var(--accent-soft)";
+  const ink = "var(--accent)";
+  return (
+    <span
+      className="relative block w-16 aspect-video overflow-hidden rounded-[3px] shrink-0"
+      style={{ background: "var(--bg)", border: "1px solid var(--line-2)" }}
+      aria-hidden
+    >
+      {mode === "cover" && (
+        <span
+          className="absolute left-1/2 top-1/2 -translate-x-1/2 -translate-y-1/2"
+          style={{ width: "72%", height: "140%", background: photo }}
+        >
+          <span
+            className="absolute left-1/2 top-[18%] -translate-x-1/2 w-[30%] aspect-square rounded-full"
+            style={{ background: ink, opacity: 0.45 }}
+          />
+        </span>
+      )}
+      {mode === "contain" && (
+        <span
+          className="absolute inset-y-0 left-1/2 -translate-x-1/2"
+          style={{ width: "58%", background: photo }}
+        >
+          <span
+            className="absolute left-1/2 top-[18%] -translate-x-1/2 w-[36%] aspect-square rounded-full"
+            style={{ background: ink, opacity: 0.45 }}
+          />
+        </span>
+      )}
+      {mode === "repeat" && (
+        <span className="absolute inset-[2px] grid grid-cols-3 grid-rows-2 gap-[2px]">
+          {Array.from({ length: 6 }, (_, i) => (
+            <span key={i} style={{ background: photo }} />
+          ))}
+        </span>
+      )}
+      {mode === "stretch" && (
+        <span className="absolute inset-0" style={{ background: photo }}>
+          <span
+            className="absolute left-1/2 top-[22%] -translate-x-1/2 h-[38%]"
+            style={{
+              width: "70%",
+              borderRadius: "50%",
+              background: ink,
+              opacity: 0.45,
+            }}
+          />
+        </span>
+      )}
+    </span>
+  );
+}
+
+export default function BgModePicker({
+  value,
+  onChange,
+  disabled,
+  ariaLabel,
+}: {
+  value: BgMode;
+  onChange: (mode: BgMode) => void;
+  disabled?: boolean;
+  ariaLabel: string;
+}) {
+  return (
+    <div className="grid grid-cols-2 gap-2" role="group" aria-label={ariaLabel}>
+      {BG_MODE_OPTIONS.map((o) => {
+        const active = value === o.key;
+        return (
+          <button
+            key={o.key}
+            type="button"
+            disabled={disabled}
+            aria-pressed={active}
+            onClick={() => {
+              if (!active) onChange(o.key);
+            }}
+            className="flex items-center gap-2.5 min-w-0 px-2.5 py-2 rounded-[var(--r-sm)] border text-left transition-colors disabled:opacity-50 disabled:cursor-not-allowed"
+            style={{
+              borderColor: active ? "var(--accent)" : "var(--line)",
+              background: active ? "var(--accent-soft)" : "var(--panel)",
+              cursor: disabled ? "not-allowed" : "pointer",
+            }}
+          >
+            <ModeGlyph mode={o.key} />
+            <span className="min-w-0">
+              <span
+                className="block text-[13px] font-medium leading-tight"
+                style={{ color: active ? "var(--accent)" : "var(--ink)" }}
+              >
+                {o.label}
+              </span>
+              <span className="block meta text-[11.5px] mt-0.5 leading-snug">{o.hint}</span>
+            </span>
+          </button>
+        );
+      })}
+    </div>
+  );
+}

frontend/components/Footer.tsx

@@ -16,7 +16,6 @@ export default function Footer({ siteName = "姜十三社区" }: { siteName?: st
 
   return (
     <footer
-      className="mt-14"
       style={{
         borderTop: "1px solid var(--line)",
         background: "var(--panel)",

frontend/lib/bg.ts

@@ -6,25 +6,18 @@ import type { CSSProperties } from "react";
 
 export type BgSurface = "site" | "admin";
 
-export type BgMode =
+export type BgMode = "cover" | "contain" | "repeat" | "stretch";
-  | "cover"
-  | "contain"
-  | "repeat"
-  | "repeat-x"
-  | "repeat-y"
-  | "stretch"
-  | "center";
 
 export const DEFAULT_BG_MODE: BgMode = "cover";
 
+/** 预览框按常见 PC 显示器 16:9（1920×1080）等比例缩放 */
+export const BG_PREVIEW_ASPECT = "16 / 9";
+
 export const BG_MODE_OPTIONS: { key: BgMode; label: string; hint: string }[] = [
-  { key: "cover", label: "覆盖铺满", hint: "裁切以铺满视口" },
+  { key: "cover", label: "填充", hint: "裁切铺满，适合照片" },
-  { key: "contain", label: "完整显示", hint: "完整放入，两侧留底色" },
+  { key: "contain", label: "适应", hint: "整图可见，可能留边" },
-  { key: "stretch", label: "拉伸填满", hint: "变形拉伸至视口" },
+  { key: "repeat", label: "平铺", hint: "原尺寸重复，适合纹理" },
-  { key: "repeat", label: "平铺", hint: "按原尺寸重复铺满" },
+  { key: "stretch", label: "拉伸", hint: "拉满屏幕，可能变形" },
-  { key: "repeat-x", label: "横向平铺", hint: "只沿水平方向重复" },
-  { key: "repeat-y", label: "纵向平铺", hint: "只沿垂直方向重复" },
-  { key: "center", label: "居中原图", hint: "不缩放，居中显示" },
 ];
 
 export interface SiteBgConfig {
@@ -72,14 +65,8 @@ function modeCSS(mode: BgMode): { size: string; repeat: string; position: string
       return { size: "contain", repeat: "no-repeat", position: "center" };
     case "repeat":
       return { size: "auto", repeat: "repeat", position: "0 0" };
-    case "repeat-x":
-      return { size: "auto", repeat: "repeat-x", position: "center top" };
-    case "repeat-y":
-      return { size: "auto", repeat: "repeat-y", position: "center top" };
     case "stretch":
       return { size: "100% 100%", repeat: "no-repeat", position: "center" };
-    case "center":
-      return { size: "auto", repeat: "no-repeat", position: "center" };
     default:
       return { size: "cover", repeat: "no-repeat", position: "center" };
   }