fix: adjust file picker for background image to allow folder navigation

apps/theming/src/components/UserSectionBackground.vue

@@ -147,7 +147,7 @@ async function pickColor(color?: string) {
 async function pickFile() {
 	await getFilePickerBuilder(t('theming', 'Select a background from your files'))
 		.allowDirectories(false)
-		.setFilter((node) => node.mime.startsWith('image/'))
+		.setMimeTypeFilter(['image/*'])
 		.setMultiSelect(false)
 		.addButton({
 			label: t('theming', 'Select background'),

tests/playwright/e2e/theming/user-settings-background.spec.ts

@@ -5,6 +5,8 @@
 
 import { expect } from '@playwright/test'
 import { test } from '../../support/fixtures/random-user-session.ts'
+import { BackgroundFilePickerDialogPage } from '../../support/sections/BackgroundFilePickerDialogPage.ts'
+import { mkdir, uploadContent } from '../../support/utils/dav.ts'
 import { getBodyThemingSnapshot, pickColor } from '../../support/utils/theming.ts'
 
 test('User can configure background and plain color', async ({ page }) => {
@@ -32,3 +34,28 @@ test('User can configure background and plain color', async ({ page }) => {
 	await page.reload()
 	await expect.poll(async () => (await getBodyThemingSnapshot(page)).backgroundImage).toBe('none')
 })
+
+test('User can pick a custom background from their files', {
+	annotation: { type: 'issue', description: 'https://github.com/nextcloud/server/issues/58645' },
+}, async ({ page, user }) => {
+	await mkdir(page.request, user, '/folder')
+
+	// this is a minimal image (1x1 red pixel), encoded as base64
+	const imageBase64 = 'iVBORw0KGgoAAAANSUhEUgAAAAEAAAABCAYAAAAfFcSJAAAADUlEQVR4AWL6z8DwHwAAAP//A3ONEwAAAAZJREFUAwAFCgIByRpMngAAAABJRU5ErkJggg=='
+	// Buffer.alloc(0) did not work when selecting image as background, using base64 image instead
+	await uploadContent(page.request, user, Buffer.from(imageBase64, 'base64'), 'image/jpeg', '/folder/image.jpg')
+
+	await page.goto('settings/user/theming')
+	await page.getByRole('heading', { name: 'Background and color' }).waitFor({ state: 'visible' })
+
+	await page.getByRole('button', { name: 'Custom background' }).click()
+
+	const filePicker = new BackgroundFilePickerDialogPage(page)
+	await filePicker.openFolder('folder')
+	await filePicker.selectFile('image.jpg')
+	await filePicker.confirm()
+
+	await expect(page.getByRole('button', { name: 'Custom background', pressed: true })).toBeVisible()
+	// backgroundImage is like this: "url(\"<nc-instance>/apps/theming/background?v=<hash>\")"
+	await expect.poll(async () => (await getBodyThemingSnapshot(page)).backgroundImage).toContain('/apps/theming/background?')
+})

tests/playwright/support/sections/BackgroundFilePickerDialogPage.ts

@@ -0,0 +1,41 @@
+/*
+ * SPDX-FileCopyrightText: 2026 Nextcloud GmbH and Nextcloud contributors
+ * SPDX-License-Identifier: AGPL-3.0-or-later
+ */
+
+import type { Locator, Page } from '@playwright/test'
+
+/**
+ * The file-picker dialog opened by the "Custom background" card/button on
+ * Personal settings > Appearance and accessibility > Background and color
+ */
+export class BackgroundFilePickerDialogPage {
+	constructor(private readonly page: Page) {}
+
+	/** The open file-picker dialog. */
+	dialog(): Locator {
+		return this.page.getByRole('dialog')
+	}
+
+	/**
+	 * Returns a row (file or folder) from inside the picker.
+	 */
+	getRow(name: string): Locator {
+		return this.dialog().getByTestId('row-name').filter({ hasText: name })
+	}
+
+	/** Navigate into a folder. */
+	async openFolder(name: string): Promise<void> {
+		await this.getRow(name).click()
+	}
+
+	/** Select a file row. */
+	async selectFile(name: string): Promise<void> {
+		await this.getRow(name).click()
+	}
+
+	/** Confirm the current selection as the new background. */
+	async confirm(): Promise<void> {
+		await this.dialog().getByRole('button', { name: 'Select background', exact: true }).click()
+	}
+}