fix(files): Correctly scroll selected file into view

Signed-off-by: Ferdinand Thiessen <opensource@fthiessen.de>

4 files changed, 402 insertions, 51 deletions

diff --git a/apps/files/src/components/FilesListTableFooter.vue b/apps/files/src/components/FilesListTableFooter.vue
index bf545aacf4f..63d692c100d 100644
--- a/apps/files/src/components/FilesListTableFooter.vue
+++ b/apps/files/src/components/FilesListTableFooter.vue
@@ -141,7 +141,7 @@ export default defineComponent({
 <style scoped lang="scss">
 // Scoped row
 tr {
-	margin-bottom: max(25vh, var(--body-container-margin));
+	margin-bottom: var(--body-container-margin);
 	border-top: 1px solid var(--color-border);
 	// Prevent hover effect on the whole row
 	background-color: transparent !important;
diff --git a/apps/files/src/components/FilesListVirtual.vue b/apps/files/src/components/FilesListVirtual.vue
index 2442dd98190..447639c3fb6 100644
--- a/apps/files/src/components/FilesListVirtual.vue
+++ b/apps/files/src/components/FilesListVirtual.vue
@@ -536,7 +536,6 @@ export default defineComponent({
 			flex-direction: column;
 			width: 100%;
 			background-color: var(--color-main-background);
-
 		}
 
 		// Table header
@@ -853,8 +852,7 @@ export default defineComponent({
 
 <style lang="scss">
 // Grid mode
-tbody.files-list__tbody.files-list__tbody--grid {
-	--half-clickable-area: calc(var(--clickable-area) / 2);
+.files-list--grid tbody.files-list__tbody {
 	--item-padding: 16px;
 	--icon-preview-size: 166px;
 	--name-height: 32px;
@@ -945,7 +943,7 @@ tbody.files-list__tbody.files-list__tbody--grid {
 
 	.files-list__row-actions {
 		position: absolute;
-		inset-inline-end: calc(var(--half-clickable-area) / 2);
+		inset-inline-end: calc(var(--clickable-area) / 4);
 		inset-block-end: calc(var(--mtime-height) / 2);
 		width: var(--clickable-area);
 		height: var(--clickable-area);
diff --git a/apps/files/src/components/VirtualList.vue b/apps/files/src/components/VirtualList.vue
index b3d1b1002f4..5ae8220d594 100644
--- a/apps/files/src/components/VirtualList.vue
+++ b/apps/files/src/components/VirtualList.vue
@@ -3,13 +3,16 @@
  - SPDX-License-Identifier: AGPL-3.0-or-later
  -->
 <template>
-	<div class="files-list" data-cy-files-list>
+	<div class="files-list"
+		:class="{ 'files-list--grid': gridMode }"
+		data-cy-files-list
+		@scroll.passive="onScroll">
 		<!-- Header -->
 		<div ref="before" class="files-list__before">
 			<slot name="before" />
 		</div>
 
-		<div class="files-list__filters">
+		<div ref="filters" class="files-list__filters">
 			<slot name="filters" />
 		</div>
 
@@ -31,7 +34,6 @@
 			<!-- Body -->
 			<tbody :style="tbodyStyle"
 				class="files-list__tbody"
-				:class="gridMode ? 'files-list__tbody--grid' : 'files-list__tbody--list'"
 				data-cy-files-list-tbody>
 				<component :is="dataComponent"
 					v-for="({key, item}, i) in renderedItems"
@@ -42,7 +44,7 @@
 			</tbody>
 
 			<!-- Footer -->
-			<tfoot v-show="isReady"
+			<tfoot ref="footer"
 				class="files-list__tfoot"
 				data-cy-files-list-tfoot>
 				<slot name="footer" />
@@ -118,6 +120,7 @@ export default defineComponent({
 		return {
 			index: this.scrollToIndex,
 			beforeHeight: 0,
+			footerHeight: 0,
 			headerHeight: 0,
 			tableHeight: 0,
 			resizeObserver: null as ResizeObserver | null,
@@ -145,16 +148,33 @@ export default defineComponent({
 			// 166px + 32px (name) + 16px (mtime) + 16px (padding top and bottom)
 			return this.gridMode ? (166 + 32 + 16 + 16 + 16) : 55
 		},
+
 		// Grid mode only
 		itemWidth() {
 			// 166px + 16px x 2 (padding left and right)
 			return 166 + 16 + 16
 		},
 
-		rowCount() {
-			return Math.ceil((this.tableHeight - this.headerHeight) / this.itemHeight) + (this.bufferItems / this.columnCount) * 2 + 1
+		/**
+		 * The number of rows currently (fully!) visible
+		 */
+		visibleRows(): number {
+			return Math.floor((this.tableHeight - this.headerHeight) / this.itemHeight)
+		},
+
+		/**
+		 * Number of rows that will be rendered.
+		 * This includes only visible + buffer rows.
+		 */
+		rowCount(): number {
+			return this.visibleRows + (this.bufferItems / this.columnCount) * 2 + 1
 		},
-		columnCount() {
+
+		/**
+		 * Number of columns.
+		 * 1 for list view otherwise depending on the file list width.
+		 */
+		columnCount(): number {
 			if (!this.gridMode) {
 				return 1
 			}
@@ -217,16 +237,18 @@ export default defineComponent({
 		 * The total number of rows that are available
 		 */
 		totalRowCount() {
-			return Math.floor(this.dataSources.length / this.columnCount)
+			return Math.ceil(this.dataSources.length / this.columnCount)
 		},
 
 		tbodyStyle() {
-			const isOverScrolled = this.startIndex + this.rowCount > this.dataSources.length
-			const lastIndex = this.dataSources.length - this.startIndex - this.shownItems
-			const hiddenAfterItems = Math.floor(Math.min(this.dataSources.length - this.startIndex, lastIndex) / this.columnCount)
+			// The number of (virtual) rows above the currently rendered ones.
+			// start index is aligned so this should always be an integer
+			const rowsAbove = Math.round(this.startIndex / this.columnCount)
+			// The number of (virtual) rows below the currently rendered ones.
+			const rowsBelow = Math.max(0, this.totalRowCount - rowsAbove - this.rowCount)
+
 			return {
-				paddingTop: `${Math.floor(this.startIndex / this.columnCount) * this.itemHeight}px`,
-				paddingBottom: isOverScrolled ? 0 : `${hiddenAfterItems * this.itemHeight}px`,
+				paddingBlock: `${rowsAbove * this.itemHeight}px ${rowsBelow * this.itemHeight}px`,
 				minHeight: `${this.totalRowCount * this.itemHeight}px`,
 			}
 		},
@@ -238,15 +260,14 @@ export default defineComponent({
 
 		totalRowCount() {
 			if (this.scrollToIndex) {
-				this.$nextTick(() => this.scrollTo(this.scrollToIndex))
+				this.scrollTo(this.scrollToIndex)
 			}
 		},
 
 		columnCount(columnCount, oldColumnCount) {
 			if (oldColumnCount === 0) {
-				// We're initializing, the scroll position
-				// is handled on mounted
-				console.debug('VirtualList: columnCount is 0, skipping scroll')
+				// We're initializing, the scroll position is handled on mounted
+				logger.debug('VirtualList: columnCount is 0, skipping scroll')
 				return
 			}
 			// If the column count changes in grid view,
@@ -256,30 +277,28 @@ export default defineComponent({
 	},
 
 	mounted() {
-		const before = this.$refs?.before as HTMLElement
-		const root = this.$el as HTMLElement
-		const thead = this.$refs?.thead as HTMLElement
+		this.$_recycledPool = {} as Record<string, DataSource[DataSourceKey]>
 
 		this.resizeObserver = new ResizeObserver(debounce(() => {
-			this.beforeHeight = before?.clientHeight ?? 0
-			this.headerHeight = thead?.clientHeight ?? 0
-			this.tableHeight = root?.clientHeight ?? 0
+			this.updateHeightVariables()
 			logger.debug('VirtualList: resizeObserver updated')
 			this.onScroll()
-		}, 100, { immediate: false }))
-
-		this.resizeObserver.observe(before)
-		this.resizeObserver.observe(root)
-		this.resizeObserver.observe(thead)
-
-		if (this.scrollToIndex) {
-			this.scrollTo(this.scrollToIndex)
-		}
-
-		// Adding scroll listener AFTER the initial scroll to index
-		this.$el.addEventListener('scroll', this.onScroll, { passive: true })
-
-		this.$_recycledPool = {} as Record<string, DataSource[DataSourceKey]>
+		}, 100))
+		this.resizeObserver.observe(this.$el)
+		this.resizeObserver.observe(this.$refs.before as HTMLElement)
+		this.resizeObserver.observe(this.$refs.filters as HTMLElement)
+		this.resizeObserver.observe(this.$refs.footer as HTMLElement)
+
+		this.$nextTick(() => {
+			// Make sure height values are initialized
+			this.updateHeightVariables()
+			// If we need to scroll to an index we do so in the next tick.
+			// This is needed to apply updates from the initialization of the height variables
+			// which will update the tbody styles until next tick.
+			if (this.scrollToIndex) {
+				this.scrollTo(this.scrollToIndex)
+			}
+		})
 	},
 
 	beforeDestroy() {
@@ -294,17 +313,56 @@ export default defineComponent({
 				return
 			}
 
-			// Check if the content is smaller than the viewport, meaning no scrollbar
-			const targetRow = Math.ceil(this.dataSources.length / this.columnCount)
-			if (targetRow < this.rowCount) {
-				logger.debug('VirtualList: Skip scrolling, nothing to scroll', { index, targetRow, rowCount: this.rowCount })
+			// Check if the content is smaller (not equal! keep the footer in mind) than the viewport
+			// meaning there is no scrollbar
+			if (this.totalRowCount < this.visibleRows) {
+				logger.debug('VirtualList: Skip scrolling, nothing to scroll', {
+					index,
+					totalRows: this.totalRowCount,
+					visibleRows: this.visibleRows,
+				})
 				return
 			}
 
-			// Scroll to one row and a half before the index
-			const scrollTop = this.indexToScrollPos(index)
-			logger.debug('VirtualList: scrolling to index ' + index, { scrollTop, columnCount: this.columnCount, beforeHeight: this.beforeHeight })
-			this.$el.scrollTop = scrollTop
+			// We can not scroll further as the last page of rows
+			// For the grid view we also need to account for all columns in that row (columnCount - 1)
+			const clampedIndex = (this.totalRowCount - this.visibleRows) * this.columnCount + (this.columnCount - 1)
+			// The scroll position
+			let scrollTop = this.indexToScrollPos(Math.min(index, clampedIndex))
+
+			// First we need to update the internal index for rendering.
+			// This will cause the <tbody> element to be resized allowing us to set the correct scroll position.
+			this.index = index
+
+			// If this is not the first row we can add a half row from above.
+			// This is to help users understand the table is scrolled and not items did not just disappear.
+			// But we also can only add a half row if we have enough rows below to scroll (visual rows / end of scrollable area)
+			if (index >= this.columnCount && index <= clampedIndex) {
+				scrollTop -= (this.itemHeight / 2)
+				// As we render one half row more we also need to adjust the internal index
+				this.index = index - this.columnCount
+			} else if (index > clampedIndex) {
+				// If we are on the last page we cannot scroll any further
+				// but we can at least scroll the footer into view
+				if (index <= (clampedIndex + this.columnCount)) {
+					// We only show have of the footer for the first of the last page
+					// To still show the previous row partly. Same reasoning as above:
+					// help the user understand that the table is scrolled not "magically trimmed"
+					scrollTop += this.footerHeight / 2
+				} else {
+					// We reached the very end of the files list and we are focussing not the first visible row
+					// so all we now can do is scroll to the end (footer)
+					scrollTop += this.footerHeight
+				}
+			}
+
+			// Now we need to wait for the <tbody> element to get resized so we can correctly apply the scrollTop position
+			this.$nextTick(() => {
+				this.$el.scrollTop = scrollTop
+				logger.debug(`VirtualList: scrolling to index ${index}`, {
+					clampedIndex, scrollTop, columnCount: this.columnCount, total: this.totalRowCount, visibleRows: this.visibleRows, beforeHeight: this.beforeHeight,
+				})
+			})
 		},
 
 		onScroll() {
@@ -333,7 +391,22 @@ export default defineComponent({
 		// Convert index to scroll position
 		// It should be the opposite of `scrollPosToIndex`
 		indexToScrollPos(index: number): number {
-			return (Math.floor(index / this.columnCount) - 0.5) * this.itemHeight + this.beforeHeight
+			return Math.floor(index / this.columnCount) * this.itemHeight + this.beforeHeight
+		},
+
+		/**
+		 * Update the height variables.
+		 * To be called by resize observer and `onMount`
+		 */
+		updateHeightVariables(): void {
+			this.tableHeight = this.$el?.clientHeight ?? 0
+			this.beforeHeight = (this.$refs.before as HTMLElement)?.clientHeight ?? 0
+			this.footerHeight = (this.$refs.footer as HTMLElement)?.clientHeight ?? 0
+
+			// Get the header height which consists of table header and filters
+			const theadHeight = (this.$refs.thead as HTMLElement)?.clientHeight ?? 0
+			const filterHeight = (this.$refs.filters as HTMLElement)?.clientHeight ?? 0
+			this.headerHeight = theadHeight + filterHeight
 		},
 	},
 })
diff --git a/cypress/e2e/files/scrolling.cy.ts b/cypress/e2e/files/scrolling.cy.ts
new file mode 100644
index 00000000000..c4ca4943a40
--- /dev/null
+++ b/cypress/e2e/files/scrolling.cy.ts
@@ -0,0 +1,280 @@
+/*!
+ * SPDX-FileCopyrightText: 2025 Nextcloud GmbH and Nextcloud contributors
+ * SPDX-License-Identifier: AGPL-3.0-or-later
+ */
+
+import type { User } from '@nextcloud/cypress'
+import { getRowForFile } from './FilesUtils'
+
+describe('files: Scrolling to selected file in file list', { testIsolation: true }, () => {
+	const fileIds = new Map<number, string>()
+	let user: User
+
+	before(() => {
+		cy.createRandomUser().then(($user) => {
+			user = $user
+
+			cy.rm(user, '/welcome.txt')
+			for (let i = 1; i <= 10; i++) {
+				cy.uploadContent(user, new Blob([]), 'text/plain', `/${i}.txt`)
+					.then((response) => fileIds.set(i, Number.parseInt(response.headers['oc-fileid']).toString()))
+			}
+		})
+	})
+
+	beforeEach(() => {
+		// Adjust height to ensure that those 10 elements can not be rendered in one list
+		cy.viewport(1200, 6 * 55 /* rows */ + 55 /* table header */ + 50 /* navigation header */ + 50 /* breadcrumbs */ + 46 /* file filters */)
+		cy.login(user)
+	})
+
+	it('Can see first file in list', () => {
+		cy.visit(`/apps/files/files/${fileIds.get(1)}`)
+
+		// See file is visible
+		getRowForFile('1.txt')
+			.should('be.visible')
+
+		// we expect also element 6 to be visible
+		getRowForFile('6.txt')
+			.should('be.visible')
+		// but not element 7 - though it should exist (be buffered)
+		getRowForFile('7.txt')
+			.should('exist')
+			.and('not.be.visible')
+	})
+
+	// Same kind of tests for partially visible top and bottom
+	for (let i = 2; i <= 5; i++) {
+		it(`correctly scrolls to row ${i}`, () => {
+			cy.visit(`/apps/files/files/${fileIds.get(i)}`)
+
+			// See file is visible
+			getRowForFile(`${i}.txt`)
+				.should('be.visible')
+				.and(notBeOverlappedByTableHeader)
+
+			// we expect also element +4 to be visible
+			// (6 visible rows -> 5 without our scrolled row -> so we only have 4 fully visible others + two 1/2 hidden rows)
+			getRowForFile(`${i + 4}.txt`)
+				.should('be.visible')
+			// but not element -1 or +5 - though it should exist (be buffered)
+			getRowForFile(`${i - 1}.txt`)
+				.should('exist')
+				.and(beOverlappedByTableHeader)
+			getRowForFile(`${i + 5}.txt`)
+				.should('exist')
+				.and('be.visible')
+				.and(notBeFullyInViewport)
+		})
+	}
+
+	// this will have half of the footer visible
+	it(`correctly scrolls to row 6`, () => {
+		cy.visit(`/apps/files/files/${fileIds.get(6)}`)
+
+		// See file is visible
+		getRowForFile(`6.txt`)
+			.should('be.visible')
+			.and(notBeOverlappedByTableHeader)
+
+		// we expect also element 7,8,9,10 visible
+		getRowForFile(`10.txt`)
+			.should('be.visible')
+		// but not row 5
+		getRowForFile(`5.txt`)
+			.should('exist')
+			.and(beOverlappedByTableHeader)
+		// see footer is only shown partly
+		cy.get('tfoot')
+			.should('exist')
+			.and(notBeFullyInViewport)
+	})
+
+	// Same kind of tests for partially visible top and bottom
+	for (let i = 7; i <= 10; i++) {
+		it(`correctly scrolls to row ${i}`, () => {
+			cy.visit(`/apps/files/files/${fileIds.get(i)}`)
+
+			// See file is visible
+			getRowForFile(`${i}.txt`)
+				.should('be.visible')
+				.and(notBeOverlappedByTableHeader)
+
+			// there are only max. 3 rows left so also row 6+ should be visible
+			getRowForFile(`6.txt`)
+				.should('be.visible')
+			getRowForFile(`10.txt`)
+				.should('be.visible')
+			// Also the footer is visible
+			cy.get('tfoot')
+				.contains('10 files')
+				.should('be.visible')
+		})
+	}
+})
+
+describe('files: Scrolling to selected file in file list (GRID MODE)', { testIsolation: true }, () => {
+	const fileIds = new Map<number, string>()
+	let user: User
+
+	before(() => {
+		cy.createRandomUser().then(($user) => {
+			user = $user
+
+			cy.rm(user, '/welcome.txt')
+			for (let i = 1; i <= 12; i++) {
+				cy.uploadContent(user, new Blob([]), 'text/plain', `/${i}.txt`)
+					.then((response) => fileIds.set(i, Number.parseInt(response.headers['oc-fileid']).toString()))
+			}
+			// Set grid mode
+			cy.login(user)
+			cy.intercept('**/apps/files/api/v1/config/grid_view').as('setGridMode')
+			cy.visit('/apps/files')
+			cy.findByRole('button', { name: 'Switch to grid view' })
+				.should('be.visible')
+				.click()
+			cy.wait('@setGridMode')
+		})
+	})
+
+	beforeEach(() => {
+		// Adjust height to ensure that those 12 files can not be rendered in one list
+		// 768px width will limit the columns to 3
+		cy.viewport(768, 3 * 246 /* rows */ + 55 /* table header */ + 50 /* navigation header */ + 50 /* breadcrumbs */ + 46 /* file filters */)
+		cy.login(user)
+	})
+
+	// First row
+	for (let i = 1; i <= 3; i++) {
+		it(`Can see files in first row (file ${i})`, () => {
+			cy.visit(`/apps/files/files/${fileIds.get(i)}`)
+
+			for (let j = 1; j <= 3; j++) {
+				// See all files of that row are visible
+				getRowForFile(`${j}.txt`)
+					.should('be.visible')
+				// we expect also the second row to be visible
+				getRowForFile(`${j+3}.txt`)
+					.should('be.visible')
+				// Because there is no half row on top we also see the third row
+				getRowForFile(`${j+6}.txt`)
+					.should('be.visible')
+				// But not the forth row
+				getRowForFile(`${j+9}.txt`)
+					.should('exist')
+					.and(notBeFullyInViewport)
+			}
+		})
+	}
+
+	// Second row
+	// Same kind of tests for partially visible top and bottom
+	for (let i = 4; i <= 6; i++) {
+		it(`correctly scrolls to second row (file ${i})`, () => {
+			cy.visit(`/apps/files/files/${fileIds.get(i)}`)
+
+			// See all three files of that row are visible
+			for (let j = 4; j <= 6; j++) {
+				getRowForFile(`${j}.txt`)
+					.should('be.visible')
+					.and(notBeOverlappedByTableHeader)
+				// we expect also the next row to be visible
+				getRowForFile(`${j + 3}.txt`)
+					.should('be.visible')
+				// but not the row below (should be half cut)
+				getRowForFile(`${j + 6}.txt`)
+					.should('exist')
+					.and(notBeFullyInViewport)
+				// Same for the row above
+				getRowForFile(`${j - 3}.txt`)
+					.should('exist')
+					.and(beOverlappedByTableHeader)
+			}
+		})
+	}
+
+	// Third row
+	// this will have half of the footer visible and half of the previous row
+	for (let i = 7; i <= 9; i++) {
+		it(`correctly scrolls to third row (file ${i})`, () => {
+			cy.visit(`/apps/files/files/${fileIds.get(i)}`)
+
+			// See all three files of that row are visible
+			for (let j = 7; j <= 9; j++) {
+				getRowForFile(`${j}.txt`)
+					.should('be.visible')
+				// we expect also the next row to be visible
+				getRowForFile(`${j + 3}.txt`)
+					.should('be.visible')
+				// but not the row above
+				getRowForFile(`${j - 3}.txt`)
+					.should('exist')
+					.and(beOverlappedByTableHeader)
+			}
+
+			// see footer is only shown partly
+			cy.get('tfoot')
+				.should('exist')
+				.and(notBeFullyInViewport)
+		})
+	}
+
+	// Forth row which only has row 4 and 3 visible and the full footer
+	for (let i = 10; i <= 12; i++) {
+		it(`correctly scrolls to forth row (file ${i})`, () => {
+			cy.visit(`/apps/files/files/${fileIds.get(i)}`)
+
+			// See all three files of that row are visible
+			for (let j = 10; j <= 12; j++) {
+				getRowForFile(`${j}.txt`)
+					.should('be.visible')
+					.and(notBeOverlappedByTableHeader)
+				// we expect also the row above to be visible
+				getRowForFile(`${j - 3}.txt`)
+					.should('be.visible')
+			}
+
+			// see footer is shown
+			cy.get('tfoot')
+				.should('be.visible')
+		})
+	}
+})
+
+/// Some helpers
+
+function notBeOverlappedByTableHeader($el: JQuery<HTMLElement>) {
+	return beOverlappedByTableHeader($el, false)
+}
+
+function beOverlappedByTableHeader($el: JQuery<HTMLElement>, expected = true) {
+	const headerRect = Cypress.$('thead').get(0)!.getBoundingClientRect()
+	const elementRect = $el.get(0)!.getBoundingClientRect()
+	const overlap = !(headerRect.right < elementRect.left || 
+		headerRect.left > elementRect.right || 
+		headerRect.bottom < elementRect.top || 
+		headerRect.top > elementRect.bottom)
+
+	if (expected) {
+		expect(overlap, 'Overlapped by table header').to.be.true
+	} else {
+		expect(overlap, 'Not overlapped by table header').to.be.false
+	}
+}
+
+function beFullyInViewport($el: JQuery<HTMLElement>, expected = true) {
+	const { top, left, bottom, right } = $el.get(0)!.getBoundingClientRect()
+	const { innerHeight, innerWidth } = window
+	const fullyVisible = top >= 0 && left >= 0 && bottom <= innerHeight && right <= innerWidth
+
+	if (expected) {
+		expect(fullyVisible, 'Fully within viewport').to.be.true
+	} else {
+		expect(fullyVisible, 'Not fully within viewport').to.be.false
+	}
+}
+
+function notBeFullyInViewport($el: JQuery<HTMLElement>) {
+	return beFullyInViewport($el, false)
+}