ViewHelpers

Fluid ViewHelpers for rendering RTE image previews in backend templates.

Table of contents

RteImagePreviewViewHelper

class RteImagePreviewViewHelper

Fully qualified name: \Netresearch\RteCKEditorImage\ViewHelpers\RteImagePreviewViewHelper

Renders a backend preview of RTE HTML content by stripping disallowed tags and truncating text while preserving HTML structure.

This ViewHelper replicates the preview logic from RteImagePreviewRenderer for use in Content Blocks and other custom backend preview templates where the built-in renderer is not available.

New in version 13.6.0

Arguments

html

Type: string
Required: true

The RTE HTML content to preview. Typically {data.bodytext} in a Content Blocks backend preview template.

maxLength

Type: int
Default: 1500

Maximum number of text characters before truncation. When exceeded, the text is truncated with an ellipsis (...). HTML tags do not count toward this limit.

allowedTags

Type: string
Default: <img><p>

HTML tags to preserve in the preview output, in strip_tags() format. All other tags are stripped (their text content is kept).

Processing Pipeline

The ViewHelper processes HTML through three stages:

Sanitization — Removes control characters (\x00-\x1F), UTF-16 surrogates, and Unicode non-characters, replacing them with U+FFFD (replacement character).
Tag stripping — Calls strip_tags() with the allowedTags argument, keeping only <img> and <p> by default.
DOM-aware truncation — Parses the remaining HTML with DOMDocument, walks the DOM tree counting text length, and truncates at maxLength while keeping all tags properly closed.

Usage with Content Blocks

Content Blocks is the official TYPO3-endorsed successor to Mask/DCE/Flux for creating custom content element types. Content Blocks registers its own backend preview templates (backend-preview.html), which do not use the built-in RteImagePreviewRenderer.

To render RTE image previews in a Content Block, use this ViewHelper in the block's backend preview template:

ContentBlocks/ContentElements/my-block/templates/backend-preview.html

<html xmlns:nr="http://typo3.org/ns/Netresearch/RteCKEditorImage/ViewHelpers"
      data-namespace-typo3-fluid="true">
<nr:rteImagePreview html="{data.bodytext}" />
</html>

Custom Tag Allowlist

To also preserve <figure> and <figcaption> in the preview:

<nr:rteImagePreview html="{data.bodytext}"
                    allowedTags="<img><p><figure><figcaption>" />

Custom Truncation Length

To show a shorter preview (e.g., in a compact list view):

<nr:rteImagePreview html="{data.bodytext}" maxLength="300" />

Standard Content Elements

For standard tt_content types with RTE bodytext, you do not need this ViewHelper. The built-in RteImagePreviewRenderer handles backend previews automatically via TYPO3's PreviewRendererInterface.