[FEATURE] Show error message when a page image cannot be loaded - #2153
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sebastian-meyer merged 3 commits intoSep 18, 2026
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When the image server is unavailable (e.g. returns HTTP 503) the page grid previously showed only broken image icons and the PageView full page image silently failed to load: the OpenLayers image source never settled, the map was never created and the viewer hung with no feedback. The page grid thumbnails now fall back to the placeholder image and reveal a localized message via an <img onerror> handler. The PageView fixes the unhandled rejection in fetchImageData()/initLayer() so the image load failure settles the deferred, and renders a localized message (including the image source URL) inside the map container. Adds translatable strings pageGrid.thumbnailError and pageview.imageError (EN/DE). Assisted-by: OpenCode / qwen3.8-27b-thinking (Alibaba Cloud) Signed-off-by: Stefan Weil <sw@weilnetz.de>
Render the real PageGrid and PageView templates (instead of the reduced inline templates used elsewhere) to assert the new error-handling markup: the page grid emits a hidden fallback placeholder image plus a per-thumbnail <img onerror> handler and a localized error message, and the page view map container carries the localized image-load error message. This requires the controller test harness to render templates with view helpers that need a request context (f:translate, f:link.page, f:image), so AbstractControllerTestCase gains a template-capable request and a helper to point a StandaloneView at a real template file with the dlf partials. Assisted-by: OpenCode / qwen3.8-27b-thinking (Alibaba Cloud) Signed-off-by: Stefan Weil <sw@weilnetz.de>
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This PR was motivates by the current downtime of digital.slub-dresden.de. A thumbnail image for a failing server now looks like this: 
The failing page image shows the same error message plus the failing URL. |
sebastian-meyer
approved these changes
Sep 18, 2026
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When the image server is unavailable (e.g. returns HTTP 503) the page grid previously showed only broken image icons and the PageView full page image silently failed to load: the OpenLayers image source never settled, the map was never created and the viewer hung with no feedback.
The page grid thumbnails now fall back to the placeholder image and reveal a localized message via an![]()
handler. The PageView fixes the unhandled rejection in fetchImageData()/initLayer() so the image load failure settles the deferred, and renders a localized message (including the image source URL) inside the map container.
Adds translatable strings pageGrid.thumbnailError and pageview.imageError (EN/DE).
Add functional tests for the image load error rendering.