I noticed a significant change in the page rendering behavior in the new Version 11, resulting in a severe performance regression depending on UI layout, screen resolution, and zoom level.
To demonstrate this, I have attached a sample PDF, which is a basic, scanned document (300 dpi, pure black-and-white bitmaps, no OCR/text layer).
The Observation:
Note: open the document fresh with the Thumbnails Pane closed first to observe the issue.
Thumbnails Pane DISABLED: Scrolling through pages in the main view is surprisingly slow. There is a noticeable delay of at least hundreds of milliseconds per page. Even worse, the rendering happens progressively, often loading the top or bottom half of the page first, followed by the rest after a distinct lag.
Thumbnails Pane ENABLED: Page flipping in the main view is lightning-fast and completely lag-free. It appears that the rendering engine unifies or shares the cache between the thumbnails and the main view.
Crucial Trigger Conditions:
This lag becomes highly noticeable under the following conditions (with a display resolution larger than ca. 3K)
- Page View is "single page", "fit-page" zoom.
- OR the document is zoomed in so that its vertical resolution exceeds approx. 2K.
In previous versions, rendering the main view was independent and fast. In v11, without the background rendering/caching triggered by the active thumbnails pane, high-resolution rendering scales poorly, making quick skimming of scanned PDFs nearly impossible due to the progressive tiling lag.
Could you please check if this change in the rendering architecture can be optimized, or if a caching/pre-rendering option can be introduced so we can get back the lightning-fast performance we have been used to from PDF-XChange Editor for decades?
Best regards,
David.P
