I have Okular configured to watch files for changes (Configure->General->Reload document on file change).  This makes it easy for me to edit a LaTeX document in an editor and get an instant preview whenever I recompile the document to PDF.  However, there is a slight annoyance: Okular blanks the window while it is reloading the file.  This makes it harder for me to see the effect of my changes.  (That is, sometimes I'll be reading the generated PDF in Okular and spot a small error.  I make some changes in Emacs and recompile, and then restore my gaze to the text in Okular to see the effect of my changes on that section of the document.  Having the display suddenly blank for a second or two while I'm doing makes me lose my position, and makes it harder for me to compare the state of the document before and after the recompilation.)

Instead of blanking the window, please consider a less instrusive "loading" notification, such as a message in the status bar, or a small throbber icon in the corner of the window.  Then immediately display the document as soon as it's loaded.  (If the document turns out to be broken, only then should the window be blanked.)

Reproducible: Always

Steps to Reproduce:
1. Make sure Configure->General->Reload document on file change) is checked
2. Load a PDF document
3. Modify the PDF on disk
Actual Results:  
4. Okular detects the file has changed, and blanks the window while it reloads the file

Expected Results:  
4. Okular should reload the file in the background and then immediately show it without any interruption in the display

I haven't tried this with anything other than PDF files, though I suspect this problem is not limited to the PDF back-end but is common to all file types.