Hi,
I’ve encountered a potential bug in Emacs when using the query-replace (via perform-replace) functions. When performing text replacements across a buffer and choosing to replace but not immediately move the point (using the , act-and-show option), the function does replace the text as expected but fails to update the highlighting to the region containing the replacement.

Steps to Reproduce:

1. Open a buffer with the following content:

   String to be replaced. Another string.
   String to be replaced. Another string.
   End
   

2. Run the following command:

   (query-replace "String to be replaced." "Replacement." nil (point-min) (point-max))
   

3. When prompted to replace a match, use the , (act-and-show) option to replace the text but pause moving to the next match.

Expected Behavior:
After a replacement is made and before moving to the next match, the highlighted region of the replaced text should be “updated” to fit the replaced text.

Actual Behavior:
The highlighting remains on the matched region. This issue can be visually confirmed in the following animation:
View Animation on Imgur

Visual Evidence:

• Highlight before using act-and-show (match):

• Highlight after using act-and-show while paused (replacement):

As demonstrated, the highlighted region post-replacement does not correspond to any current match, which is misleading and might affect further editing decisions.

Best regards,

Gabriele Nicolardi