ISearch - Paste - text in mini buffer is not same

Question

Windows 10, Emacs 25

1. Select text
2. second word is upper case.
3. Press C-s
4. Paste text

Why whole text is lower case in mini buffer?

Answer 1

isearch is case-insensitive by default, and this behaviour is connected to that.

Typing M-c while isearching calls isearch-toggle-case-fold which enables you to switch to a case-sensitive search, at which point you'll observe that your search string will retain its mixed-case when you paste it into the minibuffer.

The manual says:

Normally, when the search is case-insensitive, text yanked into the search string is converted to lower case, so that the search remains case-insensitive (*note case folding: Lax Search.). However, if the value of the variable ‘search-upper-case’ (*note search-upper-case: Lax Search.) is other than ‘not-yanks’, that disables this down-casing.

See:

• C-hig (emacs)Isearch Yank
• C-hig (emacs)Lax Search
• M-x customize-option RET search-upper-case

Answer 2

If you select the text and paste it while the pointer is still in the scratch buffer ( in your example) the text is copied all lower case.

This is corrected by moving the pointer to the minibuffer like so: copy-region: M-w, calling I-serach: C-s or M-x I-search-forward ,moving the pointer to the mini buffer: C-x o, mouse click, or whatever method you use, and yank C-y.

The text will be copied correctly.