Package: emacs;
Reported by: Keith David Bershatsky <esq <at> lawlist.com>
Date: Tue, 3 Jun 2014 17:50:01 UTC
Severity: wishlist
Found in version 24.4.50
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From: Keith David Bershatsky <esq <at> lawlist.com> To: 17678 <at> debbugs.gnu.org Subject: bug#17678: 24.4.50; Feature Request -- calculate new `window-start` & `window-end` before visual redisplay Date: Tue, 03 Jun 2014 10:48:54 -0700
At the present time, I do not believe that Emacs has the ability to calculate a new `window-start` and a new `window-end` without a redisplay occurring, because it needs to take into account things like the new cursor position, `visual-line-mode`, `linenum-mode`, etc. Functions assigned to the `post-command-hook` use the `window-start` and `window-end` positions that were previously visible before a new redisplay occurs. Example: * Long buffer of text that exceeds the `window-height`. * Jump interactively from `beginning-of-buffer` to `ending-of-buffer`, or visa-versa. * In the `post-command-hook`, have the following two elements: ** Remove overlays xyz between the *old* `window-start` and *old* `window-end`. ** Add overlays xyz between the *new* `window-start` and *new* `window-end`. The final component above (i.e., ** Add overlays xyz between the *new* . . .) cannot be done correctly without a forced `redisplay` occurring. The result of a forced redisplay is that the user will see a momentary visual representation of the buffer *without* overlays xyz. The forced redisplay permits Emacs to correctly calculate the *new* `window-start` and *new* `window-end`. In a stackoverflow thread regarding this issue, @Stefan suggested that I take a look at the `jit-lock-register`. After combing through the code in `jit-lock.el` and trying some experiments, I believe that `jit-lock.el` is more suited to a situation when buffer *modification* occurs -- it is also suited for situations where one may wish to incrementially act upon an entire buffer in small chunks at a time to increase efficiency of avaialble resources. http://stackoverflow.com/questions/23923371/emacs-calculating-new-window-start-end-without-redisplay I believe that the solution may be to have a `sneak-preview-redisplay` whereby the *new* `window-start` and *new* `window-end` could be correctly calculated without the visual buffer actually being redisplayed. Thanks, Keith ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;; In GNU Emacs 24.4.50.1 (x86_64-apple-darwin10.8.0, NS appkit-1038.36 Version 10.6.8 (Build 10K549)) of 2014-06-01 on MP.local Repository revision: 117215 lekktu <at> gmail.com-20140601162519-4dacx2w0ak528z2r Windowing system distributor `Apple', version 10.3.1038 Configured using: `configure --with-ns' Configured features: ACL LIBXML2 ZLIB Important settings: locale-coding-system: utf-8-unix Major mode: Fundamental Minor modes in effect: lawlist-scroll-bar-mode: t lawlist-delete-selection-mode: t lawlist-linum-mode: t lawlist-visual-line-mode: t vr-mode: t hr-mode: t flyspell-mode: t desktop-save-mode: t tabbar-mode: t font-lock-mode: t blink-cursor-mode: t transient-mark-mode: t Recent input: <down> <down> <down> <down> <down> <down> <down> <down> <down> <M-right> <M-right> <M-right> <M-right> <M-right> <M-right> <M-right> <M-right> <M-right> <M-right> <M-right> <M-right> <M-right> <M-right> <M-right> <M-right> <M-right> <M-right> <M-right> <M-right> <M-right> <right> <right> <right> <right> <right> <right> <right> <right> <right> <right> <right> <right> <right> <right> <right> <right> <right> <right> <right> <right> <right> <right> <right> <right> <right> <right> <right> <right> <right> <right> <right> <right> <right> <right> <right> <M-right> <M-right> <M-right> <M-right> <M-right> <M-right> <M-right> <M-right> <M-right> <s-up> <down> <down> <down> <down> <down> <down> <down> <down> <down> <down> <down> <down> <down> <down> <down> <down> <down> <down> <down> <down> <down> <down> <down> <down> <up> <M-right> <M-right> <M-right> <M-right> <M-right> <M-right> <M-right> <M-right> <M-right> <M-right> <M-right> <M-right> <M-right> <M-right> <M-right> <M-right> <M-right> <M-right> <M-right> <M-right> <M-right> <M-right> <M-right> <M-right> <M-right> <M-right> <M-right> <M-right> <M-right> <M-right> <M-right> <M-right> <M-right> <M-right> <M-right> <M-right> <M-right> <M-right> <M-left> <M-left> <M-left> <M-left> <M-left> <M-left> <M-left> <M-left> <M-left> <M-left> <M-left> <M-left> <M-left> <M-left> <M-left> <M-left> <M-left> <M-left> <M-left> <M-left> <M-left> <M-left> <M-left> <M-left> <M-left> <M-left> <wheel-down> <double-wheel-down> <triple-wheel-down> <wheel-down> <double-wheel-down> <triple-wheel-down> <wheel-down> <double-wheel-down> <triple-wheel-down> <wheel-down> <double-wheel-down> <triple-wheel-down> <triple-wheel-down> <wheel-down> <double-wheel-down> <triple-wheel-down> <wheel-down> <double-wheel-down> <triple-wheel-down> <wheel-down> <double-wheel-down> <triple-wheel-down> <wheel-up> <double-wheel-up> <triple-wheel-up> <wheel-up> <wheel-up> <double-wheel-up> <triple-wheel-up> <help-echo> <down-mouse-1> <mouse-1> <wheel-up> <double-wheel-up> <triple-wheel-up> <triple-wheel-up> <wheel-up> <double-wheel-up> <triple-wheel-up> <down> <down> <down> <down> <down> <up> <up> <up> <up> <up> <s-up> <down> <down> <down> <down> <down> <down> <down> <down> <down> <down> <down> <down> <down> <down> <down> <down> <down> <down> <down> <down> <down> <down> <down> <s-right> <left> <left> <left> <left> <left> <left> <left> <left> <left> s-N s-w k <left> <left> <left> <left> <left> <left> <left> <left> <left> s-N s-w k <escape> x e m a c s - b u g <return> <backspace> <backspace> <backspace> <backspace> <backspace> <backspace> <backspace> <backspace> <backspace> r e p o r t - e m a c s - b u g <return> Recent messages: Saving...done Mark set [k]ill or [s]ave draft? Loading msgdb for +/Users/HOME/.0.data/.0.emacs/.0.mail/msgdb/imap/mail.lawlist.com/lawlist/INBOX.Drafts/spool...done Type C-c C-x C-z to exit MIME mode, and type C-c C-x ? to get help. Saving...done Mark set [k]ill or [s]ave draft? 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