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bug#22873: Can we support multiple Cursors?
Keith David Bershatsky
bug#22873: Can we support multiple Cursors?
Sun, 25 Jun 2017 15:09:16 -0700
- Fake cursors now only appear in the selected-window if the `mc-list' is
defined -- i.e., the fake cursors are removed when the window loses focus, and
they are added again when the window acquires focus.
- `mc_color_vector_calculate` will take the familiar Emacs way of specifying
colors (e.g., "red" and "#FF0000") and convert them internally to the LSL color
vector. The conversion process is transparent to the user.
- `mc_remove_when_scrolled` will remove multiple cursors when scrolling. This
is important because `update_window_end` will not remove the cursors when
scrolling. [There was an emacs-devel thread (about 1.5 years ago) where I had
sought help tracking the multiple cursors when scrolling. It turned out that
the method of tracking cursors was not the problem (since they don't move) --
it was simply that `update_window_end` was not being called in that
- `mc_x_y_hpos_vpos' contains some extra `stuff` that is irrelevant to the
functionality of this patch -- the extra `stuff` is used by me as a workaround
to deal with the overlay after-string property that gets in the way of properly
calculating coordinates. [See the TODO section below.]
- The patch applies to commit a30e7e12ed8465e2565dd318d921bc87f52ce18e from
03/28/2016. [See apology for the inconvenience further down below.]
- Optimize drawing and removal of multiple fake cursors.
- Fix any bugs (there will surely be many).
- Implement a way to properly calculate x, y, hpos, vpos when overlays are
present -- e.g., the overlay after-string property wreaks havoc on the current
method of calculating coordinates.
- Try and convince one or more real programmers to take over from here, since
we now have a working proof concept. [I am just a weekend hobbyist without any
formal programming study.]
I would respectfully suggest to the Emacs development team that multiple
cursors be implemented in two stages:
- The first stage would be the creation and removal of fake cursors to be used
kind of like overlays. I.e., specify the `point`, cursor-style, and color.
The suggestion by Eli Z. to support specifying colors with strings like "red"
and "#FF0000" has now been implemented.
- The second stage would be to implement built-in functionality similar to the
multiple cursors library by Magnar Sveen.
[In an earlier section of this thread, I mentioned a substantial slow-down that
I experienced when using the library written by Mr. Sveen. I have since
discovered that it was due to `line-number-at-pos', and I have already reached
out to the author with an alternative suggestion to use (format-mode-line
INSTALLATION (for anyone a little less familiar):
STEP #1 (clone master branch): git clone -b master
STEP #2: cd over to the root of the `emacs` source directory cloned in the
first step above.
STEP #3 (hard reset): git reset --hard a30e7e12ed8465e2565dd318d921bc87f52ce18e
You will see a message: "HEAD is now at a30e7e1 Mention the `M-q' changes"
[We need to go back in time to 03/28/2016 as that is the master branch version
that I am still using -- sorry for the inconvenience. I will update to the
latest version of Emacs at some point in the future as time permits. Creating
patches that apply to a "moving target" is challenging.]
STEP #4 (put the patch in place): Copy the latest patch
(multiple_cursors_008.diff) to the root of the emacs source directory cloned in
the first step above.
STEP #5 (apply the patch): git apply multiple_cursors_008.diff
STEP #6: ./autogen.sh
STEP #7: Configure the build for X, MS Windows, or OSX; e.g.,: ./configure
STEP #8: make
STEP #9: make install
STEP #10: Launch the newly built Emacs, and copy the following function to the
`*scratch*` buffer, and type `M-x mc-test`.
(defun mc-test ()
"Draw fake cursors at all POS defined in the `mc-list'. Multiple fake cursors
are supported by GUI versions of Emacs built for X, Windows and OSX.
Popular forms of specifying colors such as \"red\" and \"#FF0000\" are now
supported, as well as LSL color vectors such as [1.0 0.0 0.0]. For those users
who choose the former familiar methods of specifying colors with strings,
`mc_color_vector_calculate' will convert those strings to LSL color vectors.
The color vectors are commonly referred to as LSL (The Linden Scripting
`nsterm.m' uses `NSColor', which works well with LSL. `w32term.c' uses
`PALETTERGB' or `RGB', and the conversion from LSL is done internally by
multiplying each element of the LSL color vector by 255. `xterm.c' uses
`x_make_truecolor_pixel', which uses 16-bit RGB -- the conversion from LSL
happens internally by multiplying each element of the LSL color vector by
(let ((buffer (get-buffer-create "*MC-TEST*")))
(insert "This is a test!")
(setq mc-list '((1 "hbar" "red")
(2 "bar" "yellow")
(3 "box" "#00FF00")
(4 "hollow" "#0000FF")
(5 ("hbar" 3) [1.0 0.0 1.0])
(6 ("bar" 3) [0.0 1.0 1.0]))))
(select-window (display-buffer buffer))
;;; The trigger in `keyboard.c` is not activated in this example, so we
;;; Force the multiple cursors to be drawn.
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- bug#22873: Can we support multiple Cursors?,
Keith David Bershatsky <=