I would like to be able to run Emacs without frame decorations on Win
OS. I don't like those since they break visual styles of my Emacs,
especially if I use a dark theme. Also caption bar take some of
vertical screen estate unnecessary. I didn't found any reliable way
to do this from Emacs.

It can be done via Win32 API SetWindowLongPtr by changing EMACS_CLASS
style to WS_POPUP|WS_TABSTOP|WS_VISIBLE. It can be changed back to
original by either saving old style in a variable or by setting
corresponding style bits for standard window frame. I suggest either
to implement this in a "border-width" property when border width
is set to 0, or to implement a new variable/function that can be set in
init file, such as for example "no-frame-borders t". I have made small
prototype/mockup to illustrate what I mean which can be seen on
https://www.youtube.com/watch?v=ii_gTRCuXog

Care has to be taken to note that when removing caption bar and borders
it will be no longer possible to move and resize window unless user
have other means of performing those applications. I am using a small
opensource app called alt-drag (https://stefansundin.github.io/altdrag/).
For convienience one might implement moving/resizing ops in Emacs
window procedure. For ex they can be faked by just sending corresponding
messages
back to wnd proc. I think standard way to do this is by handling
WM_NCHITTEST, as for example:
case WM_NCHITTEST: {
        LRESULT hit = DefWindowProc(hWnd, message, wParam, lParam);
        if (hit == HTCLIENT) hit = HTCAPTION;
        return hit;
    }

Similar could maybe work for HTSIZE but I haven't tested it myself
though, so I can't tell for sure.



In GNU Emacs 26.0.50.1 (x86_64-w64-mingw32)
 of 2017-01-05 built on DESKTOP-EBMFI2K
Repository revision: d88cdad2847726438c7d1de9fd2651c4be9243aa
Windowing system distributor 'Microsoft Corp.', version 10.0.14393
Recent messages:
Wrote c:/Users/Arthur/.emacs
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(source)...done
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(Shell command succeeded with no output) [2 times]

Configured using:
 'configure --without-imagemagick --with-modules --without-makeinfo'

Configured features:
XPM JPEG TIFF GIF PNG RSVG SOUND NOTIFY ACL GNUTLS LIBXML2 ZLIB
TOOLKIT_SCROLL_BARS MODULES

Important settings:
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  locale-coding-system: cp1252

Major mode: Emacs-Lisp

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Load-path shadows:
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c:/Users/Arthur/.emacs.d/plugins/helm/helm hides
c:/Users/Arthur/.emacs.d/plugins/helm-core/helm
c:/Users/Arthur/.emacs.d/plugins/helm/helm-source hides
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c:/Users/Arthur/.emacs.d/plugins/load-relative/el-get-install hides
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c:/Users/Arthur/.emacs.d/plugins/realgud/realgud hides
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c:/Users/Arthur/.emacs.d/plugins/loc-changes/test/test-basic hides
c:/Users/Arthur/.emacs.d/plugins/test-simple/test/test-basic

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