From mboxrd@z Thu Jan 1 00:00:00 1970 Path: news.gmane.io!.POSTED.blaine.gmane.org!not-for-mail From: Eli Zaretskii Newsgroups: gmane.emacs.devel Subject: Re: Can watermarking Unicode text using invisible differences sneak through Emacs, or can Emacs detect it? Date: Sun, 06 Feb 2022 10:30:37 +0200 Message-ID: <83tudcz9aq.fsf@gnu.org> References: <87mtjkt6m9.fsf@gmail.com> <83ilu8htws.fsf@gnu.org> <3E718CA2-889F-4AEE-B79C-EB3A221D1CB2@gnu.org> <83o83wc7gs.fsf@gnu.org> <8335l5brov.fsf@gnu.org> <83mtjc838i.fsf@gnu.org> <83zgna7hyd.fsf@gnu.org> <83ee4l78rw.fsf@gnu.org> <87ee4jhezi.fsf@logand.com> <8735kxe7ug.fsf@logand.com> <83iltt1k7h.fsf@gnu.org> <83h79d1jx1.fsf@gnu.org> <87h79c2369.fsf@logand.com> Injection-Info: ciao.gmane.io; posting-host="blaine.gmane.org:116.202.254.214"; logging-data="14006"; mail-complaints-to="usenet@ciao.gmane.io" Cc: psainty@orcon.net.nz, luangruo@yahoo.com, emacs-devel@gnu.org, rms@gnu.org, kevin.legouguec@gmail.com To: Tomas Hlavaty Original-X-From: emacs-devel-bounces+ged-emacs-devel=m.gmane-mx.org@gnu.org Sun Feb 06 09:33:50 2022 Return-path: Envelope-to: ged-emacs-devel@m.gmane-mx.org Original-Received: from lists.gnu.org ([209.51.188.17]) by ciao.gmane.io with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.92) (envelope-from ) id 1nGczW-0003Qn-6a for ged-emacs-devel@m.gmane-mx.org; Sun, 06 Feb 2022 09:33:50 +0100 Original-Received: from localhost ([::1]:58970 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1nGczU-000866-M4 for ged-emacs-devel@m.gmane-mx.org; Sun, 06 Feb 2022 03:33:48 -0500 Original-Received: from eggs.gnu.org ([209.51.188.92]:36446) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1nGcwn-0007E7-J9 for emacs-devel@gnu.org; Sun, 06 Feb 2022 03:31:01 -0500 Original-Received: from [2001:470:142:3::e] (port=52956 helo=fencepost.gnu.org) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1nGcwm-0003ap-PD; Sun, 06 Feb 2022 03:31:00 -0500 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=gnu.org; s=fencepost-gnu-org; h=References:Subject:In-Reply-To:To:From:Date: mime-version; bh=zr0DX69ygN3IrAQttOYJgIaBFuJcNNl8pgiV0L+ArfU=; b=iODMxwskLyXD 4ux2BE4hRRyJovUnSeNtO1XJr0nP1ROSxAnNWHUf98jQTFk7u2YwDvdewHi9Pdk9j5ebKesXgYdMg +jOkNfWlrV4x4j/ezQ9k0gcA/NIOM1vL3D7Vx+gfhgPpOX+q2W8ATzNvRQ3mhOlHZKxGRV7c7NZWv ITVtXmFAaM7DRxEzd34VFq5bkWB/GJfPqCZkkP5MMN7AIMfIuLBRaPooca36DP0cHPcKoN5n5lfGv 7V2+J9X0HxmjJXR2SaYVkO9R7wT6fQ8tE/lZmk5BxZjiDqkRZDcmXIiPf0qE+4a8bPrfrsm0yjcwl k2LAx6CtkiaEalyUXmTMEA==; Original-Received: from [87.69.77.57] (port=4141 helo=home-c4e4a596f7) by fencepost.gnu.org with esmtpsa (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1nGcwg-0003hj-Mj; Sun, 06 Feb 2022 03:30:55 -0500 In-Reply-To: <87h79c2369.fsf@logand.com> (message from Tomas Hlavaty on Sun, 06 Feb 2022 02:29:18 +0100) X-BeenThere: emacs-devel@gnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: "Emacs development discussions." List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: emacs-devel-bounces+ged-emacs-devel=m.gmane-mx.org@gnu.org Original-Sender: "Emacs-devel" Xref: news.gmane.io gmane.emacs.devel:285940 Archived-At: > From: Tomas Hlavaty > Cc: psainty@orcon.net.nz, luangruo@yahoo.com, > kevin.legouguec@gmail.com, rms@gnu.org, > emacs-devel@gnu.org > Date: Sun, 06 Feb 2022 02:29:18 +0100 > > On Sat 05 Feb 2022 at 16:12, Eli Zaretskii wrote: > >> If it's a console, does it support the ioctl issued by > >> calculate_glyph_code_table? > > > > I guess the answer is NO, because if it did, you'd see t as the return > > value, not 'unicode'. > > ok, but is it rare or surprising, that my linux console does not support > the discussed ioctl? I don't know, I'm not an expert on that. I thought the Linux console always supports that. Perhaps someone else could chime in. Failing that, how about asking about this on the forum dedicated your GNU/Linux distribution, or the specific console you are using? > I also found surprising you saying something about runtime test to > detect supported characters and choosing replacements accordingly. > That would be great if feasible. That test is part of char-displayable-p. > > So then it isn't surprising that you get false positives when your > > terminal-coding-system is UTF-8: > > There is no terminal-coding-system variable in my Emacs 27.2. It's a function, not a variable. > How can it be UTF-8? Most probably because your locale specifies UTF-8 as the codeset. > M-x occur on ~/.emacs shows me these utf-8 settings: > current-language-environment "UTF-8" > prefer-coding-system 'utf-8 These are evidence that your locale indeed specifies UTF-8. > > that coding-system can encode any > > character, and Emacs has no way of knowing which of them actually have > > glyphs in the console font if the console doesn't support the > > GIO_UNIMAP ioctl we use to find out which glyphs are actually > > available. > > Maybe the ioctl is not the sufficient source of information; emacs would > need to query the current console font and then read the avalable glyphs > from the font? We don't know of any way of querying the console except via that ioctl. If someone can suggest a more reliable or more widely supported method, let them please speak up.