From mboxrd@z Thu Jan 1 00:00:00 1970 Path: news.gmane.io!.POSTED.ciao.gmane.io!not-for-mail From: Eli Zaretskii Newsgroups: gmane.emacs.bugs Subject: bug#41544: 26.3; Possible incorrect results from color-distance Date: Fri, 05 Jun 2020 15:27:22 +0300 Message-ID: <835zc5bsut.fsf@gnu.org> References: <5C4A633D-8222-4439-BE37-9B8674F1DA6D@acm.org> <87r1v2aat3.fsf@tromey.com> <9902865C-01B4-4E50-A433-DBC8B8311234@acm.org> <83tuzueogo.fsf@gnu.org> <6272275C-560C-4437-90F1-2A8294D27019@acm.org> <83o8q2elja.fsf@gnu.org> <83mu5mel4o.fsf@gnu.org> <77F1DDD3-A69F-40ED-902D-74986D5E6596@acm.org> <83y2p5cumz.fsf@gnu.org> <83blm0cjlz.fsf@gnu.org> <83367ccf8w.fsf@gnu.org> <624D7FB8-A836-4A7E-8895-47E867214504@acm.org> <83o8pyc4bq.fsf@gnu.org> <55D73CA5-1EFB-4B0A-8F8B-FDA1D39F51BF@acm.org> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 8bit Injection-Info: ciao.gmane.io; posting-host="ciao.gmane.io:159.69.161.202"; logging-data="48194"; mail-complaints-to="usenet@ciao.gmane.io" Cc: tom@tromey.com, simon@polaris64.net, 41544@debbugs.gnu.org To: Mattias =?UTF-8?Q?Engdeg=C3=A5rd?= Original-X-From: bug-gnu-emacs-bounces+geb-bug-gnu-emacs=m.gmane-mx.org@gnu.org Fri Jun 05 14:28:10 2020 Return-path: Envelope-to: geb-bug-gnu-emacs@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 1jhBSE-000COD-D5 for geb-bug-gnu-emacs@m.gmane-mx.org; Fri, 05 Jun 2020 14:28:10 +0200 Original-Received: from localhost ([::1]:37780 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1jhBSD-0005J3-8P for geb-bug-gnu-emacs@m.gmane-mx.org; Fri, 05 Jun 2020 08:28:09 -0400 Original-Received: from eggs.gnu.org ([2001:470:142:3::10]:60500) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1jhBS6-0005Ih-LX for bug-gnu-emacs@gnu.org; Fri, 05 Jun 2020 08:28:02 -0400 Original-Received: from debbugs.gnu.org ([209.51.188.43]:36947) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_128_GCM_SHA256:128) (Exim 4.90_1) (envelope-from ) id 1jhBS6-00006H-CT for bug-gnu-emacs@gnu.org; Fri, 05 Jun 2020 08:28:02 -0400 Original-Received: from Debian-debbugs by debbugs.gnu.org with local (Exim 4.84_2) (envelope-from ) id 1jhBS6-00028e-8V for bug-gnu-emacs@gnu.org; Fri, 05 Jun 2020 08:28:02 -0400 X-Loop: help-debbugs@gnu.org Resent-From: Eli Zaretskii Original-Sender: "Debbugs-submit" Resent-CC: bug-gnu-emacs@gnu.org Resent-Date: Fri, 05 Jun 2020 12:28:02 +0000 Resent-Message-ID: Resent-Sender: help-debbugs@gnu.org X-GNU-PR-Message: followup 41544 X-GNU-PR-Package: emacs X-GNU-PR-Keywords: patch Original-Received: via spool by 41544-submit@debbugs.gnu.org id=B41544.15913600748206 (code B ref 41544); Fri, 05 Jun 2020 12:28:02 +0000 Original-Received: (at 41544) by debbugs.gnu.org; 5 Jun 2020 12:27:54 +0000 Original-Received: from localhost ([127.0.0.1]:48493 helo=debbugs.gnu.org) by debbugs.gnu.org with esmtp (Exim 4.84_2) (envelope-from ) id 1jhBRx-00028I-Si for submit@debbugs.gnu.org; Fri, 05 Jun 2020 08:27:54 -0400 Original-Received: from eggs.gnu.org ([209.51.188.92]:47600) by debbugs.gnu.org with esmtp (Exim 4.84_2) (envelope-from ) id 1jhBRw-000285-1c for 41544@debbugs.gnu.org; Fri, 05 Jun 2020 08:27:53 -0400 Original-Received: from fencepost.gnu.org ([2001:470:142:3::e]:35508) by eggs.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1jhBRq-0008R0-CA; Fri, 05 Jun 2020 08:27:46 -0400 Original-Received: from [176.228.60.248] (port=1299 helo=home-c4e4a596f7) by fencepost.gnu.org with esmtpsa (TLS1.2:RSA_AES_256_CBC_SHA1:256) (Exim 4.82) (envelope-from ) id 1jhBRd-00066j-RT; Fri, 05 Jun 2020 08:27:44 -0400 In-Reply-To: <55D73CA5-1EFB-4B0A-8F8B-FDA1D39F51BF@acm.org> (message from Mattias =?UTF-8?Q?Engdeg=C3=A5rd?= on Thu, 4 Jun 2020 17:29:06 +0200) X-BeenThere: debbugs-submit@debbugs.gnu.org X-Mailman-Version: 2.1.18 Precedence: list X-BeenThere: bug-gnu-emacs@gnu.org List-Id: "Bug reports for GNU Emacs, the Swiss army knife of text editors" List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: bug-gnu-emacs-bounces+geb-bug-gnu-emacs=m.gmane-mx.org@gnu.org Original-Sender: "bug-gnu-emacs" Xref: news.gmane.io gmane.emacs.bugs:181553 Archived-At: > From: Mattias Engdegård > Date: Thu, 4 Jun 2020 17:29:06 +0200 > Cc: tom@tromey.com, simon@polaris64.net, 41544@debbugs.gnu.org > > 1. color-name-to-rgb calls (color-values "#ffffffffffff") as a means to get the range of the colour values. There's some history to that: see bug#25890. > 2. With TERM=xterm-color, there are 8 colours. These are assumed to be the 8 first of xterm-standard-colors (xterm.el). > 3. The colour closest to "#ffffffffffff" is "white", with the values (229 229 229), or translated to 16 bit/channel, (#e5e5 #e5e5 #e5e5) which color-values returns. > 4. "blue" has the values (0 0 238), or (0 0 #xeeee). > 5. Thus color-name-to-rgb returns #xeeee/#xe5e5 for the blue channel, or 1.039, which is a clear bug. What bad results does this issue cause in practice? (Btw, in a GUI session I see (0.0 0.0 1.0), so no problem there.) > The main problem is trusting "#ffffffffffff" to match a colour with the maximum range. Why is that a problem, given the color representation we use in Emacs? > It could be argued that xterm.el shouldn't use subdued colours when only 8 are present; I didn't go far back in XTerm history to find out. Modern XTerm has default colours 0-7 that correspond to the assumptions of Emacs. > > Since we already document that the colour channel maximum is either 65535 or 65280 depending on platform, taking the very roundabout way of trying to match a sufficiently white colour and using its components is demonstrably unsafe and error-prone, as well as unnecessarily slow. Hence color-component-max in the patch. Sorry, you lost me here. I don't understand what you are saying here and what does that have to do with the problem being discussed. > This also fixes a different problem: if the display hasn't been initialised fully, such as when running in batch mode, then (color-values "#ffffffffffff") returns nil, and as we shall see later, it may be useful to be able to call color-name-to-rgb at this stage without crashing. This command: emacs -batch --eval "(message \"%s\" (color-name-to-rgb \"white\"))" yields "(1.0 1.0 1.0)" on my system with today's master branch, and this command: emacs -batch --eval "(message \"%s\" (color-values \"#ffffffffffff\"))" yields "(65535 65535 65535)", so I don't think I understand what problem you are concerned with here, and how can this cause a crash. Please elaborate.