From mboxrd@z Thu Jan 1 00:00:00 1970 Path: news.gmane.io!.POSTED.ciao.gmane.io!not-for-mail From: Mattias =?UTF-8?Q?Engdeg=C3=A5rd?= Newsgroups: gmane.emacs.bugs Subject: bug#41544: 26.3; Possible incorrect results from color-distance Date: Thu, 4 Jun 2020 17:29:06 +0200 Message-ID: <55D73CA5-1EFB-4B0A-8F8B-FDA1D39F51BF@acm.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> Mime-Version: 1.0 (Mac OS X Mail 12.4 \(3445.104.14\)) Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: quoted-printable Injection-Info: ciao.gmane.io; posting-host="ciao.gmane.io:159.69.161.202"; logging-data="94518"; mail-complaints-to="usenet@ciao.gmane.io" Cc: tom@tromey.com, simon@polaris64.net, 41544@debbugs.gnu.org To: Eli Zaretskii Original-X-From: bug-gnu-emacs-bounces+geb-bug-gnu-emacs=m.gmane-mx.org@gnu.org Thu Jun 04 17:30:45 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 1jgrpL-000OSa-Ug for geb-bug-gnu-emacs@m.gmane-mx.org; Thu, 04 Jun 2020 17:30:43 +0200 Original-Received: from localhost ([::1]:42160 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1jgrpK-0006oq-Us for geb-bug-gnu-emacs@m.gmane-mx.org; Thu, 04 Jun 2020 11:30:42 -0400 Original-Received: from eggs.gnu.org ([2001:470:142:3::10]:45000) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1jgroh-0006na-6t for bug-gnu-emacs@gnu.org; Thu, 04 Jun 2020 11:30:03 -0400 Original-Received: from debbugs.gnu.org ([209.51.188.43]:35710) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_128_GCM_SHA256:128) (Exim 4.90_1) (envelope-from ) id 1jgrog-0004OJ-Rh for bug-gnu-emacs@gnu.org; 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Thu, 04 Jun 2020 11:29:12 -0400 X-Authenticated-User: mattiase@bredband.net DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=megamailservers.eu; s=maildub; t=1591284550; bh=vhoSfDx0Wg6U5tW75QwhEcmfdbvvgQmIR5rB3QhC5j4=; h=Subject:From:In-Reply-To:Date:Cc:References:To:From; b=pFzquu8XqCoyMbJjHtagG0KJS9NN3FxRBEap6xaOnuwqbJx7lK1EibyhojYXlPtKr u4nyrtEf7pVmi10h/CJT4vLv9jjJbUGu8buEI+k2KfuiZQUOo5XqPzpr2g8nzsq8YH 9T9IiHdrG2APC7GmA5ScXIERmxGUj/el8o9cMx8Q= Feedback-ID: mattiase@acm.or Original-Received: from stanniol.lan (c-4e4ae655.032-75-73746f71.bbcust.telenor.se [85.230.74.78]) (authenticated bits=0) by mail92c50.megamailservers.eu (8.14.9/8.13.1) with ESMTP id 054FT6VY004750; Thu, 4 Jun 2020 15:29:08 +0000 In-Reply-To: <83o8pyc4bq.fsf@gnu.org> X-Mailer: Apple Mail (2.3445.104.14) X-CTCH-RefID: str=0001.0A782F1F.5ED912DC.00B2:SCFSTAT68638221, ss=1, re=-4.000, recu=0.000, reip=0.000, cl=1, cld=1, fgs=0 X-CTCH-VOD: Unknown X-CTCH-Spam: Unknown X-CTCH-Score: -4.000 X-CTCH-Flags: 0 X-CTCH-ScoreCust: 0.000 X-CSC: 0 X-CHA: v=2.3 cv=aY8fYigt c=1 sm=1 tr=0 a=klNLuyVZdLUgl+K5Uafb2A==:117 a=klNLuyVZdLUgl+K5Uafb2A==:17 a=kj9zAlcOel0A:10 a=M51BFTxLslgA:10 a=mDV3o1hIAAAA:8 a=pfK807lD-pJQ71N_UpEA:9 a=CjuIK1q_8ugA:10 a=_FVE-zBwftR9WsbkzFJk:22 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:181514 Archived-At: 4 juni 2020 kl. 16.07 skrev Eli Zaretskii : > Let's please discuss each problem in detail (I tried to understand > them from the log message you posted, but couldn't find rationale > there). >=20 > And in any case, I will prefer solutions that fix any problems > locally, not changes in low-level stuff used in many other places, > because the latter run the risk of introducing new bugs. As the > problems are quite minor, AFAICT, solving them in unsafe ways is > something to be avoided. I think we agree. There should be nothing unsafe here other than the = code being replaced, but code should be scrutinised. > You mean, the component that is 1.0393? What bad decisions caused > that, what problems does this small deviation causes in itself? Yes, this is as good a place to start as any, and the fix for this is a = good change on its own. It goes something like this: 1. color-name-to-rgb calls (color-values "#ffffffffffff") as a means to = get the range of the colour values. 2. With TERM=3Dxterm-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. The main problem is trusting "#ffffffffffff" to match a colour with the = maximum range. 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. 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.