- From: Gérard Talbot <css21testsuite@gtalbot.org>
- Date: Sat, 17 Mar 2012 04:04:19 -0400
- To: "John Daggett" <jdaggett@mozilla.com>
- Cc: "Public CSS test suite mailing list" <public-css-testsuite@w3.org>
Le Sam 17 mars 2012 3:24, John Daggett a écrit : > > Gérard Talbot wrote: > >> > Browsers typically render text with >> > subpixel antialiasing *and* with subpixel or integer-pixel >> > positioning. All browsers support subpixel anti-aliasing but only >> > Firefox/IE9 use subpixel positioning, Webkit/Opera use integer-pixel >> > positioning. Line metrics may be calculated with precise or rounded >> > metrics and where exactly the rounding occurs is not defined >> > precisely. Under Windows, hinting will also affect these metrics >> for a >> > given font size, depending on the font. All of these factors will >> > affect the >> > precise placement. Only disabling subpixel anti-aliasing will still >> > leave you with other factors that affect placement. >> >> Of course it will leave the other factors that affect placement. Why >> should we want to have many factors affect precise placement of text >> when automated checking of tests start? Why not eliminate sources of >> differential rendering, especially if such sources are entirely >> outside >> the realm of CSS spec? > > If you're seeing subpixel anti-aliasing affect a test, then it's a > sign that the text in question isn't placed precisely such that it > lands on integer pixel boundaries. So that's either a bug in the > browser or a bug in the test. For example, many tests I've seen are > in subtle ways dependent upon the metrics of the default font when > they really shouldn't be. John, please bear with me. I loaded http://www.gtalbot.org/BrowserBugsSection/css21testsuite/absolute-non-replaced-width-017-ref.xht and http://www.gtalbot.org/BrowserBugsSection/css21testsuite/absolute-non-replaced-width-017.xhtml in Firefox 11.0, Opera 11.61 and Safari 5.1.4 (each in 2 distinct, separate tabs) under Windows XP SP3 and I had anti-aliasing disabled: Start / Control Panel / Category Appearance and Themes / Display / Appearance tab / Effects button / and the checkbox "Use the following method to smooth edges of screen fonts" was UNchecked. I saw no difference whatsoever between the test and its reftest. Perfect identical rendering. Now, I do Start / Control Panel / Category Appearance and Themes / Display / Appearance tab / Effects button / and then check checkbox "Use the following method to smooth edges of screen fonts" and "Standard" is viewable. Now, there is a difference of rendering between the test and its reftest. I see a difference. When I have time, I amy convert such test and reftest to text/html just to see what happens with IE8 and with clearType. Gérard -- Contributions to the CSS 2.1 test suite: http://www.gtalbot.org/BrowserBugsSection/css21testsuite/ CSS 2.1 Test suite RC6, March 23rd 2011: http://test.csswg.org/suites/css2.1/20110323/html4/toc.html CSS 2.1 test suite harness: http://test.csswg.org/harness/ Contributing to to CSS 2.1 test suite: http://www.gtalbot.org/BrowserBugsSection/css21testsuite/web-authors-contributions-css21-testsuite.html
Received on Saturday, 17 March 2012 08:04:49 UTC