Bug 50528

Summary: SVG text smaller than 0.5px not displayed properly
Product: WebKit Reporter: Jeff Schiller <jeffschiller>
Component: SVGAssignee: Nobody <webkit-unassigned>
Status: RESOLVED DUPLICATE    
Severity: Normal CC: krit, simon.fraser, zimmermann
Priority: P2    
Version: 528+ (Nightly build)   
Hardware: PC   
OS: OS X 10.5   
URL: http://http://codedread.com/browser-tests/subpixel.svg
Attachments:
Description Flags
Test case showing the problem none

Jeff Schiller
Reported 2010-12-04 15:01:38 PST
http://codedread.com/browser-tests/subpixel.svg or <svg xmlns='http://www.w3.org/2000/svg'> <text x='10' y='30'>The two words should be the same size:</text> <g transform='scale(15)'> <text y='12' style='font-size:0.5px'>TINY</text> <text y='24' style='font-size:0.499999px'>TINY</text> </g> </svg> Both words should be small on the page. The latter one at font-size smaller than 0.5px is not displayed appropriately. Also, you can see the effect more dramatically here: http://upload.wikimedia.org/wikipedia/commons/f/f9/PI.svg
Attachments
Test case showing the problem (271 bytes, image/svg+xml)
2010-12-04 15:03 PST, Jeff Schiller 		no flags
Details
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Jeff Schiller
Comment 1 2010-12-04 15:03:29 PST
Created attachment 75617 [details] Test case showing the problem
Nikolas Zimmermann
Comment 2 2010-12-09 01:13:05 PST
Thanks for the testcase, Jeff! I've traced it down: #1 0x0426c654 in WebCore::FontCache::createFontPlatformData (this=0x1a5965c0, fontDescription=@0x1d4adda0, family=@0x1d4adda0) at /Users/nikolaszimmermann/Coding/WebKit/WebCore/platform/graphics/mac/FontCacheMac.mm:214 (gdb) p fontDescription $61 = (const class WebCore::FontDescription &) @0x1d4adda0: { m_familyList = { m_family = { m_string = { m_impl = { <WTF::FastAllocBase> = {<No data fields>}, members of WTF::RefPtr<WTF::StringImpl>: m_ptr = 0x1a56e650 } } }, m_next = { <WTF::RefPtr<WebCore::SharedFontFamily>> = { <WTF::FastAllocBase> = {<No data fields>}, members of WTF::RefPtr<WebCore::SharedFontFamily>: m_ptr = 0x0 }, <No data fields>} }, m_specifiedSize = 0.49000001, m_computedSize = 0.49000001, The font size is stored correctly in the FontDescription, but then "computedPixelSize()" is used to determine the actual font size. 193 194 FontPlatformData* FontCache::createFontPlatformData(const FontDescription& fontDescription, const AtomicString& family) 195 { 196 NSFontTraitMask traits = fontDescription.italic() ? NSFontItalicTrait : 0; 197 NSInteger weight = toAppKitFontWeight(fontDescription.weight()); 198 float size = fontDescription.computedPixelSize(); (gdb) p size $63 = 0 FontDescription.h: int computedPixelSize() const { return int(m_computedSize + 0.5f); } This is the root of the problem. Just keeping my analysis here for the record.
Nikolas Zimmermann
Comment 3 2011-02-01 04:02:52 PST
The patch on bug 12448 fixes this problem. Thanks a lot for the testcase, I've integrated it in my patch. *** This bug has been marked as a duplicate of bug 12448 ***
Simon Fraser (smfr)
Comment 4 2011-02-01 08:44:35 PST
Is it really the same thing? In this testcase the text is just a line of pixels (even if it's not sharp). In Firefox, the text is much bigger.
Nikolas Zimmermann
Comment 5 2011-02-01 09:49:33 PST
(In reply to comment #4) > Is it really the same thing? In this testcase the text is just a line of pixels (even if it's not sharp). In Firefox, the text is much bigger. Which testcase are you referring to?
Simon Fraser (smfr)
Comment 6 2011-02-01 10:00:07 PST
One in a bug that I can't find right now, but was probably marked as a duplicate of this.
Dirk Schulze
Comment 7 2011-02-01 10:03:20 PST
I guess Simon thought about bug 52892.
Simon Fraser (smfr)
Comment 8 2011-02-01 10:06:53 PST
Yep, that's the one. Sorry, I thought this was that bug.
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