Created attachment 462277 [details] testcase After scale and translate, arcTo() is invalid elliptical arc. When scale is comment out, it works fine. - Example var g = document.getElementById("canvas1").getContext("2d"); g.scale(0.9, 0.9); // It works if this line is comment out g.translate(100, 100); g.strokeStyle = "#888"; g.lineWidth = 20; g.beginPath(); g.lineCap = "round"; g.moveTo(0,0); g.arcTo(0,0, 50,0, 50); g.stroke(); g.restore();
Can we get a screenshot of this (it looks OK on Mac, I think)? Is it a regression from 3.6? I don't think this should block as-is, though.
This is definitely broken for me on Mac trunk. fx3.6 is also broken. The correct rendering is a singe small circle. Are you actually seeing that?
hoo boy is that EVER not what I get. Not a regression, though (just tested in 3.6), so I won't block on it. Would totally take a patch!
Dirk, care to look at this?
(In reply to comment #5) > Created attachment 462621 [details] [diff] [review] > fix Can you explain why this fixes it?
(In reply to comment #6) > (In reply to comment #5) > > Created attachment 462621 [details] [diff] [review] [details] > > fix > > Can you explain why this fixes it? 0:000> p eax=0013c5e8 ebx=0f190b70 ecx=0a0d1860 edx=0f190b70 esi=074a3ba0 edi=6cb5f4b0 eip=5ff75b64 esp=0013c594 ebp=0013c5fc iopl=0 nv up ei pl nz na po nc cs=0023 ss=002b ds=002b es=002b fs=0053 gs=002b efl=00000202 xul!nsCanvasRenderingContext2D::ArcTo+0x67: 5ff75b64 e8c67afcff call xul!gfxContext::CurrentPoint (5ff3d62f) 0:000> p eax=0013c5e8 ebx=0f190b70 ecx=0013c558 edx=0013c560 esi=074a3ba0 edi=6cb5f4b0 eip=5ff75b69 esp=0013c598 ebp=0013c5fc iopl=0 nv up ei pl nz ac pe nc cs=0023 ss=002b ds=002b es=002b fs=0053 gs=002b efl=00000216 xul!nsCanvasRenderingContext2D::ArcTo+0x6c: 5ff75b69 d9450c fld dword ptr [ebp+0Ch] ss:002b:0013c608=00000000 0:000> dt -r gfxPoint @eax xul!gfxPoint +0x000 x : 2.6490953928259842e-006 <--- We expect 0. But by rounding, it isn't 0.0 +0x008 y : 2.6490953928259842e-006 <--- We expect 0. But by rounding, it isn't 0.0
7 years ago
I'm not the right reviewer for this. I have no idea how any of this graphics stuff works. Please pick a reviewer who does?
Comment on attachment 462621 [details] [diff] [review] fix I guess?
Oh -- not a lot of context in the patch, I assume this is saving/restoring the matrix so that we don't actually modify the matrix outside of this function?
This needs a better explanation of why we aren't getting what we're expecting. I think it's unlikely that this would be the correct fix.
Philip/Dirk, do you have any idea of what the spec-compliant behaviour is here?