293304 - canvas: gradients with varying opacity [alpha channel] behave weirdly

Status: RESOLVED DUPLICATE of bug 293353

(Core :: Graphics: Canvas2D, defect)

Description

[Nickolay_Ponomarev]

This should draw a nice white-to-black gradient:
 ctx.fillStyle = "black";
 ctx.fillRect(0,0,500,500);

 var gradient = ctx.createLinearGradient(0, 0, 500, 0);
 gradient.addColorStop(0, "rgba(255,255,255,1)");
 gradient.addColorStop(1, "rgba(255,255,255,0)");
 ctx.fillStyle = gradient;
 ctx.fillRect(0,0,500,500);

Instead it draws vertical white/green/blue lines.

Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.8b2) Gecko/20050507
Firefox/1.0+

Comment 1

[Nickolay_Ponomarev]

Attachment: testcase

Comment 2

[Nickolay_Ponomarev]

screenshot of bad rendering: http://mozilla.doslash.org/stuff/canvas/293304bad.png
right rendering using svg: http://mozilla.doslash.org/stuff/canvas/293304good.svg

Comment 3

[Vladimir Vukicevic [:vlad] [:vladv] (needinfo me, slow to respond)]

It renders correctly on linux; this seems to be a BGR problem with windows. 
Looking into it.

Comment 4

[Stuart Parmenter]

works for me on windows... Can you give some more info on your video
card/OS/color depth/etc?

Comment 5

[Nickolay_Ponomarev]

Sure.
WinXP sp1
Geforce 2 MX400 (just noticed - relatively old drivers)
32 bits color depth (1024x768 if that matters).

Normal gradients and SVG's gradients using stop-opacity work fine though.

Comment 6

[Hermann Schwab]

Attachment: screenshot SiS6326 / 8MB / 800x600 / 24-bit / Win98

Mozilla/5.0 (Windows; U; Win98; en-US; rv:1.8b2) Gecko/20050507 Firefox/1.0+
svg enabled, gdiplus.dll installed, 

The computer is running the original factory-installed Win98. I later installed
SP1 and DX7. Screenshot is from the original driver, changing the setting from
24 bit to 16 bit or resolution from 800x600 to 1024x768 gave same result.
Updating the driver to the current version 1.32 from 2001 didn´t change my
800x600 result.
Link to a 1998 review of the capabilities of that card under DX5:
http://members.fortunecity.com/overclocker/software/sis6326.htm
I have a test installation of Sisoft sandra, telling a lot about missing
capabilities, but I can´t copy and paste and I don´t know what is needed and
what not.

Comment 7

[Jens Bannmann]

I'm seeing the same output as Nickolay. Win2K, Matrox G400 32MB, 1024x768x32bit,
GDI+ in Firefox dir, Mozilla/5.0 (Windows; U; Windows NT 5.0; en-US; rv:1.8b2)
Gecko/20050507 Firefox/1.0+

Comment 8

[Nickolay_Ponomarev]

See also bug 293353.

Comment 9

[Peter van der Woude [:Peter6]]

see bug 293353#c11
VC6. (beast) is bad, VC7.1 (vlad's) WFM

Comment 10

[(not currently active) Ted Mielczarek]

Given the fact that it works in VC7.1 builds and not VC6 builds, I'm going to
dupe this.

*** This bug has been marked as a duplicate of 293353 ***