Bug 34479 – [Qt] Canvas and CSS: blur option in shadow not working

• Component: Layout and Rendering
• Status: RESOLVED FIXED

[Chang Shu]

QtLauncher fails the following test case but Safari works fine.
http://waplabdc.nokia-boston.com/browser/users/ligman/canvas tests/shadow/shadow_offsetX.html

[Chang Shu]

LayoutTests/fast/canvas/canvas-incremental-repaint.html

[Tor Arne Vestbø]

Please follow the QtWebKit bug reporting guidelines when reporting bugs.

See http://trac.webkit.org/wiki/QtWebKitBugs

Specifically:

  - The 'QtWebKit' component should only be used for bugs/features in the
    public QtWebKit API layer, not to signify that the bug is specific to
    the Qt port of WebKit

      http://trac.webkit.org/wiki/QtWebKitBugs#Component

  - Add the keyword 'Qt' to signal that it's a Qt-related bug

      http://trac.webkit.org/wiki/QtWebKitBugs#Keywords

[qi]

Copy some comments about blur and shadow from bug 34477:
1. By the way, today, I found the similar issue with “blur”. The “blur” is
one property of “shadow”. Currently, “shadow” is implemented in
GraphicsContextQt.cpp. Since, everything (text, image, line, rect, etc) can
have “shadow”, we draw “shadow” for each one, but we didn’t apply the “blur”
pattern for “shadow” now. I am not sure, GraphicsContextQt should draw the
“shadow” or let lower level like QBrush to draw “shadow”. Anyway, currently I
find it is difficult to draw a “blur” “shadow” now in GraphicsContextQt.
2. Does QT have a "blur" or "shadow" function?
In this case, "canvas" can draw a image, rect, line, text, etc. And, each of
them can have a "shadow" and "shadow" can be "blur".
I searched in QT, I found QGraphicsBlurEffect and QGraphicsDropShadowEffect
(QGraphicsEffect)looks for this purpose. But they suppose to be taken by
QGraphicsItem, it looks heavy and not for this purpose. 
Not sure, QT has function for our purpose.
3. I found class "QPixmapDropShadowFilter" pretty much meet our requirement for
shadow and blur, but unfortunately it is private class.

[Chang Shu]

This issue depends on the support from Qt.
I found one open bug in Qt that requires support for text shadow:
http://bugreports.qt.nokia.com/browse/QTBUG-5087
Set this webkit bug to resolved.

[Chang Shu]

There is a possibility to implement blur in qtwebkit. So we reopen this bug.

[qi]

Created attachment 61551 [details]
patch

[qi]

Comment on attachment 61551 [details]
patch

This is mistake

[Ariya Hidayat]

Add and assign to myself.

Chang Su: feel free to take it over if you are working on this again :)

[Ariya Hidayat]

I am afraid the current situation with shadow painting in GraphicsContextQt is a bit of a mess. I will start by posting patches which cleans up and refactors the code. Also, hopefully one small patch at a time is easier to review.

[Ariya Hidayat]

Same problem with CSS, adjust the title to point this out.

[Ariya Hidayat]

Created attachment 64327 [details]
Patch

[Simon Hausmann]

Comment on attachment 64327 [details]
Patch

Nice cleanup!

[Chang Shu]

Awesome! Simon, can you cherry-pick this to 2.1 once it's in? Thanks!

[Chang Shu]

Btw, this patch must make some philip's tests work (LayoutTests/canvas/philip/tests). Can you identify them and remove them from skip list?

[Ariya Hidayat]

> Btw, this patch must make some philip's tests
> work(LayoutTests/canvas/philip/tests). 
> Can you identify them and remove them from skip list?

Of course, once I'm done with it :)
The first patch is only cleanup and does not add anything yet.

[Chang Shu]

My bad, I didn't realize this is the 1st patch. :)

[Ariya Hidayat]

Created attachment 64350 [details]
Patch 2

[Ariya Hidayat]

Hmm, accidently obsolete patch 1 :(

For reference, it was already r+ by hausmann.

[Ariya Hidayat]

Patch 1: Manually committed r65331: http://trac.webkit.org/changeset/65331

[WebKit Review Bot]

http://trac.webkit.org/changeset/65331 might have broken Qt Linux Release

[Ariya Hidayat]

Few tests I missed in Patch 1:

canvas/philip/tests/2d.shadow.enable.blur.html
canvas/philip/tests/2d.shadow.offset.positiveX.html
canvas/philip/tests/2d.shadow.offset.positiveY.html
fast/canvas/canvas-shadow.html

[Ariya Hidayat]

Instead of polluting this bug, I'll create new bug entries for the small patchsets and make this one as a master bug.

[Ariya Hidayat]

*** Bug 42156 has been marked as a duplicate of this bug. ***

[Ariya Hidayat]

*** Bug 49131 has been marked as a duplicate of this bug. ***

[Noam Rosenthal]

Time to close this.