112988 - Add support for subpieces of an image to the XUL image frame

Status: VERIFIED FIXED

(Core Graveyard :: Skinability, defect)

Description

[David Hyatt]

The idea behidn this bug is to be able to extract a piece of an image from a
larger image and use it when painting.  

Something like

foo.gif#0,0,16,16

where the numbers to the right are top,left,width,height of the subimage to extract.

Comment 1

[David Hyatt]

Attachment: Patch that enables -moz-image-region support in CSS.

Patch to implement support.

Comment 2

[David Hyatt]

Attachment: Test case that shows subregions working in both scaled and unscaled modes.

Testcase.

Comment 3

[David Hyatt]

This patch does the following:
(1) Adds support for a new property, -moz-image-region, that is a rect.  Its 
syntax is identical to the CSS 'clip' property.  This rect, if specified, is 
used by XUL image frames to carve out a piece of a larger image and only paint 
that piece as part of the image frame.
(2) Cleans up and removes #ifdefs from the XUL image frame.
(3) Fixes a perf problem related to allocating many needless URIs whenever the 
style context for a XUL image frame changed.
(4) Patches a bug in the rendering context's DrawImage routine. It was adding 
in the src rect's x/y offsets to the destination point, which is not what 
DrawScaledImage does with its dest rect's x/y.  Fixing this inconsistency 
involved tweaking the HTML image frame a little bit.

Comment 4

[David Hyatt]

Note that this fix to the DrawImage routine has fixed some printing issues 
when images are split across pages.  The incorrect offsetting was messing up 
images in that case.

For an example of how this bug has fixed that problem, see the 1.x megabyte 
images in this directory:

http://rsd.gsfc.nasa.gov/goesg/earth/Weather/GOES-8/jpg/vis/4km/

Although there are numerous painting issues that still plague this case when 
printing, and I suspect they are related to the dirty rect intersection 
optimization in HTMLImageFrame, this patch clearly makes things a bit better. 

Comment 5

[Ben Goodger (use ben at mozilla dot org for email)]

shouldn't the default dimensions of the image region (when 'auto' is used?) be
the width and height of the image, rather than 0?

Comment 6

[David Hyatt]

Probably, but I'd have to add an extra member variable to the style struct like
clip does for auto, and I don't want to bloat the style struct just for purity's
sake. :)

Basically I'd have to have an mImageRegionFlags member variable like mClipFlags
does for clip that stored the fact that the rect was auto.  I found it easier to
just use (0,0,0,0) as the auto values and make the code use the full rect when
it got a 0,0,0,0 subrect.

Comment 7

[Ben Goodger (use ben at mozilla dot org for email)]

Comment on attachment 60101 [details] [diff] [review]
Patch that enables -moz-image-region support in CSS.

ok.
r=[e-mail]

Comment 8

[Joe Hewitt (gone)]

Comment on attachment 60101 [details] [diff] [review]
Patch that enables -moz-image-region support in CSS.

sr=hewitt

Comment 9

[David Hyatt]

Fixed.  I moved image-region into the list struct so that it would inherit. 
Other than that, the patch stayed the same.

Comment 10

[Patty Mac]

Verified the patch

Comment 11

[David Baron :dbaron: (⌚️UTC-4, no longer working on Mozilla)]

This patch didn't update the nsStyleList copy constructor, and thus caused bug
220717.