285029 - GDK dithering has wrong alignment

Status: RESOLVED FIXED

(Core Graveyard :: GFX: Gtk, defect)

Description

[Robert O'Callahan (:roc) (email my personal email if necessary)]

From http://weblogs.mozillazine.org/roc/archives/2005/03/visual_regressi.html

A bug in nsImageGTK::UpdateCachedImage where it copies image pixels into the
image pixmap using gdk_draw_rgb_image_dithalign and specifies a "dither
alignment" of rect->x, rect->y. It turns out that GTK already adds alignment to
rect->x, rect->y so that we end up with the coordinates double-counted and
incorrect alignment. This means when an image gets filled in in one shot we get
one dithering, but when the image is filled in in multiple passes (e.g. data
loads slowly from the network), the later sections get dithered slightly
differently to the one-shot case. So on <24-bit displays, you get slight
variations in colouration in some rendered images (not visible to the naked
eye), but only when the network is slow.

Comment 1

[Robert O'Callahan (:roc) (email my personal email if necessary)]

Attachment: fix

trivial fix

Comment 2

[Robert O'Callahan (:roc) (email my personal email if necessary)]

checked in