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pixel droppings around the GuidedTour arrow
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Description

shows pixel glitches

The arrow that GuidedTour sometimes draws on guiders has some pixel glitches. In the attachment you can see obvious pixels below the arrow tip , and I think a faint darkening above the arrow.

I think this occurs because CSS "sprites" the arrow heads from the png modules/ext.guidedTour.arrows.png[1] , and in this the pixels from the shadow around one arrowhead bleed into the crop rectangle of the nearby arrowhead.

The fix is to remake the png with a bigger gap between each arrowhead so the shadow pixels don't overlap bounding rectangles, then adjust the CSS.

[1] https://gerrit.wikimedia.org/r/gitweb?p=mediawiki/extensions/GuidedTour.git;a=blob;f=modules/ext.guidedTour.arrows.png;


Version: master
Severity: minor

Attached:

Details

Reference
bz45826

Event Timeline

bzimport raised the priority of this task from to Needs Triage.Nov 22 2014, 1:25 AM
bzimport set Reference to bz45826.

There is no need to use sprites here, especially if it's causing problems. ResourceLoader instead lets use a separate image for each arrow, all of which will be embedded into the CSS as data URLs (in modern browsers, but there is a working fallback for older ones).

massaf wrote:

I agree that sprites made this a lot more troublesome, especially since we're drawing shadows around the guiders. I wonder if it's better to just do raw shapes and draw the shadows via CSS. I'll play around with that a little.

I discovered Guiders actually has a _arrowSize field, which we may need to update.

massaf wrote:

Fix here: https://gerrit.wikimedia.org/r/#/c/55100/

Using CSS to shape our arrows would reduce browser support, so sprites will remain for now. We can tackle _arrowSize in another bug.