CGDisplayScreenSize() returning incorrect dimensions on some machines

Originator:jeremy.knope
Number:rdar://12016584 Date Originated:02-Aug-2012 12:30 PM
Status:Open Resolved:
Product:Mac OS X Product Version:10.8/12A269
Classification:Other Bug Reproducible:Always
 
Summary:
When using CGDisplayScreenSize() to query a display for it's dimensions, on an iMac9,1 the results returned are incorrect.  The width dimension is about half of what it should be.  This problem didn't exist on 10.7.  Other resolutions don't cause this problem, just the native resolution.

Steps to Reproduce:
1. Make sure iMac display is set to native resolution
2. Call CGDisplayScreenSize() on the main iMac display on 10.8

Expected Results:
Should get something at least close to:
{518.80850284657583, 320.84210044459292}

Actual Results:
{262.19354444934476, 324.25531427910988}

Where width is way off. It ends up being about 10" when the width of the iMac 24" screen is around 20".  I'm wanting to get the dpi of the screen and this bug ends up getting me 186dpi for width and 94 dpi for height when they should be about the same.

Regression:
Worked on 10.7 returning {518.80850284657583, 320.84210044459292} which produces roughly 94dpi in both directions and is the expected dimensions of the screen.

Comments

Reproduced on iMac8,1 running OS X 10.7.5, so the bug does extend back to 10.7 series, at least for this model. There's a report [1] that it works on 10.7.4, but I cannot confirm. If the report is correct, then it seems this bug was introduced in 10.7.5.

[1] http://comments.gmane.org/gmane.comp.lang.r.mac/7457

Anyone know if this information is in a resource file somewhere that can be hand-edited?

By michael at Dec. 10, 2012, 3:23 p.m. (reply...)

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