[FLEX-16785] [Flash Player] Setting scrollRect or mask on a DisplayObject breaks sub-pixel font rendering in Adobe AIR

• Type: Bug
• Status: Closed
• Priority: Major
• Resolution: Fixed
• Affects Version/s: Adobe Flex SDK 3.2 (Release)
• Component/s: mx: Label
• Environment: Affected OS(s): Mac; Affected OS(s): Mac OS 10.5; Language Found: English
• Assignee: Adobe JIRA
• Reporter: Adobe JIRA
• Created: 03/Dec/08 14:03
• Updated: 01/Mar/10 11:26
• Resolved: 01/Mar/10 11:25

Description

Steps to reproduce:
1. Add a scrollRect or mask to any dislpay object that contains a TextField or TextLine using the Adobe AIR runtime on MacOS (have not checked Windows behavior). This bug does not affect Flash Player 10
2. For best results set a white background with black text.

See attached AirSubPixelBug.mxml to see text with and without a scrollRect applied. The attached image shows the differences in pixels with and without a scrollRect using a pixel magnification tool like Pixie or xScope on MacOS or the mangifier tool on windows. The top line is without a scrollRect and correct sub-pixel rendering, the bottom is with a scrollRect and incorrect pixel rendering.

Actual Results:

Fonts should be rendered pixel-for-pixel as they were without the mask or scrollRect. Instead the color values have been removed and replace with a grey-scale, which breaks sub-pixel rendering and distorts font appearance.

Expected Results:

Fonts should render pixel-for-pixel the same with or without a scrollRect or clipping mask.

Workaround (if any):

None if you need to use scrollRect or mask to clip content.