[FLEX-33897] MediaQueryParser should not allocate memory for expressions already cached

• Type: Improvement
• Status: Resolved
• Priority: Minor
• Resolution: Fixed
• Affects Version/s: Apache Flex 4.11.0
• Fix Version/s: Apache Flex 4.12.0
• Component/s: Mobile: Performance, Styles
• Labels: memory performance
• Environment: desktop mobile
• Assignee: Justin Mclean
• Reporter: Benoit Wiart
• Created: 12/Nov/13 10:57
• Updated: 29/Dec/13 00:39
• Resolved: 29/Dec/13 00:39

Description

When using @media from default sdk styles or custom styles
the mxml compiler generates code like :

if (styleManager.acceptMediaList("(application-dpi:160)"))
{
this.focusThickness = 3;
this.fontSize = 24;
}
if (styleManager.acceptMediaList("(application-dpi:320)"))
{
this.fontSize = 24;
}
if (styleManager.acceptMediaList("(application-dpi:480)"))
{
this.focusThickness = 3;
this.fontSize = 24;
}
...

The acceptMediaList is often called, it delegates to MediaQueryParser which has a cache of known media expressions.
But MediaQueryParser#parse allocates some memory even if the expression is in the cache. these allocations come from the string manipulation.

this patch use the original expression as the key in the cache instead of the 'lowercased' expression.
It will increase the cache size (by a small percentage) only if you have the same media expression in different case.