Experimental change to pixmap rendering. Switch from using NSImage to NSBitmapImageRef to store the image. This is closer to the core backing store used to display images. Using this I was able to avoid using lockFocus on the images and instead set the graphics context manually allowing us to draw directly on the backing image. However NSBitmapImageRef is a more simple format and didn't work with the flipped Y axis... so... I had to perform some voodoo to get the flipping to work with the graphics context. Not sure it is 100% right.

/* XPM */
static char * FOLDER_xpm[] = {
"16 16 10 1",
" 	c None",
".	c #000000",
"+	c #AA9200",
"@	c #FFFFAA",
"#	c #FFDB55",
"$	c #AA6D00",
"%	c #F7F7F7",
"&	c #D59255",
"*	c #FFDBAA",
"=	c #D5B655",
"                ",
"  &&&&          ",
" &%%%%&         ",
"&%@@@@%+++++$   ",
"&@@@@@@%%%%%$   ",
"&@*++++++++++++ ",
"&#+%%%%%%%%%*%+$",
"&#+@@@@@@@@@#@+$",
"&#+@@@@@@@@@.@+$",
"&#+@@**@**@@=@+$",
"&#+@########=@+$",
"&#+@########=@+$",
" ++++++++++++++$",
"  $$$$$$$$$$$$$ ",
"                ",
"                "};