[platform-swt-dev] new Image(ImageData) can never be "fast" on Kepler/Li

[Josef Pixsie <dev.pixsie.mobi@xxxxxxxxx>]

Hi all,

Although there is a path marked as "fast" in the code related to new
Image(Device, ImageData), it appears that at least on
Kepler/Linux64/Gtk this path is never taken and the Image creation
happens via the processing path labelled "comprehensive".

Does this mean that image creation on Kepler/Linux64/Gtk is slower
than on other platforms ? Is this intended or a bug ?

Not surprisingly I arrived at this point while debugging the
performance behaviour of image creation...


Here's my line of deduction*:

1) From see org.eclipse.swt.graphics.Image.init(org.eclipse.swt.graphics.ImageData)
it follows that:
1a) For not OS.BIG_ENDIAN, the destOrder is always LSB_FIRST
1b) The destDepth is hardcoded =32
==> dtype is always TYPE_GENERIC_32_LSB in
org.eclipse.swt.graphics.ImageData.blit(int, byte[], int, int, int,
int, int, int, int, int, int, int, int, byte[], int, int, int, byte[],
int, int, int, int, int, int, int, int, int, int, boolean, boolean)

2) From org.eclipse.swt.graphics.ImageData.getByteOrder() is follows that:
srcOder is always LSB_FIRST for 16bit depth and MSB_FIRST for 24/32 bit depth

3) From (2) and org.eclipse.swt.graphics.ImageData.blit(int, byte[],
int, int, int, int, int, int, int, int, int, int, int, byte[], int,
int, int, byte[], int, int, int, int, int, int, int, int, int, int,
boolean, boolean) it follows that:
==> stype is never TYPE_GENERIC_32_LSB

Consequently stype != dtype and dtype != TYPE_GENERIC_32_MSB (on my
platform) and therefore ImageData.blit will always take the route with
comment "Comprehensive blit (apply transformations)".

Now without further looking at this I suspect that the comprehensive
blit is significantly slower compared to what is labelled "fast" ?

Any feedback appreciated,
Diego


*On Kepler, Linux 64bit,
org.eclipse.swt.gtk.linux.x86_64.source_3.102.0.v20130501-2152.jar