[Vm-dev] pb with primitive #primitiveScreenDepth on Linux ?
bert at freudenbergs.de
Thu Feb 2 20:31:19 UTC 2017
On Thu, Feb 2, 2017 at 10:44 AM, Christophe Demarey <
christophe.demarey at inria.fr> wrote:
> Hello Bert,
> Le 31 janv. 2017 à 18:18, Bert Freudenberg <bert at freudenbergs.de> a écrit
> On Tue, Jan 31, 2017 at 10:44 AM, Christophe Demarey <christophe.demarey@
> inria.fr> wrote:
>> With Pavel, we discovered a strange behavior of the primitive
>> #primitiveScreenDepth on Linux. It returns a value of 24 bits per pixel
>> (True colors) that looks valid but not supported (at least by Pharo).
>> DisplayScreen actualScreenDepth "(calling the primitive screenDepth)"
>> => 32 on OS X [OK]
>> => 24 on Linux [KO]
>> Also, it is not consistent with the primitive 91
>> DisplayScreen new supportsDisplayDepth: DisplayScreen actualScreenDepth
>> => true on OS X
>> => false on Linux
>> There are some safeguard image-side but it would be great if someone
>> could check that vm side.
> That seems wrong indeed, since BitBlt can only handle power-of-two depths
> currently. It should answer 32 or -32 in this case.
> Actually ... is there a difference in pixel layout for 32 bit MSB vs LSB
> forms? A quick test in SqueakJS suggests there isn’t.
> I do not get what you mean by 32 bits MSB vs LSB form. Could you give an
> example of what to test?
> If you mean a difference between depth 32 or -32, I do not see any
I was thinking about if it's safe to ignore endianness in this VM
primitive. And I think it's safe in 32 bpp, but not in lower bit depths.
#(1 -1 16 -16 32 -32) collect: [:d | ((Form extent: 1 at 1 depth: d) colorAt:
0 at 0 put: Color red; bits) first hex]
==> #('16r80000000' '16r1' '16r7C000000' '16r7C00' '16rFFFF0000'
So from the image's perspective, there is no difference for little endian /
big endian forms in the raw bitmap values in 32 bpp.
And to the VM it looks the same. It just needs to know that on a little
endian architecture it's BGRA while on big endian it's ARGB. Neither helps
should add a WebGL rendering path ... the swizzling would be easy in a
- Bert -
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