Oberon implementation: the story continues

John Stout jstout "at" cusp.co.uk
Wed, 08 Jul 1998 23:01:47 +0000


Well, last night I got the first screen image transmitted from the NT server
to the W95 client. That's all it does at the moment, then closes the
connection, the image colours are really strange but that's because I'm just
using the pixel code transmitted as the colour directly rather than
translating it, BUT, the image is upside down!

It looks as though the x coordinates are OK, in the that Start button is at
the left, but at the top of the displayed image. No problem I thought, just
set y to frameBufferHeight - y and that will reflect it: however, although
that makes it look better in the sense that everything is the right way
round, the image is unreadable. As an example, if the Microsoft Outlook icon
is displayed, the M of Microsoft looks like:
|  |
V

i.e. as if the vertical bars are going up from the tips of the V rather than
down. I can't see anything wrong with the Oberon code: if you just read the
coordinates and display the rectangles you get it looking good but upside
down, add a y := frameBufferHeight - y before displaying the rectangles
(this is in the EncodingRRE case of the switch (rfb.updateRectEncoding)
statement in the Java code for vncCanvas.processNormalProtocol) then I get
this strange effect.

I was hoping that writing it down would give me an Ah Ha!, but it hasn't.
frameBufferHeight is 600 (displaying an 800 x 600 screen on a 1024 x 768
screen). The C++ code doesn't seem to help either, although it does give a
lot of ideas for speeding it up.

Any thoughts? I can't see it being anything to do with the translations
which I haven't done anything with yet.

John Stout



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