Re: [Plplot-devel] plGetCursor() return value (was Should plgetpos ...)

[Alan W. I. <ir...@be...>]

Using the return value in two different ways is a little awkward because I
believe the first sub-page is numbered zero rather than one.  We could
return i+1 but that could lead to all sorts of misunderstandings.  So how
about just changing the API?  It is possible this might hurt some of our
users since it is public API, but I feel this is not too likely since it is
not part of the documented common API.

If we agree that it is okay to change the API, I am thinking of returning
the window number in the argument list and returning success or failure as
before.  But I am no API expert so any other suggestions are welcome
especially if there is some obvious data structure where the returned
window number could be stored.

As far as the common API version is concerned (let's call it c_plgwc where
"gwc" stands for get world coordinates), I also intend to have a return of 1
for success and 0 for failure. Essentially it will be identical to the
current plTranslateCursor except it will have x and y "absolute" coordinates
as input, and world coordinates and window number as output rather than
assuming those data are accessible to/from a PLGraphicsIn struct.  The new
plTranslateCursor would then consist essentially of a call to c_plgwc with
an argument transformation from a PLGraphicsIn struct to the simple input
variables of c_plgwc on input and the reverse on the returned variables.

I intend to implement these ideas right away, and after checking that it
works I will commit it subject to change if anybody has some API ideas
in the meanwhile.

Alan

email: ir...@be...
phone: 250-727-2902	FAX: 250-721-7715
snail-mail:
Dr. Alan W. Irwin
Department of Physics and Astronomy,
University of Victoria, P.O. Box 3055,
Victoria, British Columbia, Canada, V8W 3P6
__________________________

Linux-powered astrophysics
__________________________

On Wed, 27 Feb 2002, Joao Cardoso wrote:

> On Wednesday 27 February 2002 04:07, Alan W. Irwin wrote:
> | I would appreciate further discussion of one aspect of the
> | plTranslateCursor code.
> |
> | It goes through a reversed list of windows (I assume these are
> | sub-windows?) and for the first one where the cursor is inside the
> | sub-window it does the transformation and returns.
> |
> | If I have this interpretation right, then it looks like the pyqt
> | group's plgetpos using data in the PLStream struct won't really
> | work since on a page with subwindowing, the world coordinates can
> | vary wildly form sub-window to sub-window (e.g., example 1), and
> | their code doesn't take account of this.  So my guess is they are
> | going to be forced (by example 1) to go to the plTranslateCursor
> | type of transformation.
>
> One problem with plGetCursor() is that it doesn't give information on
> which sub-page the mouse event occurred. I always found this a
> serious limitation.
>
> Perhaps using the "i" variable as the return value from
> plGetCursor()? of course existing code that relies on a "1" to be
> returned would fail, but I guess that most code is just checking for
> a zero/non-zero return value. An advantage of this approach is that
> it wouldn't break API compatibility.
>
> Joao
>
> |
> | Do you agree?
> |
> | Alan
> |
> | email: ir...@be...
> | phone: 250-727-2902	FAX: 250-721-7715
> | snail-mail:
> | Dr. Alan W. Irwin
> | Department of Physics and Astronomy,
> | University of Victoria, P.O. Box 3055,
> | Victoria, British Columbia, Canada, V8W 3P6
> | __________________________
> |
> | Linux-powered astrophysics
> | __________________________
> |
> |
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