Re: [Plplot-devel] Cairo-related devices and interactive capabilities of PLplot

[Hazen B. <hba...@ma...>]

On May 17, 2007, at 2:12 AM, Alan W. Irwin wrote:

> On 2007-05-16 23:18-0400 Hazen Babcock wrote:
>
>> On May 16, 2007, at 12:30 AM, Alan W. Irwin wrote:
>>> [...]Speaking of which, do you have any near-term plans for  
>>> xwinttf or the
>>> further Cairo devices you proposed?
>>
>> Near term? I'd like to finish this project up in the next few  
>> months and
>> hopefully I can find the time. My plan is to put xwinttf and all  
>> the other
>> Cairo drivers into one file, probably cairo.c,  as was done for  
>> the GD
>> driver.
>
> [..]
> Since display device drivers potentially have interactive  
> considerations to
> take into account (how to move from one page to the next, full cursor
> capability [see below], and other GUI considerations) and output  
> device
> drivers do not, I suggest you split the proposed cairo-based set of  
> devices
> into two separate drivers (one for display devices and one for file  
> output
> devices) with two separate files for the source.

True, but these differences occur mostly in the initialization,  
escape and cleanup parts. Since most of the plot drawing routines  
would be common to all the devices in this family I think it would be  
clearer if all the code was in one file.

>> I've come to believe (perhaps incorrectly?) that one of the major
>> shortcomings of PLplot is that it is difficult to use in an  
>> interactive
>> environment. The library only supports output to one stream at a  
>> time and
>> even if it did support multiple streams the stream is an internal  
>> structure
>> in the library, you can't even get an generic pointer to it so  
>> that you could
>> cache it, draw something else, and go back to drawing the original  
>> plot.
>
> Note, you can randomly switch between various streams using the
> plsstrm command (see the 14th example).  And the device driver  
> interface is

Thanks! That works pretty nicely. I knew I was wrong :).

> If you do decide to implement interactive features for xwinttf, I hope
> you would give priority to the full cursor capability described  
> above as
> well as the ability to move from one random page to another. In my  
> book such
> capabilities are of fundamental importance for interactive use.

This feature sounds pretty straightforward to add. Would we pass back  
the key pressed in the keysym element of the PLGraphicsIn structure?  
How about the Encoding, i.e. ASCII? utf8? ucs4?

-Hazen