Hi Hazen, As you suggested, I am going to put this thread on plplot_devel because it will probably be of interest to the other developers there.
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. Note, the proposed cairo-based devices would belong both to the PLplot display device driver family (xwinttf and others?) and to the PLplot output file device driver family (postscript, and others). For a discussion of those two families of devices see http://plplot.sourceforge.net/docbook-manual/plplot-html-5.7.3/x-drivers.html and http://plplot.sourceforge.net/docbook-manual/plplot-html-5.7.3/output-drivers.html. 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. > > I'm not sure how to proceed with the xwinttf driver regarding the > interactivity issues that you mentioned. We could make it behave the same as > the xwin driver, i.e. only use one window and keep clearing after each plot, > but this is not ideal for "interactive" environments, such as Perl / PDL > where it is nice to be able to keep a couple plotting windows open, even if > you might not be able to update them. On OS-X the operating system takes care > of keeping them updated when you cover them with another example or whatever, > so they don't even need to handle refresh events. > > 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 written generally enough (with an escape function) so that devices can have a tremendous amount of capability. However, your general comments on interactive PLplot struck a nerve with me. In my opinion where PLplot does very poorly on the interactive front is the severely limited interactive GUI devices that have been implemented so far. For example, the -dev gcw "GUI" allows selection of pages to display, and that is about it. -dev tk is our most extensively developed GUI for PLplot at the moment. It has zooming capability, a colour pallette adjustment, and perhaps even cursor capability. (I know that -dev xwin has cross-hairs [or cursor] capability. However, I have forgotten how to fire it up and IIRC, the world coordinates of the cross-hairs are printed out rather than returned to the calling routine which is sort of useless. I think -dev tk may have the same limited cursor capability as well). In my opinion what is truly needed for interactive plotting capability is full cursor capability where the world coordinates of the cursor when a keyboard key was struck _and_ the identity of that key are returned from the device to the PLplot library and then back to the routine calling the PLplot library. Currently no PLplot API exists for returning full cursor data, but it should be straightforward to extend the API appropriately with plgcursor. Such a function should make an interactive device wait until the user struck a key and then the function would return the x, y, (and z?) world coordinates of the cursor position when the key was struck as well as the identity (X keycode) of the key that was struck. I well recall a spectrum analysis programme I used extensively in the early 80's whose plotting device drivers had that full cursor capability which allowed an application that used the library to have a very large menu of possible transformations or measurements of the spectrum being plotted depending on where the user placed the cursor and what key was struck. I have a potential interactive research software project that would require exactly such an approach. I have put off the project in favour of other research projects for a number of reasons. But one of those reasons is I am currently not allowed to implement that project software with PLplot because no PLplot GUI devices currently have the full cursor capability that I described above. 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. Alan __________________________ Alan W. Irwin Astronomical research affiliation with Department of Physics and Astronomy, University of Victoria (astrowww.phys.uvic.ca). Programming affiliations with the FreeEOS equation-of-state implementation for stellar interiors (freeeos.sf.net); PLplot scientific plotting software package (plplot.org); the libLASi project (unifont.org/lasi); the Loads of Linux Links project (loll.sf.net); and the Linux Brochure Project (lbproject.sf.net). __________________________ Linux-powered Science __________________________ ------------------------------------------------------------------------- This SF.net email is sponsored by DB2 Express Download DB2 Express C - the FREE version of DB2 express and take control of your XML. No limits. Just data. 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