Arjen Markus wrote:
> On 2009-08-05 23:04, Hezekiah M. Carty wrote:
>> On Wed, Aug 5, 2009 at 4:22 PM, Hazen Babcock<hbabc...@mac.com> wrote:
>
>>> I like this idea/approach. Is there a reason not to reduce it even further?
>>>
>>> plget(const char *, void *)
>>> plset(const char *, void *)
>>>
>>> It seems that either way the user would have to call the function as
>>> intended to avoid memory corruption.
>>>
>>> Any objections to my implementing this & attempting to make it fairly
>>> comprehensively cover most of what can gotten and set in PLplot core?
>>> Likely the bulk of the work would be done post 5.10.
>> While I like the API simplification this could provide, I have two
>> primary concerns:
>>
>> First, could the first argument - the field to get/set - be an
>> enumerated type of some sort? This should help catch typos at compile
>> time rather than run time. (PL_LINE_WIDTH rather than "line width").
>> Additional fields would then require adding elements to the
>> enumeration which, as I understand, should not break existing code.
>>
>> Second, the void* approach may not translate well to other languages.
>> I'm not sure if there is a way to do this in C that would translate
>> well to the other PLplot-supported languages though.
>>
>
> I agree that a void * argument would be very bad for most languages,
> if not all, and it leaves the interpretation of the value up to the
> programmer. What about filling a structure instead?
>
> Something like:
>
> type struct _plAttribute {
> PLINT attributeType; /* enumerated: integer, float, boolean, ... */
> PLINT intValue; /* value reserved for attributes that can be
> represented as integers - at least in C */
> PLFLT floatValue; /* ditto: floating point attributes */
> char *stringValue; /* ditto: character string attributes */
> } plAttribute;
>
> void plget( char *attribute, plAttribute *attValue );
> void plset( char *attribute, plAttribute *attValue );
>
> The various language bindings could then easily distinguish the
> proper type of the attribute (overloading the functions) or
> fill a similar structure and pass that.
>
> In C you could use the idiom:
>
> plget( "myattribute", &attValue );
> if ( attValue.attributeType == PL_ATT_INT ) {
> attValue.intValue = newValue;
> plset( "myattribute, &attValue );
> }
I've made a first passing at implementing this in v10518. Below is a
simple C program that demonstrates how to use what I have done so far.
Suggestions? If everyone is more or less happy with this then I will
flesh it out more in the future.
Changes:
(1) Added two functions to the api, plget & plset.
(2) Added some enums & a new struct to plplot.h
(3) Added a new file src/plgset.c
-Hazen
/*
* Demo of the PLplot plget & plset functions.
*
* Hazen 10/09
*/
#include <math.h>
#include <string.h>
#include <ctype.h>
#include "plplot/plplot.h"
static PLFLT px[] = {0.1, 0.9, 0.9, 0.1, 0.1};
static PLFLT py[] = {0.1, 0.1, 0.9, 0.9, 0.1};
int main(int argc, const char *argv[])
{
int i,j;
PLAttribute *pen_attr;
PLAttribute *col_attr;
pen_attr = (PLAttribute *)malloc(sizeof(PLAttribute));
col_attr = (PLAttribute *)malloc(sizeof(PLAttribute));
plsdev("xcairo");
plinit();
pladv(0);
plvpor(0.0, 1.0, 0.0, 1.0);
plwind(0.0, 1.0, 0.0, 1.0);
/* draw smaller & smaller rectangle w/ increasing width & changing
color */
for(i=0;i<10;i++){
plget(PL_PENWIDTH, pen_attr);
plget(PL_CURCOLOR, col_attr);
printf("%d)\n",i);
printf(" Pen width: %d\n", pen_attr->intValue);
printf(" Pen color: %3d, %3d, %3d\n\n",
col_attr->colorValue.r,
col_attr->colorValue.g,
col_attr->colorValue.b);
plline(5, px, py);
pen_attr->intValue++;
col_attr->colorValue.r -= 25;
col_attr->colorValue.b += 25;
plset(PL_PENWIDTH, *pen_attr);
plset(PL_CURCOLOR, *col_attr);
for(j=0;j<5;j++){
if (px[j] < 0.5){
px[j] += 0.02;
} else {
px[j] -= 0.02;
}
if (py[j] < 0.5){
py[j] += 0.02;
} else {
py[j] -= 0.02;
}
}
}
plend();
free(pen_attr);
free(col_attr);
}
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