circle.c

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/*****************************************************************************
 * ugBASIC - an isomorphic BASIC language compiler for retrocomputers        *
 *****************************************************************************
 * Copyright 2021-2026 Marco Spedaletti (asimov@mclink.it)
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 *----------------------------------------------------------------------------
 * Concesso in licenza secondo i termini della Licenza Apache, versione 2.0
 * (la "Licenza"); è proibito usare questo file se non in conformità alla
 * Licenza. Una copia della Licenza è disponibile all'indirizzo:
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Se non richiesto dalla legislazione vigente o concordato per iscritto,
 * il software distribuito nei termini della Licenza è distribuito
 * "COSÌ COM'È", SENZA GARANZIE O CONDIZIONI DI ALCUN TIPO, esplicite o
 * implicite. Consultare la Licenza per il testo specifico che regola le
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/****************************************************************************
 * INCLUDE SECTION 
 ****************************************************************************/
 
#include "../../ugbc.h"
 
/****************************************************************************
 * CODE SECTION 
 ****************************************************************************/

/* <usermanual>
@keyword CIRCLE
 
@english
 
The ''CIRCLE'' command in BASIC draws a circle on the screen. In other words, it defines 
a complete circle based on the coordinates and radius that you specify. 
 
This command allows you to draw a circle with starting coordinates in ''(x,y)'' 
and radius ''r''. The color is indicated by the parameter ''c''. If the abscissa 
and/or ordinate is omitted, the last graphic position drawn will be used. In 
addition, the color can also be omitted and, if necessary, the last color set with the 
''PEN'' or ''INK'' command will be used. 
 
There is also another additional syntax, that can be used 
to draw ellipses: you can give both the radii ''rx'' and ''ry'' in the color determined 
by ''fq'' (see ''HIRES''). 
 
The accuracy of the circle depends on the resolution of your screen. Lower-resolution screens 
may display less sharp circles.
 
@italian
 
Il comando ''CIRCLE'' in BASIC disegna un cerchio sullo schermo. In altre parole, 
definisce un cerchio completo in base alle coordinate e al raggio specificati.
 
Questo comando consente di disegnare un cerchio con coordinate iniziali in ''(x,y)'' 
e raggio ''r''. Il colore è indicato dal parametro ''c''. Se l'ascissa e/o l'ordinata 
vengono omesse, verrà utilizzata l'ultima posizione grafica disegnata. Inoltre, è 
possibile omettere anche il colore e, se necessario, verrà utilizzato l'ultimo colore 
impostato con il comando ''PEN'' o ''INK''.
 
Esiste anche un'altra sintassi aggiuntiva, che può essere utilizzata per disegnare 
ellissi: è possibile specificare sia i raggi ''rx'' che ''ry'' nel colore determinato 
da ''fq'' (vedere ''HIRES'').
 
La precisione del cerchio dipende dalla risoluzione dello schermo. Gli schermi a 
bassa risoluzione potrebbero visualizzare cerchi meno nitidi.
 
@syntax CIRCLE [x], [y], r[, c]
@syntax CIRCLE x, y, rx, ry[, c]
 
@example ' Draw a circle
@example CIRCLE 100,100,42
@example ' Draw an ellipse
@example CIRCLE 100,100,21,42
@example CIRCLE ,,21,RED
@usedInExample graphics_position_01.bas
@usedInExample graphics_position_02.bas
@usedInExample graphics_shapes_02.bas
 
@seeAlso ELLIPSE
 
@target all
</usermanual> */
void circle( Environment * _environment, char * _x, char * _y, char * _r, char * _c, int _preserve_color ) {
 
    Variable * xCentre = variable_retrieve_or_define( _environment, _x, VT_POSITION, 0 );
    Variable * yCentre = variable_retrieve_or_define( _environment, _y, VT_POSITION, 0 );
    Variable * r = variable_retrieve_or_define( _environment, _r, VT_POSITION, 0 );
 
    Variable * x = variable_temporary( _environment, VT_POSITION, "(x)" );
    variable_move( _environment, r->name, x->name );
    Variable * y = variable_temporary( _environment, VT_POSITION, "(y)" );
    variable_store( _environment, y->name, 0 );
    Variable * p = variable_temporary( _environment, VT_SWORD, "(p)" );
 
    plot( _environment, variable_add( _environment, x->name, xCentre->name )->name, variable_add( _environment, y->name, yCentre->name )->name, _c, 0 );
    plot( _environment, variable_sub( _environment, xCentre->name, x->name )->name, variable_add( _environment, y->name, yCentre->name )->name, _c, 0 );
    plot( _environment, variable_add( _environment, x->name, xCentre->name )->name, variable_sub( _environment, yCentre->name,  y->name )->name, _c, 0 );
    plot( _environment, variable_sub( _environment, xCentre->name, x->name )->name, variable_sub( _environment, yCentre->name,  y->name )->name, _c, 0 );
    
    variable_move( _environment, variable_complement_const( _environment, r->name, 1 )->name, p->name );
 
      begin_while( _environment );  
      begin_while_condition( _environment, variable_greater_than( _environment, x->name, y->name, 1 )->name );  
 
        if_then( _environment, variable_less_than_const( _environment, p->name, 0, 1 )->name );
            variable_move( _environment, variable_add( _environment, variable_sl_const( _environment, y->name, 1 )->name, p->name )->name, p->name );
            variable_increment( _environment, p->name );
        else_if_then_label( _environment );              
        else_if_then( _environment, NULL );              
            variable_decrement( _environment, x->name );
            variable_move( _environment, variable_add( _environment, variable_sl_const( _environment, y->name, 1 )->name, p->name )->name, p->name );
            variable_move( _environment, variable_sub( _environment, p->name, variable_sl_const( _environment, x->name, 1 )->name )->name, p->name );
            variable_increment( _environment, p->name );
        end_if_then( _environment );
 
        if_then( _environment, variable_less_than( _environment, x->name, y->name, 0 )->name );
            exit_loop( _environment, 0 );
        end_if_then( _environment );
 
        plot( _environment, variable_add( _environment, x->name, xCentre->name )->name, variable_add( _environment, y->name, yCentre->name )->name, _c, _preserve_color );
        plot( _environment, variable_sub( _environment, xCentre->name, x->name )->name, variable_add( _environment, y->name, yCentre->name )->name, _c, _preserve_color );
        plot( _environment, variable_add( _environment, x->name, xCentre->name )->name, variable_sub( _environment, yCentre->name,  y->name )->name, _c, _preserve_color );
        plot( _environment, variable_sub( _environment, xCentre->name, x->name )->name, variable_sub( _environment, yCentre->name,  y->name )->name, _c, _preserve_color );
          
        //if_then( _environment, variable_compare_not( _environment, x->name, y->name )->name );
            plot( _environment, variable_add( _environment, y->name, xCentre->name )->name, variable_add( _environment, x->name, yCentre->name )->name, _c, _preserve_color );
            plot( _environment, variable_sub( _environment, xCentre->name, y->name )->name, variable_add( _environment, x->name, yCentre->name )->name, _c, _preserve_color );
            plot( _environment, variable_add( _environment, y->name, xCentre->name )->name, variable_sub( _environment, yCentre->name,  x->name )->name, _c, _preserve_color );
            plot( _environment, variable_sub( _environment, xCentre->name, y->name )->name, variable_sub( _environment, yCentre->name,  x->name )->name, _c, _preserve_color );
 
        //end_if_then( _environment );
 
        variable_increment( _environment, y->name );
                  
    end_while( _environment );
 
}