gsd_prim.c

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/*!
   \file lib/ogsf/gsd_prim.c
 
   \brief OGSF library - primitive drawing functions (lower level functions)
 
   GRASS OpenGL gsurf OGSF Library
 
   SPDX-FileCopyrightText: 1999-2008, 2018 GRASS Development Team
   SPDX-License-Identifier: GPL-2.0-or-later
 
   \author Bill Brown USACERL (January 1993)
   \author Doxygenized by Martin Landa <landa.martin gmail.com> (May 2008)
   \author Support for framebuffer objects by Huidae Cho <grass4u gmail.com>
   (July 2018)
 */
 
#include <stdlib.h>
#include <string.h>
 
#include <grass/config.h>
 
#if defined(OPENGL_X11)
#include <GL/gl.h>
#include <GL/glu.h>
#include <GL/glx.h>
#elif defined(OPENGL_AQUA)
#include <OpenGL/gl.h>
#include <OpenGL/glu.h>
#if defined(OPENGL_AGL)
#include <AGL/agl.h>
#endif
#elif defined(OPENGL_WINDOWS)
#include <GL/gl.h>
#include <GL/glu.h>
#include <wingdi.h>
#endif
 
#include <grass/gis.h>
#include <grass/ogsf.h>
#include <grass/glocale.h>
 
#define USE_GL_NORMALIZE
 
#define RED_MASK         0x000000FF
#define GRN_MASK         0x0000FF00
#define BLU_MASK         0x00FF0000
#define ALP_MASK         0xFF000000
 
#define INT_TO_RED(i, r) (r = (i & RED_MASK))
#define INT_TO_GRN(i, g) (g = (i & GRN_MASK) >> 8)
#define INT_TO_BLU(i, b) (b = (i & BLU_MASK) >> 16)
#define INT_TO_ALP(i, a) (a = (i & ALP_MASK) >> 24)
 
#define MAX_OBJS         64
/* ^ TMP - move to gstypes */
 
/* define border width (pixels) for viewport check */
#define border           15
 
static GLuint ObjList[MAX_OBJS];
static int numobjs = 0;
 
static int Shade;
 
static float ogl_light_amb[MAX_LIGHTS][4];
static float ogl_light_diff[MAX_LIGHTS][4];
static float ogl_light_spec[MAX_LIGHTS][4];
static float ogl_light_pos[MAX_LIGHTS][4];
static float ogl_mat_amb[4];
static float ogl_mat_diff[4];
static float ogl_mat_spec[4];
static float ogl_mat_emis[4];
static float ogl_mat_shin;
 
/*!
   \brief Mostly for flushing drawing commands across a network
 
   glFlush doesn't block, so if blocking is desired use glFinish.
 */
void gsd_flush(void)
{
    glFlush();
 
    return;
}
 
/*!
   \brief Set color mode
 
   Call glColorMaterial before enabling the GL_COLOR_MATERIAL
 
   \param cm color mode value
 */
void gsd_colormode(int cm)
{
    switch (cm) {
    case CM_COLOR:
 
        glDisable(GL_COLOR_MATERIAL);
        glDisable(GL_LIGHTING);
 
        break;
    case CM_EMISSION:
 
        glColorMaterial(GL_FRONT_AND_BACK, GL_EMISSION);
        glEnable(GL_COLOR_MATERIAL);
        glEnable(GL_LIGHTING);
 
        break;
    case CM_DIFFUSE:
 
        glColorMaterial(GL_FRONT, GL_DIFFUSE);
        glEnable(GL_COLOR_MATERIAL);
        glEnable(GL_LIGHTING);
 
        break;
    case CM_AD:
 
        glColorMaterial(GL_FRONT, GL_AMBIENT_AND_DIFFUSE);
        glEnable(GL_COLOR_MATERIAL);
        glEnable(GL_LIGHTING);
 
        break;
    case CM_NULL:
 
        /* OGLXXX
         * lmcolor: if LMC_NULL,  use:
         * glDisable(GL_COLOR_MATERIAL);
         * LMC_NULL: use glDisable(GL_COLOR_MATERIAL);
         */
        glDisable(GL_COLOR_MATERIAL);
        glEnable(GL_LIGHTING);
 
        break;
    default:
 
        glDisable(GL_COLOR_MATERIAL);
        break;
    }
 
    return;
}
 
/*!
   \brief Print color mode to stderr
 */
void show_colormode(void)
{
    GLint mat;
 
    glGetIntegerv(GL_COLOR_MATERIAL_PARAMETER, &mat);
    G_message(_("Color Material: %d"), mat);
 
    return;
}
 
/*!
   \brief ADD
 
   \param x,y
   \param rad
 */
void gsd_circ(float x, float y, float rad)
{
    GLUquadricObj *qobj = gluNewQuadric();
 
    gluQuadricDrawStyle(qobj, GLU_SILHOUETTE);
    glPushMatrix();
    glTranslatef(x, y, 0.);
    gluDisk(qobj, 0., rad, 32, 1);
    glPopMatrix();
    gluDeleteQuadric(qobj);
 
    return;
}
 
/*!
   \brief ADD
 
   \param x,y,z
   \param rad
 */
void gsd_disc(float x, float y, float z, float rad)
{
    GLUquadricObj *qobj = gluNewQuadric();
 
    gluQuadricDrawStyle(qobj, GLU_FILL);
    glPushMatrix();
    glTranslatef(x, y, z);
    gluDisk(qobj, 0., rad, 32, 1);
    glPopMatrix();
    gluDeleteQuadric(qobj);
 
    return;
}
 
/*!
   \brief ADD
 
   \param center center-point
   \param siz size value
 */
void gsd_sphere(float *center, float siz)
{
    static int first = 1;
    static GLUquadricObj *QOsphere;
 
    if (first) {
        QOsphere = gluNewQuadric();
 
        if (QOsphere) {
            gluQuadricNormals(QOsphere, GLU_SMOOTH);      /* default */
            gluQuadricTexture(QOsphere, GL_FALSE);        /* default */
            gluQuadricOrientation(QOsphere, GLU_OUTSIDE); /* default */
            gluQuadricDrawStyle(QOsphere, GLU_FILL);
        }
 
        first = 0;
    }
 
    glPushMatrix();
    glTranslatef(center[0], center[1], center[2]);
    gluSphere(QOsphere, (double)siz, 24, 24);
    glPopMatrix();
 
    return;
}
 
/*!
   \brief Write out z-mask
 
   Enable or disable writing into the depth buffer
 
   \param n Specifies whether the depth buffer is enabled for
   writing
 */
void gsd_zwritemask(unsigned long n)
{
    /* OGLXXX glDepthMask is boolean only */
    glDepthMask((GLboolean)(n));
 
    return;
}
 
/*!
   \brief ADD
 
   \param n
 */
void gsd_backface(int n)
{
    glCullFace(GL_BACK);
    (n) ? glEnable(GL_CULL_FACE) : glDisable(GL_CULL_FACE);
 
    return;
}
 
/*!
   \brief Set width of rasterized lines
 
   \param n line width
 */
void gsd_linewidth(short n)
{
    glLineWidth((GLfloat)(n));
 
    return;
}
 
/*!
   \brief ADD
 */
void gsd_bgnqstrip(void)
{
    glBegin(GL_QUAD_STRIP);
 
    return;
}
 
/*!
   \brief ADD
 */
void gsd_endqstrip(void)
{
    glEnd();
 
    return;
}
 
/*!
   \brief ADD
 */
void gsd_bgntmesh(void)
{
    glBegin(GL_TRIANGLE_STRIP);
 
    return;
}
 
/*!
   \brief ADD
 */
void gsd_endtmesh(void)
{
    glEnd();
 
    return;
}
 
/*!
   \brief ADD
 */
void gsd_bgntstrip(void)
{
    glBegin(GL_TRIANGLE_STRIP);
 
    return;
}
 
/*!
   \brief ADD
 */
void gsd_endtstrip(void)
{
    glEnd();
 
    return;
}
 
/*!
   \brief ADD
 */
void gsd_bgntfan(void)
{
    glBegin(GL_TRIANGLE_FAN);
 
    return;
}
 
/*!
   \brief ADD
 */
void gsd_endtfan(void)
{
    glEnd();
 
    return;
}
 
/*!
   \brief ADD
 */
void gsd_swaptmesh(void)
{
    /* OGLXXX
     * swaptmesh not supported, maybe glBegin(GL_TRIANGLE_FAN)
     * swaptmesh()
     */
 
    /*DELETED*/;
 
    return;
}
 
/*!
   \brief Delimit the vertices of a primitive or a group of like primitives
 */
void gsd_bgnpolygon(void)
{
    /* OGLXXX
     * special cases for polygons:
     *  independent quads: use GL_QUADS
     *  independent triangles: use GL_TRIANGLES
     */
    glBegin(GL_POLYGON);
 
    return;
}
 
/*!
   \brief Delimit the vertices of a primitive or a group of like primitives
 */
void gsd_endpolygon(void)
{
    glEnd();
 
    return;
}
 
/*!
   \brief Begin line
 */
void gsd_bgnline(void)
{
    /* OGLXXX for multiple, independent line segments: use GL_LINES */
    glBegin(GL_LINE_STRIP);
    return;
}
 
/*!
   \brief End line
 */
void gsd_endline(void)
{
    glEnd();
 
    return;
}
 
/*!
   \brief Set shaded model
 
   \param shade non-zero for GL_SMOOTH otherwise GL_FLAT
 */
void gsd_shademodel(int shade)
{
    Shade = shade;
 
    if (shade) {
        glShadeModel(GL_SMOOTH);
    }
    else {
        glShadeModel(GL_FLAT);
    }
 
    return;
}
 
/*!
   \brief Get shaded model
 
   \return shade
 */
int gsd_getshademodel(void)
{
    return (Shade);
}
 
/*!
   \brief Draw to the front and back buffers
 */
void gsd_bothbuffers(void)
{
#if !defined(OPENGL_FBO)
    /* OGLXXX bothbuffer: other possibilities include GL_FRONT, GL_BACK */
    glDrawBuffer(GL_FRONT_AND_BACK);
#endif
    return;
}
 
/*!
   \brief Draw to the front buffer
 */
void gsd_frontbuffer(void)
{
#if !defined(OPENGL_FBO)
    /* OGLXXX frontbuffer: other possibilities include GL_FRONT_AND_BACK */
    glDrawBuffer(GL_FRONT);
#endif
    return;
}
 
/*!
   \brief Draw to the back buffer
 */
void gsd_backbuffer(void)
{
#if !defined(OPENGL_FBO)
    /* OGLXXX backbuffer: other possibilities include GL_FRONT_AND_BACK */
    glDrawBuffer(GL_BACK);
#endif
    return;
}
 
/*!
   \brief Swap buffers
 */
void gsd_swapbuffers(void)
{
#if !defined(OPENGL_FBO)
    /* OGLXXX swapbuffers: copy the back buffer to the front;
     * the back buffer becomes undefined afterward */
#if defined(OPENGL_X11)
    glXSwapBuffers(glXGetCurrentDisplay(), glXGetCurrentDrawable());
#elif defined(OPENGL_AGL)
    aglSwapBuffers(aglGetCurrentContext());
#elif defined(OPENGL_WINDOWS)
    SwapBuffers(wglGetCurrentDC());
#endif
#endif
    return;
}
 
/*!
   \brief Pop the current matrix stack
 */
void gsd_popmatrix(void)
{
    glPopMatrix();
 
    return;
}
 
/*!
   \brief Push the current matrix stack
 */
void gsd_pushmatrix(void)
{
    glPushMatrix();
 
    return;
}
 
/*!
   \brief Multiply the current matrix by a general scaling matrix
 
   \param xs x scale value
   \param ys y scale value
   \param zs z scale value
 */
void gsd_scale(float xs, float ys, float zs)
{
    glScalef(xs, ys, zs);
 
    return;
}
 
/*!
   \brief Multiply the current matrix by a translation matrix
 
   \param dx x translation value
   \param dy y translation value
   \param dz z translation value
 */
void gsd_translate(float dx, float dy, float dz)
{
    glTranslatef(dx, dy, dz);
 
    return;
}
 
/*!
   \brief Get viewport
 
   \param[out] window
   \param viewport
   \param modelMatrix model matrix
   \param projMatrix projection matrix
 */
void gsd_getwindow(int *window, int *viewport, double *modelMatrix,
                   double *projMatrix)
{
    gsd_pushmatrix();
    gsd_do_scale(1);
 
    glGetDoublev(GL_MODELVIEW_MATRIX, modelMatrix);
    glGetDoublev(GL_PROJECTION_MATRIX, projMatrix);
    glGetIntegerv(GL_VIEWPORT, viewport);
    gsd_popmatrix();
 
    window[0] = viewport[1] + viewport[3] + border;
    window[1] = viewport[1] - border;
    window[2] = viewport[0] - border;
    window[3] = viewport[0] + viewport[2] + border;
 
    return;
}
 
/*!
   \brief ADD
 
   \param pt
   \param window
   \param viewport
   \param doubleMatrix
   \param projMatrix
 
   \return 0
   \return 1
 */
int gsd_checkpoint(float pt[4], int window[4], int viewport[4],
                   double modelMatrix[16], double projMatrix[16])
{
    GLdouble fx, fy, fz;
 
    gluProject((GLdouble)pt[X], (GLdouble)pt[Y], (GLdouble)pt[Z], modelMatrix,
               projMatrix, viewport, &fx, &fy, &fz);
 
    if (fx < window[2] || fx > window[3] || fy < window[1] || fy > window[0])
        return 1;
    else
        return 0;
}
 
/*!
   \brief ADD
 
   \param angle
   \param axis
 */
void gsd_rot(float angle, char axis)
{
    GLfloat x;
    GLfloat y;
    GLfloat z;
 
    switch (axis) {
    case 'x':
    case 'X':
 
        x = 1.0;
        y = 0.0;
        z = 0.0;
 
        break;
    case 'y':
    case 'Y':
 
        x = 0.0;
        y = 1.0;
        z = 0.0;
 
        break;
    case 'z':
    case 'Z':
 
        x = 0.0;
        y = 0.0;
        z = 1.0;
 
        break;
    default:
 
        G_warning(_("gsd_rot(): %c is an invalid axis "
                    "specification. Rotation ignored. "
                    "Please advise GRASS developers of this error"),
                  axis);
        return;
    }
 
    glRotatef((GLfloat)angle, x, y, z);
 
    return;
}
 
/*!
   \brief Set the current normal vector & specify vertex
 
   \param norm normal vector
   \param col color value
   \param pt point (model coordinates)
 */
void gsd_litvert_func(float *norm, unsigned long col, float *pt)
{
    glNormal3fv(norm);
    gsd_color_func(col);
    glVertex3fv(pt);
 
    return;
}
 
/*!
   \brief ADD
 
   \param norm
   \param col [unused]
   \param pt
 */
void gsd_litvert_func2(float *norm, unsigned long col G_UNUSED, float *pt)
{
    glNormal3fv(norm);
    glVertex3fv(pt);
 
    return;
}
 
/*!
   \brief ADD
 
   \param pt
 */
void gsd_vert_func(float *pt)
{
    glVertex3fv(pt);
 
    return;
}
 
/*!
   \brief Set current color
 
   \param col color value
 */
void gsd_color_func(unsigned int col)
{
    GLbyte r, g, b, a;
 
    /* OGLXXX
     * cpack: if argument is not a variable
     * might need to be:
     *  glColor4b(($1)&0xff, ($1)>>8&0xff, ($1)>>16&0xff, ($1)>>24&0xff)
     */
    INT_TO_RED(col, r);
    INT_TO_GRN(col, g);
    INT_TO_BLU(col, b);
    INT_TO_ALP(col, a);
    glColor4ub(r, g, b, a);
 
    return;
}
 
/*!
   \brief Initialize model light
 */
void gsd_init_lightmodel(void)
{
 
    glEnable(GL_LIGHTING);
 
    /* normal vector renormalization */
#ifdef USE_GL_NORMALIZE
    {
        glEnable(GL_NORMALIZE);
    }
#endif
 
    /* OGLXXX
     * Ambient:
     *  If this is a light model lmdef, then use
     *      glLightModelf and GL_LIGHT_MODEL_AMBIENT.
     *      Include ALPHA parameter with ambient
     */
 
    /* Default is front face lighting, infinite viewer
     */
    ogl_mat_amb[0] = 0.1;
    ogl_mat_amb[1] = 0.1;
    ogl_mat_amb[2] = 0.1;
    ogl_mat_amb[3] = 1.0;
 
    ogl_mat_diff[0] = 0.8;
    ogl_mat_diff[1] = 0.8;
    ogl_mat_diff[2] = 0.8;
    ogl_mat_diff[3] = 0.8;
 
    ogl_mat_spec[0] = 0.8;
    ogl_mat_spec[1] = 0.8;
    ogl_mat_spec[2] = 0.8;
    ogl_mat_spec[3] = 0.8;
 
    ogl_mat_emis[0] = 0.0;
    ogl_mat_emis[1] = 0.0;
    ogl_mat_emis[2] = 0.0;
    ogl_mat_emis[3] = 0.0;
 
    ogl_mat_shin = 25.0;
 
    /* OGLXXX
     * attenuation: see glLightf man page: (ignored for infinite lights)
     * Add GL_LINEAR_ATTENUATION.
     sgi_lmodel[0] = GL_CONSTANT_ATTENUATION;
     sgi_lmodel[1] = 1.0;
     sgi_lmodel[2] = 0.0;
     sgi_lmodel[3] = ;
     */
 
    /* OGLXXX
     * lmdef other possibilities include:
     *  glLightf(light, pname, *params);
     *  glLightModelf(pname, param);
     * Check list numbering.
     * Translate params as needed.
     */
    glMaterialfv(GL_FRONT_AND_BACK, GL_AMBIENT, ogl_mat_amb);
    glMaterialfv(GL_FRONT_AND_BACK, GL_DIFFUSE, ogl_mat_diff);
    glMaterialfv(GL_FRONT_AND_BACK, GL_SPECULAR, ogl_mat_spec);
    glMaterialfv(GL_FRONT_AND_BACK, GL_EMISSION, ogl_mat_emis);
    glMaterialf(GL_FRONT_AND_BACK, GL_SHININESS, ogl_mat_shin);
 
    /* OGLXXX lmbind: check object numbering. */
    /* OGLXXX
     * lmbind: check object numbering.
     * Use GL_FRONT in call to glMaterialf.
     * Use GL_FRONT in call to glMaterialf.
     if(1) {glCallList(1); glEnable(LMODEL);} else glDisable(LMODEL);
     if(1) {glCallList(1); glEnable(GL_FRONT);} else glDisable(GL_FRONT);
     */
 
    return;
}
 
/*!
   \brief Set material
 
   \param set_shin,set_emis  flags
   \param sh,em should be 0. - 1.
   \param emcolor packed colors to use for emission
 */
void gsd_set_material(int set_shin, int set_emis, float sh, float em,
                      int emcolor)
{
    if (set_shin) {
        ogl_mat_spec[0] = sh;
        ogl_mat_spec[1] = sh;
        ogl_mat_spec[2] = sh;
        ogl_mat_spec[3] = sh;
 
        glMaterialfv(GL_FRONT_AND_BACK, GL_SPECULAR, ogl_mat_spec);
 
        ogl_mat_shin = 60. + (int)(sh * 68.);
 
        glMaterialf(GL_FRONT_AND_BACK, GL_SHININESS, ogl_mat_shin);
    }
 
    if (set_emis) {
        ogl_mat_emis[0] = (em * (emcolor & 0x0000FF)) / 255.;
        ogl_mat_emis[1] = (em * ((emcolor & 0x00FF00) >> 8)) / 255.;
        ogl_mat_emis[2] = (em * ((emcolor & 0xFF0000) >> 16)) / 255.;
 
        glMaterialfv(GL_FRONT_AND_BACK, GL_EMISSION, ogl_mat_emis);
    }
 
    return;
}
 
/*!
   \brief Define light
 
   \param num light id (starts with 1)
   \param vals position(x,y,z,w), color, ambientm, emission
 */
void gsd_deflight(int num, struct lightdefs *vals)
{
    if (num > 0 && num <= MAX_LIGHTS) {
        ogl_light_pos[num - 1][0] = vals->position[X];
        ogl_light_pos[num - 1][1] = vals->position[Y];
        ogl_light_pos[num - 1][2] = vals->position[Z];
        ogl_light_pos[num - 1][3] = vals->position[W];
 
        glLightfv(GL_LIGHT0 + num, GL_POSITION, ogl_light_pos[num - 1]);
 
        ogl_light_diff[num - 1][0] = vals->color[0];
        ogl_light_diff[num - 1][1] = vals->color[1];
        ogl_light_diff[num - 1][2] = vals->color[2];
        ogl_light_diff[num - 1][3] = .3;
 
        glLightfv(GL_LIGHT0 + num, GL_DIFFUSE, ogl_light_diff[num - 1]);
 
        ogl_light_amb[num - 1][0] = vals->ambient[0];
        ogl_light_amb[num - 1][1] = vals->ambient[1];
        ogl_light_amb[num - 1][2] = vals->ambient[2];
        ogl_light_amb[num - 1][3] = .3;
 
        glLightfv(GL_LIGHT0 + num, GL_AMBIENT, ogl_light_amb[num - 1]);
 
        ogl_light_spec[num - 1][0] = vals->color[0];
        ogl_light_spec[num - 1][1] = vals->color[1];
        ogl_light_spec[num - 1][2] = vals->color[2];
        ogl_light_spec[num - 1][3] = .3;
 
        glLightfv(GL_LIGHT0 + num, GL_SPECULAR, ogl_light_spec[num - 1]);
    }
 
    return;
}
 
/*!
   \brief Switch light on/off
 
   \param num
   \param on 1 for 'on', 0 turns them off
 */
void gsd_switchlight(int num, int on)
{
    short defin;
 
    defin = on ? num : 0;
 
    if (defin) {
        glEnable(GL_LIGHT0 + num);
    }
    else {
        glDisable(GL_LIGHT0 + num);
    }
 
    return;
}
 
/*!
   \brief Get image of current GL screen
 
   \param pixbuf data buffer
   \param[out] xsize,ysize picture dimension
 
   \return 0 on failure
   \return 1 on success
 */
int gsd_getimage(unsigned char **pixbuf, unsigned int *xsize,
                 unsigned int *ysize)
{
    GLuint l, r, b, t;
 
    /* OGLXXX
     * get GL_VIEWPORT:
     * You can probably do better than this.
     */
    GLint tmp[4];
 
    glGetIntegerv(GL_VIEWPORT, tmp);
    l = tmp[0];
    r = tmp[0] + tmp[2] - 1;
    b = tmp[1];
    t = tmp[1] + tmp[3] - 1;
 
    *xsize = r - l + 1;
    *ysize = t - b + 1;
 
    if (!*xsize || !*ysize)
        return (0);
 
    *pixbuf =
        (unsigned char *)G_malloc((*xsize) * (*ysize) * 4); /* G_fatal_error */
 
    if (!*pixbuf)
        return (0);
 
#if !defined(OPENGL_FBO)
    glReadBuffer(GL_FRONT);
#endif
 
    /* OGLXXX lrectread: see man page for glReadPixels */
    glReadPixels(l, b, (r) - (l) + 1, (t) - (b) + 1, GL_RGBA, GL_UNSIGNED_BYTE,
                 *pixbuf);
 
    return (1);
}
 
/*!
   \brief Get viewpoint
 
   \param tmp
   \param num
 
   \return 1
 */
int gsd_getViewport(GLint tmp[4], GLint num[2])
{
 
    /* Save current viewport to tmp */
    glGetIntegerv(GL_VIEWPORT, tmp);
    glGetIntegerv(GL_MAX_VIEWPORT_DIMS, num);
 
    return (1);
}
 
/*!
   \brief Write view
 
   \param pixbuf data buffer
   \param xsize,ysize picture dimension
 
   \return 0 on failure
   \return 1 on success
 */
int gsd_writeView(unsigned char **pixbuf, unsigned int xsize,
                  unsigned int ysize)
{
 
    /* Malloc Buffer for image */
    *pixbuf = (unsigned char *)G_malloc(xsize * ysize * 4); /* G_fatal_error */
    if (!*pixbuf) {
        return (0);
    }
 
#if !defined(OPENGL_FBO)
    /* Read image buffer */
    glReadBuffer(GL_FRONT);
#endif
 
    /* Read Pixels into Buffer */
    glReadPixels(0, 0, xsize, ysize, GL_RGBA, GL_UNSIGNED_BYTE, *pixbuf);
    return (1);
}
 
/*!
   \brief Specify pixel arithmetic
 
   \param yesno turn on/off
 */
void gsd_blend(int yesno)
{
    if (yesno) {
        glEnable(GL_BLEND);
        glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);
    }
    else {
        glDisable(GL_BLEND);
        glBlendFunc(GL_ONE, GL_ZERO);
    }
 
    return;
}
 
/*!
   \brief Define clip plane
 
   \param num
   \param params
 */
void gsd_def_clipplane(int num, double *params)
{
    int wason = 0;
 
    /* OGLXXX see man page for glClipPlane equation */
    if (glIsEnabled(GL_CLIP_PLANE0 + (num))) {
        wason = 1;
    }
 
    glClipPlane(GL_CLIP_PLANE0 + (num), params);
 
    if (wason) {
        glEnable(GL_CLIP_PLANE0 + (num));
    }
    else {
        glDisable(GL_CLIP_PLANE0 + (num));
    }
 
    return;
}
 
/*!
   \brief Set clip plane
 
   \param num
   \param able
 */
void gsd_set_clipplane(int num, int able)
{
    /* OGLXXX see man page for glClipPlane equation */
    if (able) {
        glEnable(GL_CLIP_PLANE0 + (num));
    }
    else {
        glDisable(GL_CLIP_PLANE0 + (num));
    }
 
    return;
}
 
/*!
   \brief Finish
 
   Does nothing, only called from src.contrib/GMSL/NVIZ2.2/src/glwrappers.c
 */
void gsd_finish(void)
{
    return;
}
 
/*!
   \brief Set the viewport
 
   <i>l</i>, <i>b</i> specify the lower left corner of the viewport
   rectangle, in pixels.
 
   <i>r</i>, <i>t</i> specify the width and height of the viewport.
 
   \param l left
   \param r right
   \param b bottom
   \param t top
 */
void gsd_viewport(int l, int r, int b, int t)
{
    /* Screencoord */
    glViewport(l, b, r, t);
 
    return;
}
 
/*!
   \brief ADD
 
   First time called, gets a bunch of objects, then hands them back
   when needed
 
   \return -1 on failure
   \return number of objects
 */
int gsd_makelist(void)
{
    int i;
 
    if (numobjs) {
        if (numobjs < MAX_OBJS) {
            numobjs++;
 
            return (numobjs);
        }
 
        return (-1);
    }
    else {
        ObjList[0] = glGenLists(MAX_OBJS);
 
        for (i = 1; i < MAX_OBJS; i++) {
            ObjList[i] = ObjList[0] + i;
        }
        numobjs = 1;
 
        return (numobjs);
    }
}
 
/*!
   \brief ADD
 
   \param listno
   \param do_draw
 */
void gsd_bgnlist(int listno, int do_draw)
{
    if (do_draw) {
        glNewList(ObjList[listno], GL_COMPILE_AND_EXECUTE);
    }
    else {
        glNewList(ObjList[listno], GL_COMPILE);
    }
 
    return;
}
 
/*!
   \brief End list
 */
void gsd_endlist(void)
{
    glEndList();
 
    return;
}
 
/*!
   \brief Delete list
 
   \param listno
   \param range [unused]
 */
void gsd_deletelist(GLuint listno, int range G_UNUSED)
{
    unsigned int i;
 
    for (i = 1; i < MAX_OBJS; i++) {
        if (i == listno) {
            glDeleteLists(ObjList[i], 1);
            numobjs--;
            if (numobjs < 1)
                numobjs = 1;
            return;
        }
    }
}
 
/*!
   \brief ADD
 
   \param listno
 */
void gsd_calllist(int listno)
{
    glCallList(ObjList[listno]);
 
    return;
}
 
/*!
   \brief ADD
 
   \param listno [unused]
 */
void gsd_calllists(int listno G_UNUSED)
{
    int i;
 
    gsd_pushmatrix();
    for (i = 1; i < MAX_OBJS; i++) {
        glCallList(ObjList[i]);
        glFlush();
    }
    gsd_popmatrix();
 
    gsd_call_label();
 
    return;
}