elements/GL/SoGLLineWidthElement.cpp

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/*!
  \class SoGLLineWidthElement Inventor/elements/SoGLLineWidthElement.h
  \brief The SoGLLineWidthElement class changes the linewidth setting of the OpenGL render state.

  \ingroup elements

  Requests from the scenegraph to change the linewidth when rendering
  OpenGL line primitives will be made through this element, which
  forwards it to the appropriate native OpenGL call.

  The Coin library does not place any bounds on the values of the
  linewidths, but be aware that the range and granularity of what is
  valid linewidths depends on the underlying OpenGL
  implementation. Application programmers using line primitives
  (typically through the SoLineSet or SoIndexedLineSet nodes) should
  heed these boundary values. They can be acquired by running the
  following code from within a valid OpenGL context:

  \code
    GLfloat bounds[2];
    glGetFloatv(GL_LINE_WIDTH_RANGE, bounds);
    GLfloat granularity[1];
    glGetFloatv(GL_LINE_WIDTH_GRANULARITY, granularity);
  \endcode

  Another, perhaps more convenient, way of acquiring the OpenGL
  implementation limits with regard to pointsizes is to use the
  So\@Gui\@GLWidget\::getPointSizeLimits() method in the GUI "glue" interface
  library you are using (SoQt, SoXt, SoGtk, SoWin, ...).
*/

#include <Inventor/elements/SoGLLineWidthElement.h>
#include "coindefs.h"

#include <cfloat>
#ifdef HAVE_CONFIG_H
#include <config.h>
#endif // HAVE_CONFIG_H

#include <Inventor/system/gl.h>

#include <cassert>
#include <Inventor/errors/SoDebugError.h>

// Important note: do _not_ use a "static const" variable instead, as
// it is then not given that it will be initialized before the static
// "sizerange" class variable array below.
#define RANGE_NOT_CHECKED FLT_MAX

float SoGLLineWidthElement::sizerange[2] = { RANGE_NOT_CHECKED, -1.0f};


SO_ELEMENT_SOURCE(SoGLLineWidthElement);

// doc in super
void
SoGLLineWidthElement::initClass(void)
{
  SO_ELEMENT_INIT_CLASS(SoGLLineWidthElement, inherited);
}

/*!
  Destructor.
*/
SoGLLineWidthElement::~SoGLLineWidthElement(void)
{
}

// doc in super
void
SoGLLineWidthElement::init(SoState * stateptr)
{
  inherited::init(stateptr);
}

// doc in super
void
SoGLLineWidthElement::push(SoState * stateptr)
{
  SoGLLineWidthElement * prev = (SoGLLineWidthElement*)this->getNextInStack();
  this->data = prev->data;
  // capture previous element since we might or might not change the
  // GL state in set/pop
  prev->capture(stateptr);
}

// doc in super
void
SoGLLineWidthElement::pop(SoState * COIN_UNUSED_ARG(stateptr), const SoElement * prevTopElement)
{
  SoGLLineWidthElement * prev = (SoGLLineWidthElement*)prevTopElement;
  if (this->data != prev->data) {
    this->updategl();
  }
}

// doc in super
void
SoGLLineWidthElement::setElt(float width)
{
  if (width != this->data) {
    this->data = width;
    this->updategl();
  }
}

// private
void
SoGLLineWidthElement::updategl(void)
{
  if (SoGLLineWidthElement::sizerange[0] == RANGE_NOT_CHECKED) {
    GLfloat vals[2];
    glGetFloatv(GL_LINE_WIDTH_RANGE, vals);

    // Matthias Koenig reported on coin-discuss that the OpenGL
    // implementation on SGI Onyx 2 InfiniteReality returns 0 for the
    // lowest linewidth, but it will still set the return value of
    // glGetError() to GL_INVALID_VALUE if this size is attempted
    // used. This is a workaround for what looks like an OpenGL bug.

    if (vals[0] <= 0.0f) { vals[0] = SbMin(1.0f, vals[1]); }

    SoGLLineWidthElement::sizerange[0] = vals[0];
    SoGLLineWidthElement::sizerange[1] = vals[1];
  }

  float useval = this->data;

  // 0.0f is used as a "dummy" default value by our superclass and by
  // SoDrawStyle::lineWidth, so handle that case outside of the
  // rangecheck below.

  if (this->data == 0.0f) { useval = 1.0f; }

  // Range checks.

  if (useval < SoGLLineWidthElement::sizerange[0]) {
    useval = SoGLLineWidthElement::sizerange[0];
  }
  if (useval > SoGLLineWidthElement::sizerange[1]) {
    useval = SoGLLineWidthElement::sizerange[1];
  }


  if (COIN_DEBUG) {
    // Detect invalid values and warn the application programmer.
    // (0.0f is used as a "dummy" default value by our superclass and
    // by SoDrawStyle::lineWidth, so ignore that case.)
    if ((useval != this->data) && (this->data != 0.0f)) {
      // Only warn once for each case.
      static SbBool warn_below = TRUE;
      static SbBool warn_above = TRUE;
      if ((warn_below && (useval > this->data)) ||
          (warn_above && (useval < this->data))) {
        if (useval > this->data) { warn_below = FALSE; }
        if (useval < this->data) { warn_above = FALSE; }
        SoDebugError::postWarning("SoGLLineWidthElement::updategl",
                                  "%f is outside the legal range of [%f, %f] "
                                  "for this OpenGL implementation's "
                                  "glLineWidth() settings. It was now clamped.\n\n"
                                  "See the documentation of SoGLLineWidthElement for "
                                  "information on how the application programmer should "
                                  "acquire the boundary values for the legal "
                                  "range.",
                                  this->data,
                                  SoGLLineWidthElement::sizerange[0],
                                  SoGLLineWidthElement::sizerange[1]);
      }
    }
  }

  // Forward to OpenGL state.

  glLineWidth(useval);
}

#undef RANGE_NOT_CHECKED