s_stencil.c

Mesa is an open-source implementation of the OpenGL specification - a system for rendering interacti

	       }
	       else {
		  fail[i] = 1;
		  mask[i] = 0;
	       }
	    }
	    else {
	       fail[i] = 0;
	    }
	 }
	 break;
      case GL_NOTEQUAL:
	 r = (GLstencil) (ctx->Stencil.Ref[face] & valueMask);
	 for (i=0;i<n;i++) {
	    if (mask[i]) {
               const GLstencil *sptr = STENCIL_ADDRESS(x[i],y[i]);
	       s = (GLstencil) (*sptr & valueMask);
	       if (r != s) {
		  /* passed */
		  fail[i] = 0;
	       }
	       else {
		  fail[i] = 1;
		  mask[i] = 0;
	       }
	    }
	    else {
	       fail[i] = 0;
	    }
	 }
	 break;
      case GL_ALWAYS:
	 /* always pass */
	 for (i=0;i<n;i++) {
	    fail[i] = 0;
	 }
	 break;
      default:
         _mesa_problem(ctx, "Bad stencil func in gl_stencil_pixels");
         return 0;
   }

   if (ctx->Stencil.FailFunc[face] != GL_KEEP) {
      apply_stencil_op_to_pixels( ctx, n, x, y, ctx->Stencil.FailFunc[face],
                                  face, fail );
   }

   return !allfail;
}




/**
 * Apply stencil and depth testing to an array of pixels.
 * This is used both for software and hardware stencil buffers.
 *
 * The comments in this function are a bit sparse but the code is
 * almost identical to stencil_and_ztest_span(), which is well
 * commented.
 *
 * Input:  n - number of pixels in the array
 *         x, y - array of [n] pixel positions
 *         z - array [n] of z values
 *         mask - array [n] of flags  (1=test this pixel, 0=skip the pixel)
 * Output: mask - array [n] of flags (1=stencil and depth test passed)
 * Return: GL_FALSE - all fragments failed the testing
 *         GL_TRUE - one or more fragments passed the testing
 */
static GLboolean
stencil_and_ztest_pixels( GLcontext *ctx, SWspan *span, GLuint face )
{
   GLubyte passMask[MAX_WIDTH], failMask[MAX_WIDTH], origMask[MAX_WIDTH];
   struct gl_framebuffer *fb = ctx->DrawBuffer;
   struct gl_renderbuffer *rb = fb->_StencilBuffer;
   const GLuint n = span->end;
   const GLint *x = span->array->x;
   const GLint *y = span->array->y;
   GLubyte *mask = span->array->mask;

   ASSERT(span->arrayMask & SPAN_XY);
   ASSERT(ctx->Stencil.Enabled);
   ASSERT(n <= MAX_WIDTH);

   if (!rb->GetPointer(ctx, rb, 0, 0)) {
      /* No direct access */
      GLstencil stencil[MAX_WIDTH];

      ASSERT(rb->DataType == GL_UNSIGNED_BYTE);
      _swrast_get_values(ctx, rb, n, x, y, stencil, sizeof(GLubyte));

      _mesa_memcpy(origMask, mask, n * sizeof(GLubyte));          

      (void) do_stencil_test(ctx, face, n, stencil, mask);

      if (ctx->Depth.Test == GL_FALSE) {
         apply_stencil_op(ctx, ctx->Stencil.ZPassFunc[face], face,
                          n, stencil, mask);
      }
      else {
         GLubyte tmpMask[MAX_WIDTH]; 
         _mesa_memcpy(tmpMask, mask, n * sizeof(GLubyte));

         _swrast_depth_test_span(ctx, span);

         compute_pass_fail_masks(n, tmpMask, mask, passMask, failMask);

         if (ctx->Stencil.ZFailFunc[face] != GL_KEEP) {
            apply_stencil_op(ctx, ctx->Stencil.ZFailFunc[face], face,
                             n, stencil, failMask);
         }
         if (ctx->Stencil.ZPassFunc[face] != GL_KEEP) {
            apply_stencil_op(ctx, ctx->Stencil.ZPassFunc[face], face,
                             n, stencil, passMask);
         }
      }

      /* Write updated stencil values into hardware stencil buffer */
      rb->PutValues(ctx, rb, n, x, y, stencil, origMask);

      return GL_TRUE;
   }
   else {
      /* Direct access to stencil buffer */

      if (stencil_test_pixels(ctx, face, n, x, y, mask) == GL_FALSE) {
         /* all fragments failed the stencil test, we're done. */
         return GL_FALSE;
      }

      if (ctx->Depth.Test==GL_FALSE) {
         apply_stencil_op_to_pixels(ctx, n, x, y,
                                    ctx->Stencil.ZPassFunc[face], face, mask);
      }
      else {
         _mesa_memcpy(origMask, mask, n * sizeof(GLubyte));

         _swrast_depth_test_span(ctx, span);

         compute_pass_fail_masks(n, origMask, mask, passMask, failMask);

         if (ctx->Stencil.ZFailFunc[face] != GL_KEEP) {
            apply_stencil_op_to_pixels(ctx, n, x, y,
                                       ctx->Stencil.ZFailFunc[face],
                                       face, failMask);
         }
         if (ctx->Stencil.ZPassFunc[face] != GL_KEEP) {
            apply_stencil_op_to_pixels(ctx, n, x, y,
                                       ctx->Stencil.ZPassFunc[face],
                                       face, passMask);
         }
      }

      return GL_TRUE;  /* one or more fragments passed both tests */
   }
}


/**
 * /return GL_TRUE = one or more fragments passed,
 * GL_FALSE = all fragments failed.
 */
GLboolean
_swrast_stencil_and_ztest_span(GLcontext *ctx, SWspan *span)
{
   if (span->arrayMask & SPAN_XY)
      return stencil_and_ztest_pixels(ctx, span, span->facing);
   else
      return stencil_and_ztest_span(ctx, span, span->facing);
}


#if 0
GLuint
clip_span(GLuint bufferWidth, GLuint bufferHeight,
          GLint x, GLint y, GLuint *count)
{
   GLuint n = *count;
   GLuint skipPixels = 0;

   if (y < 0 || y >= bufferHeight || x + n <= 0 || x >= bufferWidth) {
      /* totally out of bounds */
      n = 0;
   }
   else {
      /* left clip */
      if (x < 0) {
         skipPixels = -x;
         x = 0;
         n -= skipPixels;
      }
      /* right clip */
      if (x + n > bufferWidth) {
         GLint dx = x + n - bufferWidth;
         n -= dx;
      }
   }

   *count = n;

   return skipPixels;
}
#endif


/**
 * Return a span of stencil values from the stencil buffer.
 * Used for glRead/CopyPixels
 * Input:  n - how many pixels
 *         x,y - location of first pixel
 * Output:  stencil - the array of stencil values
 */
void
_swrast_read_stencil_span(GLcontext *ctx, struct gl_renderbuffer *rb,
                          GLint n, GLint x, GLint y, GLstencil stencil[])
{
   if (y < 0 || y >= (GLint) rb->Height ||
       x + n <= 0 || x >= (GLint) rb->Width) {
      /* span is completely outside framebuffer */
      return; /* undefined values OK */
   }

   if (x < 0) {
      GLint dx = -x;
      x = 0;
      n -= dx;
      stencil += dx;
   }
   if (x + n > (GLint) rb->Width) {
      GLint dx = x + n - rb->Width;
      n -= dx;
   }
   if (n <= 0) {
      return;
   }

   rb->GetRow(ctx, rb, n, x, y, stencil);
}



/**
 * Write a span of stencil values to the stencil buffer.  This function
 * applies the stencil write mask when needed.
 * Used for glDraw/CopyPixels
 * Input:  n - how many pixels
 *         x, y - location of first pixel
 *         stencil - the array of stencil values
 */
void
_swrast_write_stencil_span(GLcontext *ctx, GLint n, GLint x, GLint y,
                           const GLstencil stencil[] )
{
   struct gl_framebuffer *fb = ctx->DrawBuffer;
   struct gl_renderbuffer *rb = fb->_StencilBuffer;
   const GLuint stencilMax = (1 << fb->Visual.stencilBits) - 1;
   const GLuint stencilMask = ctx->Stencil.WriteMask[0];

   if (y < 0 || y >= (GLint) rb->Height ||
       x + n <= 0 || x >= (GLint) rb->Width) {
      /* span is completely outside framebuffer */
      return; /* undefined values OK */
   }
   if (x < 0) {
      GLint dx = -x;
      x = 0;
      n -= dx;
      stencil += dx;
   }
   if (x + n > (GLint) rb->Width) {
      GLint dx = x + n - rb->Width;
      n -= dx;
   }
   if (n <= 0) {
      return;
   }

   if ((stencilMask & stencilMax) != stencilMax) {
      /* need to apply writemask */
      GLstencil destVals[MAX_WIDTH], newVals[MAX_WIDTH];
      GLint i;
      rb->GetRow(ctx, rb, n, x, y, destVals);
      for (i = 0; i < n; i++) {
         newVals[i]
            = (stencil[i] & stencilMask) | (destVals[i] & ~stencilMask);
      }
      rb->PutRow(ctx, rb, n, x, y, newVals, NULL);
   }
   else {
      rb->PutRow(ctx, rb, n, x, y, stencil, NULL);
   }
}



/**
 * Clear the stencil buffer.
 */
void
_swrast_clear_stencil_buffer( GLcontext *ctx, struct gl_renderbuffer *rb )
{
   const GLubyte stencilBits = ctx->DrawBuffer->Visual.stencilBits;
   const GLuint mask = ctx->Stencil.WriteMask[0];
   const GLuint invMask = ~mask;
   const GLuint clearVal = (ctx->Stencil.Clear & mask);
   const GLuint stencilMax = (1 << stencilBits) - 1;
   GLint x, y, width, height;

   if (!rb || mask == 0)
      return;

   ASSERT(rb->DataType == GL_UNSIGNED_BYTE ||
          rb->DataType == GL_UNSIGNED_SHORT);

   ASSERT(rb->_BaseFormat == GL_STENCIL_INDEX);

   /* compute region to clear */
   x = ctx->DrawBuffer->_Xmin;
   y = ctx->DrawBuffer->_Ymin;
   width  = ctx->DrawBuffer->_Xmax - ctx->DrawBuffer->_Xmin;
   height = ctx->DrawBuffer->_Ymax - ctx->DrawBuffer->_Ymin;

   if (rb->GetPointer(ctx, rb, 0, 0)) {
      /* Direct buffer access */
      if ((mask & stencilMax) != stencilMax) {
         /* need to mask the clear */
         if (rb->DataType == GL_UNSIGNED_BYTE) {
            GLint i, j;
            for (i = 0; i < height; i++) {
               GLubyte *stencil = (GLubyte*) rb->GetPointer(ctx, rb, x, y + i);
               for (j = 0; j < width; j++) {
                  stencil[j] = (stencil[j] & invMask) | clearVal;
               }
            }
         }
         else {
            GLint i, j;
            for (i = 0; i < height; i++) {
               GLushort *stencil = (GLushort*) rb->GetPointer(ctx, rb, x, y + i);
               for (j = 0; j < width; j++) {
                  stencil[j] = (stencil[j] & invMask) | clearVal;
               }
            }
         }
      }
      else {
         /* no bit masking */
         if (width == (GLint) rb->Width && rb->DataType == GL_UNSIGNED_BYTE) {
            /* optimized case */
            /* Note: bottom-to-top raster assumed! */
            GLubyte *stencil = (GLubyte *) rb->GetPointer(ctx, rb, x, y);
            GLuint len = width * height * sizeof(GLubyte);
            _mesa_memset(stencil, clearVal, len);
         }
         else {
            /* general case */
            GLint i;
            for (i = 0; i < height; i++) {
               GLvoid *stencil = rb->GetPointer(ctx, rb, x, y + i);
               if (rb->DataType == GL_UNSIGNED_BYTE) {
                  _mesa_memset(stencil, clearVal, width);
               }
               else {
                  _mesa_memset16((short unsigned int*) stencil, clearVal, width);
               }
            }
         }
      }
   }
   else {
      /* no direct access */
      if ((mask & stencilMax) != stencilMax) {
         /* need to mask the clear */
         if (rb->DataType == GL_UNSIGNED_BYTE) {
            GLint i, j;
            for (i = 0; i < height; i++) {
               GLubyte stencil[MAX_WIDTH];
               rb->GetRow(ctx, rb, width, x, y + i, stencil);
               for (j = 0; j < width; j++) {
                  stencil[j] = (stencil[j] & invMask) | clearVal;
               }
               rb->PutRow(ctx, rb, width, x, y + i, stencil, NULL);
            }
         }
         else {
            GLint i, j;
            for (i = 0; i < height; i++) {
               GLushort stencil[MAX_WIDTH];
               rb->GetRow(ctx, rb, width, x, y + i, stencil);
               for (j = 0; j < width; j++) {
                  stencil[j] = (stencil[j] & invMask) | clearVal;
               }
               rb->PutRow(ctx, rb, width, x, y + i, stencil, NULL);
            }
         }
      }
      else {
         /* no bit masking */
         const GLubyte clear8 = (GLubyte) clearVal;
         const GLushort clear16 = (GLushort) clearVal;
         const void *clear;
         GLint i;
         if (rb->DataType == GL_UNSIGNED_BYTE) {
            clear = &clear8;
         }
         else {
            clear = &clear16;
         }
         for (i = 0; i < height; i++) {
            rb->PutMonoRow(ctx, rb, width, x, y + i, clear, NULL);
         }
      }
   }
}