static GLboolean compute_zoomed_bounds	(	GLcontext *	ctx,
		GLint	imageX,
		GLint	imageY,
		GLint	spanX,
		GLint	spanY,
		GLint	width,
		GLint *	x0,
		GLint *	x1,
		GLint *	y0,
		GLint *	y1
	)		`[static]`

Compute the bounds of the region resulting from zooming a pixel span. The resulting region will be entirely inside the window/scissor bounds so no additional clipping is needed.

Parameters:

imageX,imageY	position of the mage being drawn (gl WindowPos)
spanX,spanY	position of span being drawing
width	number of pixels in span
x0,x1	returned X bounds of zoomed region [x0, x1)
y0,y1	returned Y bounds of zoomed region [y0, y1)

Returns:: GL_TRUE if any zoomed pixels visible, GL_FALSE if totally clipped

Definition at line 48 of file s_zoom.c.

Referenced by _swrast_write_zoomed_stencil_span(), _swrast_write_zoomed_z_span(), and zoom_span().

{
   const struct gl_framebuffer *fb = ctx->DrawBuffer;
   GLint c0, c1, r0, r1;

   ASSERT(spanX >= imageX);
   ASSERT(spanY >= imageY);

   /*
    * Compute destination columns: [c0, c1)
    */
   c0 = imageX + (GLint) ((spanX - imageX) * ctx->Pixel.ZoomX);
   c1 = imageX + (GLint) ((spanX + width - imageX) * ctx->Pixel.ZoomX);
   if (c1 < c0) {
      /* swap */
      GLint tmp = c1;
      c1 = c0;
      c0 = tmp;
   }
   c0 = CLAMP(c0, fb->_Xmin, fb->_Xmax);
   c1 = CLAMP(c1, fb->_Xmin, fb->_Xmax);
   if (c0 == c1) {
      return GL_FALSE; /* no width */
   }

   /*
    * Compute destination rows: [r0, r1)
    */
   r0 = imageY + (GLint) ((spanY - imageY) * ctx->Pixel.ZoomY);
   r1 = imageY + (GLint) ((spanY + 1 - imageY) * ctx->Pixel.ZoomY);
   if (r1 < r0) {
      /* swap */
      GLint tmp = r1;
      r1 = r0;
      r0 = tmp;
   }
   r0 = CLAMP(r0, fb->_Ymin, fb->_Ymax);
   r1 = CLAMP(r1, fb->_Ymin, fb->_Ymax);
   if (r0 == r1) {
      return GL_FALSE; /* no height */
   }

   *x0 = c0;
   *x1 = c1;
   *y0 = r0;
   *y1 = r1;

   return GL_TRUE;
}

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