X-Git-Url: https://git.libre-soc.org/?a=blobdiff_plain;f=src%2Fmesa%2Fswrast%2Fs_zoom.c;h=f224627d50eac2ac8b8b3eceed4ed6db2d4cdd1b;hb=86af037e6a1643284f87c5e01c3fcb09dd07bf35;hp=852905f681de7bce2550cbaa018598eb205d524f;hpb=4039cb8ca82d59451a6de8902fe35e693cdca3ba;p=mesa.git

diff --git a/src/mesa/swrast/s_zoom.c b/src/mesa/swrast/s_zoom.c
index 852905f681d..f224627d50e 100644
--- a/src/mesa/swrast/s_zoom.c
+++ b/src/mesa/swrast/s_zoom.c
@@ -1,10 +1,8 @@
-/* $Id: s_zoom.c,v 1.22 2003/02/25 19:26:02 brianp Exp $ */
-
 /*
  * Mesa 3-D graphics library
- * Version:  5.1
+ * Version:  7.1
  *
- * Copyright (C) 1999-2003  Brian Paul   All Rights Reserved.
+ * Copyright (C) 1999-2008  Brian Paul   All Rights Reserved.
  *
  * Permission is hereby granted, free of charge, to any person obtaining a
  * copy of this software and associated documentation files (the "Software"),
@@ -24,10 +22,10 @@
  * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
  */
 
-#include "glheader.h"
-#include "macros.h"
-#include "imports.h"
-#include "colormac.h"
+#include "main/glheader.h"
+#include "main/macros.h"
+#include "main/imports.h"
+#include "main/colormac.h"
 
 #include "s_context.h"
 #include "s_span.h"
@@ -35,217 +33,286 @@
 #include "s_zoom.h"
 
 
-/*
- * Helper function called from _mesa_write_zoomed_rgba/rgb/index_span().
+/**
+ * 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.
+ * \param imageX, imageY  position of the mage being drawn (gl WindowPos)
+ * \param spanX, spanY  position of span being drawing
+ * \param width  number of pixels in span
+ * \param x0, x1  returned X bounds of zoomed region [x0, x1)
+ * \param y0, y1  returned Y bounds of zoomed region [y0, y1)
+ * \return GL_TRUE if any zoomed pixels visible, GL_FALSE if totally clipped
  */
-static void
-zoom_span( GLcontext *ctx, const struct sw_span *span,
-           const GLvoid *src, GLint y0, GLenum format, GLint skipPixels )
+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)
 {
-   GLint r0, r1, row;
-   GLint c0, c1, skipCol;
-   GLint i, j;
-   const GLuint maxWidth = MIN2( ctx->DrawBuffer->Width, MAX_WIDTH );
-   GLchan rgbaSave[MAX_WIDTH][4];
-   GLuint indexSave[MAX_WIDTH];
-   const GLchan (*rgba)[4] = (const GLchan (*)[4]) src;
-   const GLchan (*rgb)[3] = (const GLchan (*)[3]) src;
-   const GLuint *indexes = (const GLuint *) src;
-   struct sw_span zoomed;
-   struct span_arrays zoomed_arrays;  /* this is big! */
-
-   /* no pixel arrays! */
-   ASSERT((span->arrayMask & SPAN_XY) == 0);
-   ASSERT(span->primitive == GL_BITMAP);
-
-   INIT_SPAN(zoomed, GL_BITMAP, 0, 0, 0);
-   zoomed.array = &zoomed_arrays;
+   const struct gl_framebuffer *fb = ctx->DrawBuffer;
+   GLint c0, c1, r0, r1;
 
-   zoomed.z = span->z;
-   zoomed.zStep = span->zStep;  /* span->zStep == 0 */
-   zoomed.fog = span->fog;
-   zoomed.fogStep = span->fogStep;
-   if (format == GL_RGBA || format == GL_RGB) {
-      zoomed.interpMask = span->interpMask & ~SPAN_RGBA;
-      zoomed.arrayMask |= SPAN_RGBA;
-   }
-   else if (format == GL_COLOR_INDEX) {
-      zoomed.interpMask = span->interpMask & ~SPAN_INDEX;
-      zoomed.arrayMask |= SPAN_INDEX;
-   }
+   ASSERT(spanX >= imageX);
+   ASSERT(spanY >= imageY);
 
    /*
-    * Compute which columns to draw: [c0, c1)
+    * Compute destination columns: [c0, c1)
     */
-#if 0
-   c0 = (GLint) span->x;
-   c1 = (GLint) (span->x + span->end * ctx->Pixel.ZoomX);
-#else
-   c0 = (GLint) (span->x + skipPixels * ctx->Pixel.ZoomX);
-   c1 = (GLint) (span->x + (skipPixels + span->end) * ctx->Pixel.ZoomX);
-#endif
-   if (c0 == c1) {
-      return;
-   }
-   else if (c1 < c0) {
+   c0 = imageX + (GLint) ((spanX - imageX) * ctx->Pixel.ZoomX);
+   c1 = imageX + (GLint) ((spanX + width - imageX) * ctx->Pixel.ZoomX);
+   if (c1 < c0) {
       /* swap */
-      GLint ctmp = c1;
+      GLint tmp = c1;
       c1 = c0;
-      c0 = ctmp;
-   }
-   if (c0 < 0) {
-      zoomed.x = 0;
-      zoomed.start = 0;
-      zoomed.end = c1;
-      skipCol = -c0;
+      c0 = tmp;
    }
-   else {
-      zoomed.x = c0;
-      zoomed.start = 0;
-      zoomed.end = c1 - c0;
-      skipCol = 0;
+   c0 = CLAMP(c0, fb->_Xmin, fb->_Xmax);
+   c1 = CLAMP(c1, fb->_Xmin, fb->_Xmax);
+   if (c0 == c1) {
+      return GL_FALSE; /* no width */
    }
-   if (zoomed.end > maxWidth)
-      zoomed.end = maxWidth;
 
    /*
-    * Compute which rows to draw: [r0, r1)
+    * Compute destination rows: [r0, r1)
     */
-   row = span->y - y0;
-   r0 = y0 + (GLint) (row * ctx->Pixel.ZoomY);
-   r1 = y0 + (GLint) ((row+1) * ctx->Pixel.ZoomY);
-   if (r0 == r1) {
-      return;
-   }
-   else if (r1 < r0) {
+   r0 = imageY + (GLint) ((spanY - imageY) * ctx->Pixel.ZoomY);
+   r1 = imageY + (GLint) ((spanY + 1 - imageY) * ctx->Pixel.ZoomY);
+   if (r1 < r0) {
       /* swap */
-      GLint rtmp = r1;
+      GLint tmp = r1;
       r1 = r0;
-      r0 = rtmp;
+      r0 = tmp;
+   }
+   r0 = CLAMP(r0, fb->_Ymin, fb->_Ymax);
+   r1 = CLAMP(r1, fb->_Ymin, fb->_Ymax);
+   if (r0 == r1) {
+      return GL_FALSE; /* no height */
    }
 
-   ASSERT(r0 < r1);
-   ASSERT(c0 < c1);
+   *x0 = c0;
+   *x1 = c1;
+   *y0 = r0;
+   *y1 = r1;
+
+   return GL_TRUE;
+}
 
+
+/**
+ * Convert a zoomed x image coordinate back to an unzoomed x coord.
+ * 'zx' is screen position of a pixel in the zoomed image, who's left edge
+ * is at 'imageX'.
+ * return corresponding x coord in the original, unzoomed image.
+ * This can use this for unzooming X or Y values.
+ */
+static INLINE GLint
+unzoom_x(GLfloat zoomX, GLint imageX, GLint zx)
+{
    /*
-    * Trivial clip rejection testing.
-    */
-   if (r1 < 0) /* below window */
-      return;
-   if (r0 >= (GLint) ctx->DrawBuffer->Height) /* above window */
-      return;
-   if (c1 < 0) /* left of window */
-      return;
-   if (c0 >= (GLint) ctx->DrawBuffer->Width) /* right of window */
+   zx = imageX + (x - imageX) * zoomX;
+   zx - imageX = (x - imageX) * zoomX;
+   (zx - imageX) / zoomX = x - imageX;
+   */
+   GLint x;
+   if (zoomX < 0.0)
+      zx++;
+   x = imageX + (GLint) ((zx - imageX) / zoomX);
+   return x;
+}
+
+
+
+/**
+ * Helper function called from _swrast_write_zoomed_rgba/rgb/
+ * index/depth_span().
+ */
+static void
+zoom_span( GLcontext *ctx, GLint imgX, GLint imgY, const SWspan *span,
+           const GLvoid *src, GLenum format )
+{
+   SWcontext *swrast = SWRAST_CONTEXT(ctx);
+   SWspan zoomed;
+   GLint x0, x1, y0, y1;
+   GLint zoomedWidth;
+
+   if (!compute_zoomed_bounds(ctx, imgX, imgY, span->x, span->y, span->end,
+                              &x0, &x1, &y0, &y1)) {
+      return;  /* totally clipped */
+   }
+
+   if (!swrast->ZoomedArrays) {
+      /* allocate on demand */
+      swrast->ZoomedArrays = (SWspanarrays *) CALLOC(sizeof(SWspanarrays));
+      if (!swrast->ZoomedArrays)
+         return;
+   }
+
+   zoomedWidth = x1 - x0;
+   ASSERT(zoomedWidth > 0);
+   ASSERT(zoomedWidth <= MAX_WIDTH);
+
+   /* no pixel arrays! must be horizontal spans. */
+   ASSERT((span->arrayMask & SPAN_XY) == 0);
+   ASSERT(span->primitive == GL_BITMAP);
+
+   INIT_SPAN(zoomed, GL_BITMAP);
+   zoomed.x = x0;
+   zoomed.end = zoomedWidth;
+   zoomed.array = swrast->ZoomedArrays;
+   zoomed.array->ChanType = span->array->ChanType;
+   if (zoomed.array->ChanType == GL_UNSIGNED_BYTE)
+      zoomed.array->rgba = (GLchan (*)[4]) zoomed.array->rgba8;
+   else if (zoomed.array->ChanType == GL_UNSIGNED_SHORT)
+      zoomed.array->rgba = (GLchan (*)[4]) zoomed.array->rgba16;
+   else
+      zoomed.array->rgba = (GLchan (*)[4]) zoomed.array->attribs[FRAG_ATTRIB_COL0];
+
+   COPY_4V(zoomed.attrStart[FRAG_ATTRIB_WPOS], span->attrStart[FRAG_ATTRIB_WPOS]);
+   COPY_4V(zoomed.attrStepX[FRAG_ATTRIB_WPOS], span->attrStepX[FRAG_ATTRIB_WPOS]);
+   COPY_4V(zoomed.attrStepY[FRAG_ATTRIB_WPOS], span->attrStepY[FRAG_ATTRIB_WPOS]);
+
+   zoomed.attrStart[FRAG_ATTRIB_FOGC][0] = span->attrStart[FRAG_ATTRIB_FOGC][0];
+   zoomed.attrStepX[FRAG_ATTRIB_FOGC][0] = span->attrStepX[FRAG_ATTRIB_FOGC][0];
+   zoomed.attrStepY[FRAG_ATTRIB_FOGC][0] = span->attrStepY[FRAG_ATTRIB_FOGC][0];
+
+   if (format == GL_RGBA || format == GL_RGB) {
+      /* copy Z info */
+      zoomed.z = span->z;
+      zoomed.zStep = span->zStep;
+      /* we'll generate an array of colorss */
+      zoomed.interpMask = span->interpMask & ~SPAN_RGBA;
+      zoomed.arrayMask |= SPAN_RGBA;
+      zoomed.arrayAttribs |= FRAG_BIT_COL0;  /* we'll produce these values */
+      ASSERT(span->arrayMask & SPAN_RGBA);
+   }
+   else if (format == GL_DEPTH_COMPONENT) {
+      /* Copy color info */
+      zoomed.red = span->red;
+      zoomed.green = span->green;
+      zoomed.blue = span->blue;
+      zoomed.alpha = span->alpha;
+      zoomed.redStep = span->redStep;
+      zoomed.greenStep = span->greenStep;
+      zoomed.blueStep = span->blueStep;
+      zoomed.alphaStep = span->alphaStep;
+      /* we'll generate an array of depth values */
+      zoomed.interpMask = span->interpMask & ~SPAN_Z;
+      zoomed.arrayMask |= SPAN_Z;
+      ASSERT(span->arrayMask & SPAN_Z);
+   }
+   else {
+      _mesa_problem(ctx, "Bad format in zoom_span");
       return;
+   }
 
    /* zoom the span horizontally */
    if (format == GL_RGBA) {
-      if (ctx->Pixel.ZoomX == -1.0F) {
-         /* common case */
-         for (j = (GLint) zoomed.start; j < (GLint) zoomed.end; j++) {
-            i = span->end - (j + skipCol) - 1;
-            COPY_CHAN4(zoomed.array->rgba[j], rgba[i]);
+      if (zoomed.array->ChanType == GL_UNSIGNED_BYTE) {
+         const GLubyte (*rgba)[4] = (const GLubyte (*)[4]) src;
+         GLint i;
+         for (i = 0; i < zoomedWidth; i++) {
+            GLint j = unzoom_x(ctx->Pixel.ZoomX, imgX, x0 + i) - span->x;
+            ASSERT(j >= 0);
+            ASSERT(j < (GLint) span->end);
+            COPY_4UBV(zoomed.array->rgba8[i], rgba[j]);
+         }
+      }
+      else if (zoomed.array->ChanType == GL_UNSIGNED_SHORT) {
+         const GLushort (*rgba)[4] = (const GLushort (*)[4]) src;
+         GLint i;
+         for (i = 0; i < zoomedWidth; i++) {
+            GLint j = unzoom_x(ctx->Pixel.ZoomX, imgX, x0 + i) - span->x;
+            ASSERT(j >= 0);
+            ASSERT(j < (GLint) span->end);
+            COPY_4V(zoomed.array->rgba16[i], rgba[j]);
          }
       }
       else {
-         /* general solution */
-         const GLfloat xscale = 1.0F / ctx->Pixel.ZoomX;
-         for (j = (GLint) zoomed.start; j < (GLint) zoomed.end; j++) {
-            i = (GLint) ((j + skipCol) * xscale);
-            if (ctx->Pixel.ZoomX < 0.0) {
-               ASSERT(i <= 0);
-               i = span->end + i - 1;
-            }
-            ASSERT(i >= 0);
-            ASSERT(i < (GLint)  span->end);
-            COPY_CHAN4(zoomed.array->rgba[j], rgba[i]);
+         const GLfloat (*rgba)[4] = (const GLfloat (*)[4]) src;
+         GLint i;
+         for (i = 0; i < zoomedWidth; i++) {
+            GLint j = unzoom_x(ctx->Pixel.ZoomX, imgX, x0 + i) - span->x;
+            ASSERT(j >= 0);
+            ASSERT(j < span->end);
+            COPY_4V(zoomed.array->attribs[FRAG_ATTRIB_COL0][i], rgba[j]);
          }
       }
    }
    else if (format == GL_RGB) {
-      if (ctx->Pixel.ZoomX == -1.0F) {
-         /* common case */
-         for (j = (GLint) zoomed.start; j < (GLint) zoomed.end; j++) {
-            i = span->end - (j + skipCol) - 1;
-            zoomed.array->rgba[j][0] = rgb[i][0];
-            zoomed.array->rgba[j][1] = rgb[i][1];
-            zoomed.array->rgba[j][2] = rgb[i][2];
-            zoomed.array->rgba[j][3] = CHAN_MAX;
+      if (zoomed.array->ChanType == GL_UNSIGNED_BYTE) {
+         const GLubyte (*rgb)[3] = (const GLubyte (*)[3]) src;
+         GLint i;
+         for (i = 0; i < zoomedWidth; i++) {
+            GLint j = unzoom_x(ctx->Pixel.ZoomX, imgX, x0 + i) - span->x;
+            ASSERT(j >= 0);
+            ASSERT(j < (GLint) span->end);
+            zoomed.array->rgba8[i][0] = rgb[j][0];
+            zoomed.array->rgba8[i][1] = rgb[j][1];
+            zoomed.array->rgba8[i][2] = rgb[j][2];
+            zoomed.array->rgba8[i][3] = 0xff;
          }
       }
-      else {
-         /* general solution */
-         const GLfloat xscale = 1.0F / ctx->Pixel.ZoomX;
-         for (j = (GLint) zoomed.start; j < (GLint) zoomed.end; j++) {
-            i = (GLint) ((j + skipCol) * xscale);
-            if (ctx->Pixel.ZoomX < 0.0) {
-               ASSERT(i <= 0);
-               i = span->end + i - 1;
-            }
-            ASSERT(i >= 0);
-            ASSERT(i < (GLint) span->end);
-            zoomed.array->rgba[j][0] = rgb[i][0];
-            zoomed.array->rgba[j][1] = rgb[i][1];
-            zoomed.array->rgba[j][2] = rgb[i][2];
-            zoomed.array->rgba[j][3] = CHAN_MAX;
-         }
-      }
-   }
-   else if (format == GL_COLOR_INDEX) {
-      if (ctx->Pixel.ZoomX == -1.0F) {
-         /* common case */
-         for (j = (GLint) zoomed.start; j < (GLint) zoomed.end; j++) {
-            i = span->end - (j + skipCol) - 1;
-            zoomed.array->index[j] = indexes[i];
+      else if (zoomed.array->ChanType == GL_UNSIGNED_SHORT) {
+         const GLushort (*rgb)[3] = (const GLushort (*)[3]) src;
+         GLint i;
+         for (i = 0; i < zoomedWidth; i++) {
+            GLint j = unzoom_x(ctx->Pixel.ZoomX, imgX, x0 + i) - span->x;
+            ASSERT(j >= 0);
+            ASSERT(j < (GLint) span->end);
+            zoomed.array->rgba16[i][0] = rgb[j][0];
+            zoomed.array->rgba16[i][1] = rgb[j][1];
+            zoomed.array->rgba16[i][2] = rgb[j][2];
+            zoomed.array->rgba16[i][3] = 0xffff;
          }
       }
       else {
-         /* general solution */
-         const GLfloat xscale = 1.0F / ctx->Pixel.ZoomX;
-         for (j = (GLint) zoomed.start; j < (GLint) zoomed.end; j++) {
-            i = (GLint) ((j + skipCol) * xscale);
-            if (ctx->Pixel.ZoomX < 0.0) {
-               ASSERT(i <= 0);
-               i = span->end + i - 1;
-            }
-            ASSERT(i >= 0);
-            ASSERT(i < (GLint) span->end);
-            zoomed.array->index[j] = indexes[i];
+         const GLfloat (*rgb)[3] = (const GLfloat (*)[3]) src;
+         GLint i;
+         for (i = 0; i < zoomedWidth; i++) {
+            GLint j = unzoom_x(ctx->Pixel.ZoomX, imgX, x0 + i) - span->x;
+            ASSERT(j >= 0);
+            ASSERT(j < span->end);
+            zoomed.array->attribs[FRAG_ATTRIB_COL0][i][0] = rgb[j][0];
+            zoomed.array->attribs[FRAG_ATTRIB_COL0][i][1] = rgb[j][1];
+            zoomed.array->attribs[FRAG_ATTRIB_COL0][i][2] = rgb[j][2];
+            zoomed.array->attribs[FRAG_ATTRIB_COL0][i][3] = 1.0F;
          }
       }
    }
+   else if (format == GL_DEPTH_COMPONENT) {
+      const GLuint *zValues = (const GLuint *) src;
+      GLint i;
+      for (i = 0; i < zoomedWidth; i++) {
+         GLint j = unzoom_x(ctx->Pixel.ZoomX, imgX, x0 + i) - span->x;
+         ASSERT(j >= 0);
+         ASSERT(j < (GLint) span->end);
+         zoomed.array->z[i] = zValues[j];
+      }
+      /* Now, fall into the RGB path below */
+      format = GL_RGBA;
+   }
 
    /* write the span in rows [r0, r1) */
    if (format == GL_RGBA || format == GL_RGB) {
       /* Writing the span may modify the colors, so make a backup now if we're
-       * going to call _mesa_write_zoomed_span() more than once.
+       * going to call _swrast_write_zoomed_span() more than once.
        * Also, clipping may change the span end value, so store it as well.
        */
       const GLint end = zoomed.end; /* save */
-      if (r1 - r0 > 1) {
-         MEMCPY(rgbaSave, zoomed.array->rgba, zoomed.end * 4 * sizeof(GLchan));
-      }
-      for (zoomed.y = r0; zoomed.y < r1; zoomed.y++) {
-         _mesa_write_rgba_span(ctx, &zoomed);
-         zoomed.end = end;  /* restore */
-         if (r1 - r0 > 1) {
-            /* restore the colors */
-            MEMCPY(zoomed.array->rgba, rgbaSave, zoomed.end*4 * sizeof(GLchan));
-         }
-      }
-   }
-   else if (format == GL_COLOR_INDEX) {
-      const GLint end = zoomed.end; /* save */
-      if (r1 - r0 > 1) {
-         MEMCPY(indexSave, zoomed.array->index, zoomed.end * sizeof(GLuint));
+      GLuint rgbaSave[MAX_WIDTH][4];
+      const GLint pixelSize =
+         (zoomed.array->ChanType == GL_UNSIGNED_BYTE) ? 4 * sizeof(GLubyte) :
+         ((zoomed.array->ChanType == GL_UNSIGNED_SHORT) ? 4 * sizeof(GLushort)
+          : 4 * sizeof(GLfloat));
+      if (y1 - y0 > 1) {
+         memcpy(rgbaSave, zoomed.array->rgba, zoomed.end * pixelSize);
       }
-      for (zoomed.y = r0; zoomed.y < r1; zoomed.y++) {
-         _mesa_write_index_span(ctx, &zoomed);
+      for (zoomed.y = y0; zoomed.y < y1; zoomed.y++) {
+         _swrast_write_rgba_span(ctx, &zoomed);
          zoomed.end = end;  /* restore */
-         if (r1 - r0 > 1) {
+         if (y1 - y0 > 1) {
             /* restore the colors */
-            MEMCPY(zoomed.array->index, indexSave, zoomed.end * sizeof(GLuint));
+            memcpy(zoomed.array->rgba, rgbaSave, zoomed.end * pixelSize);
          }
       }
    }
@@ -253,118 +320,114 @@ zoom_span( GLcontext *ctx, const struct sw_span *span,
 
 
 void
-_mesa_write_zoomed_rgba_span( GLcontext *ctx, const struct sw_span *span,
-                              CONST GLchan rgba[][4], GLint y0,
-                              GLint skipPixels )
+_swrast_write_zoomed_rgba_span(GLcontext *ctx, GLint imgX, GLint imgY,
+                               const SWspan *span, const GLvoid *rgba)
 {
-   zoom_span(ctx, span, (const GLvoid *) rgba, y0, GL_RGBA, skipPixels);
+   zoom_span(ctx, imgX, imgY, span, rgba, GL_RGBA);
 }
 
 
 void
-_mesa_write_zoomed_rgb_span( GLcontext *ctx, const struct sw_span *span,
-                             CONST GLchan rgb[][3], GLint y0,
-                             GLint skipPixels )
+_swrast_write_zoomed_rgb_span(GLcontext *ctx, GLint imgX, GLint imgY,
+                              const SWspan *span, const GLvoid *rgb)
 {
-   zoom_span(ctx, span, (const GLvoid *) rgb, y0, GL_RGB, skipPixels);
+   zoom_span(ctx, imgX, imgY, span, rgb, GL_RGB);
 }
 
 
 void
-_mesa_write_zoomed_index_span( GLcontext *ctx, const struct sw_span *span,
-                               GLint y0, GLint skipPixels )
+_swrast_write_zoomed_depth_span(GLcontext *ctx, GLint imgX, GLint imgY,
+                                const SWspan *span)
 {
-  zoom_span(ctx, span, (const GLvoid *) span->array->index, y0,
-            GL_COLOR_INDEX, skipPixels);
+   zoom_span(ctx, imgX, imgY, span,
+             (const GLvoid *) span->array->z, GL_DEPTH_COMPONENT);
 }
 
 
-/*
- * As above, but write stencil values.
+/**
+ * Zoom/write stencil values.
+ * No per-fragment operations are applied.
  */
 void
-_mesa_write_zoomed_stencil_span( GLcontext *ctx,
-                                 GLuint n, GLint x, GLint y,
-                                 const GLstencil stencil[], GLint y0,
-                                 GLint skipPixels )
+_swrast_write_zoomed_stencil_span(GLcontext *ctx, GLint imgX, GLint imgY,
+                                  GLint width, GLint spanX, GLint spanY,
+                                  const GLstencil stencil[])
 {
-   GLint m;
-   GLint r0, r1, row, r;
-   GLint i, j, skipcol;
-   GLstencil zstencil[MAX_WIDTH];  /* zoomed stencil values */
-   GLint maxwidth = MIN2( ctx->DrawBuffer->Width, MAX_WIDTH );
+   GLstencil zoomedVals[MAX_WIDTH];
+   GLint x0, x1, y0, y1, y;
+   GLint i, zoomedWidth;
 
-   (void) skipPixels;  /* XXX this shouldn't be ignored */
-
-   /* compute width of output row */
-   m = (GLint) ABSF( n * ctx->Pixel.ZoomX );
-   if (m==0) {
-      return;
-   }
-   if (ctx->Pixel.ZoomX<0.0) {
-      /* adjust x coordinate for left/right mirroring */
-      x = x - m;
+   if (!compute_zoomed_bounds(ctx, imgX, imgY, spanX, spanY, width,
+                              &x0, &x1, &y0, &y1)) {
+      return;  /* totally clipped */
    }
 
-   /* compute which rows to draw */
-   row = y - y0;
-   r0 = y0 + (GLint) (row * ctx->Pixel.ZoomY);
-   r1 = y0 + (GLint) ((row+1) * ctx->Pixel.ZoomY);
-   if (r0==r1) {
-      return;
-   }
-   else if (r1<r0) {
-      GLint rtmp = r1;
-      r1 = r0;
-      r0 = rtmp;
-   }
+   zoomedWidth = x1 - x0;
+   ASSERT(zoomedWidth > 0);
+   ASSERT(zoomedWidth <= MAX_WIDTH);
 
-   /* return early if r0...r1 is above or below window */
-   if (r0<0 && r1<0) {
-      /* below window */
-      return;
-   }
-   if (r0 >= (GLint) ctx->DrawBuffer->Height &&
-       r1 >= (GLint) ctx->DrawBuffer->Height) {
-      /* above window */
-      return;
+   /* zoom the span horizontally */
+   for (i = 0; i < zoomedWidth; i++) {
+      GLint j = unzoom_x(ctx->Pixel.ZoomX, imgX, x0 + i) - spanX;
+      ASSERT(j >= 0);
+      ASSERT(j < width);
+      zoomedVals[i] = stencil[j];
    }
 
-   /* check if left edge is outside window */
-   skipcol = 0;
-   if (x<0) {
-      skipcol = -x;
-      m += x;
-   }
-   /* make sure span isn't too long or short */
-   if (m>maxwidth) {
-      m = maxwidth;
+   /* write the zoomed spans */
+   for (y = y0; y < y1; y++) {
+      _swrast_write_stencil_span(ctx, zoomedWidth, x0, y, zoomedVals);
    }
-   else if (m<=0) {
-      return;
+}
+
+
+/**
+ * Zoom/write z values (16 or 32-bit).
+ * No per-fragment operations are applied.
+ */
+void
+_swrast_write_zoomed_z_span(GLcontext *ctx, GLint imgX, GLint imgY,
+                            GLint width, GLint spanX, GLint spanY,
+                            const GLvoid *z)
+{
+   struct gl_renderbuffer *rb = ctx->DrawBuffer->_DepthBuffer;
+   GLushort zoomedVals16[MAX_WIDTH];
+   GLuint zoomedVals32[MAX_WIDTH];
+   GLint x0, x1, y0, y1, y;
+   GLint i, zoomedWidth;
+
+   if (!compute_zoomed_bounds(ctx, imgX, imgY, spanX, spanY, width,
+                              &x0, &x1, &y0, &y1)) {
+      return;  /* totally clipped */
    }
 
-   ASSERT( m <= MAX_WIDTH );
+   zoomedWidth = x1 - x0;
+   ASSERT(zoomedWidth > 0);
+   ASSERT(zoomedWidth <= MAX_WIDTH);
 
    /* zoom the span horizontally */
-   if (ctx->Pixel.ZoomX==-1.0F) {
-      /* n==m */
-      for (j=0;j<m;j++) {
-         i = n - (j+skipcol) - 1;
-         zstencil[j] = stencil[i];
+   if (rb->DataType == GL_UNSIGNED_SHORT) {
+      for (i = 0; i < zoomedWidth; i++) {
+         GLint j = unzoom_x(ctx->Pixel.ZoomX, imgX, x0 + i) - spanX;
+         ASSERT(j >= 0);
+         ASSERT(j < width);
+         zoomedVals16[i] = ((GLushort *) z)[j];
       }
+      z = zoomedVals16;
    }
    else {
-      GLfloat xscale = 1.0F / ctx->Pixel.ZoomX;
-      for (j=0;j<m;j++) {
-         i = (GLint) ((j+skipcol) * xscale);
-         if (i<0)  i = n + i - 1;
-         zstencil[j] = stencil[i];
+      ASSERT(rb->DataType == GL_UNSIGNED_INT);
+      for (i = 0; i < zoomedWidth; i++) {
+         GLint j = unzoom_x(ctx->Pixel.ZoomX, imgX, x0 + i) - spanX;
+         ASSERT(j >= 0);
+         ASSERT(j < width);
+         zoomedVals32[i] = ((GLuint *) z)[j];
       }
+      z = zoomedVals32;
    }
 
-   /* write the span */
-   for (r=r0; r<r1; r++) {
-      _mesa_write_stencil_span( ctx, m, x+skipcol, r, zstencil );
+   /* write the zoomed spans */
+   for (y = y0; y < y1; y++) {
+      rb->PutRow(ctx, rb, zoomedWidth, x0, y, z, NULL);
    }
 }