swrast: Adjust colors based on ReadBuffer visual, not context visual

In the presence of FBOs, the visual of the context may not match the,
possibly fake, visual of the current ReadBuffer.  Note that the caller
of adjust_colors correctly uses the visual of the ReadBuffer.

Signed-off-by: Ian Romanick <ian.d.romanick@intel.com>

diff --git a/src/mesa/swrast/s_readpix.c b/src/mesa/swrast/s_readpix.c
index ecabac6..368311e 100644 (file)
--- a/src/mesa/swrast/s_readpix.c
+++ b/src/mesa/swrast/s_readpix.c
@@ -253,21 +253,21 @@ fast_read_rgba_pixels( GLcontext *ctx,
 /**
  * When we're using a low-precision color buffer (like 16-bit 5/6/5)
  * we have to adjust our color values a bit to pass conformance.
- * The problem is when a 5 or 6-bit color value is convert to an 8-bit
+ * The problem is when a 5 or 6-bit color value is converted to an 8-bit
  * value and then a floating point value, the floating point values don't
  * increment uniformly as the 5 or 6-bit value is incremented.
  *
  * This function adjusts floating point values to compensate.
  */
 static void
-adjust_colors(GLcontext *ctx, GLuint n, GLfloat rgba[][4])
+adjust_colors(const struct gl_framebuffer *fb, GLuint n, GLfloat rgba[][4])
 {
-   const GLuint rShift = 8 - ctx->Visual.redBits;
-   const GLuint gShift = 8 - ctx->Visual.greenBits;
-   const GLuint bShift = 8 - ctx->Visual.blueBits;
-   const GLfloat rScale = 1.0F / (GLfloat) ((1 << ctx->Visual.redBits  ) - 1);
-   const GLfloat gScale = 1.0F / (GLfloat) ((1 << ctx->Visual.greenBits) - 1);
-   const GLfloat bScale = 1.0F / (GLfloat) ((1 << ctx->Visual.blueBits ) - 1);
+   const GLuint rShift = 8 - fb->Visual.redBits;
+   const GLuint gShift = 8 - fb->Visual.greenBits;
+   const GLuint bShift = 8 - fb->Visual.blueBits;
+   const GLfloat rScale = 1.0F / (GLfloat) ((1 << fb->Visual.redBits  ) - 1);
+   const GLfloat gScale = 1.0F / (GLfloat) ((1 << fb->Visual.greenBits) - 1);
+   const GLfloat bScale = 1.0F / (GLfloat) ((1 << fb->Visual.blueBits ) - 1);
    GLuint i;
    for (i = 0; i < n; i++) {
       GLint r, g, b;
@@ -390,7 +390,7 @@ read_rgba_pixels( GLcontext *ctx,
          if (fb->Visual.redBits < 8 ||
              fb->Visual.greenBits < 8 ||
              fb->Visual.blueBits < 8) {
-            adjust_colors(ctx, width, rgba);
+            adjust_colors(fb, width, rgba);
          }
 
          /* pack the row of RGBA pixels into user's buffer */