The glean exactRGBA test has always failed with Mesa (with sw
rendering at least). The failures come from a sequence of
int->float->int conversions which don't meet the GL spec.
In particular, when glColor4us() or glColor4ui() are used to set the
drawing color, the N-bit integer frame buffer values should match the
upper N bits of the GLushort or GLuint value originally passed in.
Because of int->float->int conversions it's a little tricky to
maintain the N-bit identity requirement.
The attached patch fixes the exactRGBA failures. I haven't seen any
regressions but some additional eyes should take a look.
There are two parts:
1. Convert float->ubyte with floor(x*255.999) instead of iround(x*255.0)
2. Convert uint->float with floor((u >> 16) / 65535.0) instead of
floor(u / 4294967295.0) This effectively converts the GLuint to a
GLushort. This isn't ideal but I think it's "good enough" until we
find otherwise.
-Brian
diff --git a/src/mesa/main/imports.h b/src/mesa/main/imports.h
index 7b61e22..70fde6b 100644
--- a/src/mesa/main/imports.h
+++ b/src/mesa/main/imports.h
@@ -423,21 +423,21 @@ _mesa_is_pow_two(int x)
else if (__tmp.i >= IEEE_0996) \
UB = (GLubyte) 255; \
else { \
- __tmp.f = __tmp.f * (255.0F/256.0F) + 32768.0F; \
- UB = (GLubyte) __tmp.i; \
+ __tmp.f = __tmp.f * 255.999F + 256.0F; \
+ UB = (GLubyte) ((__tmp.i & 0x7fffff) >> 15); \
} \
} while (0)
#define CLAMPED_FLOAT_TO_UBYTE(UB, F) \
do { \
fi_type __tmp; \
- __tmp.f = (F) * (255.0F/256.0F) + 32768.0F; \
- UB = (GLubyte) __tmp.i; \
+ __tmp.f = (F) * 255.999F + 256.0F; \
+ UB = (GLubyte) ((__tmp.i & 0x7fffff) >> 15);
\
} while (0)
#else
#define UNCLAMPED_FLOAT_TO_UBYTE(ub, f) \
- ub = ((GLubyte) IROUND(CLAMP((f), 0.0F, 1.0F) * 255.0F))
+ ub = ((GLubyte) IFLOOR(CLAMP((f), 0.0F, 1.0F) * 255.999F))
#define CLAMPED_FLOAT_TO_UBYTE(ub, f) \
- ub = ((GLubyte) IROUND((f) * 255.0F))
+ ub = ((GLubyte) IFLOOR((f) * 255.999F))
#endif
diff --git a/src/mesa/main/macros.h b/src/mesa/main/macros.h
index 4ca7957..90013e7 100644
--- a/src/mesa/main/macros.h
+++ b/src/mesa/main/macros.h
@@ -83,7 +83,7 @@ extern GLfloat _mesa_ubyte_to_float_color_tab[256];
/** Convert GLuint in [0,4294967295] to GLfloat in [0.0,1.0] */
-#define UINT_TO_FLOAT(U) ((GLfloat) (U) * (1.0F / 4294967295.0))
+#define UINT_TO_FLOAT(U) ((GLfloat) ((U) >> 16) * (1.0F / 65535.0F))
/** Convert GLfloat in [0.0,1.0] to GLuint in [0,4294967295] */
#define FLOAT_TO_UINT(X) ((GLuint) ((X) * 4294967295.0))
------------------------------------------------------------------------------
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