[Mesa-dev] [PATCH 2/2] mesa: check bits per channel for GL_RGBA_SIGNED_COMPONENTS_EXT query

[Brian Paul]

If a channel has zero bits it's not signed.
---
 src/mesa/main/get.c |   28 +++++++++++++++++++++-------
 1 file changed, 21 insertions(+), 7 deletions(-)

diff --git a/src/mesa/main/get.c b/src/mesa/main/get.c
index c45a8d1..bb138c8 100644
--- a/src/mesa/main/get.c
+++ b/src/mesa/main/get.c
@@ -769,13 +769,27 @@ find_custom_value(struct gl_context *ctx, const struct value_desc *d, union valu
          /* Note: we only check the 0th color attachment. */
          const struct gl_renderbuffer *rb =
             ctx->DrawBuffer->_ColorDrawBuffers[0];
-         const GLboolean is_signed =
-            rb ? _mesa_is_format_signed(rb->Format) : GL_FALSE;
-         /* At this time, all color channels have same signedness */
-         v->value_int_4[0] =
-         v->value_int_4[1] =
-         v->value_int_4[2] =
-         v->value_int_4[3] = is_signed;
+         if (rb && _mesa_is_format_signed(rb->Format)) {
+            /* Issue 17 of GL_EXT_packed_float:  If a component (such as
+             * alpha) has zero bits, the component should not be considered
+             * signed and so the bit for the respective component should be
+             * zeroed.
+             */
+            v->value_int_4[0] =
+               _mesa_get_format_bits(rb->Format, GL_RED_BITS) > 0;
+            v->value_int_4[1] =
+               _mesa_get_format_bits(rb->Format, GL_GREEN_BITS) > 0;
+            v->value_int_4[2] =
+               _mesa_get_format_bits(rb->Format, GL_BLUE_BITS) > 0;
+            v->value_int_4[3] =
+               _mesa_get_format_bits(rb->Format, GL_ALPHA_BITS) > 0;
+         }
+         else {
+            v->value_int_4[0] =
+            v->value_int_4[1] =
+            v->value_int_4[2] =
+            v->value_int_4[3] = 0;
+         }
       }
       break;
 
-- 
1.7.10.4