Mesa (7.9): mesa: implement glGetShaderPrecisionFormat()

[Ian Romanick]

Module: Mesa
Branch: 7.9
Commit: 9c8d677a16f08f9ea9bc065d8acc03ba30d51977
URL:    http://cgit.freedesktop.org/mesa/mesa/commit/?id=9c8d677a16f08f9ea9bc065d8acc03ba30d51977

Author: Brian Paul <brianp at vmware.com>
Date:   Wed Jan 19 07:41:20 2011 -0700

mesa: implement glGetShaderPrecisionFormat()

Drivers should override the default range/precision info as needed.
No drivers do this yet.

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

(cherry picked from commit 3ee60a3558a3546b3c3a0a9732d384afcf02994a)

---

 src/mesa/main/context.c   |   10 ++++++++++
 src/mesa/main/mtypes.h    |   14 ++++++++++++++
 src/mesa/main/shaderapi.c |   45 ++++++++++++++++++++++++++++++++++++++++++++-
 3 files changed, 68 insertions(+), 1 deletions(-)

diff --git a/src/mesa/main/context.c b/src/mesa/main/context.c
index 4cf5e7d..f9ce8da 100644
--- a/src/mesa/main/context.c
+++ b/src/mesa/main/context.c
@@ -522,6 +522,16 @@ init_program_limits(GLenum type, struct gl_program_constants *prog)
    prog->MaxNativeTemps = 0;
    prog->MaxNativeAddressRegs = 0;
    prog->MaxNativeParameters = 0;
+
+   /* Set GLSL datatype range/precision info assuming IEEE float values.
+    * Drivers should override these defaults as needed.
+    */
+   prog->MediumFloat.RangeMin = 127;
+   prog->MediumFloat.RangeMax = 127;
+   prog->MediumFloat.Precision = 23;
+   prog->LowFloat = prog->HighFloat = prog->MediumFloat;
+   /* assume ints are stored as floats for now */
+   prog->LowInt = prog->MediumInt = prog->HighInt = prog->MediumFloat;
 }
 
 
diff --git a/src/mesa/main/mtypes.h b/src/mesa/main/mtypes.h
index b559b59..ece5b90 100644
--- a/src/mesa/main/mtypes.h
+++ b/src/mesa/main/mtypes.h
@@ -2515,6 +2515,17 @@ struct gl_framebuffer
 
 
 /**
+ * Precision info for shader datatypes.  See glGetShaderPrecisionFormat().
+ */
+struct gl_precision
+{
+   GLushort RangeMin;   /**< min value exponent */
+   GLushort RangeMax;   /**< max value exponent */
+   GLushort Precision;  /**< number of mantissa bits */
+};
+
+
+/**
  * Limits for vertex and fragment programs/shaders.
  */
 struct gl_program_constants
@@ -2548,6 +2559,9 @@ struct gl_program_constants
    GLuint MaxGeometryUniformComponents;
    GLuint MaxGeometryOutputVertices;
    GLuint MaxGeometryTotalOutputComponents;
+   /* ES 2.0 and GL_ARB_ES2_compatibility */
+   struct gl_precision LowFloat, MediumFloat, HighFloat;
+   struct gl_precision LowInt, MediumInt, HighInt;
 };
 
 
diff --git a/src/mesa/main/shaderapi.c b/src/mesa/main/shaderapi.c
index e419199..b1eac97 100644
--- a/src/mesa/main/shaderapi.c
+++ b/src/mesa/main/shaderapi.c
@@ -1522,8 +1522,51 @@ void GLAPIENTRY
 _mesa_GetShaderPrecisionFormat(GLenum shadertype, GLenum precisiontype,
                                GLint* range, GLint* precision)
 {
+   const struct gl_program_constants *limits;
+   const struct gl_precision *p;
    GET_CURRENT_CONTEXT(ctx);
-   _mesa_error(ctx, GL_INVALID_OPERATION, __FUNCTION__);
+
+   switch (shadertype) {
+   case GL_VERTEX_SHADER:
+      limits = &ctx->Const.VertexProgram;
+      break;
+   case GL_FRAGMENT_SHADER:
+      limits = &ctx->Const.FragmentProgram;
+      break;
+   default:
+      _mesa_error(ctx, GL_INVALID_ENUM,
+                  "glGetShaderPrecisionFormat(shadertype)");
+      return;
+   }
+
+   switch (precisiontype) {
+   case GL_LOW_FLOAT:
+      p = &limits->LowFloat;
+      break;
+   case GL_MEDIUM_FLOAT:
+      p = &limits->MediumFloat;
+      break;
+   case GL_HIGH_FLOAT:
+      p = &limits->HighFloat;
+      break;
+   case GL_LOW_INT:
+      p = &limits->LowInt;
+      break;
+   case GL_MEDIUM_INT:
+      p = &limits->MediumInt;
+      break;
+   case GL_HIGH_INT:
+      p = &limits->HighInt;
+      break;
+   default:
+      _mesa_error(ctx, GL_INVALID_ENUM,
+                  "glGetShaderPrecisionFormat(precisiontype)");
+      return;
+   }
+
+   range[0] = p->RangeMin;
+   range[1] = p->RangeMax;
+   precision[0] = p->Precision;
 }