3 files changed, 68 insertions, 5 deletions

diff --git a/src/mesa/main/context.c b/src/mesa/main/context.c
index 958ea10a422..fe370fa369b 100644
--- a/src/mesa/main/context.c
+++ b/src/mesa/main/context.c
@@ -526,6 +526,16 @@ 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 a6445b18368..ac2957ac8d5 100644
--- a/src/mesa/main/mtypes.h
+++ b/src/mesa/main/mtypes.h
@@ -2549,6 +2549,17 @@ 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
@@ -2582,6 +2593,9 @@ 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 2ffd8be0eb4..e831175235e 100644
--- a/src/mesa/main/shaderapi.c
+++ b/src/mesa/main/shaderapi.c
@@ -1628,12 +1628,51 @@ 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);
-   (void) shadertype;
-   (void) precisiontype;
-   (void) range;
-   (void) precision;
-   _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;
 }