main: Use _mesa_geometric_samples to calculate the value of GL_SAMPLES

Otherwise it won't take into account the default samples for
framebuffers with no attachments.

Reviewed-by: Ilia Mirkin <imirkin@alum.mit.edu>

src/mesa/main/get.c

@@ -1085,6 +1085,10 @@ find_custom_value(struct gl_context *ctx, const struct value_desc *d, union valu
    case GL_DISPATCH_INDIRECT_BUFFER_BINDING:
       v->value_int = ctx->DispatchIndirectBuffer->Name;
       break;
+   /* GL_ARB_multisample */
+   case GL_SAMPLES:
+      v->value_int = _mesa_geometric_samples(ctx->DrawBuffer);
+      break;
    }
 }
 

src/mesa/main/get_hash_params.py

@@ -81,7 +81,7 @@ descriptor=[
   [ "SAMPLE_COVERAGE_VALUE_ARB", "CONTEXT_FLOAT(Multisample.SampleCoverageValue), NO_EXTRA" ],
   [ "SAMPLE_COVERAGE_INVERT_ARB", "CONTEXT_BOOL(Multisample.SampleCoverageInvert), NO_EXTRA" ],
   [ "SAMPLE_BUFFERS_ARB", "BUFFER_INT(Visual.sampleBuffers), extra_new_buffers" ],
-  [ "SAMPLES_ARB", "BUFFER_INT(Visual.samples), extra_new_buffers" ],
+  [ "SAMPLES_ARB", "LOC_CUSTOM, TYPE_INT, 0, extra_new_buffers" ],
 
 # GL_ARB_sample_shading
   [ "SAMPLE_SHADING_ARB", "CONTEXT_BOOL(Multisample.SampleShading), extra_gl40_ARB_sample_shading" ],