[Mesa-dev] [PATCH 2/3] mesa: helper for checking renderbuffer sample count

[Chris Forbes]

Pulls the checking of the sample count into a helper function, and
extends the existing logic to include the interactions with both
ARB_texture_multisample and ARB_internalformat_query.

_mesa_check_sample_count() checks a desired sample count against a
a combination of target/internalformat, and returns the error enum
to be produced, if any. Unfortunately the conditions are messy and the
errors vary:

On p205 of the GL3.1 spec:

   "... or if samples is greater than MAX_SAMPLES, then the error
   INVALID_VALUE is generated."

Or with ARB_texture_multisample (or GL3.2):

   "... or if <samples> is greater than the value of MAX_SAMPLES, then
   the error INVALID_VALUE is generated.
   If <internalformat> is a signed or unsigned integer format and
   <samples> is greater than the value of MAX_INTEGER_SAMPLES, then the
   error INVALID_OPERATION is generated.

Or with ARB_internalformat_query (or GL4.2):

   "If <samples> is greater than the maximum number of samples supported
   for <internalformat> then the error INVALID_OPERATION is generated
   (see GetInternalformativ in section 6.X)."

Signed-off-by: Chris Forbes <chrisf at ijw.co.nz>
---
 src/mesa/main/fbobject.c | 43 +++++++++++++++++++++++++++++++++++++++----
 src/mesa/main/fbobject.h |  4 ++++
 2 files changed, 43 insertions(+), 4 deletions(-)

diff --git a/src/mesa/main/fbobject.c b/src/mesa/main/fbobject.c
index c89e728..50339c2 100644
--- a/src/mesa/main/fbobject.c
+++ b/src/mesa/main/fbobject.c
@@ -1449,6 +1449,35 @@ invalidate_rb(GLuint key, void *data, void *userData)
 }
 
 
+GLenum
+_mesa_check_sample_count(struct gl_context *ctx, GLenum target,
+                         GLenum internalFormat, GLsizei samples)
+{
+   /* If ARB_internalformat_query is supported, then treat its highest returned sample
+    * count as the absolute maximum for this format; it is allowed to exceed MAX_SAMPLES.
+    */
+   if (ctx->Extensions.ARB_internalformat_query) {
+      GLint buffer[16];
+      int count = ctx->Driver.QuerySamplesForFormat(ctx, target, internalFormat, buffer);
+      int limit = count ? buffer[0] : -1;
+
+      return (samples > limit) ? GL_INVALID_OPERATION : GL_NO_ERROR;
+   }
+
+   /* If ARB_texture_multisample is supported, we have separate limits for
+    * integer formats.
+    */
+
+   if (ctx->Extensions.ARB_texture_multisample) {
+      if (_mesa_is_enum_format_integer(internalFormat))
+         return samples > ctx->Const.MaxIntegerSamples ? GL_INVALID_OPERATION : GL_NO_ERROR;
+   }
+
+   /* No more specific limit is available, so just use MAX_SAMPLES */
+   return samples > ctx->Const.MaxSamples ? GL_INVALID_VALUE : GL_NO_ERROR;
+}
+
+
 /** sentinal value, see below */
 #define NO_SAMPLES 1000
 
@@ -1509,10 +1538,16 @@ renderbuffer_storage(GLenum target, GLenum internalFormat,
       /* NumSamples == 0 indicates non-multisampling */
       samples = 0;
    }
-   else if (samples > (GLsizei) ctx->Const.MaxSamples) {
-      /* note: driver may choose to use more samples than what's requested */
-      _mesa_error(ctx, GL_INVALID_VALUE, "%s(samples)", func);
-      return;
+
+   {  /* check the sample count;
+       * note: driver may choose to use more samples than what's requested
+       */
+      GLenum sample_count_error = _mesa_check_sample_count(ctx, target,
+            internalFormat, samples);
+      if (sample_count_error != GL_NO_ERROR) {
+         _mesa_error(ctx, sample_count_error, "%s(samples)", func);
+         return;
+      }
    }
 
    rb = ctx->CurrentRenderbuffer;
diff --git a/src/mesa/main/fbobject.h b/src/mesa/main/fbobject.h
index 9207f59..9adee3a 100644
--- a/src/mesa/main/fbobject.h
+++ b/src/mesa/main/fbobject.h
@@ -123,6 +123,10 @@ _mesa_is_legal_color_format(const struct gl_context *ctx, GLenum baseFormat);
 extern GLenum
 _mesa_base_fbo_format(struct gl_context *ctx, GLenum internalFormat);
 
+extern GLenum
+_mesa_check_sample_count(struct gl_context *ctx, GLenum target,
+                   GLenum internalFormat, GLsizei samples);
+
 extern GLboolean GLAPIENTRY
 _mesa_IsRenderbuffer(GLuint renderbuffer);
 
-- 
1.8.1.3