gallium: implement clamping controls (ARB_color_buffer_float)

BTW this changes the gallium interface.
Some rather cosmetic changes by Marek.

Squashed commit of the following:

commit 513b37d484f0318311e84bb86ed4c93cdff71f13
Author: Luca Barbieri <luca@luca-barbieri.com>
Date:   Thu Aug 26 18:17:54 2010 +0200

    mesa/st: respect fragment clamping in st_DrawPixels

commit 546a31e42cad459d7a7a10ebf77fc5ffcf89e9b8
Author: Luca Barbieri <luca@luca-barbieri.com>
Date:   Thu Aug 26 18:17:28 2010 +0200

    mesa/st: support fragment and vertex color clamping

commit c406514a1fbee6891da4cf9ac3eebe4e4407ec13
Author: Luca Barbieri <luca@luca-barbieri.com>
Date:   Tue Aug 24 21:56:37 2010 +0200

    mesa/st: expose ARB_color_buffer_float if unclamping is supported

commit d0c5ea11b6f75f3da2f4ca989115f150ebc7cf8d
Author: Luca Barbieri <luca@luca-barbieri.com>
Date:   Thu Aug 26 17:53:41 2010 +0200

    mesa/st: use unclamped colors

    This assumes that Gallium is to be interpreted as given drivers the
    responsibility to clamp these colors if necessary.

commit aef5c3c6be6edd076e955e37c80905bc447f8a82
Author: Luca Barbieri <luca@luca-barbieri.com>
Date:   Thu Aug 26 18:12:34 2010 +0200

    mesa, mesa/st: handle read color clamping properly

    We set IMAGE_CLAMP_BIT in the caller based on _ClampReadColor, where
    the operation mandates it. (see the removed XXX comment. -Marek)

    TODO: did I get the set of operations mandating it right?

commit 76bdfcfe3ff4145a1818e6cb6e227b730a5f12d8
Author: Luca Barbieri <luca@luca-barbieri.com>
Date:   Thu Aug 26 18:18:25 2010 +0200

    gallium: add color clamping to the interface

src/gallium/docs/source/cso/rasterizer.rst

@@ -7,6 +7,30 @@ The rasterizer state controls the rendering of points, lines and triangles.
 Attributes include polygon culling state, line width, line stipple,
 multisample state, scissoring and flat/smooth shading.
 
+Linkage
+
+clamp_vertex_color
+^^^^^^^^^^^^^^^^^^
+
+If set, TGSI_SEMANTIC_COLOR registers are clamped to the [0, 1] range after
+the execution of the vertex shader, before being passed to the geometry
+shader or fragment shader.
+
+OpenGL: glClampColor(GL_CLAMP_VERTEX_COLOR) in GL 3.0 or GL_ARB_color_buffer_float
+
+D3D11: seems always disabled
+
+clamp_fragment_color
+^^^^^^^^^^^^^^^^^^^^
+
+Controls whether TGSI_SEMANTIC_COLOR outputs of the fragment shader
+are clamped to [0, 1].
+
+OpenGL: glClampColor(GL_CLAMP_FRAGMENT_COLOR) in GL 3.0 or ARB_color_buffer_float
+
+D3D11: seems always disabled
+
+
 Shading
 -------
 

src/gallium/include/pipe/p_defines.h

@@ -463,6 +463,8 @@ enum pipe_cap {
    PIPE_CAP_SHADER_STENCIL_EXPORT,
    PIPE_CAP_TGSI_INSTANCEID,
    PIPE_CAP_VERTEX_ELEMENT_INSTANCE_DIVISOR,
+   PIPE_CAP_VERTEX_COLOR_CLAMP_CONTROL,
+   PIPE_CAP_FRAGMENT_COLOR_CLAMP_CONTROL
 };
 
 /* Shader caps not specific to any single stage */

src/gallium/include/pipe/p_state.h

@@ -81,6 +81,8 @@ struct pipe_rasterizer_state
 {
    unsigned flatshade:1;
    unsigned light_twoside:1;
+   unsigned clamp_vertex_color:1;
+   unsigned clamp_fragment_color:1;
    unsigned front_ccw:1;
    unsigned cull_face:2;      /**< PIPE_FACE_x */
    unsigned fill_front:2;     /**< PIPE_POLYGON_MODE_x */

src/mesa/state_tracker/st_atom_blend.c

@@ -286,7 +286,7 @@ update_blend( struct st_context *st )
 
    {
       struct pipe_blend_color bc;
-      COPY_4FV(bc.color, st->ctx->Color.BlendColor);
+      COPY_4FV(bc.color, st->ctx->Color.BlendColorUnclamped);
       cso_set_blend_color(st->cso_context, &bc);
    }
 }

src/mesa/state_tracker/st_atom_depth.c

@@ -142,7 +142,7 @@ update_depth_stencil_alpha(struct st_context *st)
    if (ctx->Color.AlphaEnabled) {
       dsa->alpha.enabled = 1;
       dsa->alpha.func = st_compare_func_to_pipe(ctx->Color.AlphaFunc);
-      dsa->alpha.ref_value = ctx->Color.AlphaRef;
+      dsa->alpha.ref_value = ctx->Color.AlphaRefUnclamped;
    }
 
    cso_set_depth_stencil_alpha(st->cso_context, dsa);

src/mesa/state_tracker/st_atom_rasterizer.c

@@ -112,6 +112,8 @@ static void update_raster_state( struct st_context *st )
       raster->light_twoside = 1;
    }
 
+   raster->clamp_vertex_color = ctx->Light._ClampVertexColor;
+
    /* _NEW_POLYGON
     */
    if (ctx->Polygon.CullFlag) {
@@ -252,6 +254,9 @@ static void update_raster_state( struct st_context *st )
    if (ctx->Scissor.Enabled)
       raster->scissor = 1;
 
+   /* _NEW_FRAG_CLAMP */
+   raster->clamp_fragment_color = ctx->Color._ClampFragmentColor;
+
    raster->gl_rasterization_rules = 1;
 
    cso_set_rasterizer(st->cso_context, raster);
@@ -267,7 +272,8 @@ const struct st_tracked_state st_update_rasterizer = {
        _NEW_POINT |
        _NEW_POLYGON |
        _NEW_PROGRAM |
-       _NEW_SCISSOR),      /* mesa state dependencies*/
+       _NEW_SCISSOR |
+       _NEW_FRAG_CLAMP),      /* mesa state dependencies*/
       ST_NEW_VERTEX_PROGRAM,  /* state tracker dependencies */
    },
    update_raster_state     /* update function */

src/mesa/state_tracker/st_cb_clear.c

@@ -323,7 +323,7 @@ clear_with_quad(struct gl_context *ctx,
    set_vertex_shader(st);
 
    if (ctx->DrawBuffer->_ColorDrawBuffers[0]) {
-      st_translate_color(ctx->Color.ClearColor,
+      st_translate_color(ctx->Color.ClearColorUnclamped,
                          ctx->DrawBuffer->_ColorDrawBuffers[0]->_BaseFormat,
                          clearColor);
    }
@@ -585,7 +585,7 @@ st_Clear(struct gl_context *ctx, GLbitfield mask)
                             clearColor);
       }
 
-      st->pipe->clear(st->pipe, clear_buffers, ctx->Color.ClearColor,
+      st->pipe->clear(st->pipe, clear_buffers, ctx->Color.ClearColorUnclamped,
                       ctx->Depth.Clear, ctx->Stencil.Clear);
    }
    if (mask & BUFFER_BIT_ACCUM)

src/mesa/state_tracker/st_cb_drawpixels.c

@@ -582,6 +582,7 @@ draw_textured_quad(struct gl_context *ctx, GLint x, GLint y, GLfloat z,
    {
       struct pipe_rasterizer_state rasterizer;
       memset(&rasterizer, 0, sizeof(rasterizer));
+      rasterizer.clamp_fragment_color = ctx->Color._ClampFragmentColor;
       rasterizer.gl_rasterization_rules = 1;
       rasterizer.scissor = ctx->Scissor.Enabled;
       cso_set_rasterizer(cso, &rasterizer);

src/mesa/state_tracker/st_cb_readpixels.c

@@ -331,7 +331,7 @@ st_readpixels(struct gl_context *ctx, GLint x, GLint y, GLsizei width, GLsizei h
    struct st_context *st = st_context(ctx);
    struct pipe_context *pipe = st->pipe;
    GLfloat (*temp)[4];
-   const GLbitfield transferOps = ctx->_ImageTransferState;
+   GLbitfield transferOps = ctx->_ImageTransferState;
    GLsizei i, j;
    GLint yStep, dfStride;
    GLfloat *df;
@@ -391,7 +391,10 @@ st_readpixels(struct gl_context *ctx, GLint x, GLint y, GLsizei width, GLsizei h
       return;
    }
 
-   if (format == GL_RGBA && type == GL_FLOAT) {
+   if(ctx->Color._ClampReadColor)
+      transferOps |= IMAGE_CLAMP_BIT;
+
+   if (format == GL_RGBA && type == GL_FLOAT && !transferOps) {
       /* write tile(row) directly into user's buffer */
       df = (GLfloat *) _mesa_image_address2d(&clippedPacking, dest, width,
                                              height, format, type, 0, 0);

src/mesa/state_tracker/st_extensions.c

@@ -508,6 +508,13 @@ void st_init_extensions(struct st_context *st)
       ctx->Extensions.ARB_depth_clamp = GL_TRUE;
    }
 
+   /* this extension does not actually require support of floating point
+    * render targets, just clamping controls
+    */
+   if(screen->get_param(screen, PIPE_CAP_FRAGMENT_COLOR_CLAMP_CONTROL) &&
+      screen->get_param(screen, PIPE_CAP_VERTEX_COLOR_CLAMP_CONTROL))
+      ctx->Extensions.ARB_color_buffer_float = GL_TRUE;
+
    if (screen->get_param(screen, PIPE_CAP_SHADER_STENCIL_EXPORT)) {
       ctx->Extensions.ARB_shader_stencil_export = GL_TRUE;
    }