tgsi: add properties for fragment coord conventions (v3)

Changes in v3:
- Documented the new properties
- Added comments for property values
- Rebased to current master

Changes in v2:
- Caps are added in a separate, subsequent patch

This adds two TGSI fragment program properties that indicate the
fragment coord conventions.

The properties behave as described in the extension spec for
GL_ARB_fragment_coord_conventions, but the default origin in
upper left instead of lower left as in OpenGL.

The syntax is:
PROPERTY FS_COORD_ORIGIN [UPPER_LEFT|LOWER_LEFT]
PROPERTY FS_COORD_PIXEL_CENTER [HALF_INTEGER|INTEGER]

The names have been chosen for consistency with the GS properties
and the OpenGL extension spec.

The defaults are of course the previously assumed conventions:
UPPER_LEFT and HALF_INTEGER.

src/gallium/auxiliary/tgsi/tgsi_dump.c

@@ -159,7 +159,9 @@ static const char *property_names[] =
 {
    "GS_INPUT_PRIMITIVE",
    "GS_OUTPUT_PRIMITIVE",
-   "GS_MAX_OUTPUT_VERTICES"
+   "GS_MAX_OUTPUT_VERTICES",
+   "FS_COORD_ORIGIN",
+   "FS_COORD_PIXEL_CENTER"
 };
 
 static const char *primitive_names[] =
@@ -176,6 +178,18 @@ static const char *primitive_names[] =
    "POLYGON"
 };
 
+static const char *fs_coord_origin_names[] =
+{
+   "UPPER_LEFT",
+   "LOWER_LEFT"
+};
+
+static const char *fs_coord_pixel_center_names[] =
+{
+   "HALF_INTEGER",
+   "INTEGER"
+};
+
 
 static void
 _dump_register_dst(
@@ -366,6 +380,12 @@ iter_property(
       case TGSI_PROPERTY_GS_OUTPUT_PRIM:
          ENM(prop->u[i].Data, primitive_names);
          break;
+      case TGSI_PROPERTY_FS_COORD_ORIGIN:
+         ENM(prop->u[i].Data, fs_coord_origin_names);
+         break;
+      case TGSI_PROPERTY_FS_COORD_PIXEL_CENTER:
+         ENM(prop->u[i].Data, fs_coord_pixel_center_names);
+         break;
       default:
          SID( prop->u[i].Data );
          break;

src/gallium/auxiliary/tgsi/tgsi_text.c

@@ -1129,7 +1129,9 @@ static const char *property_names[] =
 {
    "GS_INPUT_PRIMITIVE",
    "GS_OUTPUT_PRIMITIVE",
-   "GS_MAX_OUTPUT_VERTICES"
+   "GS_MAX_OUTPUT_VERTICES",
+   "FS_COORD_ORIGIN",
+   "FS_COORD_PIXEL_CENTER"
 };
 
 static const char *primitive_names[] =
@@ -1146,6 +1148,19 @@ static const char *primitive_names[] =
    "POLYGON"
 };
 
+static const char *fs_coord_origin_names[] =
+{
+   "UPPER_LEFT",
+   "LOWER_LEFT"
+};
+
+static const char *fs_coord_pixel_center_names[] =
+{
+   "HALF_INTEGER",
+   "INTEGER"
+};
+
+
 static boolean
 parse_primitive( const char **pcur, uint *primitive )
 {
@@ -1163,6 +1178,40 @@ parse_primitive( const char **pcur, uint *primitive )
    return FALSE;
 }
 
+static boolean
+parse_fs_coord_origin( const char **pcur, uint *fs_coord_origin )
+{
+   uint i;
+
+   for (i = 0; i < sizeof(fs_coord_origin_names) / sizeof(fs_coord_origin_names[0]); i++) {
+      const char *cur = *pcur;
+
+      if (str_match_no_case( &cur, fs_coord_origin_names[i])) {
+         *fs_coord_origin = i;
+         *pcur = cur;
+         return TRUE;
+      }
+   }
+   return FALSE;
+}
+
+static boolean
+parse_fs_coord_pixel_center( const char **pcur, uint *fs_coord_pixel_center )
+{
+   uint i;
+
+   for (i = 0; i < sizeof(fs_coord_pixel_center_names) / sizeof(fs_coord_pixel_center_names[0]); i++) {
+      const char *cur = *pcur;
+
+      if (str_match_no_case( &cur, fs_coord_pixel_center_names[i])) {
+         *fs_coord_pixel_center = i;
+         *pcur = cur;
+         return TRUE;
+      }
+   }
+   return FALSE;
+}
+
 
 static boolean parse_property( struct translate_ctx *ctx )
 {
@@ -1204,6 +1253,18 @@ static boolean parse_property( struct translate_ctx *ctx )
          ctx->implied_array_size = u_vertices_per_prim(values[0]);
       }
       break;
+   case TGSI_PROPERTY_FS_COORD_ORIGIN:
+      if (!parse_fs_coord_origin(&ctx->cur, &values[0] )) {
+         report_error( ctx, "Unknown coord origin as property: must be UPPER_LEFT or LOWER_LEFT!" );
+         return FALSE;
+      }
+      break;
+   case TGSI_PROPERTY_FS_COORD_PIXEL_CENTER:
+      if (!parse_fs_coord_pixel_center(&ctx->cur, &values[0] )) {
+         report_error( ctx, "Unknown coord pixel center as property: must be HALF_INTEGER or INTEGER!" );
+         return FALSE;
+      }
+      break;
    default:
       if (!parse_uint(&ctx->cur, &values[0] )) {
          report_error( ctx, "Expected unsigned integer as property!" );

src/gallium/auxiliary/tgsi/tgsi_ureg.c

@@ -142,6 +142,8 @@ struct ureg_program
    unsigned property_gs_input_prim;
    unsigned property_gs_output_prim;
    unsigned property_gs_max_vertices;
+   unsigned char property_fs_coord_origin; /* = TGSI_FS_COORD_ORIGIN_* */
+   unsigned char property_fs_coord_pixel_center; /* = TGSI_FS_COORD_PIXEL_CENTER_* */
 
    unsigned nr_addrs;
    unsigned nr_preds;
@@ -265,6 +267,20 @@ ureg_property_gs_max_vertices(struct ureg_program *ureg,
    ureg->property_gs_max_vertices = max_vertices;
 }
 
+void
+ureg_property_fs_coord_origin(struct ureg_program *ureg,
+                            unsigned fs_coord_origin)
+{
+   ureg->property_fs_coord_origin = fs_coord_origin;
+}
+
+void
+ureg_property_fs_coord_pixel_center(struct ureg_program *ureg,
+                            unsigned fs_coord_pixel_center)
+{
+   ureg->property_fs_coord_pixel_center = fs_coord_pixel_center;
+}
+
 
 
 struct ureg_src 
@@ -1202,6 +1218,22 @@ static void emit_decls( struct ureg_program *ureg )
                     ureg->property_gs_max_vertices);
    }
 
+   if (ureg->property_fs_coord_origin) {
+      assert(ureg->processor == TGSI_PROCESSOR_FRAGMENT);
+
+      emit_property(ureg,
+                    TGSI_PROPERTY_FS_COORD_ORIGIN,
+                    ureg->property_fs_coord_origin);
+   }
+
+   if (ureg->property_fs_coord_pixel_center) {
+      assert(ureg->processor == TGSI_PROCESSOR_FRAGMENT);
+
+      emit_property(ureg,
+                    TGSI_PROPERTY_FS_COORD_PIXEL_CENTER,
+                    ureg->property_fs_coord_pixel_center);
+   }
+
    if (ureg->processor == TGSI_PROCESSOR_VERTEX) {
       for (i = 0; i < UREG_MAX_INPUT; i++) {
          if (ureg->vs_inputs[i/32] & (1 << (i%32))) {

src/gallium/auxiliary/tgsi/tgsi_ureg.h

@@ -136,6 +136,13 @@ void
 ureg_property_gs_max_vertices(struct ureg_program *ureg,
                               unsigned max_vertices);
 
+void
+ureg_property_fs_coord_origin(struct ureg_program *ureg,
+                            unsigned fs_coord_origin);
+
+void
+ureg_property_fs_coord_pixel_center(struct ureg_program *ureg,
+                            unsigned fs_coord_pixel_center);
 
 /***********************************************************************
  * Build shader declarations:

src/gallium/docs/source/tgsi.rst

@@ -1319,9 +1319,8 @@ are the Cartesian coordinates, and ``w`` is the homogenous coordinate and used
 for the perspective divide, if enabled.
 
 As a vertex shader output, position should be scaled to the viewport. When
-used in fragment shaders, position will ---
+used in fragment shaders, position will be in window coordinates. The convention
-
+used depends on the FS_COORD_ORIGIN and FS_COORD_PIXEL_CENTER properties.
-XXX --- wait a minute. Should position be in [0,1] for x and y?
 
 XXX additionally, is there a way to configure the perspective divide? it's
 accelerated on most chipsets AFAIK...
@@ -1400,3 +1399,45 @@ TGSI_SEMANTIC_EDGEFLAG
 """"""""""""""""""""""
 
 XXX no clue
+
+
+Properties
+^^^^^^^^^^^^^^^^^^^^^^^^
+
+
+  Properties are general directives that apply to the whole TGSI program.
+
+FS_COORD_ORIGIN
+"""""""""""""""
+
+Specifies the fragment shader TGSI_SEMANTIC_POSITION coordinate origin.
+The default value is UPPER_LEFT.
+
+If UPPER_LEFT, the position will be (0,0) at the upper left corner and
+increase downward and rightward.
+If LOWER_LEFT, the position will be (0,0) at the lower left corner and
+increase upward and rightward.
+
+OpenGL defaults to LOWER_LEFT, and is configurable with the
+GL_ARB_fragment_coord_conventions extension.
+
+DirectX 9/10 use UPPER_LEFT.
+
+FS_COORD_PIXEL_CENTER
+"""""""""""""""""""""
+
+Specifies the fragment shader TGSI_SEMANTIC_POSITION pixel center convention.
+The default value is HALF_INTEGER.
+
+If HALF_INTEGER, the fractionary part of the position will be 0.5
+If INTEGER, the fractionary part of the position will be 0.0
+
+Note that this does not affect the set of fragments generated by
+rasterization, which is instead controlled by gl_rasterization_rules in the
+rasterizer.
+
+OpenGL defaults to HALF_INTEGER, and is configurable with the
+GL_ARB_fragment_coord_conventions extension.
+
+DirectX 9 uses INTEGER.
+DirectX 10 uses HALF_INTEGER.

src/gallium/include/pipe/p_shader_tokens.h

@@ -170,7 +170,9 @@ union tgsi_immediate_data
 #define TGSI_PROPERTY_GS_INPUT_PRIM          0
 #define TGSI_PROPERTY_GS_OUTPUT_PRIM         1
 #define TGSI_PROPERTY_GS_MAX_VERTICES        2
-#define TGSI_PROPERTY_COUNT                  3
+#define TGSI_PROPERTY_FS_COORD_ORIGIN        3
+#define TGSI_PROPERTY_FS_COORD_PIXEL_CENTER  4
+#define TGSI_PROPERTY_COUNT                  5
 
 struct tgsi_property {
    unsigned Type         : 4;  /**< TGSI_TOKEN_TYPE_PROPERTY */
@@ -179,6 +181,12 @@ struct tgsi_property {
    unsigned Padding      : 12;
 };
 
+#define TGSI_FS_COORD_ORIGIN_UPPER_LEFT 0
+#define TGSI_FS_COORD_ORIGIN_LOWER_LEFT 1
+
+#define TGSI_FS_COORD_PIXEL_CENTER_HALF_INTEGER 0
+#define TGSI_FS_COORD_PIXEL_CENTER_INTEGER 1
+
 struct tgsi_property_data {
    unsigned Data;
 };