gallium: add caps for MIN/MAX texel offsets.

As per Brian's suggestion, add caps for drivers that support texture
offsets to advertise a min/max via TGSI, also use it in the state tracker.

Signed-off-by: Dave Airlie <airlied@redhat.com>
Reviewed-by: Brian Paul <brianp@vmware.com>

src/gallium/drivers/r600/r600_pipe.c

@@ -407,6 +407,12 @@ static int r600_get_param(struct pipe_screen* pscreen, enum pipe_cap param)
 	case PIPE_CAP_TIMER_QUERY:
 		return r600_get_clock_crystal_freq(rscreen->radeon) != 0;
 
+	case PIPE_CAP_MIN_TEXEL_OFFSET:
+		return -8;
+
+	case PIPE_CAP_MAX_TEXEL_OFFSET:
+		return 7;
+
 	default:
 		R600_ERR("r600: unknown param %d\n", param);
 		return 0;

src/gallium/drivers/softpipe/sp_screen.c

@@ -131,6 +131,10 @@ softpipe_get_param(struct pipe_screen *screen, enum pipe_cap param)
       return 1;
    case PIPE_CAP_ARRAY_TEXTURES:
       return 1;
+   case PIPE_CAP_MIN_TEXEL_OFFSET:
+      return -8;
+   case PIPE_CAP_MAX_TEXEL_OFFSET:
+      return 7;
    default:
       return 0;
    }

src/gallium/include/pipe/p_defines.h

@@ -471,7 +471,9 @@ enum pipe_cap {
    PIPE_CAP_MIXED_COLORBUFFER_FORMATS = 46,
    PIPE_CAP_SEAMLESS_CUBE_MAP = 47,
    PIPE_CAP_SEAMLESS_CUBE_MAP_PER_TEXTURE = 48,
-   PIPE_CAP_SCALED_RESOLVE = 49
+   PIPE_CAP_SCALED_RESOLVE = 49,
+   PIPE_CAP_MIN_TEXEL_OFFSET = 50,
+   PIPE_CAP_MAX_TEXEL_OFFSET = 51,
 };
 
 /* Shader caps not specific to any single stage */

src/mesa/state_tracker/st_extensions.c

@@ -203,6 +203,9 @@ void st_init_limits(struct st_context *st)
 
    /* XXX we'll need a better query here someday */
    if (screen->get_param(screen, PIPE_CAP_GLSL)) {
+      c->MinProgramTexelOffset = screen->get_param(screen, PIPE_CAP_MIN_TEXEL_OFFSET);
+      c->MaxProgramTexelOffset = screen->get_param(screen, PIPE_CAP_MAX_TEXEL_OFFSET);
+
       c->GLSLVersion = 120;
    }
 }