+/**
+ * Emit fragment position/ooordinate code.
+ */
+static void
+emit_wpos(struct st_context *st,
+ struct st_translate *t,
+ const struct gl_program *program,
+ struct ureg_program *ureg)
+{
+ const struct gl_fragment_program *fp =
+ (const struct gl_fragment_program *) program;
+ struct pipe_screen *pscreen = st->pipe->screen;
+ GLfloat adjX = 0.0f;
+ GLfloat adjY[2] = { 0.0f, 0.0f };
+ boolean invert = FALSE;
+
+ /* Query the pixel center conventions supported by the pipe driver and set
+ * adjX, adjY to help out if it cannot handle the requested one internally.
+ *
+ * The bias of the y-coordinate depends on whether y-inversion takes place
+ * (adjY[1]) or not (adjY[0]), which is in turn dependent on whether we are
+ * drawing to an FBO (causes additional inversion), and whether the the pipe
+ * driver origin and the requested origin differ (the latter condition is
+ * stored in the 'invert' variable).
+ *
+ * For height = 100 (i = integer, h = half-integer, l = lower, u = upper):
+ *
+ * center shift only:
+ * i -> h: +0.5
+ * h -> i: -0.5
+ *
+ * inversion only:
+ * l,i -> u,i: ( 0.0 + 1.0) * -1 + 100 = 99
+ * l,h -> u,h: ( 0.5 + 0.0) * -1 + 100 = 99.5
+ * u,i -> l,i: (99.0 + 1.0) * -1 + 100 = 0
+ * u,h -> l,h: (99.5 + 0.0) * -1 + 100 = 0.5
+ *
+ * inversion and center shift:
+ * l,i -> u,h: ( 0.0 + 0.5) * -1 + 100 = 99.5
+ * l,h -> u,i: ( 0.5 + 0.5) * -1 + 100 = 99
+ * u,i -> l,h: (99.0 + 0.5) * -1 + 100 = 0.5
+ * u,h -> l,i: (99.5 + 0.5) * -1 + 100 = 0
+ */
+ if (fp->OriginUpperLeft) {
+ /* Fragment shader wants origin in upper-left */
+ if (pscreen->get_param(pscreen, PIPE_CAP_TGSI_FS_COORD_ORIGIN_UPPER_LEFT)) {
+ /* the driver supports upper-left origin */
+ }
+ else if (pscreen->get_param(pscreen, PIPE_CAP_TGSI_FS_COORD_ORIGIN_LOWER_LEFT)) {
+ /* the driver supports lower-left origin, need to invert Y */
+ ureg_property_fs_coord_origin(ureg, TGSI_FS_COORD_ORIGIN_LOWER_LEFT);
+ invert = TRUE;
+ }
+ else
+ assert(0);
+ }
+ else {
+ /* Fragment shader wants origin in lower-left */
+ if (pscreen->get_param(pscreen, PIPE_CAP_TGSI_FS_COORD_ORIGIN_LOWER_LEFT))
+ /* the driver supports lower-left origin */
+ ureg_property_fs_coord_origin(ureg, TGSI_FS_COORD_ORIGIN_LOWER_LEFT);
+ else if (pscreen->get_param(pscreen, PIPE_CAP_TGSI_FS_COORD_ORIGIN_UPPER_LEFT))
+ /* the driver supports upper-left origin, need to invert Y */
+ invert = TRUE;
+ else
+ assert(0);
+ }
+
+ if (fp->PixelCenterInteger) {
+ /* Fragment shader wants pixel center integer */
+ if (pscreen->get_param(pscreen, PIPE_CAP_TGSI_FS_COORD_PIXEL_CENTER_INTEGER)) {
+ /* the driver supports pixel center integer */
+ adjY[1] = 1.0f;
+ ureg_property_fs_coord_pixel_center(ureg, TGSI_FS_COORD_PIXEL_CENTER_INTEGER);
+ }
+ else if (pscreen->get_param(pscreen, PIPE_CAP_TGSI_FS_COORD_PIXEL_CENTER_HALF_INTEGER)) {
+ /* the driver supports pixel center half integer, need to bias X,Y */
+ adjX = -0.5f;
+ adjY[0] = -0.5f;
+ adjY[1] = 0.5f;
+ }
+ else
+ assert(0);
+ }
+ else {
+ /* Fragment shader wants pixel center half integer */
+ if (pscreen->get_param(pscreen, PIPE_CAP_TGSI_FS_COORD_PIXEL_CENTER_HALF_INTEGER)) {
+ /* the driver supports pixel center half integer */
+ }
+ else if (pscreen->get_param(pscreen, PIPE_CAP_TGSI_FS_COORD_PIXEL_CENTER_INTEGER)) {
+ /* the driver supports pixel center integer, need to bias X,Y */
+ adjX = adjY[0] = adjY[1] = 0.5f;
+ ureg_property_fs_coord_pixel_center(ureg, TGSI_FS_COORD_PIXEL_CENTER_INTEGER);
+ }
+ else
+ assert(0);
+ }
+
+ /* we invert after adjustment so that we avoid the MOV to temporary,
+ * and reuse the adjustment ADD instead */
+ emit_wpos_adjustment(t, program, invert, adjX, adjY);
+}
+
+