Add object type specific device halftones to the graphics state.

PostScript 'sethalftone' has an optional parameter "ObjectType" that allows
one of the three object specific types to be set: Vector, Image or Text.

Also add a new PostScript operator to set the current halftone (dev_ht,
set by sethalftone) as the device halftone to be used for an object type:
path, image and text.

For non-PostScript clients, the gs_halftone structure adds a 'objtype'
element (enum) that can be set prior to calling gs_sethalftone.

The gs_gstate_s dev_ht is now an array of HT_OBJTYPE_COUNT elements,
indexed by the gs_HT_objtype_t enum, with HT_OBJTYPE_DEFAULT (value 0)
used for prior sethalftone/setscreen/setcolorscreen operations.

NOTE: adding object types beyond the default+3 entries will require modification
of gx_select_dev_ht since it only uses 3 bits of the 'tag' to get the index
for the dev_ht[] array.

For code style, change to use != NULL instead of != 0 in most places that
this commit touched (but we may want a general cleanup of this everywhere).

TBD: Command line options for all PDL's will need a method to take a
halftone specification -- most likely a file that may be "PS-lite" syntax
and may be limited to a threshold array. Discussions are in progress.

1 files changed, 1 insertions, 1 deletions

diff --git a/base/gxshade.c b/base/gxshade.c
index a0ddf2900..08b9edcc2 100644
--- a/base/gxshade.c
+++ b/base/gxshade.c
@@ -365,7 +365,7 @@ top:
         }
     if (num_colors <= 32) {
         /****** WRONG FOR MULTI-PLANE HALFTONES ******/
-        num_colors *= pgs->dev_ht->components[0].corder.num_levels;
+        num_colors *= pgs->dev_ht[HT_OBJTYPE_DEFAULT]->components[0].corder.num_levels;
     }
     if (psh->head.type == 2 || psh->head.type == 3) {
         max_error *= 0.25;