Squash some warnings with gs_swapcolors_quick breaking const.

At various places in the code, we call gs_swapcolors_quick where
we only have a const pgs.

Properly, we should copy the pgs to a non-const pgs, and then use
that, but that would be a performance hit.

In all cases, we change the graphics state, then restore it before
exit, so effectively it is const over the entire call of the
enclosing procedure.

Rather than having lots of small hacky casts removing const, we
push the const breakage into gs_swapcolors_quick itself where we
do it in the "approved" way using a union.

5 files changed, 42 insertions, 18 deletions

diff --git a/base/gdevp14.c b/base/gdevp14.c
index 9666dea51..fc58e2c95 100644
--- a/base/gdevp14.c
+++ b/base/gdevp14.c
@@ -3316,10 +3316,10 @@ pdf14_fill_stroke_path(gx_device *dev, const gs_gstate *pgs, gx_path *ppath,
         }
 
         if (pgs->strokeconstantalpha > 0) {
-            gs_swapcolors_quick((gs_gstate*)pgs);	/* flips stroke_color_index (to stroke) */
+            gs_swapcolors_quick(pgs);	/* flips stroke_color_index (to stroke) */
             ((pdf14_device*)dev)->op_state = PDF14_OP_STATE_STROKE;
             code = pdf14_stroke_path(dev, pgs, ppath, stroke_params, pdcolor_stroke, pcpath);
-            gs_swapcolors_quick((gs_gstate*)pgs);	/* this flips pgs->stroke_color_index back as well */
+            gs_swapcolors_quick(pgs);	/* this flips pgs->stroke_color_index back as well */
             if (code < 0)
                 goto cleanup;       /* bail out (with colors swapped back to fill) */
         }
@@ -3373,23 +3373,29 @@ pdf14_fill_stroke_path(gx_device *dev, const gs_gstate *pgs, gx_path *ppath,
         code = gs_setopacityalpha((gs_gstate*) pgs, pgs->strokeconstantalpha);
         if (code < 0)
             goto cleanup;
-        gs_swapcolors_quick((gs_gstate*) pgs);
+        gs_swapcolors_quick(pgs);
         ((pdf14_device*)dev)->op_state = PDF14_OP_STATE_STROKE;
         if (pgs->stroke_overprint && dev->color_info.polarity == GX_CINFO_POLARITY_SUBTRACTIVE) {
             code = gs_setblendmode((gs_gstate*)pgs, BLEND_MODE_CompatibleOverprint);
-            if (code < 0)
+            if (code < 0) {
+                gs_swapcolors_quick(pgs);
                 goto cleanup;
+            }
         }
         code = pdf14_stroke_path(dev, pgs, ppath, stroke_params, pdcolor_stroke, pcpath);
-        if (code < 0)
+        if (code < 0) {
+            gs_swapcolors_quick(pgs);
             goto cleanup;
+        }
 
         if (pgs->stroke_overprint && dev->color_info.polarity == GX_CINFO_POLARITY_SUBTRACTIVE) {
             code = gs_setblendmode((gs_gstate*)pgs, blend_mode);
-            if (code < 0)
+            if (code < 0) {
+                gs_swapcolors_quick(pgs);
                 goto cleanup;
+            }
         }
-        gs_swapcolors_quick((gs_gstate*) pgs);
+        gs_swapcolors_quick(pgs);
     }
 
     /* Now during the pop do the compositing with alpha of 1.0 and normal blend */
@@ -4367,7 +4373,7 @@ pdf14_set_params(gs_gstate * pgs,
     if (pparams->changed & PDF14_SET_STROKECONSTANTALPHA)
         pgs->strokeconstantalpha = pparams->strokeconstantalpha;
     if (pparams->changed & PDF_SET_FILLSTROKE_STATE) {
-        gs_swapcolors_quick((gs_gstate*)pgs);
+        gs_swapcolors_quick(pgs);
     }
     pdf14_set_marking_params(dev, pgs);
 }
diff --git a/base/gsstate.c b/base/gsstate.c
index 90cb28718..cbb70548a 100644
--- a/base/gsstate.c
+++ b/base/gsstate.c
@@ -1436,8 +1436,13 @@ gs_id gx_get_clip_path_id(gs_gstate *pgs)
     return pgs->clip_path->id;
 }
 
-void gs_swapcolors_quick(gs_gstate *pgs)
+void gs_swapcolors_quick(const gs_gstate *cpgs)
 {
+    union {
+        const gs_gstate *cpgs;
+        gs_gstate *pgs;
+    } const_breaker;
+    gs_gstate *pgs;
     struct gx_cie_joint_caches_s *tmp_cie;
     gs_devicen_color_map          tmp_ccm;
     gs_client_color              *tmp_cc;
@@ -1445,6 +1450,11 @@ void gs_swapcolors_quick(gs_gstate *pgs)
     gx_device_color              *tmp_dc;
     gs_color_space               *tmp_cs;
 
+    /* Break const just once, neatly, here rather than
+     * hackily in every caller. */
+    const_breaker.cpgs = cpgs;
+    pgs = const_breaker.pgs;
+
     tmp_cc               = pgs->color[0].ccolor;
     pgs->color[0].ccolor = pgs->color[1].ccolor;
     pgs->color[1].ccolor = tmp_cc;
diff --git a/base/gxfill.c b/base/gxfill.c
index 1abea4911..68bcdafcc 100644
--- a/base/gxfill.c
+++ b/base/gxfill.c
@@ -681,9 +681,9 @@ gx_default_fill_stroke_path(gx_device * pdev, const gs_gstate * pgs,
     if (code < 0)
         return code;
     /* Swap colors to make sure the pgs colorspace is correct for stroke */
-    gs_swapcolors_quick((gs_gstate *) pgs);
+    gs_swapcolors_quick(pgs);
     code = dev_proc(pdev, stroke_path)(pdev, pgs, ppath, params_stroke, pdevc_stroke, pcpath);
-    gs_swapcolors_quick((gs_gstate*) pgs);
+    gs_swapcolors_quick(pgs);
     return code;
 }
 
diff --git a/base/gxgstate.h b/base/gxgstate.h
index 33f642027..e6dd92f75 100644
--- a/base/gxgstate.h
+++ b/base/gxgstate.h
@@ -438,7 +438,15 @@ int gs_currentscreenphase_pgs(const gs_gstate *, gs_int_point *, gs_color_select
     (pgs)->current_point.x = xx;\
     (pgs)->current_point.y = yy;
 
-void gs_swapcolors_quick(gs_gstate *);
+/* The const is a lie. The swapcolors stuff is a bit of a hack; a late
+ * addition to the graphics library, which has to be used in many places
+ * where the device interface only has a const gs_gstate available to it
+ * rather than a non-const one. In all these cases, we flip the colors
+ * during a call to a function, then swap it back again before we leave,
+ * so the net effect of the call remains that the gstate is not changed.
+ * Rather than breaking const at every single callsite, we move the const
+ * breaking into the function itself. */
+void gs_swapcolors_quick(const gs_gstate *);
 
 /* Set the graphics_type_tag iff the requested tag bit is not set in the dev_color and	*/
 /* unset the dev_color so that gx_set_dev_color will remap (encode) with the new tag.	*/
diff --git a/devices/vector/gdevpdfd.c b/devices/vector/gdevpdfd.c
index 4973d71fd..1e62bad1c 100644
--- a/devices/vector/gdevpdfd.c
+++ b/devices/vector/gdevpdfd.c
@@ -1896,9 +1896,9 @@ gdev_pdf_fill_stroke_path(gx_device *dev, const gs_gstate *pgs, gx_path *ppath,
         code = gdev_pdf_fill_path(dev, pgs, ppath, fill_params, pdcolor_fill, pcpath);
         if (code < 0)
             return code;
-        gs_swapcolors_quick((gs_gstate *)pgs);
+        gs_swapcolors_quick(pgs);
         code = gdev_pdf_stroke_path(dev, pgs, ppath, stroke_params, pdcolor_stroke, pcpath);
-        gs_swapcolors_quick((gs_gstate *)pgs);
+        gs_swapcolors_quick(pgs);
         return code;
     } else {
         bool set_ctm;
@@ -2031,17 +2031,17 @@ gdev_pdf_fill_stroke_path(gx_device *dev, const gs_gstate *pgs, gx_path *ppath,
             if (code < 0)
                 return code;
             /* Swap colors to make sure the pgs colorspace is correct for stroke */
-            gs_swapcolors_quick((gs_gstate*) pgs);
+            gs_swapcolors_quick(pgs);
             code = gdev_pdf_stroke_path(dev, pgs, ppath, stroke_params, pdcolor_stroke, pcpath);
-            gs_swapcolors_quick((gs_gstate*) pgs);
+            gs_swapcolors_quick(pgs);
             return code;
         }
 
         /* Swap colors to make sure the pgs colorspace is correct for stroke */
-        gs_swapcolors_quick((gs_gstate*) pgs);
+        gs_swapcolors_quick(pgs);
         code = gdev_vector_prepare_stroke((gx_device_vector *)pdev, pgs, stroke_params,
                                           pdcolor_stroke, scale);
-        gs_swapcolors_quick((gs_gstate*) pgs);
+        gs_swapcolors_quick(pgs);
         if (code < 0) {
             code = gdev_pdf_fill_path(dev, pgs, ppath, fill_params, pdcolor_fill, pcpath);
             if (code < 0)