Index: trunk/src/draw_composite.c
===================================================================
--- trunk/src/draw_composite.c	(revision 10310)
+++ trunk/src/draw_composite.c	(revision 10311)
@@ -207,7 +207,8 @@
 /* Draw a layer group with fake or real compositing */
 static void comp_draw_layer(comp_ctx_t *ctx, void (*draw_auto)(comp_ctx_t *ctx, void *data), void *auto_data)
 {
-	if (pcb_draw_layergrp_is_comp(ctx->grp))
+	int enable_fake = (pcb_gui != NULL) && (pcb_gui->enable_fake_composite);
+	if (!enable_fake || pcb_draw_layergrp_is_comp(ctx->grp))
 		comp_draw_layer_real(ctx, draw_auto, auto_data);
 	else
 		comp_draw_layer_fake(ctx, draw_auto, auto_data);
Index: trunk/src/hid.h
===================================================================
--- trunk/src/hid.h	(revision 10310)
+++ trunk/src/hid.h	(revision 10311)
@@ -195,6 +195,14 @@
 	   punches through everything. */
 	unsigned holes_after:1;
 
+	/* If set, enable the fake composite layer draw optimization, that is:
+	   if all layers in a compositing layer group are positive, no composition
+	   is done but layers are just drawn. Useful for software render HIDs with
+	   no transluency; causes problems with transluent rendering: different
+	   layers within the same group will be darker on overlap */
+	unsigned enable_fake_composite:1;
+
+
 	/* lesstif allows positive AND negative drawing in HID_MASK_CLEAR.
 	   gtk only allows negative drawing.
 	   using the mask is to get rat transparency */
Index: trunk/src_plugins/hid_gtk2_gdk/gtkhid-main.c
===================================================================
--- trunk/src_plugins/hid_gtk2_gdk/gtkhid-main.c	(revision 10310)
+++ trunk/src_plugins/hid_gtk2_gdk/gtkhid-main.c	(revision 10311)
@@ -47,6 +47,7 @@
 	ghid_win32_init();
 
 	ghid_glue_hid_init(&gtk2_gdk_hid);
+	gtk2_gdk_hid.enable_fake_composite = 1;
 	ghid_glue_common_init();
 
 	gtk2_gdk_hid.parse_arguments = gtk2_gdk_parse_arguments;
Index: trunk/src_plugins/hid_lesstif/main.c
===================================================================
--- trunk/src_plugins/hid_lesstif/main.c	(revision 10310)
+++ trunk/src_plugins/hid_lesstif/main.c	(revision 10311)
@@ -3730,6 +3730,7 @@
 	lesstif_hid.gui = 1;
 	lesstif_hid.poly_before = 1;
 	lesstif_hid.can_mask_clear_rats = 1;
+	lesstif_hid.enable_fake_composite = 1;
 
 	lesstif_hid.get_export_options = lesstif_get_export_options;
 	lesstif_hid.do_export = lesstif_do_export;