selection chemistry: implement z-stack order

Bug #1395452

"raise and lower objects" used to stack objects above/below the next overlapping object,
which makes it impossible to change the z-order of objects that don't overlap.

Fixes also the object manager panel

Conflicts:
	src/selection-chemistry.cpp
	src/selection-chemistry.h
	src/sp-item.cpp

(bzr r15698.1.7)

1 files changed, 39 insertions, 0 deletions

diff --git a/src/selection-chemistry.cpp b/src/selection-chemistry.cpp
index 39846ba2c..7d5d921b0 100644
--- a/src/selection-chemistry.cpp
+++ b/src/selection-chemistry.cpp
@@ -1140,6 +1140,45 @@ void ObjectSet::lowerToBottom(bool skip_undo){
     }
 }
 
+void ObjectSet::stackUp(bool skip_undo) {
+    if (isEmpty()) {
+        selection_display_message(desktop(), Inkscape::WARNING_MESSAGE, _("Select <b>object(s)</b> to stack up."));
+        return;
+    }
+
+    std::vector<SPItem*> selection(items().begin(), items().end());
+    sort(selection.begin(), selection.end(), sp_item_repr_compare_position_bool);
+
+    for (auto item: selection | boost::adaptors::reversed) {
+        if (!item->raiseOne()) // stop if top was reached
+            break;
+    }
+
+    if(document() && !skip_undo)
+        DocumentUndo::done(document(), SP_VERB_SELECTION_STACK_UP,
+           //TRANSLATORS: undo history: "stack up" means to raise an object of its ordinal position by 1
+           C_("Undo action", "stack up"));
+}
+
+void ObjectSet::stackDown(bool skip_undo) {
+    if (isEmpty()) {
+        selection_display_message(desktop(), Inkscape::WARNING_MESSAGE, _("Select <b>object(s)</b> to stack down."));
+        return;
+    }
+
+    std::vector<SPItem*> selection(items().begin(), items().end());
+    sort(selection.begin(), selection.end(), sp_item_repr_compare_position_bool);
+
+    for (auto item: selection) {
+        if (!item->lowerOne()) // stop if bottom was reached
+            break;
+    }
+
+    if(document() && !skip_undo)
+        DocumentUndo::done(document(), SP_VERB_SELECTION_STACK_DOWN,
+           //TRANSLATORS: undo history: "stack down" means to lower an object of its ordinal position by 1
+           C_("Undo action", "stack down"));
+}
 
 void
 sp_undo(SPDesktop *desktop, SPDocument *)