1 files changed, 207 insertions, 0 deletions
diff --git a/src/layer-fns.cpp b/src/layer-fns.cpp
new file mode 100644
index 0000000..81c722d
--- /dev/null
+++ b/src/layer-fns.cpp
@@ -0,0 +1,207 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Inkscape::SelectionDescriber - shows messages describing selection
+ *
+ * Authors:
+ *   MenTaLguY <mental@rydia.net>
+ *   Jon A. Cruz <jon@joncruz.org>
+ *
+ * Copyright (C) 2004 MenTaLguY
+ *
+ * Released under GNU GPL v2+, read the file 'COPYING' for more information.
+ */
+
+#include "document.h"
+#include "layer-fns.h"
+
+#include "object/sp-item-group.h"
+
+#include "util/find-last-if.h"
+
+#include "xml/repr.h"
+
+// TODO move the documentation comments into the .h file
+
+namespace Inkscape {
+
+namespace {
+
+static bool is_layer(SPObject &object) {
+    return SP_IS_GROUP(&object) &&
+           SP_GROUP(&object)->layerMode() == SPGroup::LAYER;
+}
+
+/** Finds the next sibling layer for a \a layer
+ *
+ *  @returns NULL if there are no further layers under a parent
+ */
+static SPObject *next_sibling_layer(SPObject *layer) {
+    if (layer->parent == nullptr) {
+      return nullptr;
+    }
+    SPObject::ChildrenList &list = layer->parent->children;
+    auto l = std::find_if(++list.iterator_to(*layer), list.end(), &is_layer);
+    return l != list.end() ? &*l : nullptr;
+}
+
+/** Finds the previous sibling layer for a \a layer
+ *
+ *  @returns NULL if there are no further layers under a parent
+ */
+static SPObject *previous_sibling_layer(SPObject *layer) {
+    using Inkscape::Algorithms::find_last_if;
+
+    SPObject::ChildrenList &list = layer->parent->children;
+    auto l = find_last_if(list.begin(), list.iterator_to(*layer), &is_layer);
+    return l != list.iterator_to(*layer) ? &*(l) : nullptr;
+}
+
+/** Finds the first child of a \a layer
+ *
+ *  @returns the layer itself if layer has no sublayers
+ */
+static SPObject *first_descendant_layer(SPObject *layer) {
+    while (true) {
+        auto first_descendant = std::find_if(layer->children.begin(), layer->children.end(), &is_layer);
+        if (first_descendant == layer->children.end()) {
+            break;
+        }
+        layer = &*first_descendant;
+    }
+
+    return layer;
+}
+
+/** Finds the last (topmost) child of a \a layer
+ *
+ *  @returns NULL if layer has no sublayers
+ */
+static SPObject *last_child_layer(SPObject *layer) {
+    using Inkscape::Algorithms::find_last_if;
+
+    auto l = find_last_if(layer->children.begin(), layer->children.end(), &is_layer);
+    return l != layer->children.end() ? &*l : nullptr;
+}
+
+static SPObject *last_elder_layer(SPObject *root, SPObject *layer) {
+    using Inkscape::Algorithms::find_last_if;
+    SPObject *result = nullptr;
+
+    while ( layer != root ) {
+        SPObject *sibling(previous_sibling_layer(layer));
+        if (sibling) {
+            result = sibling;
+            break;
+        }
+        layer = layer->parent;
+    }
+
+    return result;
+}
+
+}
+
+/** Finds the next layer under \a root, relative to \a layer in
+ *  depth-first order.
+ *
+ *  @returns NULL if there are no further layers under \a root
+ */
+SPObject *next_layer(SPObject *root, SPObject *layer) {
+    g_return_val_if_fail(layer != nullptr, NULL);
+    SPObject *result = nullptr;
+
+    SPObject *sibling = next_sibling_layer(layer);
+    if (sibling) {
+        result = first_descendant_layer(sibling);
+    } else if ( layer->parent != root ) {
+        result = layer->parent;
+    }
+
+    return result;
+}
+
+
+/** Finds the previous layer under \a root, relative to \a layer in
+ *  depth-first order.
+ *
+ *  @returns NULL if there are no prior layers under \a root.
+ */
+SPObject *previous_layer(SPObject *root, SPObject *layer) {
+    using Inkscape::Algorithms::find_last_if;
+
+    g_return_val_if_fail(layer != nullptr, NULL);
+    SPObject *result = nullptr;
+
+    SPObject *child = last_child_layer(layer);
+    if (child) {
+        result = child;
+    } else if ( layer != root ) {
+        SPObject *sibling = previous_sibling_layer(layer);
+        if (sibling) {
+            result = sibling;
+        } else {
+            result = last_elder_layer(root, layer->parent);
+        }
+    }
+
+    return result;
+}
+
+/**
+*  Creates a new layer.  Advances to the next layer id indicated
+ *  by the string "layerNN", then creates a new group object of
+ *  that id with attribute inkscape:groupmode='layer', and finally
+ *  appends the new group object to \a root after object \a layer.
+ *
+ *  \pre \a root should be either \a layer or an ancestor of it
+ */
+SPObject *create_layer(SPObject *root, SPObject *layer, LayerRelativePosition position) {
+    SPDocument *document = root->document;
+
+    static int layer_suffix=1;
+    gchar *id=nullptr;
+    do {
+        g_free(id);
+        id = g_strdup_printf("layer%d", layer_suffix++);
+    } while (document->getObjectById(id));
+
+    Inkscape::XML::Document *xml_doc = document->getReprDoc();
+    Inkscape::XML::Node *repr = xml_doc->createElement("svg:g");
+    repr->setAttribute("inkscape:groupmode", "layer");
+    repr->setAttribute("id", id);
+    g_free(id);
+
+    if ( LPOS_CHILD == position ) {
+        root = layer;
+        SPObject *child_layer = Inkscape::last_child_layer(layer);
+        if ( nullptr != child_layer ) {
+            layer = child_layer;
+        }
+    }
+
+    if ( root == layer ) {
+        root->getRepr()->appendChild(repr);
+    } else {
+        Inkscape::XML::Node *layer_repr = layer->getRepr();
+        layer_repr->parent()->addChild(repr, layer_repr);
+
+        if ( LPOS_BELOW == position ) {
+            SP_ITEM(document->getObjectByRepr(repr))->lowerOne();
+        }
+    }
+
+    return document->getObjectByRepr(repr);
+}
+
+}
+
+/*
+  Local Variables:
+  mode:c++
+  c-file-style:"stroustrup"
+  c-file-offsets:((innamespace . 0)(inline-open . 0)(case-label . +))
+  indent-tabs-mode:nil
+  fill-column:99
+  End:
+*/
+// vim: filetype=cpp:expandtab:shiftwidth=4:tabstop=8:softtabstop=4:fileencoding=utf-8:textwidth=99 :