Units: make it absolutely clear that Document properties unit dropdown is for UI Display Units. Upon document load, calculate the units used for SVG values, if a viewbox is available. If not, default to "px" SVG units.

Change all code to use either Display units OR svg units.

(bzr r13751)

33 files changed, 120 insertions, 75 deletions

diff --git a/src/document.cpp b/src/document.cpp
index f5269eab3..3715d8e6e 100644
--- a/src/document.cpp
+++ b/src/document.cpp
@@ -599,6 +599,14 @@ Inkscape::Util::Unit const* SPDocument::getDefaultUnit() const
     return nv ? nv->getDefaultUnit() : unit_table.getUnit("pt");
 }
 
+/// guaranteed not to return nullptr
+// returns 'px' units as default, like legacy Inkscape
+Inkscape::Util::Unit const& SPDocument::getSVGUnit() const
+{
+    SPNamedView const* nv = sp_document_namedview(this, NULL);
+    return nv ? nv->getSVGUnit() : *unit_table.getUnit("px");
+}
+
 Inkscape::Util::Quantity SPDocument::getWidth() const
 {
     g_return_val_if_fail(this->priv != NULL, Inkscape::Util::Quantity(0.0, unit_table.getUnit("")));
diff --git a/src/document.h b/src/document.h
index 4ace249ae..065c5f323 100644
--- a/src/document.h
+++ b/src/document.h
@@ -242,6 +242,7 @@ public:
     SPDocument *doRef();
     SPDocument *doUnref();
     Inkscape::Util::Unit const* getDefaultUnit() const;
+    Inkscape::Util::Unit const& getSVGUnit() const;
     Inkscape::Util::Quantity getWidth() const;
     Inkscape::Util::Quantity getHeight() const;
     Geom::Point getDimensions() const;
diff --git a/src/extension/internal/emf-print.cpp b/src/extension/internal/emf-print.cpp
index 0f43fbca1..f7b6626c4 100644
--- a/src/extension/internal/emf-print.cpp
+++ b/src/extension/internal/emf-print.cpp
@@ -144,7 +144,7 @@ unsigned int PrintEmf::begin(Inkscape::Extension::Print *mod, SPDocument *doc)
     // width and height in px
     _width  = doc->getWidth().value("px");
     _height = doc->getHeight().value("px");
-    _doc_unit_scale = Inkscape::Util::Quantity::convert(1, (doc->getDefaultUnit()), "px");
+    _doc_unit_scale = Inkscape::Util::Quantity::convert(1, &doc->getSVGUnit(), "px");
 
     // initialize a few global variables
     hbrush = hbrushOld = hpen = 0;
diff --git a/src/extension/internal/grid.cpp b/src/extension/internal/grid.cpp
index 0059bbec2..f4e0e5843 100644
--- a/src/extension/internal/grid.cpp
+++ b/src/extension/internal/grid.cpp
@@ -113,7 +113,7 @@ Grid::effect (Inkscape::Extension::Effect *module, Inkscape::UI::View::View *doc
         bounding_area = temprec;
     }
 
-    gdouble scale = Inkscape::Util::Quantity::convert(1, "px", (document->doc())->getDefaultUnit());
+    gdouble scale = Inkscape::Util::Quantity::convert(1, "px", &document->doc()->getSVGUnit());
     bounding_area *= Geom::Scale(scale);
     Geom::Point spacings( scale * module->get_param_float("xspacing"),
                           scale * module->get_param_float("yspacing") );
diff --git a/src/live_effects/lpe-roughen.cpp b/src/live_effects/lpe-roughen.cpp
index 07d9e63e8..8cef9a3a3 100644
--- a/src/live_effects/lpe-roughen.cpp
+++ b/src/live_effects/lpe-roughen.cpp
@@ -160,11 +160,11 @@ double LPERoughen::sign(double randNumber)
 
 Geom::Point LPERoughen::randomize()
 {
-    Inkscape::Util::Unit const *doc_units = SP_ACTIVE_DESKTOP->namedview->doc_units;
+    Inkscape::Util::Unit const *svg_units = SP_ACTIVE_DESKTOP->namedview->svg_units;
     double displaceXParsed = Inkscape::Util::Quantity::convert(
-                                 displaceX * globalRandomize, unit.get_abbreviation(), doc_units->abbr);
+                                 displaceX * globalRandomize, unit.get_abbreviation(), svg_units->abbr);
     double displaceYParsed = Inkscape::Util::Quantity::convert(
-                                 displaceY * globalRandomize, unit.get_abbreviation(), doc_units->abbr);
+                                 displaceY * globalRandomize, unit.get_abbreviation(), svg_units->abbr);
 
     Geom::Point output = Geom::Point(sign(displaceXParsed), sign(displaceYParsed));
     return output;
@@ -175,7 +175,7 @@ void LPERoughen::doEffect(SPCurve *curve)
     Geom::PathVector const original_pathv =
         pathv_to_linear_and_cubic_beziers(curve->get_pathvector());
     curve->reset();
-    Inkscape::Util::Unit const *doc_units = SP_ACTIVE_DESKTOP->namedview->doc_units;
+    Inkscape::Util::Unit const *svg_units = SP_ACTIVE_DESKTOP->namedview->svg_units;
     for (Geom::PathVector::const_iterator path_it = original_pathv.begin();
             path_it != original_pathv.end(); ++path_it) {
         if (path_it->empty())
@@ -221,7 +221,7 @@ void LPERoughen::doEffect(SPCurve *curve)
                 nCurve->lineto(A3);
             }
             double length = Inkscape::Util::Quantity::convert(
-                                curve_it1->length(0.001), doc_units->abbr, unit.get_abbreviation());
+                                curve_it1->length(0.001), svg_units->abbr, unit.get_abbreviation());
             std::size_t splits = 0;
             if (method == DM_SEGMENTS) {
                 splits = segments;
diff --git a/src/seltrans.cpp b/src/seltrans.cpp
index 96c7fb49b..a9ae9e465 100644
--- a/src/seltrans.cpp
+++ b/src/seltrans.cpp
@@ -1306,8 +1306,8 @@ gboolean Inkscape::SelTrans::centerRequest(Geom::Point &pt, guint state)
     // status text
     Inkscape::Util::Quantity x_q = Inkscape::Util::Quantity(pt[Geom::X], "px");
     Inkscape::Util::Quantity y_q = Inkscape::Util::Quantity(pt[Geom::Y], "px");
-    GString *xs = g_string_new(x_q.string(_desktop->namedview->doc_units).c_str());
-    GString *ys = g_string_new(y_q.string(_desktop->namedview->doc_units).c_str());
+    GString *xs = g_string_new(x_q.string(_desktop->namedview->display_units).c_str());
+    GString *ys = g_string_new(y_q.string(_desktop->namedview->display_units).c_str());
     _message_context.setF(Inkscape::NORMAL_MESSAGE, _("Move <b>center</b> to %s, %s"), xs->str, ys->str);
     g_string_free(xs, FALSE);
     g_string_free(ys, FALSE);
@@ -1460,8 +1460,8 @@ void Inkscape::SelTrans::moveTo(Geom::Point const &xy, guint state)
     // status text
     Inkscape::Util::Quantity x_q = Inkscape::Util::Quantity(dxy[Geom::X], "px");
     Inkscape::Util::Quantity y_q = Inkscape::Util::Quantity(dxy[Geom::Y], "px");
-    GString *xs = g_string_new(x_q.string(_desktop->namedview->doc_units).c_str());
-    GString *ys = g_string_new(y_q.string(_desktop->namedview->doc_units).c_str());
+    GString *xs = g_string_new(x_q.string(_desktop->namedview->display_units).c_str());
+    GString *ys = g_string_new(y_q.string(_desktop->namedview->display_units).c_str());
     _message_context.setF(Inkscape::NORMAL_MESSAGE, _("<b>Move</b> by %s, %s; with <b>Ctrl</b> to restrict to horizontal/vertical; with <b>Shift</b> to disable snapping"), xs->str, ys->str);
     g_string_free(xs, TRUE);
     g_string_free(ys, TRUE);
diff --git a/src/sp-guide.cpp b/src/sp-guide.cpp
index 581c8a440..74a0d829c 100644
--- a/src/sp-guide.cpp
+++ b/src/sp-guide.cpp
@@ -410,8 +410,8 @@ char* SPGuide::description(bool const verbose) const
 
         Inkscape::Util::Quantity x_q = Inkscape::Util::Quantity(this->point_on_line[X], "px");
         Inkscape::Util::Quantity y_q = Inkscape::Util::Quantity(this->point_on_line[Y], "px");
-        GString *position_string_x = g_string_new(x_q.string(namedview->doc_units).c_str());
-        GString *position_string_y = g_string_new(y_q.string(namedview->doc_units).c_str());
+        GString *position_string_x = g_string_new(x_q.string(namedview->display_units).c_str());
+        GString *position_string_y = g_string_new(y_q.string(namedview->display_units).c_str());
 
         gchar *shortcuts = g_strdup_printf("; %s", _("<b>Shift+drag</b> to rotate, <b>Ctrl+drag</b> to move origin, <b>Del</b> to delete"));
 
diff --git a/src/sp-namedview.cpp b/src/sp-namedview.cpp
index b68421dc6..09d383e3c 100644
--- a/src/sp-namedview.cpp
+++ b/src/sp-namedview.cpp
@@ -76,7 +76,9 @@ SPNamedView::SPNamedView() : SPObjectGroup(), snap_manager(this) {
 	this->window_x = 0;
 	this->cy = 0;
 	this->window_y = 0;
-	this->doc_units = NULL;
+    this->svg_units = unit_table.getUnit("px"); // legacy behavior: if no viewbox present, default to 'px' units
+    this->display_units = NULL;
+	this->page_size_units = NULL;
 	this->pagecolor = 0;
 	this->cx = 0;
 	this->pageshadow = 0;
@@ -262,6 +264,14 @@ void SPNamedView::build(SPDocument *document, Inkscape::XML::Node *repr) {
 
     // backwards compatibility with grid settings (pre 0.46)
     sp_namedview_generate_old_grid(this, document, repr);
+
+    // If viewbox defined: try to calculate the SVG unit from document width and viewbox
+    if (document->getRoot()->viewBox_set) {
+        Inkscape::Util::Quantity svgwidth = document->getWidth();
+        Geom::Rect viewbox = document->getRoot()->viewBox;
+        double factor = svgwidth.value(unit_table.primary(Inkscape::Util::UNIT_TYPE_LINEAR)) / viewbox.width(); 
+        svg_units = unit_table.findUnit(factor, Inkscape::Util::UNIT_TYPE_LINEAR);
+    }
 }
 
 void SPNamedView::release() {
@@ -540,22 +550,13 @@ void SPNamedView::set(unsigned int key, const gchar* value) {
             this->requestModified(SP_OBJECT_MODIFIED_FLAG);
             break;
     case SP_ATTR_INKSCAPE_DOCUMENT_UNITS: {
-            /* The default unit if the document doesn't override this: e.g. for files saved as
+            /* The default display unit if the document doesn't override this: e.g. for files saved as
              * `plain SVG', or non-inkscape files, or files created by an inkscape 0.40 &
              * earlier.
              *
-             * Here we choose `px': useful for screen-destined SVGs, and fewer bug reports
-             * about "not the same numbers as what's in the SVG file" (at least for documents
-             * without a viewBox attribute on the root <svg> element).  Similarly, it's also
-             * the most reliable unit (i.e. least likely to be wrong in different viewing
-             * conditions) for viewBox-less SVG files given that it's the unit that inkscape
-             * uses for all coordinates.
+             * Note that these units are not the same as the units used for the values in SVG!
              *
-             * For documents that do have a viewBox attribute on the root <svg> element, it
-             * might be better if we used either viewBox coordinates or if we used the unit of
-             * say the width attribute of the root <svg> element.  However, these pose problems
-             * in that they aren't in general absolute units as currently required by
-             * doc_units.
+             * We default to `px'.
              */
             static Inkscape::Util::Unit const *px = unit_table.getUnit("px");
             Inkscape::Util::Unit const *new_unit = px;
@@ -576,7 +577,7 @@ void SPNamedView::set(unsigned int key, const gchar* value) {
                     /* fixme: Don't use g_log (see above). */
                 }
             }
-            this->doc_units = new_unit;
+            this->display_units = new_unit;
             this->requestModified(SP_OBJECT_MODIFIED_FLAG);
             break;
     }
@@ -1133,7 +1134,13 @@ double SPNamedView::getMarginLength(gchar const * const key,
  */
 Inkscape::Util::Unit const * SPNamedView::getDefaultUnit() const
 {
-    return doc_units ? doc_units : unit_table.getUnit("pt");
+    return display_units ? display_units : unit_table.getUnit("pt");
+}
+
+Inkscape::Util::Unit const & SPNamedView::getSVGUnit() const
+{
+    assert(svg_units);
+    return *svg_units; 
 }
 
 /**
diff --git a/src/sp-namedview.h b/src/sp-namedview.h
index 4746b2962..64bf14a8b 100644
--- a/src/sp-namedview.h
+++ b/src/sp-namedview.h
@@ -61,7 +61,8 @@ public:
     GSList * grids;
     bool grids_visible;
 
-    Inkscape::Util::Unit const *doc_units;
+    Inkscape::Util::Unit const *svg_units;   // Units used for the values in SVG
+    Inkscape::Util::Unit const *display_units;   // Units used for the UI (*not* the same as units of SVG coordinates)
     Inkscape::Util::Unit const *page_size_units; // Only used in "Custom size" part of Document Properties dialog 
     
     GQuark default_layer_id;
@@ -86,6 +87,7 @@ public:
     unsigned int getViewCount();
     GSList const *getViewList() const;
     Inkscape::Util::Unit const * getDefaultUnit() const;
+    Inkscape::Util::Unit const & getSVGUnit() const;
 
     void translateGuides(Geom::Translate const &translation);
     void translateGrids(Geom::Translate const &translation);
diff --git a/src/sp-text.cpp b/src/sp-text.cpp
index 93d81e47b..8922d3c73 100644
--- a/src/sp-text.cpp
+++ b/src/sp-text.cpp
@@ -362,7 +362,7 @@ gchar* SPText::description() const {
     char *n = xml_quote_strdup( style->font_family.value );
 
     Inkscape::Util::Quantity q = Inkscape::Util::Quantity(style->font_size.computed, "px");
-    GString *xs = g_string_new(q.string(sp_desktop_namedview(SP_ACTIVE_DESKTOP)->doc_units).c_str());
+    GString *xs = g_string_new(q.string(sp_desktop_namedview(SP_ACTIVE_DESKTOP)->display_units).c_str());
 
     char const *trunc = "";
     Inkscape::Text::Layout const *layout = te_get_layout((SPItem *) this);
diff --git a/src/ui/dialog/clonetiler.cpp b/src/ui/dialog/clonetiler.cpp
index d1a675735..7a776a9b8 100644
--- a/src/ui/dialog/clonetiler.cpp
+++ b/src/ui/dialog/clonetiler.cpp
@@ -1096,7 +1096,7 @@ CloneTiler::CloneTiler (void) :
                 // unitmenu
                 unit_menu = new Inkscape::UI::Widget::UnitMenu();
                 unit_menu->setUnitType(Inkscape::Util::UNIT_TYPE_LINEAR);
-                unit_menu->setUnit(sp_desktop_namedview(SP_ACTIVE_DESKTOP)->doc_units->abbr);
+                unit_menu->setUnit(sp_desktop_namedview(SP_ACTIVE_DESKTOP)->display_units->abbr);
                 unitChangedConn = unit_menu->signal_changed().connect(sigc::mem_fun(*this, &CloneTiler::clonetiler_unit_changed));
 
                 {
@@ -2251,7 +2251,7 @@ void CloneTiler::clonetiler_apply(GtkWidget */*widget*/, GtkWidget *dlg)
 
     clonetiler_remove (NULL, dlg, false);
 
-    double scale_units = Inkscape::Util::Quantity::convert(1, "px", sp_desktop_document(desktop)->getDefaultUnit());
+    double scale_units = Inkscape::Util::Quantity::convert(1, "px", &sp_desktop_document(desktop)->getSVGUnit());
 
     double shiftx_per_i = 0.01 * prefs->getDoubleLimited(prefs_path + "shiftx_per_i", 0, -10000, 10000);
     double shifty_per_i = 0.01 * prefs->getDoubleLimited(prefs_path + "shifty_per_i", 0, -10000, 10000);
diff --git a/src/ui/dialog/document-properties.cpp b/src/ui/dialog/document-properties.cpp
index 9ab607ed2..f7701655c 100644
--- a/src/ui/dialog/document-properties.cpp
+++ b/src/ui/dialog/document-properties.cpp
@@ -1480,8 +1480,8 @@ void DocumentProperties::update()
     _rcb_antialias.set_xml_target(root->getRepr(), dt->getDocument());
     _rcb_antialias.setActive(root->style->shape_rendering.computed != SP_CSS_SHAPE_RENDERING_CRISPEDGES);
 
-    if (nv->doc_units) {
-        _rum_deflt.setUnit (nv->doc_units->abbr);
+    if (nv->display_units) {
+        _rum_deflt.setUnit (nv->display_units->abbr);
     }
 
     double doc_w = sp_desktop_document(dt)->getRoot()->width.value;
diff --git a/src/ui/dialog/export.cpp b/src/ui/dialog/export.cpp
index b044a6e2c..37022a186 100644
--- a/src/ui/dialog/export.cpp
+++ b/src/ui/dialog/export.cpp
@@ -206,7 +206,7 @@ Export::Export (void) :
 
         SPDesktop *desktop = SP_ACTIVE_DESKTOP;
         if (desktop) {
-            unit_selector.setUnit(sp_desktop_namedview(desktop)->doc_units->abbr);
+            unit_selector.setUnit(sp_desktop_namedview(desktop)->display_units->abbr);
         }
         unitChangedConn = unit_selector.signal_changed().connect(sigc::mem_fun(*this, &Export::onUnitChanged));
         unitbox.pack_end(unit_selector, false, false, 0);
diff --git a/src/ui/dialog/guides.cpp b/src/ui/dialog/guides.cpp
index 4519a905f..221f9a1c0 100644
--- a/src/ui/dialog/guides.cpp
+++ b/src/ui/dialog/guides.cpp
@@ -216,8 +216,8 @@ void GuidelinePropertiesDialog::_setup() {
     /* fixme: We should allow percents here too, as percents of the canvas size */
     _unit_menu.setUnitType(UNIT_TYPE_LINEAR);
     _unit_menu.setUnit("px");
-    if (_desktop->namedview->doc_units) {
-        _unit_menu.setUnit( _desktop->namedview->doc_units->abbr );
+    if (_desktop->namedview->display_units) {
+        _unit_menu.setUnit( _desktop->namedview->display_units->abbr );
     }
     _spin_angle.setUnit(_angle_unit_status);
 
diff --git a/src/ui/dialog/transformation.cpp b/src/ui/dialog/transformation.cpp
index 3e135b9b2..6dbcf4a05 100644
--- a/src/ui/dialog/transformation.cpp
+++ b/src/ui/dialog/transformation.cpp
@@ -208,8 +208,8 @@ void Transformation::layoutPageMove()
     // Setting default unit to document unit
     SPDesktop *dt = getDesktop();
     SPNamedView *nv = sp_desktop_namedview(dt);
-    if (nv->doc_units) {
-        _units_move.setUnit(nv->doc_units->abbr);
+    if (nv->display_units) {
+        _units_move.setUnit(nv->display_units->abbr);
     }
     
     _scalar_move_horizontal.initScalar(-1e6, 1e6);
diff --git a/src/ui/tool/node.cpp b/src/ui/tool/node.cpp
index 8a1ca0b90..8c22f7c6e 100644
--- a/src/ui/tool/node.cpp
+++ b/src/ui/tool/node.cpp
@@ -566,9 +566,9 @@ Glib::ustring Handle::_getDragTip(GdkEventMotion */*event*/) const
     Inkscape::Util::Quantity x_q = Inkscape::Util::Quantity(dist[Geom::X], "px");
     Inkscape::Util::Quantity y_q = Inkscape::Util::Quantity(dist[Geom::Y], "px");
     Inkscape::Util::Quantity len_q = Inkscape::Util::Quantity(length(), "px");
-    GString *x = g_string_new(x_q.string(_desktop->namedview->doc_units).c_str());
-    GString *y = g_string_new(y_q.string(_desktop->namedview->doc_units).c_str());
-    GString *len = g_string_new(len_q.string(_desktop->namedview->doc_units).c_str());
+    GString *x = g_string_new(x_q.string(_desktop->namedview->display_units).c_str());
+    GString *y = g_string_new(y_q.string(_desktop->namedview->display_units).c_str());
+    GString *len = g_string_new(len_q.string(_desktop->namedview->display_units).c_str());
     Glib::ustring ret = format_tip(C_("Path handle tip",
         "Move handle by %s, %s; angle %.2f°, length %s"), x->str, y->str, angle, len->str);
     g_string_free(x, TRUE);
@@ -1490,8 +1490,8 @@ Glib::ustring Node::_getDragTip(GdkEventMotion */*event*/) const
     
     Inkscape::Util::Quantity x_q = Inkscape::Util::Quantity(dist[Geom::X], "px");
     Inkscape::Util::Quantity y_q = Inkscape::Util::Quantity(dist[Geom::Y], "px");
-    GString *x = g_string_new(x_q.string(_desktop->namedview->doc_units).c_str());
-    GString *y = g_string_new(y_q.string(_desktop->namedview->doc_units).c_str());
+    GString *x = g_string_new(x_q.string(_desktop->namedview->display_units).c_str());
+    GString *y = g_string_new(y_q.string(_desktop->namedview->display_units).c_str());
     Glib::ustring ret = format_tip(C_("Path node tip", "Move node by %s, %s"), x->str, y->str);
     g_string_free(x, TRUE);
     g_string_free(y, TRUE);
diff --git a/src/ui/tools/arc-tool.cpp b/src/ui/tools/arc-tool.cpp
index 4f64ade25..9c3195a42 100644
--- a/src/ui/tools/arc-tool.cpp
+++ b/src/ui/tools/arc-tool.cpp
@@ -405,8 +405,8 @@ void ArcTool::drag(Geom::Point pt, guint state) {
 
     Inkscape::Util::Quantity rdimx_q = Inkscape::Util::Quantity(rdimx, "px");
     Inkscape::Util::Quantity rdimy_q = Inkscape::Util::Quantity(rdimy, "px");
-    GString *xs = g_string_new(rdimx_q.string(desktop->namedview->doc_units).c_str());
-    GString *ys = g_string_new(rdimy_q.string(desktop->namedview->doc_units).c_str());
+    GString *xs = g_string_new(rdimx_q.string(desktop->namedview->display_units).c_str());
+    GString *ys = g_string_new(rdimy_q.string(desktop->namedview->display_units).c_str());
 
     if (state & GDK_CONTROL_MASK) {
         int ratio_x, ratio_y;
diff --git a/src/ui/tools/pen-tool.cpp b/src/ui/tools/pen-tool.cpp
index 92937a135..fbcdf6142 100644
--- a/src/ui/tools/pen-tool.cpp
+++ b/src/ui/tools/pen-tool.cpp
@@ -1366,7 +1366,7 @@ void PenTool::_setAngleDistanceStatusMessage(Geom::Point const p, int pc_point_t
 
     Geom::Point rel = p - this->p[pc_point_to_compare];
     Inkscape::Util::Quantity q = Inkscape::Util::Quantity(Geom::L2(rel), "px");
-    GString *dist = g_string_new(q.string(desktop->namedview->doc_units).c_str());
+    GString *dist = g_string_new(q.string(desktop->namedview->display_units).c_str());
     double angle = atan2(rel[Geom::Y], rel[Geom::X]) * 180 / M_PI;
     Inkscape::Preferences *prefs = Inkscape::Preferences::get();
     if (prefs->getBool("/options/compassangledisplay/value", 0) != 0) {
diff --git a/src/ui/tools/rect-tool.cpp b/src/ui/tools/rect-tool.cpp
index de91dcff4..67df0d9a5 100644
--- a/src/ui/tools/rect-tool.cpp
+++ b/src/ui/tools/rect-tool.cpp
@@ -422,8 +422,8 @@ void RectTool::drag(Geom::Point const pt, guint state) {
 
     Inkscape::Util::Quantity rdimx_q = Inkscape::Util::Quantity(rdimx, "px");
     Inkscape::Util::Quantity rdimy_q = Inkscape::Util::Quantity(rdimy, "px");
-    GString *xs = g_string_new(rdimx_q.string(desktop->namedview->doc_units).c_str());
-    GString *ys = g_string_new(rdimy_q.string(desktop->namedview->doc_units).c_str());
+    GString *xs = g_string_new(rdimx_q.string(desktop->namedview->display_units).c_str());
+    GString *ys = g_string_new(rdimy_q.string(desktop->namedview->display_units).c_str());
 
     if (state & GDK_CONTROL_MASK) {
         int ratio_x, ratio_y;
diff --git a/src/ui/tools/spiral-tool.cpp b/src/ui/tools/spiral-tool.cpp
index 18c3e4e2d..31c4e8829 100644
--- a/src/ui/tools/spiral-tool.cpp
+++ b/src/ui/tools/spiral-tool.cpp
@@ -395,7 +395,7 @@ void SpiralTool::drag(Geom::Point const &p, guint state) {
 
     /* status text */
     Inkscape::Util::Quantity q = Inkscape::Util::Quantity(rad, "px");
-    GString *rads = g_string_new(q.string(desktop->namedview->doc_units).c_str());
+    GString *rads = g_string_new(q.string(desktop->namedview->display_units).c_str());
     this->message_context->setF(Inkscape::IMMEDIATE_MESSAGE,
                                _("<b>Spiral</b>: radius %s, angle %5g&#176;; with <b>Ctrl</b> to snap angle"),
                                rads->str, sp_round((arg + 2.0*M_PI*this->spiral->revo)*180/M_PI, 0.0001));
diff --git a/src/ui/tools/star-tool.cpp b/src/ui/tools/star-tool.cpp
index 7604ba04e..b5544d263 100644
--- a/src/ui/tools/star-tool.cpp
+++ b/src/ui/tools/star-tool.cpp
@@ -411,7 +411,7 @@ void StarTool::drag(Geom::Point p, guint state)
 
     /* status text */
     Inkscape::Util::Quantity q = Inkscape::Util::Quantity(r1, "px");
-    GString *rads = g_string_new(q.string(desktop->namedview->doc_units).c_str());
+    GString *rads = g_string_new(q.string(desktop->namedview->display_units).c_str());
     this->message_context->setF(Inkscape::IMMEDIATE_MESSAGE,
                                ( this->isflatsided?
                                  _("<b>Polygon</b>: radius %s, angle %5g&#176;; with <b>Ctrl</b> to snap angle")
diff --git a/src/ui/tools/text-tool.cpp b/src/ui/tools/text-tool.cpp
index a72748733..578add843 100644
--- a/src/ui/tools/text-tool.cpp
+++ b/src/ui/tools/text-tool.cpp
@@ -590,8 +590,8 @@ bool TextTool::root_handler(GdkEvent* event) {
                 // status text
                 Inkscape::Util::Quantity x_q = Inkscape::Util::Quantity(fabs((p - this->p0)[Geom::X]), "px");
                 Inkscape::Util::Quantity y_q = Inkscape::Util::Quantity(fabs((p - this->p0)[Geom::Y]), "px");
-                GString *xs = g_string_new(x_q.string(desktop->namedview->doc_units).c_str());
-                GString *ys = g_string_new(y_q.string(desktop->namedview->doc_units).c_str());
+                GString *xs = g_string_new(x_q.string(desktop->namedview->display_units).c_str());
+                GString *ys = g_string_new(y_q.string(desktop->namedview->display_units).c_str());
                 this->message_context->setF(Inkscape::IMMEDIATE_MESSAGE, _("<b>Flowed text frame</b>: %s &#215; %s"), xs->str, ys->str);
 
                 g_string_free(xs, FALSE);
diff --git a/src/ui/widget/page-sizer.cpp b/src/ui/widget/page-sizer.cpp
index 32e357c57..b775b3c49 100644
--- a/src/ui/widget/page-sizer.cpp
+++ b/src/ui/widget/page-sizer.cpp
@@ -313,8 +313,8 @@ PageSizer::PageSizer(Registry & _wr)
     _wr.setUpdating (true);
     if (nv->page_size_units) {
         _dimensionUnits.setUnit(nv->page_size_units->abbr);
-    } else if (nv->doc_units) {
-        _dimensionUnits.setUnit(nv->doc_units->abbr);
+    } else if (nv->display_units) {
+        _dimensionUnits.setUnit(nv->display_units->abbr);
     }
     _wr.setUpdating (false);
     
diff --git a/src/ui/widget/selected-style.cpp b/src/ui/widget/selected-style.cpp
index d22c59aa4..aebef2c4e 100644
--- a/src/ui/widget/selected-style.cpp
+++ b/src/ui/widget/selected-style.cpp
@@ -498,7 +498,7 @@ SelectedStyle::setDesktop(SPDesktop *desktop)
             this )
     ));
 
-    _sw_unit = sp_desktop_namedview(desktop)->doc_units;
+    _sw_unit = sp_desktop_namedview(desktop)->display_units;
 
     // Set the doc default unit active in the units list
     gint length = g_slist_length(_unit_mis);
diff --git a/src/util/units.cpp b/src/util/units.cpp
index 3d635e2d2..8ad3560dd 100644
--- a/src/util/units.cpp
+++ b/src/util/units.cpp
@@ -21,6 +21,8 @@
 #include <glibmm/fileutils.h>
 #include <glibmm/markup.h>
 
+#include <2geom/coord.h>
+
 #include "util/units.h"
 #include "path-prefix.h"
 #include "streq.h"
@@ -279,6 +281,28 @@ Unit const *UnitTable::getUnit(SVGLength::Unit u) const
     return &_empty_unit;
 }
 
+Unit const *UnitTable::findUnit(double factor, UnitType type) const
+{
+    const double eps = factor * 0.01; // allow for 1% deviation
+
+    UnitCodeMap::const_iterator cit = _unit_map.begin();
+    while (cit != _unit_map.end()) {
+        if (cit->second->type == type) {
+            if (Geom::are_near(cit->second->factor, factor, eps)) {
+                // unit found!
+                break;
+            }
+        }
+        ++cit;
+    }
+
+    if (cit != _unit_map.end()) {
+        return cit->second;
+    } else {
+        return getUnit(_primary_unit[type]);
+    }
+}
+
 Quantity UnitTable::parseQuantity(Glib::ustring const &q) const
 {
     Glib::MatchInfo match_info;
diff --git a/src/util/units.h b/src/util/units.h
index efe1dbec7..13777fd1b 100644
--- a/src/util/units.h
+++ b/src/util/units.h
@@ -141,6 +141,9 @@ public:
     /** Retrieve a given unit based on its string identifier */
     Unit const *getUnit(Glib::ustring const &name) const;
     Unit const *getUnit(char const *name) const;
+
+    /** Try to find a unit based on its conversion factor to the primary */
+    Unit const *findUnit(double factor, UnitType type) const;
     
     /** Retrieve a given unit based on its SVGLength unit */
     Unit const *getUnit(SVGLength::Unit u) const;
diff --git a/src/verbs.cpp b/src/verbs.cpp
index b4743751e..33810fba2 100644
--- a/src/verbs.cpp
+++ b/src/verbs.cpp
@@ -1860,7 +1860,7 @@ void ZoomVerb::perform(SPAction *action, void *data)
 
     double zcorr = 1.0;
     Glib::ustring abbr = prefs->getString("/options/zoomcorrection/unit");
-    if (dt->namedview->doc_units && dt->namedview->doc_units->abbr == abbr)
+    if (dt->namedview->display_units && (dt->namedview->display_units->abbr == abbr))
         zcorr = prefs->getDouble("/options/zoomcorrection/value", 1.0);
 
     Geom::Rect const d = dt->get_display_area();
diff --git a/src/widgets/desktop-widget.cpp b/src/widgets/desktop-widget.cpp
index 9c8dac7dc..2aab68812 100644
--- a/src/widgets/desktop-widget.cpp
+++ b/src/widgets/desktop-widget.cpp
@@ -1665,7 +1665,7 @@ SPDesktopWidget* SPDesktopWidget::createInstance(SPNamedView *namedview)
 {
     SPDesktopWidget *dtw = static_cast<SPDesktopWidget*>(g_object_new(SP_TYPE_DESKTOP_WIDGET, NULL));
 
-    dtw->dt2r = 1. / namedview->doc_units->factor;
+    dtw->dt2r = 1. / namedview->display_units->factor;
 
     dtw->ruler_origin = Geom::Point(0,0); //namedview->gridorigin;   Why was the grid origin used here?
 
@@ -1737,7 +1737,7 @@ void SPDesktopWidget::namedviewModified(SPObject *obj, guint flags)
     SPNamedView *nv=SP_NAMEDVIEW(obj);
 
     if (flags & SP_OBJECT_MODIFIED_FLAG) {
-        this->dt2r = 1. / nv->doc_units->factor;
+        this->dt2r = 1. / nv->display_units->factor;
         this->ruler_origin = Geom::Point(0,0); //nv->gridorigin;   Why was the grid origin used here?
 
         sp_ruler_set_unit(SP_RULER (this->vruler), nv->getDefaultUnit());
@@ -1771,14 +1771,14 @@ void SPDesktopWidget::namedviewModified(SPObject *obj, guint flags)
                         if (tracker == NULL) // it's null when inkscape is first opened
                             continue;
 
-                        tracker->setActiveUnit( nv->doc_units );
+                        tracker->setActiveUnit( nv->display_units );
                     } // grandchildren
                 } // if child is a container
             } // children
         } // if aux_toolbox is a container
 
-        gtk_widget_set_tooltip_text(this->hruler_box, gettext(nv->doc_units->name_plural.c_str()));
-        gtk_widget_set_tooltip_text(this->vruler_box, gettext(nv->doc_units->name_plural.c_str()));
+        gtk_widget_set_tooltip_text(this->hruler_box, gettext(nv->display_units->name_plural.c_str()));
+        gtk_widget_set_tooltip_text(this->vruler_box, gettext(nv->display_units->name_plural.c_str()));
 
         sp_desktop_widget_update_rulers(this);
         ToolboxFactory::updateSnapToolbox(this->desktop, 0, this->snap_toolbox);
diff --git a/src/widgets/lpe-toolbar.cpp b/src/widgets/lpe-toolbar.cpp
index a85f3ae78..c6da46956 100644
--- a/src/widgets/lpe-toolbar.cpp
+++ b/src/widgets/lpe-toolbar.cpp
@@ -280,7 +280,7 @@ static void lpetool_toolbox_watch_ec(SPDesktop* dt, Inkscape::UI::Tools::ToolBas
 void sp_lpetool_toolbox_prep(SPDesktop *desktop, GtkActionGroup* mainActions, GObject* holder)
 {
     UnitTracker* tracker = new UnitTracker(Inkscape::Util::UNIT_TYPE_LINEAR);
-    tracker->setActiveUnit(sp_desktop_namedview(desktop)->doc_units);
+    tracker->setActiveUnit(sp_desktop_namedview(desktop)->display_units);
     g_object_set_data(holder, "tracker", tracker);
     Unit const *unit = tracker->getActiveUnit();
     g_return_if_fail(unit != NULL);
diff --git a/src/widgets/node-toolbar.cpp b/src/widgets/node-toolbar.cpp
index 467325d08..1224ab355 100644
--- a/src/widgets/node-toolbar.cpp
+++ b/src/widgets/node-toolbar.cpp
@@ -330,7 +330,7 @@ static void node_toolbox_watch_ec(SPDesktop* dt, Inkscape::UI::Tools::ToolBase*
 void sp_node_toolbox_prep(SPDesktop *desktop, GtkActionGroup* mainActions, GObject* holder)
 {
     UnitTracker* tracker = new UnitTracker(Inkscape::Util::UNIT_TYPE_LINEAR);
-    Unit doc_units = *sp_desktop_namedview(desktop)->doc_units;
+    Unit doc_units = *sp_desktop_namedview(desktop)->display_units;
     tracker->setActiveUnit(&doc_units);
     g_object_set_data( holder, "tracker", tracker );
 
diff --git a/src/widgets/rect-toolbar.cpp b/src/widgets/rect-toolbar.cpp
index b6b7e435d..5356ebb0d 100644
--- a/src/widgets/rect-toolbar.cpp
+++ b/src/widgets/rect-toolbar.cpp
@@ -109,7 +109,7 @@ static void sp_rtb_value_changed(GtkAdjustment *adj, GObject *tbl, gchar const *
     for (GSList const *items = selection->itemList(); items != NULL; items = items->next) {
         if (SP_IS_RECT(items->data)) {
             if (gtk_adjustment_get_value(adj) != 0) {
-                (SP_RECT(items->data)->*setter)(Quantity::convert(gtk_adjustment_get_value(adj), unit, sp_desktop_namedview(desktop)->doc_units));
+                (SP_RECT(items->data)->*setter)(Quantity::convert(gtk_adjustment_get_value(adj), unit, sp_desktop_namedview(desktop)->svg_units));
             } else {
                 SP_OBJECT(items->data)->getRepr()->setAttribute(value_name, NULL);
             }
@@ -181,7 +181,7 @@ static void rect_tb_event_attr_changed(Inkscape::XML::Node * /*repr*/, gchar con
 
     UnitTracker* tracker = reinterpret_cast<UnitTracker*>( g_object_get_data( tbl, "tracker" ) );
     Unit const *unit = tracker->getActiveUnit();
-    Unit const *doc_unit = sp_desktop_namedview(SP_ACTIVE_DESKTOP)->doc_units;
+    Unit const *svg_unit = sp_desktop_namedview(SP_ACTIVE_DESKTOP)->svg_units;
     g_return_if_fail(unit != NULL);
 
     gpointer item = g_object_get_data( tbl, "item" );
@@ -190,28 +190,28 @@ static void rect_tb_event_attr_changed(Inkscape::XML::Node * /*repr*/, gchar con
             GtkAdjustment *adj = GTK_ADJUSTMENT( g_object_get_data( tbl, "rx" ) );
 
             gdouble rx = SP_RECT(item)->getVisibleRx();
-            gtk_adjustment_set_value(adj, Quantity::convert(rx, doc_unit, unit));
+            gtk_adjustment_set_value(adj, Quantity::convert(rx, svg_unit, unit));
         }
 
         {
             GtkAdjustment *adj = GTK_ADJUSTMENT( g_object_get_data( tbl, "ry" ) );
 
             gdouble ry = SP_RECT(item)->getVisibleRy();
-            gtk_adjustment_set_value(adj, Quantity::convert(ry, doc_unit, unit));
+            gtk_adjustment_set_value(adj, Quantity::convert(ry, svg_unit, unit));
         }
 
         {
             GtkAdjustment *adj = GTK_ADJUSTMENT( g_object_get_data( tbl, "width" ) );
 
             gdouble width = SP_RECT(item)->getVisibleWidth();
-            gtk_adjustment_set_value(adj, Quantity::convert(width, doc_unit, unit));
+            gtk_adjustment_set_value(adj, Quantity::convert(width, svg_unit, unit));
         }
 
         {
             GtkAdjustment *adj = GTK_ADJUSTMENT( g_object_get_data( tbl, "height" ) );
 
             gdouble height = SP_RECT(item)->getVisibleHeight();
-            gtk_adjustment_set_value(adj, Quantity::convert(height, doc_unit, unit));
+            gtk_adjustment_set_value(adj, Quantity::convert(height, svg_unit, unit));
         }
     }
 
@@ -307,7 +307,7 @@ void sp_rect_toolbox_prep(SPDesktop *desktop, GtkActionGroup* mainActions, GObje
     UnitTracker* tracker = new UnitTracker(Inkscape::Util::UNIT_TYPE_LINEAR);
     //tracker->addUnit( SP_UNIT_PERCENT, 0 );
     // fixme: add % meaning per cent of the width/height
-    tracker->setActiveUnit( sp_desktop_namedview(desktop)->doc_units );
+    tracker->setActiveUnit( sp_desktop_namedview(desktop)->display_units );
     g_object_set_data( holder, "tracker", tracker );
 
     /* W */
diff --git a/src/widgets/select-toolbar.cpp b/src/widgets/select-toolbar.cpp
index 08a46354e..80fe93356 100644
--- a/src/widgets/select-toolbar.cpp
+++ b/src/widgets/select-toolbar.cpp
@@ -488,7 +488,7 @@ void sp_select_toolbox_prep(SPDesktop *desktop, GtkActionGroup* mainActions, GOb
     // Create the units menu.
     UnitTracker* tracker = new UnitTracker(Inkscape::Util::UNIT_TYPE_LINEAR);
     tracker->addUnit(unit_table.getUnit("%"));
-    tracker->setActiveUnit( sp_desktop_namedview(desktop)->doc_units );
+    tracker->setActiveUnit( sp_desktop_namedview(desktop)->display_units );
 
     g_object_set_data( G_OBJECT(spw), "tracker", tracker );
     g_signal_connect( G_OBJECT(spw), "destroy", G_CALLBACK(destroy_tracker), spw );
diff --git a/src/widgets/stroke-style.cpp b/src/widgets/stroke-style.cpp
index 02dd5df6e..7c85689a2 100644
--- a/src/widgets/stroke-style.cpp
+++ b/src/widgets/stroke-style.cpp
@@ -204,8 +204,8 @@ StrokeStyle::StrokeStyle() :
     unitSelector->addUnit(*unit_table.getUnit("%"));
     _old_unit = unitSelector->getUnit();
     if (desktop) {
-        unitSelector->setUnit(sp_desktop_namedview(desktop)->doc_units->abbr);
-        _old_unit = sp_desktop_namedview(desktop)->doc_units;
+        unitSelector->setUnit(sp_desktop_namedview(desktop)->svg_units->abbr);
+        _old_unit = sp_desktop_namedview(desktop)->svg_units;
     }
     widthSpin->setUnitMenu(unitSelector);
     unitChangedConn = unitSelector->signal_changed().connect(sigc::mem_fun(*this, &StrokeStyle::unitChangedCB));
@@ -839,7 +839,7 @@ StrokeStyle::updateLine()
             // same width, or only one object; no sense to keep percent, switch to absolute
             Inkscape::Util::Unit const *tempunit = unitSelector->getUnit();
             if (tempunit->type != Inkscape::Util::UNIT_TYPE_LINEAR) {
-                unitSelector->setUnit(sp_desktop_namedview(SP_ACTIVE_DESKTOP)->doc_units->abbr);
+                unitSelector->setUnit(sp_desktop_namedview(SP_ACTIVE_DESKTOP)->display_units->abbr);
             }
         }