New option to invert y-axis

Replaces all hard coded or implicit desktop coordinate usage with
doc2dt multiplication.

New global preference: Interface > Origin at upper left

https://bugs.launchpad.net/inkscape/+bug/170049

3 files changed, 22 insertions, 2 deletions

diff --git a/src/ui/dialog/align-and-distribute.cpp b/src/ui/dialog/align-and-distribute.cpp
index 7ad8a5e18..b21fd2956 100644
--- a/src/ui/dialog/align-and-distribute.cpp
+++ b/src/ui/dialog/align-and-distribute.cpp
@@ -130,7 +130,7 @@ void ActionAlign::do_action(SPDesktop *desktop, int index)
     std::vector<SPItem*> selected(selection->items().begin(), selection->items().end());
     if (selected.empty()) return;
 
-    const Coeffs &a = _allCoeffs[index];
+    Coeffs a = _allCoeffs[index]; // copy
     SPItem *focus = nullptr;
     Geom::OptRect b = Geom::OptRect();
     Selection::CompareSize horiz = (a.mx0 != 0.0) || (a.mx1 != 0.0)
@@ -168,6 +168,13 @@ void ActionAlign::do_action(SPDesktop *desktop, int index)
         b = focus->desktopPreferredBounds();
     g_return_if_fail(b);
 
+    if (horiz == Selection::HORIZONTAL && desktop->is_yaxisdown()) {
+        a.my0 = 1. - a.my0;
+        a.my1 = 1. - a.my1;
+        a.sy0 = 1. - a.sy0;
+        a.sy1 = 1. - a.sy1;
+    }
+
     // Generate the move point from the selected bounding box
     Geom::Point mp = Geom::Point(a.mx0 * b->min()[Geom::X] + a.mx1 * b->max()[Geom::X],
                                  a.my0 * b->min()[Geom::Y] + a.my1 * b->max()[Geom::Y]);
@@ -303,6 +310,13 @@ private :
         ++second;
         if (second == selected.end()) return;
 
+        double kBegin = _kBegin;
+        double kEnd = _kEnd;
+        if (_orientation == Geom::Y && desktop->is_yaxisdown()) {
+            kBegin = 1. - kBegin;
+            kEnd = 1. - kEnd;
+        }
+
         Inkscape::Preferences *prefs = Inkscape::Preferences::get();
         int prefs_bbox = prefs->getBool("/tools/bounding_box");
         std::vector< BBoxSort  > sorted;
@@ -312,7 +326,7 @@ private :
             SPItem *item = *it;
             Geom::OptRect bbox = !prefs_bbox ? (item)->desktopVisualBounds() : (item)->desktopGeometricBounds();
             if (bbox) {
-                sorted.emplace_back(item, *bbox, _orientation, _kBegin, _kEnd);
+                sorted.emplace_back(item, *bbox, _orientation, kBegin, kEnd);
             }
         }
         //sort bbox by anchors
diff --git a/src/ui/dialog/inkscape-preferences.cpp b/src/ui/dialog/inkscape-preferences.cpp
index ecf470d21..bb15d771d 100644
--- a/src/ui/dialog/inkscape-preferences.cpp
+++ b/src/ui/dialog/inkscape-preferences.cpp
@@ -771,6 +771,11 @@ void InkscapePreferences::initPageUI()
                         _("Selects whether the dockbar switcher will show text labels, icons, or both"), false);
     }
 
+    _ui_yaxisdown.init( _("Origin at upper left with y-axis pointing down (requires restart)"), "/options/yaxisdown", false);
+    _page_ui.add_line( false, "", _ui_yaxisdown, "",
+                       _("When off, origin is at lower left corner and y-axis points up"), true);
+
+
     // Theme
     _page_theme.add_group_header(_("Theme changes"));
     {
diff --git a/src/ui/dialog/inkscape-preferences.h b/src/ui/dialog/inkscape-preferences.h
index 55ea35f63..d0b51fa83 100644
--- a/src/ui/dialog/inkscape-preferences.h
+++ b/src/ui/dialog/inkscape-preferences.h
@@ -385,6 +385,7 @@ protected:
     UI::Widget::PrefSpinButton  _misc_recent;
     UI::Widget::PrefCheckButton _ui_partialdynamic;
     UI::Widget::ZoomCorrRulerSlider _ui_zoom_correction;
+    UI::Widget::PrefCheckButton _ui_yaxisdown;
 
     //Spellcheck
     UI::Widget::PrefCombo       _spell_language;