Fix and improve window size/position handling/restoration

- Fix broken window size/position restoration after gtk3 deprecation
  fixes in fa8a2ee7e2539b145a87ac9af0d9748effa91631
- Use monitor geometry of the monitor Inkscape will be shown on
  instead of defaulting to the primary monitor which is often wrong
- Let gtk+ / window manager handle window size/position sanitization
  (confirmed working on Windows and Ubuntu 16.04) and remove custom
  code which was prone to errors and did not always work as desired
- Make default window size "Small" work again (was broken in gtk3)
  and add a new preference "Default" which uses the native window
  size (i.e. tries to make just enough room for all controls)

10 files changed, 254 insertions, 218 deletions

diff --git a/src/enums.h b/src/enums.h
index 2a30fc4a8..592cb81e9 100644
--- a/src/enums.h
+++ b/src/enums.h
@@ -111,5 +111,22 @@ enum PrefsMaskobjectGrouping {
     PREFS_MASKOBJECT_GROUPING_ALL = 2,
 };
 
+/* save window geometry preference values (/options/savewindowgeometry/value) */
+
+enum PrefsSaveWindowGeometry {
+    PREFS_WINDOW_GEOMETRY_NONE = 0,
+    PREFS_WINDOW_GEOMETRY_FILE = 1,
+    PREFS_WINDOW_GEOMETRY_LAST = 2,
+};
+
+/* default window size preference values (/options/defaultwindowsize/value) */
+
+enum PrefsDefaultWindowSize {
+    PREFS_WINDOW_SIZE_NATURAL = -1,
+    PREFS_WINDOW_SIZE_SMALL = 0,
+    PREFS_WINDOW_SIZE_LARGE = 1,
+    PREFS_WINDOW_SIZE_MAXIMIZED = 2,
+};
+
 #endif
 
diff --git a/src/sp-namedview.cpp b/src/sp-namedview.cpp
index 99cc6fbfc..59c7129f6 100644
--- a/src/sp-namedview.cpp
+++ b/src/sp-namedview.cpp
@@ -27,6 +27,8 @@
 #include "document.h"
 #include "document-undo.h"
 #include "desktop-events.h"
+#include "enums.h"
+#include "ui/monitor.h"
 
 #include "sp-guide.h"
 #include "sp-item-group.h"
@@ -37,12 +39,6 @@
 #include "sp-root.h"
 #include <gtkmm/window.h>
 
-#if GTKMM_CHECK_VERSION(3,22,0)
-# include <gdkmm/monitor.h>
-#else
-# include <gdkmm/screen.h>
-#endif
-
 using Inkscape::DocumentUndo;
 using Inkscape::Util::unit_table;
 
@@ -736,41 +732,6 @@ void SPNamedView::show(SPDesktop *desktop)
     desktop->showGrids(grids_visible, false);
 }
 
-namespace {
-
-gint const MIN_ONSCREEN_DISTANCE = 100;
-gdouble const NEWDOC_X_SCALE = 0.75;
-gdouble const NEWDOC_Y_SCALE = NEWDOC_X_SCALE;
-
-Geom::Point calcAnchorPoint(gint const x, gint const y,
-                            gint const w, gint const h, gint const minOnscreen)
-{
-#if GTKMM_CHECK_VERSION(3,22,0)
-    Gdk::Rectangle screen_geometry;
-
-    auto const display = Gdk::Display::get_default();
-    auto const monitor = display->get_primary_monitor();
-    monitor->get_geometry(screen_geometry);
-    int screen_width  = screen_geometry.get_width();
-    int screen_height = screen_geometry.get_height();
-#else
-    int screen_width  = gdk_screen_width();
-    int screen_height = gdk_screen_height();
-#endif
-
-    // prevent the window from moving off the screen to the right or to the bottom
-    gint ax = MIN(screen_width  - minOnscreen, x);
-    gint ay = MIN(screen_height - minOnscreen, y);
-
-    // prevent the window from moving off the screen to the left or to the top
-    ax = MAX(minOnscreen - w, ax);
-    ay = MAX(minOnscreen - h, ay);
-
-    return Geom::Point(ax, ay);
-}
-
-} // namespace
-
 /*
  * Restores window geometry from the document settings or defaults in prefs
  */
@@ -778,54 +739,49 @@ void sp_namedview_window_from_document(SPDesktop *desktop)
 {
     SPNamedView *nv = desktop->namedview;
     Inkscape::Preferences *prefs = Inkscape::Preferences::get();
-    bool geometry_from_file = (1 == prefs->getInt("/options/savewindowgeometry/value", 0));
-    bool geometry_from_last = (2 == prefs->getInt("/options/savewindowgeometry/value", 0));
-    gint default_geometry = prefs->getInt("/options/defaultwindowsize/value", 1);
+    int window_geometry = prefs->getInt("/options/savewindowgeometry/value", PREFS_WINDOW_GEOMETRY_NONE);
+    int default_size = prefs->getInt("/options/defaultwindowsize/value", PREFS_WINDOW_SIZE_NATURAL);
     bool new_document = (nv->window_width <= 0) || (nv->window_height <= 0);
     bool show_dialogs = true;
 
     // restore window size and position stored with the document
-    if (geometry_from_last) {
+    Gtk::Window *win = desktop->getToplevel();
+    g_assert(win);
+    if (window_geometry == PREFS_WINDOW_GEOMETRY_LAST) {
         // do nothing, as we already have code for that in interface.cpp
         // TODO: Probably should not do similar things in two places
-    } else if ((geometry_from_file && nv->window_maximized) || (new_document && (default_geometry == 2))) {
-        Gtk::Window *win = desktop->getToplevel();
-        if (win) {
-            win->maximize();
-        }
+    } else if ((window_geometry == PREFS_WINDOW_GEOMETRY_FILE && nv->window_maximized) ||
+               (new_document && (default_size == PREFS_WINDOW_SIZE_MAXIMIZED))) {
+        win->maximize();
     } else {
-
-        // TODO: account for multi-monitor setups (i.e. on which monitor do we want to display Inkscape?)
-        Gdk::Rectangle monitor_geometry;
-
-#if GTKMM_CHECK_VERSION(3,22,0)
-        auto const display = Gdk::Display::get_default();
-        auto const monitor = display->get_primary_monitor();
-
-        // If user hasn't configured a primary monitor, nullptr is returned.
-        if (monitor) {
-            monitor->get_geometry(monitor_geometry);
-        }
-#else
-        auto const default_screen = Gdk::Screen::get_default();
-        auto const monitor_number = default_screen->get_primary_monitor();
-        default_screen->get_monitor_geometry(monitor_number, monitor_geometry);
-#endif
-
-        int w = monitor_geometry.get_width();
-        int h = monitor_geometry.get_height();
-
+        const int MIN_WINDOW_SIZE = 600;
+        int w = 0;
+        int h = 0;
         bool move_to_screen = false;
-        if (geometry_from_file and !new_document) {
-            w = MIN(w, nv->window_width);
-            h = MIN(h, nv->window_height);          
+        if (window_geometry == PREFS_WINDOW_GEOMETRY_FILE && !new_document) {
+            Gdk::Rectangle monitor_geometry = Inkscape::UI::get_monitor_geometry_at_point(nv->window_x, nv->window_y);
+            w = MIN(monitor_geometry.get_width(), nv->window_width);
+            h = MIN(monitor_geometry.get_height(), nv->window_height);      
             move_to_screen = true;
-        } else if (default_geometry == 1) {
-            w *= NEWDOC_X_SCALE;
-            h *= NEWDOC_Y_SCALE;
-        } else if (default_geometry == 0) {
-            w = h = 0; // use the smallest possible window size; could be a factor like NEWDOC_X_SCALE in future
-        } 
+        } else if (default_size == PREFS_WINDOW_SIZE_LARGE) {
+            Gdk::Rectangle monitor_geometry = Inkscape::UI::get_monitor_geometry_at_window(win->get_window());
+            w = MAX(0.75 * monitor_geometry.get_width(), MIN_WINDOW_SIZE);
+            h = MAX(0.75 * monitor_geometry.get_height(), MIN_WINDOW_SIZE);
+        } else if (default_size == PREFS_WINDOW_SIZE_SMALL) {
+            w = h = MIN_WINDOW_SIZE;
+        } else if (default_size == PREFS_WINDOW_SIZE_NATURAL) {
+            // don't set size (i.e. keep the gtk+ default, which will be the natural size)
+            // unless gtk+ decided it would be a good idea to show a window that is larger than the screen
+            Gdk::Rectangle monitor_geometry = Inkscape::UI::get_monitor_geometry_at_window(win->get_window());
+            int monitor_width =  monitor_geometry.get_width();
+            int monitor_height = monitor_geometry.get_height();
+            int window_width, window_height;
+            win->get_size(window_width, window_height);
+            if (window_width > monitor_width || window_height > monitor_height) {
+                w = std::min(monitor_width, window_width);
+                h = std::min(monitor_height, window_height);
+            }
+        }
         if ((w > 0) && (h > 0)) {
 #ifndef WIN32
             gint dx= 0;
@@ -841,8 +797,9 @@ void sp_namedview_window_from_document(SPDesktop *desktop)
 #endif
             desktop->setWindowSize(w, h);
             if (move_to_screen) {
-                Geom::Point origin = calcAnchorPoint(nv->window_x, nv->window_y, w, h, MIN_ONSCREEN_DISTANCE);
-                desktop->setWindowPosition(origin);
+                win->hide();
+                desktop->setWindowPosition(Geom::Point(nv->window_x, nv->window_y));
+                win->show();
             }
         }
     }
@@ -912,7 +869,8 @@ void sp_namedview_update_layers_from_document (SPDesktop *desktop)
 void sp_namedview_document_from_window(SPDesktop *desktop)
 {
     Inkscape::Preferences *prefs = Inkscape::Preferences::get();
-    bool save_geometry_in_file = (1 == prefs->getInt("/options/savewindowgeometry/value", 0));
+    int window_geometry = prefs->getInt("/options/savewindowgeometry/value", PREFS_WINDOW_GEOMETRY_NONE);
+    bool save_geometry_in_file = window_geometry == PREFS_WINDOW_GEOMETRY_FILE;
     bool save_viewport_in_file = prefs->getBool("/options/savedocviewport/value", true);
     Inkscape::XML::Node *view = desktop->namedview->getRepr();
     Geom::Rect const r = desktop->get_display_area();
diff --git a/src/svg-view-slideshow.cpp b/src/svg-view-slideshow.cpp
index 0e50d582b..430fd9ce5 100644
--- a/src/svg-view-slideshow.cpp
+++ b/src/svg-view-slideshow.cpp
@@ -30,11 +30,6 @@
 #endif
 
 #include <glibmm/main.h>
-
-#if GTKMM_CHECK_VERSION(3,22,0)
-# include <gdkmm/monitor.h>
-#endif
-
 #include <gtkmm/button.h>
 #include <gtkmm/buttonbox.h>
 #include <gtkmm/image.h>
@@ -42,16 +37,13 @@
 
 #include "document.h"
 #include "ui/icon-names.h"
+#include "ui/monitor.h"
 #include "util/units.h"
 
 #include "svg-view.h"
 #include "svg-view-slideshow.h"
 #include "svg-view-widget.h"
 
-#if GTKMM_CHECK_VERSION(3,22,0)
-# include <gdkmm/monitor.h>
-#endif
-
 
 SPSlideShow::SPSlideShow(std::vector<Glib::ustring> const &slides, bool full_screen, int timer, double scale)
     : _slides(slides)
@@ -64,34 +56,9 @@ SPSlideShow::SPSlideShow(std::vector<Glib::ustring> const &slides, bool full_scr
     , _ctrlwin(NULL)
 {
     // setup initial document
-#if GTKMM_CHECK_VERSION(3,22,0)
-    auto display = Gdk::Display::get_default();
-    auto monitor = display->get_primary_monitor();
-
-    // Fallback to monitor number 0 if the user hasn't configured a primary monitor
-    if (!monitor) {
-        monitor = display->get_monitor(0);
-    }
-
-    if (monitor) {
-        Gdk::Rectangle monitor_geometry;
-        monitor->get_geometry(monitor_geometry);
-
-        auto const monitor_width  = monitor_geometry.get_width();
-        auto const monitor_height = monitor_geometry.get_height();
-
-#else
-    auto default_screen = Gdk::Screen::get_default();
-
-    if (default_screen) {
-        auto const monitor_width  = default_screen->get_width();
-        auto const monitor_height = default_screen->get_height();
-#endif
-
-        set_default_size(MIN ((int)_doc->getWidth().value("px")*_scale,  monitor_width  - 64),
-                         MIN ((int)_doc->getHeight().value("px")*_scale, monitor_height - 64));
-
-    }
+    Gdk::Rectangle monitor_geometry = Inkscape::UI::get_monitor_geometry_primary(); // TODO: is inkview always launched on primary monitor?
+    set_default_size(MIN ((int)_doc->getWidth().value("px")*_scale,  monitor_geometry.get_width()  - 64),
+                     MIN ((int)_doc->getHeight().value("px")*_scale, monitor_geometry.get_height() - 64));
 
     _view = sp_svg_view_widget_new(_doc);
     SP_SVG_VIEW_WIDGET(_view)->setResize( false, _doc->getWidth().value("px"), _doc->getHeight().value("px") );
diff --git a/src/ui/CMakeLists.txt b/src/ui/CMakeLists.txt
index fecb14a91..b9933bba6 100644
--- a/src/ui/CMakeLists.txt
+++ b/src/ui/CMakeLists.txt
@@ -5,6 +5,7 @@ set(ui_SRC
 	dialog-events.cpp
 	draw-anchor.cpp
 	interface.cpp
+    monitor.cpp
 	previewholder.cpp
 	selected-color.cpp
 	shape-editor.cpp
@@ -186,6 +187,7 @@ set(ui_SRC
 	event-debug.h
 	icon-names.h
 	interface.h
+    monitor.h
 	previewable.h
 	previewfillable.h
 	previewholder.h
diff --git a/src/ui/dialog/dialog.cpp b/src/ui/dialog/dialog.cpp
index 3d949a8c9..f7e9a1bed 100644
--- a/src/ui/dialog/dialog.cpp
+++ b/src/ui/dialog/dialog.cpp
@@ -20,13 +20,10 @@
 #include "dialog-manager.h"
 #include <gtkmm/dialog.h>
 
-#if GTKMM_CHECK_VERSION(3,22,0)
-# include <gdkmm/monitor.h>
-#endif
-
 #include <gdk/gdkkeysyms.h>
 
 #include "inkscape.h"
+#include "ui/monitor.h"
 #include "ui/tools/tool-base.h"
 #include "desktop.h"
 
@@ -166,26 +163,9 @@ void Dialog::read_geometry()
         resize(w, h);
     }
 
-#if GTKMM_CHECK_VERSION(3,22,0)
-    auto const display = Gdk::Display::get_default();
-    auto monitor = display->get_primary_monitor();
-
-    // If user hasn't configured a primary monitor, nullptr is returned so try first monitor.
-    if (!monitor) {
-        std::cerr << "Dialog::read_geometry: no primary monitor configured!" << std::endl;
-        monitor = display->get_monitor(0);
-    }
-
-    Gdk::Rectangle screen_geometry;
-    if (monitor) {
-        monitor->get_geometry(screen_geometry);
-    }
-    auto const screen_width  = screen_geometry.get_width();
-    auto const screen_height = screen_geometry.get_height();
-#else
-    auto const screen_width  = gdk_screen_width();
-    auto const screen_height = gdk_screen_height();
-#endif
+    Gdk::Rectangle monitor_geometry = Inkscape::UI::get_monitor_geometry_primary();
+    auto const screen_width  = monitor_geometry.get_width();
+    auto const screen_height = monitor_geometry.get_height();
 
     // If there are stored values for where the dialog should be
     // located, then restore the dialog to that position.
diff --git a/src/ui/dialog/inkscape-preferences.cpp b/src/ui/dialog/inkscape-preferences.cpp
index 0ac12d15c..7b7bd6548 100644
--- a/src/ui/dialog/inkscape-preferences.cpp
+++ b/src/ui/dialog/inkscape-preferences.cpp
@@ -684,9 +684,9 @@ void InkscapePreferences::initPageUI()
     }
 
     // Windows
-    _win_save_geom.init ( _("Save and restore window geometry for each document"), "/options/savewindowgeometry/value", 1, true, 0);
-    _win_save_geom_prefs.init ( _("Remember and use last window's geometry"), "/options/savewindowgeometry/value", 2, false, &_win_save_geom);
-    _win_save_geom_off.init ( _("Don't save window geometry"), "/options/savewindowgeometry/value", 0, false, &_win_save_geom);
+    _win_save_geom.init ( _("Save and restore window geometry for each document"), "/options/savewindowgeometry/value", PREFS_WINDOW_GEOMETRY_FILE, true, 0);
+    _win_save_geom_prefs.init ( _("Remember and use last window's geometry"), "/options/savewindowgeometry/value", PREFS_WINDOW_GEOMETRY_LAST, false, &_win_save_geom);
+    _win_save_geom_off.init ( _("Don't save window geometry"), "/options/savewindowgeometry/value", PREFS_WINDOW_GEOMETRY_NONE, false, &_win_save_geom);
 
     _win_save_dialog_pos_on.init ( _("Save and restore dialogs status"), "/options/savedialogposition/value", 1, true, 0);
     _win_save_dialog_pos_off.init ( _("Don't save dialogs status"), "/options/savedialogposition/value", 0, false, &_win_save_dialog_pos_on);
@@ -707,10 +707,16 @@ void InkscapePreferences::initPageUI()
     _win_ontop_agressive.init ( _("Aggressive"), "/options/transientpolicy/value", 2, false, &_win_ontop_none);
 
     {
-        Glib::ustring defaultSizeLabels[] = {C_("Window size", "Small"), C_("Window size", "Large"), C_("Window size", "Maximized")};
-        int defaultSizeValues[] = {0, 1, 2};
-
-        _win_default_size.init( "/options/defaultwindowsize/value", defaultSizeLabels, defaultSizeValues, G_N_ELEMENTS(defaultSizeLabels), 1 );
+        Glib::ustring defaultSizeLabels[] = {C_("Window size", "Default"),
+                                             C_("Window size", "Small"),
+                                             C_("Window size", "Large"),
+                                             C_("Window size", "Maximized")};
+        int defaultSizeValues[] = {PREFS_WINDOW_SIZE_NATURAL,
+                                   PREFS_WINDOW_SIZE_SMALL,
+                                   PREFS_WINDOW_SIZE_LARGE,
+                                   PREFS_WINDOW_SIZE_MAXIMIZED};
+
+        _win_default_size.init( "/options/defaultwindowsize/value", defaultSizeLabels, defaultSizeValues, G_N_ELEMENTS(defaultSizeLabels), PREFS_WINDOW_SIZE_NATURAL);
         _page_windows.add_line( false, _("Default window size:"),  _win_default_size, "",
                            _("Set the default window size"), false);
     }
diff --git a/src/ui/interface.cpp b/src/ui/interface.cpp
index 826737c2c..7df3502f7 100644
--- a/src/ui/interface.cpp
+++ b/src/ui/interface.cpp
@@ -30,10 +30,7 @@
 #include "file.h"
 #include <glibmm/miscutils.h>
 
-#if GTKMM_CHECK_VERSION(3,22,0)
-# include <gdkmm/monitor.h>
-#endif
-
+#include "enums.h"
 #include "inkscape.h"
 #include "extension/db.h"
 #include "extension/effect.h"
@@ -43,6 +40,7 @@
 #include "document.h"
 
 #include "ui/interface.h"
+#include "ui/monitor.h"
 #include "desktop.h"
 #include "selection-chemistry.h"
 #include "svg-view-widget.h"
@@ -136,8 +134,6 @@ static void sp_ui_menu_item_set_name(GtkWidget *data,
                                      Glib::ustring const &name);
 static void sp_recent_open(GtkRecentChooser *, gpointer);
 
-static const int MIN_ONSCREEN_DISTANCE = 50;
-
 void
 sp_create_window(SPViewWidget *vw, bool editable)
 {
@@ -165,9 +161,8 @@ sp_create_window(SPViewWidget *vw, bool editable)
         win->signal_focus_in_event().connect(sigc::mem_fun(*desktop_widget, &SPDesktopWidget::onFocusInEvent));
 
         Inkscape::Preferences *prefs = Inkscape::Preferences::get();
-        gint prefs_geometry =
-            (2==prefs->getInt("/options/savewindowgeometry/value", 0));
-        if (prefs_geometry) {
+        int window_geometry = prefs->getInt("/options/savewindowgeometry/value", PREFS_WINDOW_GEOMETRY_NONE);
+        if (window_geometry == PREFS_WINDOW_GEOMETRY_LAST) {
             gint pw = prefs->getInt("/desktop/geometry/width", -1);
             gint ph = prefs->getInt("/desktop/geometry/height", -1);
             gint px = prefs->getInt("/desktop/geometry/x", -1);
@@ -175,39 +170,11 @@ sp_create_window(SPViewWidget *vw, bool editable)
             gint full = prefs->getBool("/desktop/geometry/fullscreen");
             gint maxed = prefs->getBool("/desktop/geometry/maximized");
             if (pw>0 && ph>0) {
-#if GTKMM_CHECK_VERSION(3,22,0)
-                auto const display = Gdk::Display::get_default();
-                auto const monitor = display->get_primary_monitor();
-
-                // A Gdk::Rectangle in "application pixel" units
-                Gdk::Rectangle screen_geometry;
-                monitor->get_geometry(screen_geometry);
-                auto const screen_width  = screen_geometry.get_width();
-                auto const screen_height = screen_geometry.get_height();
-#else
-                auto const screen_width  = gdk_screen_width();
-                auto const screen_height = gdk_screen_height();
-#endif
-                gint w = MIN(screen_width,  pw);
-                gint h = MIN(screen_height, ph);
-                gint x = MIN(screen_width  - MIN_ONSCREEN_DISTANCE, px);
-                gint y = MIN(screen_height - MIN_ONSCREEN_DISTANCE, py);
-                if (w>0 && h>0) {
-                    x = MIN(screen_width - w,  x);
-                    y = MIN(screen_height - h, y);
-                    desktop->setWindowSize(w, h);
-                }
-
-                // Only restore xy for the first window so subsequent windows don't overlap exactly
-                // with first.  (Maybe rule should be only restore xy if it's different from xy of
-                // other desktops?)
-
-                // Empirically it seems that active_desktop==this desktop only the first time a
-                // desktop is created.
-                SPDesktop *active_desktop = SP_ACTIVE_DESKTOP;
-                if (active_desktop == desktop || active_desktop==NULL) {
-                    desktop->setWindowPosition(Geom::Point(x, y));
-                }
+                Gdk::Rectangle monitor_geometry = Inkscape::UI::get_monitor_geometry_at_point(px, py);
+                pw = std::min(pw, monitor_geometry.get_width());
+                ph = std::min(ph, monitor_geometry.get_height());      
+                desktop->setWindowSize(pw, ph);
+                desktop->setWindowPosition(Geom::Point(px, py));
             }
             if (maxed) {
                 win->maximize();
@@ -216,8 +183,7 @@ sp_create_window(SPViewWidget *vw, bool editable)
                 win->fullscreen();
             }
         }
-
-    } 
+    }
 
     if ( completeDropTargets == 0 || completeDropTargetsCount == 0 )
     {
diff --git a/src/ui/monitor.cpp b/src/ui/monitor.cpp
new file mode 100644
index 000000000..3e0c983fe
--- /dev/null
+++ b/src/ui/monitor.cpp
@@ -0,0 +1,107 @@
+/**
+ * \file
+ * \brief helper functions for retrieving monitor geometry, etc.
+ *//*
+ * Authors:
+ *   Eduard Braun <eduard.braun2@gmx.de>
+ *
+ * Copyright 2018 Authors
+ *
+ * This file is part of Inkscape.
+ *
+ * Inkscape is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * Inkscape is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with Inkscape.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#ifdef HAVE_CONFIG_H
+# include "config.h"
+#endif
+
+#include <gdkmm/rectangle.h>
+#include <gdkmm/window.h>
+
+#if GTKMM_CHECK_VERSION(3,22,0)
+# include <gdkmm/monitor.h>
+#else
+# include <gdkmm/screen.h>
+#endif
+
+
+namespace Inkscape {
+namespace UI {
+
+/** get monitor geometry of primary monitor */
+Gdk::Rectangle get_monitor_geometry_primary() {
+    Gdk::Rectangle monitor_geometry;
+#if GTKMM_CHECK_VERSION(3,22,0)
+    auto const display = Gdk::Display::get_default();
+    auto const monitor = display->get_primary_monitor();
+
+    // Fallback to monitor number 0 if the user hasn't configured a primary monitor
+    if (!monitor) {
+        monitor = display->get_monitor(0);
+    }
+
+    monitor->get_geometry(monitor_geometry);
+#else
+    auto const default_screen = Gdk::Screen::get_default();
+    auto const monitor_number = default_screen->get_primary_monitor();
+    default_screen->get_monitor_geometry(monitor_number, monitor_geometry);
+#endif
+    return monitor_geometry;
+}
+
+/** get monitor geometry of monitor containing largest part of window */
+Gdk::Rectangle get_monitor_geometry_at_window(const Glib::RefPtr<Gdk::Window>& window) {
+    Gdk::Rectangle monitor_geometry;
+#if GTKMM_CHECK_VERSION(3,22,0)
+    auto const display = Gdk::Display::get_default();
+    auto const monitor = display->get_monitor_at_window(window);
+    monitor->get_geometry(monitor_geometry);
+#else
+    auto const default_screen = Gdk::Screen::get_default();
+    auto const monitor_number = default_screen->get_monitor_at_window(window);
+    default_screen->get_monitor_geometry(monitor_number, monitor_geometry);
+#endif
+    return monitor_geometry;
+}
+
+/** get monitor geometry of monitor at (or closest to) point on combined screen area */
+Gdk::Rectangle get_monitor_geometry_at_point(int x, int y) {
+    Gdk::Rectangle monitor_geometry;
+#if GTKMM_CHECK_VERSION(3,22,0)
+    auto const display = Gdk::Display::get_default();
+    auto const monitor = display->get_monitor_at_point(x ,y);
+    monitor->get_geometry(monitor_geometry);
+#else
+    auto const default_screen = Gdk::Screen::get_default();
+    auto const monitor_number = default_screen->get_monitor_at_point(x, y);
+    default_screen->get_monitor_geometry(monitor_number, monitor_geometry);
+#endif
+    return monitor_geometry;
+}
+
+}
+}
+
+
+/*
+  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:
diff --git a/src/ui/monitor.h b/src/ui/monitor.h
new file mode 100644
index 000000000..696a8ed73
--- /dev/null
+++ b/src/ui/monitor.h
@@ -0,0 +1,51 @@
+/**
+ * \file
+ * \brief helper functions for retrieving monitor geometry, etc.
+ *//*
+ * Authors:
+ *   Eduard Braun <eduard.braun2@gmx.de>
+ *
+ * Copyright 2018 Authors
+ *
+ * This file is part of Inkscape.
+ *
+ * Inkscape is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * Inkscape is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with Inkscape.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#ifndef SEEN_MONITOR_H
+#define SEEN_MONITOR_H
+
+#include <gdkmm/rectangle.h>
+#include <gdkmm/window.h>
+
+namespace Inkscape {
+namespace UI {
+    Gdk::Rectangle get_monitor_geometry_primary();
+    Gdk::Rectangle get_monitor_geometry_at_window(const Glib::RefPtr<Gdk::Window>& window);
+    Gdk::Rectangle get_monitor_geometry_at_point(int x, int y);
+}
+}
+
+#endif // SEEN_MONITOR_H
+
+/*
+  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:
diff --git a/src/ui/uxmanager.cpp b/src/ui/uxmanager.cpp
index f48f40879..3ec38edf9 100644
--- a/src/ui/uxmanager.cpp
+++ b/src/ui/uxmanager.cpp
@@ -17,12 +17,10 @@
 
 #include "uxmanager.h"
 #include "desktop.h"
+#include "ui/monitor.h"
 #include "util/ege-tags.h"
 #include "widgets/toolbox.h"
 
-#if GTKMM_CHECK_VERSION(3,22,0)
-# include <gdkmm/monitor.h>
-#endif
 
 using std::vector;
 
@@ -125,27 +123,11 @@ UXManagerImpl::UXManagerImpl() :
     tags.addTag(ege::Tag("Icons"));
 
     // Figure out if we're on a widescreen display
-#if GTKMM_CHECK_VERSION(3,22,0)
-    auto display = Gdk::Display::get_default();
-    auto monitor = display->get_primary_monitor();
-
-    // Fallback to monitor number 0 if the user hasn't configured a primary monitor
-    if (!monitor) {
-        monitor = display->get_monitor(0);
-    }
+    Gdk::Rectangle monitor_geometry = Inkscape::UI::get_monitor_geometry_primary();
+    int const width  = monitor_geometry.get_width();
+    int const height = monitor_geometry.get_height();
 
-    if(monitor) {
-        Gdk::Rectangle monitor_geometry;
-        monitor->get_geometry(monitor_geometry);
-
-        int const width  = monitor_geometry.get_width();
-        int const height = monitor_geometry.get_height();
-#else
-    Glib::RefPtr<Gdk::Screen> defaultScreen = Gdk::Screen::get_default();
-    if (defaultScreen) {
-        int width = defaultScreen->get_width();
-        int height = defaultScreen->get_height();
-#endif
+    if (width && height) {
         gdouble aspect = static_cast<gdouble>(width) / static_cast<gdouble>(height);
         if (aspect > 1.65) {
             _widescreen = true;