Fix alignment of ruler ticks

5 files changed, 25 insertions, 27 deletions

diff --git a/src/desktop.cpp b/src/desktop.cpp
index ebc3e5591..4c28cd918 100644
--- a/src/desktop.cpp
+++ b/src/desktop.cpp
@@ -940,9 +940,9 @@ SPDesktop::set_display_area( Geom::Rect const &r, double border, bool log)
 /**
  * Return viewbox dimensions. FixMe: Doesn't handle rotation. FixMe InvertedY
  */
-Geom::Rect SPDesktop::get_display_area() const
+Geom::Rect SPDesktop::get_display_area(bool use_integer_viewbox) const
 {
-    Geom::Rect const viewbox = canvas->getViewbox();
+    Geom::Rect const viewbox = use_integer_viewbox ? canvas->getViewboxIntegers() : canvas->getViewbox();
     double const scale = _current_affine.getZoom();
 
     return viewbox * Geom::Scale(1. / scale, _doc2dt[3] / scale);
diff --git a/src/desktop.h b/src/desktop.h
index 69ccd7bd9..66fad5a65 100644
--- a/src/desktop.h
+++ b/src/desktop.h
@@ -331,7 +331,7 @@ public:
     void set_display_area (bool log = true);
     void set_display_area (Geom::Point const &c, Geom::Point const &w, bool log = true);
     void set_display_area (Geom::Rect const &a, Geom::Coord border, bool log = true);
-    Geom::Rect get_display_area() const;
+    Geom::Rect get_display_area(bool use_integer_viewbox = false) const;
 
     void zoom_absolute_keep_point   (Geom::Point const &c, double const zoom);
     void zoom_relative_keep_point   (Geom::Point const &c, double const zoom);
diff --git a/src/display/sp-canvas.cpp b/src/display/sp-canvas.cpp
index e8a36a3a7..bb8848a18 100644
--- a/src/display/sp-canvas.cpp
+++ b/src/display/sp-canvas.cpp
@@ -2814,8 +2814,7 @@ Geom::Rect SPCanvas::getViewbox() const
     GtkAllocation allocation;
 
     gtk_widget_get_allocation (GTK_WIDGET (this), &allocation);
-    return Geom::Rect(Geom::Point(_dx0, _dy0),
-                      Geom::Point(_dx0 + allocation.width, _dy0 + allocation.height));
+    return Geom::Rect::from_xywh(_dx0, _dy0, allocation.width, allocation.height);
 }
 
 /**
@@ -2826,10 +2825,7 @@ Geom::IntRect SPCanvas::getViewboxIntegers() const
     GtkAllocation allocation;
 
     gtk_widget_get_allocation (GTK_WIDGET(this), &allocation);
-    Geom::IntRect ret;
-    ret.setMin(Geom::IntPoint(_x0, _y0));
-    ret.setMax(Geom::IntPoint(_x0 + allocation.width, _y0 + allocation.height));
-    return ret;
+    return Geom::IntRect::from_xywh(_x0, _y0, allocation.width, allocation.height);
 }
 
 inline int sp_canvas_tile_floor(int x)
diff --git a/src/widgets/desktop-widget.cpp b/src/widgets/desktop-widget.cpp
index 40bada366..32ca1bac2 100644
--- a/src/widgets/desktop-widget.cpp
+++ b/src/widgets/desktop-widget.cpp
@@ -1713,14 +1713,19 @@ SPDesktopWidget* SPDesktopWidget::createInstance(SPDocument *document)
 void
 SPDesktopWidget::update_rulers()
 {
-    Geom::Rect viewbox = desktop->get_display_area();
+    Geom::Rect viewbox = desktop->get_display_area(true); 
+    // "true" means: Use integer values of the canvas for calculating the display area, similar
+    // to the integer values used for positioning the grid lines. (see SPCanvas::scrollTo(), 
+    // where ix and iy are rounded integer values; these values are stored in SPCanvasBuf->rect,
+    // and used for drawing the grid). By using the integer values here too, the ruler ticks 
+    // will be perfectly aligned to the grid
 
     double lower_x = _dt2r * (viewbox.left()  - _ruler_origin[Geom::X]);
     double upper_x = _dt2r * (viewbox.right() - _ruler_origin[Geom::X]);
     sp_ruler_set_range(SP_RULER(_hruler->gobj()),
-	      	       lower_x,
-		       upper_x,
-		       (upper_x - lower_x));
+                       lower_x,
+                       upper_x,
+                       upper_x - lower_x);
 
     double lower_y = _dt2r * (viewbox.bottom() - _ruler_origin[Geom::Y]);
     double upper_y = _dt2r * (viewbox.top()    - _ruler_origin[Geom::Y]);
@@ -1729,8 +1734,8 @@ SPDesktopWidget::update_rulers()
     }
     sp_ruler_set_range(SP_RULER(_vruler->gobj()),
                        lower_y,
-		       upper_y,
-		       (upper_y - lower_y));
+                       upper_y,
+                       upper_y - lower_y);
 }
 
 
diff --git a/src/widgets/gimp/ruler.cpp b/src/widgets/gimp/ruler.cpp
index 1d196d2b0..48ed4a5dd 100644
--- a/src/widgets/gimp/ruler.cpp
+++ b/src/widgets/gimp/ruler.cpp
@@ -1088,7 +1088,7 @@ sp_ruler_draw_ticks (SPRuler *ruler)
     gint             digit_offset;
     gchar            digit_str[2] = { '\0', '\0' };
     gint             text_size;
-    gint             pos;
+    gdouble          pos;
     gdouble          max_size;
     Inkscape::Util::Unit const *unit = nullptr;
     SPRulerMetric    ruler_metric = ruler_metric_general; /* The metric to use for this unit system */
@@ -1123,6 +1123,8 @@ sp_ruler_draw_ticks (SPRuler *ruler)
 
     cr = cairo_create (priv->backing_store);
     
+    cairo_set_line_width(cr, 1.0);
+
     cairo_set_operator (cr, CAIRO_OPERATOR_CLEAR);
     cairo_paint (cr);
     cairo_set_operator (cr, CAIRO_OPERATOR_OVER);
@@ -1221,24 +1223,19 @@ sp_ruler_draw_ticks (SPRuler *ruler)
 
         for (cur = start; cur <= end; cur += subd_incr)
           {
-            // due to the typical values for cur, lower and increment, pos will often end up to
-            // be e.g. 641.50000000000; rounding behaviour is not defined in such a case (see round.h)
-            // and jitter will be apparent (upon redrawing some of the lines on the ruler might jump a
-            // by a pixel, and jump back on the next redraw). This is suppressed by adding 1e-9 (that's only one nanopixel ;-))
-            pos = gint(round((cur - lower) * increment + 1e-12));
+            pos = floor((cur - lower) * increment) + 0.5;
 
             if (priv->orientation == GTK_ORIENTATION_HORIZONTAL)
              {
-               cairo_rectangle (cr,
-                                pos, height + border.top - length,
-                                1,   length);
+               cairo_move_to(cr, pos, height + border.top - length);
+               cairo_line_to(cr, pos, height + border.top);
              }
             else 
              {
-               cairo_rectangle (cr,
-                                height + border.left - length, pos,
-                                length,                        1);
+               cairo_move_to(cr, height + border.left - length, pos);
+               cairo_line_to(cr, height + border.left         , pos);
              }
+             cairo_stroke(cr);
 
             /* draw label */
             double label_spacing_px = fabs(increment*(double)ruler_metric.ruler_scale[scale]/ruler_metric.subdivide[i]);