[evince] libview: Use a larger damage area to redraw selections

[Carlos Garcia Campos <carlosgc src gnome org>]

commit a497fb42613536292a883d7fdd7f5b484566c37d
Author: Carlos Garcia Campos <carlosgc gnome org>
Date:   Thu Jun 27 14:54:50 2013 +0200

    libview: Use a larger damage area to redraw selections
    
    Depending on the zoom level the area actually drawn by cairo can be a
    bit larger than the selected region due to rounding errors or pixel
    alignment. We use the selected region to build the damage area to
    invalidate when drawing selections which in many cases is not large
    enough. This causes that sometimes when removing a selections some small
    rectangles keep drawn because they are not redrawn. To avoid this we
    grow the damage area computed from selected regions.

 libview/ev-view.c |   52 +++++++++++++++++++++++++---------------------------
 1 files changed, 25 insertions(+), 27 deletions(-)
---
diff --git a/libview/ev-view.c b/libview/ev-view.c
index 042a621..234775b 100644
--- a/libview/ev-view.c
+++ b/libview/ev-view.c
@@ -7290,27 +7290,6 @@ merge_selection_region (EvView *view,
                                         * have changed */
                                        region = cairo_region_copy (old_sel->covered_region);
                                        cairo_region_union (region, new_sel->covered_region);
-
-                                       if (cairo_region_is_empty (region)) {
-                                               cairo_region_destroy (region);
-                                               region = NULL;
-                                       } else {
-                                               gint num_rectangles = cairo_region_num_rectangles (region);
-                                               GdkRectangle r;
-
-                                               /* We need to make the damage region a little bigger
-                                                * because the edges of the old selection might change
-                                                */
-                                               cairo_region_get_rectangle (region, 0, &r);
-                                               r.x -= 5;
-                                               r.width = 5;
-                                               cairo_region_union_rectangle (region, &r);
-
-                                               cairo_region_get_rectangle (region, num_rectangles - 1, &r);
-                                               r.x += r.width;
-                                               r.width = 5;
-                                               cairo_region_union_rectangle (region, &r);
-                                       }
                                }
                        } else if (old_sel->covered_region) {
                                region = cairo_region_copy (old_sel->covered_region);
@@ -7331,15 +7310,34 @@ merge_selection_region (EvView *view,
 
                /* Redraw the damaged region! */
                if (region) {
-                       GdkRectangle page_area;
-                       GtkBorder    border;
+                       GdkRectangle    page_area;
+                       GtkBorder       border;
+                       cairo_region_t *damage_region;
+                       gint            i, n_rects;
 
                        ev_view_get_page_extents (view, cur_page, &page_area, &border);
-                       cairo_region_translate (region,
-                                          page_area.x + border.left - view->scroll_x,
-                                          page_area.y + border.top - view->scroll_y);
-                       gdk_window_invalidate_region (gtk_widget_get_window (GTK_WIDGET (view)), region, 
TRUE);
+
+                       damage_region = cairo_region_create ();
+                       /* Translate the region and grow it 2 pixels because for some zoom levels
+                        * the area actually drawn by cairo is larger than the selected region, due
+                        * to rounding errors or pixel alignment.
+                        */
+                       n_rects = cairo_region_num_rectangles (region);
+                       for (i = 0; i < n_rects; i++) {
+                               cairo_rectangle_int_t rect;
+
+                               cairo_region_get_rectangle (region, i, &rect);
+                               rect.x += page_area.x + border.left - view->scroll_x - 2;
+                               rect.y += page_area.y + border.top - view->scroll_y - 2;
+                               rect.width += 4;
+                               rect.height += 4;
+                               cairo_region_union_rectangle (damage_region, &rect);
+                       }
                        cairo_region_destroy (region);
+
+                       gdk_window_invalidate_region (gtk_widget_get_window (GTK_WIDGET (view)),
+                                                     damage_region, TRUE);
+                       cairo_region_destroy (damage_region);
                }
        }