[libview] Scroll one screen leaving one line context

See bgo#170871

diff --git a/libview/ev-view.c b/libview/ev-view.c
index ea26824ac1b179bb59823e9995f9d3673410f3b7..973da901eb5be6aaaa2f7194e47873086be2d3e3 100644 (file)
--- a/libview/ev-view.c
+++ b/libview/ev-view.c
@@ -767,6 +767,79 @@ add_scroll_binding_keypad (GtkBindingSet  *binding_set,
                                G_TYPE_BOOLEAN, horizontal);
 }
 
+static gdouble
+compute_scroll_increment (EvView        *view,
+                         GtkScrollType  scroll)
+{
+       GtkWidget *widget = GTK_WIDGET (view);
+       GtkAdjustment *adjustment = view->vadjustment;
+       GdkRegion *text_region, *region;
+       gint page;
+       GdkRectangle rect;
+       EvRectangle doc_rect;
+       GdkRectangle page_area;
+       GtkBorder border;
+       GdkRectangle *recs;
+       gint n_recs;
+       gdouble fraction = 1.0;
+
+       if (scroll != GTK_SCROLL_PAGE_BACKWARD && scroll != GTK_SCROLL_PAGE_FORWARD)
+               return adjustment->page_size;
+
+       page = scroll == GTK_SCROLL_PAGE_BACKWARD ? view->start_page : view->end_page;
+
+       text_region = ev_pixbuf_cache_get_text_mapping (view->pixbuf_cache, page);
+       if (!text_region || gdk_region_empty (text_region))
+               return adjustment->page_size;
+
+       get_page_extents (view, page, &page_area, &border);
+       rect.x = page_area.x + view->scroll_x;
+       rect.y = view->scroll_y + (scroll == GTK_SCROLL_PAGE_BACKWARD ? 5 : widget->allocation.height - 5);
+       rect.width = page_area.width;
+       rect.height = 1;
+       view_rect_to_doc_rect (view, &rect, &page_area, &doc_rect);
+
+       /* Convert the doc rectangle into a GdkRectangle */
+       rect.x = doc_rect.x1;
+       rect.y = doc_rect.y1;
+       rect.width = doc_rect.x2 - doc_rect.x1;
+       rect.height = MAX (1, doc_rect.y2 - doc_rect.y1);
+       region = gdk_region_rectangle (&rect);
+
+       gdk_region_intersect (region, text_region);
+       gdk_region_get_rectangles (region, &recs, &n_recs);
+       gdk_region_destroy (region);
+       if (n_recs > 0) {
+               EvRenderContext *rc;
+               EvPage  *ev_page;
+
+               ev_page = ev_document_get_page (view->document, page);
+               rc = ev_render_context_new (ev_page, view->rotation, view->scale);
+               g_object_unref (ev_page);
+               /* Get the selection region to know the height of the line */
+               doc_rect.x1 = doc_rect.x2 = recs[0].x + 0.5;
+               doc_rect.y1 = doc_rect.y2 = recs[0].y + 0.5;
+
+               ev_document_doc_mutex_lock ();
+               region = ev_selection_get_selection_region (EV_SELECTION (view->document),
+                                                           rc, EV_SELECTION_STYLE_LINE,
+                                                           &doc_rect);
+               ev_document_doc_mutex_unlock ();
+
+               g_object_unref (rc);
+               g_free (recs);
+               gdk_region_get_rectangles (region, &recs, &n_recs);
+               gdk_region_destroy (region);
+               if (n_recs > 0) {
+                       fraction = 1 - (recs[0].height / adjustment->page_size);
+               }
+               g_free (recs);
+       }
+
+       return adjustment->page_size * fraction;
+
+}
+
 void
 ev_view_scroll (EvView        *view,
                GtkScrollType  scroll,
@@ -797,7 +870,6 @@ ev_view_scroll (EvView        *view,
 
        /* Assign values for increment and vertical adjustment */
        adjustment = horizontal ? view->hadjustment : view->vadjustment;
-       increment = adjustment->page_size * 0.75;
        value = adjustment->value;
 
        /* Assign boolean for first and last page */
@@ -817,6 +889,7 @@ ev_view_scroll (EvView        *view,
                                ev_view_previous_page (view);
                                /* Jump to the top */
                        } else {
+                               increment = compute_scroll_increment (view, GTK_SCROLL_PAGE_BACKWARD);
                                value = MAX (value - increment, adjustment->lower);
                        }
                        break;
@@ -830,6 +903,7 @@ ev_view_scroll (EvView        *view,
                                ev_view_next_page (view);
                        /* Jump to the bottom */
                        } else {
+                               increment = compute_scroll_increment (view, GTK_SCROLL_PAGE_FORWARD);
                                value = MIN (value + increment, adjustment->upper - adjustment->page_size);
                        }
                        break;