[evince] libview: Scroll small pages in non-continuous mode

[Marek Kašík <mkasik src gnome org>]

commit 077bab6928be8de0eeb44b04f732e85a471cca7b
Author: Marek Kasik <mkasik redhat com>
Date:   Mon May 9 12:57:20 2016 +0200

    libview: Scroll small pages in non-continuous mode
    
    Check whether currently shown page fits actual view and allow user to scroll
    to previous/next page in that case (also in Dual page mode).
    Allow also scrolling if only one axis fits the view and the event
    happenned in the same axis.
    
    https://bugzilla.gnome.org/show_bug.cgi?id=562257

 libview/ev-view.c |   97 +++++++++++++++++++++++++++++++++++++++++++++--------
 1 files changed, 83 insertions(+), 14 deletions(-)
---
diff --git a/libview/ev-view.c b/libview/ev-view.c
index f76eca8..f96ad4b 100644
--- a/libview/ev-view.c
+++ b/libview/ev-view.c
@@ -262,6 +262,8 @@ static void         ev_view_zoom_for_size_dual_page                (EvView *view,
 static void    ev_view_zoom_for_size_single_page              (EvView *view,
                                                                int     width,
                                                                int     height);
+static gboolean        ev_view_page_fits                              (EvView         *view,
+                                                               GtkOrientation  orientation);
 /*** Cursors ***/
 static void       ev_view_set_cursor                         (EvView             *view,
                                                              EvViewCursor        new_cursor);
@@ -996,7 +998,8 @@ ev_view_scroll (EvView        *view,
 
        view->jump_to_find_result = FALSE;
 
-       if (view->sizing_mode == EV_SIZING_FIT_PAGE) {
+       if ((!horizontal && ev_view_page_fits (view, GTK_ORIENTATION_HORIZONTAL)) ||
+           (horizontal && ev_view_page_fits (view, GTK_ORIENTATION_VERTICAL))) {
                switch (scroll) {
                        case GTK_SCROLL_PAGE_BACKWARD:
                        case GTK_SCROLL_STEP_BACKWARD:
@@ -4113,6 +4116,7 @@ ev_view_scroll_event (GtkWidget *widget, GdkEventScroll *event)
 {
        EvView *view = EV_VIEW (widget);
        guint state;
+       gboolean fit_width, fit_height;
 
        state = event->state & gtk_accelerator_get_default_mod_mask ();
 
@@ -4170,34 +4174,57 @@ ev_view_scroll_event (GtkWidget *widget, GdkEventScroll *event)
                state &= ~GDK_SHIFT_MASK;
        }
 
-       if (state == 0 && view->sizing_mode == EV_SIZING_FIT_PAGE && !view->continuous) {
+       fit_width = ev_view_page_fits (view, GTK_ORIENTATION_HORIZONTAL);
+       fit_height = ev_view_page_fits (view, GTK_ORIENTATION_VERTICAL);
+       if (state == 0 && !view->continuous && (fit_width || fit_height)) {
                switch (event->direction) {
                case GDK_SCROLL_DOWN:
+                       if (fit_height) {
+                               ev_view_next_page (view);
+                               return TRUE;
+                       }
+                       break;
                case GDK_SCROLL_RIGHT:
-                       ev_view_next_page (view);
+                       if (fit_width) {
+                               ev_view_next_page (view);
+                               return TRUE;
+                       }
                        break;
                case GDK_SCROLL_UP:
+                       if (fit_height) {
+                               ev_view_previous_page (view);
+                               return TRUE;
+                       }
+                       break;
                case GDK_SCROLL_LEFT:
-                       ev_view_previous_page (view);
+                       if (fit_width) {
+                               ev_view_previous_page (view);
+                               return TRUE;
+                       }
                        break;
                case GDK_SCROLL_SMOOTH: {
                        gdouble decrement;
+                       if ((fit_width && fit_height) ||
+                           ((fit_height && event->delta_x == 0.0) ||
+                            (fit_width && event->delta_y == 0.0))) {
+                               /* Emulate normal scrolling by summing the deltas */
+                               view->total_delta += event->delta_x + event->delta_y;
+
+                               decrement = view->total_delta < 0 ? -1.0 : 1.0;
+                               for (; fabs (view->total_delta) >= 1.0; view->total_delta -= decrement) {
+                                       if (decrement < 0)
+                                               ev_view_previous_page (view);
+                                       else
+                                               ev_view_next_page (view);
+                               }
 
-                       /* Emulate normal scrolling by summing the deltas */
-                       view->total_delta += event->delta_x + event->delta_y;
-
-                       decrement = view->total_delta < 0 ? -1.0 : 1.0;
-                       for (; fabs (view->total_delta) >= 1.0; view->total_delta -= decrement) {
-                               if (decrement < 0)
-                                       ev_view_previous_page (view);
-                               else
-                                       ev_view_next_page (view);
+                               return TRUE;
                        }
                }
                        break;
                }
 
-               return TRUE;
+               return FALSE;
        }
 
        return FALSE;
@@ -8544,6 +8571,48 @@ ev_view_zoom_for_size (EvView *view,
                ev_view_zoom_for_size_single_page (view, width, height);
 }
 
+static gboolean
+ev_view_page_fits (EvView         *view,
+                  GtkOrientation  orientation)
+{
+       GtkRequisition requisition;
+       GtkAllocation  allocation;
+       double         size;
+
+       if (view->sizing_mode == EV_SIZING_FIT_PAGE)
+               return TRUE;
+
+       if (orientation == GTK_ORIENTATION_HORIZONTAL &&
+           (view->sizing_mode == EV_SIZING_FIT_WIDTH ||
+            view->sizing_mode == EV_SIZING_AUTOMATIC))
+               return TRUE;
+
+       gtk_widget_get_allocation (GTK_WIDGET (view), &allocation);
+       ev_view_size_request (GTK_WIDGET (view), &requisition);
+
+       if (orientation == GTK_ORIENTATION_HORIZONTAL) {
+               if (requisition.width == 1) {
+                       size = 1.0;
+               } else {
+                       if (allocation.width > 0.0)
+                               size = (double) requisition.width / allocation.width;
+                       else
+                               size = 1.0;
+               }
+       } else {
+               if (requisition.height == 1) {
+                       size = 1.0;
+               } else {
+                       if (allocation.height > 0.0)
+                               size = (double) requisition.height / allocation.height;
+                       else
+                               size = 1.0;
+               }
+       }
+
+       return size <= 1.0;
+}
+
 /*** Find ***/
 static gint
 ev_view_find_get_n_results (EvView *view, gint page)