[evince] libview: Pre-cache some prev/next pages to the current page range.

[Carlos Garcia Campos <carlosgc src gnome org>]

commit ac3800a5a77648f047d630f28c93dcaa04f7264a
Author: Antia Puentes <apuentes igalia com>
Date:   Fri Jun 28 12:55:59 2013 +0200

    libview: Pre-cache some prev/next pages to the current page range.
    
    https://bugzilla.gnome.org/show_bug.cgi?id=702767

 libview/ev-page-cache.c |   70 ++++++++++++++++++++++++++++++++---------------
 1 files changed, 48 insertions(+), 22 deletions(-)
---
diff --git a/libview/ev-page-cache.c b/libview/ev-page-cache.c
index 598dcda..020db3a 100644
--- a/libview/ev-page-cache.c
+++ b/libview/ev-page-cache.c
@@ -74,6 +74,7 @@ struct _EvPageCacheClass {
        EV_PAGE_DATA_INCLUDE_FORMS        | \
        EV_PAGE_DATA_INCLUDE_ANNOTS)
 
+#define PRE_CACHE_SIZE 1
 
 static void job_page_data_finished_cb (EvJob       *job,
                                       EvPageCache *cache);
@@ -303,41 +304,66 @@ job_page_data_cancelled_cb (EvJob           *job,
        data->job = NULL;
 }
 
+static void
+ev_page_cache_schedule_job_if_needed (EvPageCache *cache,
+                                     gint page)
+{
+       EvPageCacheData   *data = &cache->page_list[page];
+       EvJobPageDataFlags flags;
+
+       if (data->flags == cache->flags && !data->dirty && (data->done || data->job))
+               return;
+
+       if (data->job)
+               ev_job_cancel (data->job);
+
+       flags = ev_page_cache_get_flags_for_data (cache, data);
+
+       data->flags = cache->flags;
+       data->job = ev_job_page_data_new (cache->document, page, flags);
+       g_signal_connect (data->job, "finished",
+                         G_CALLBACK (job_page_data_finished_cb),
+                         cache);
+       g_signal_connect (data->job, "cancelled",
+                         G_CALLBACK (job_page_data_cancelled_cb),
+                         data);
+       ev_job_scheduler_push_job (data->job, EV_JOB_PRIORITY_NONE);
+
+}
+
 void
 ev_page_cache_set_page_range (EvPageCache *cache,
                              gint         start,
                              gint         end)
 {
        gint i;
+        gint pages_to_pre_cache;
 
        if (cache->flags == EV_PAGE_DATA_INCLUDE_NONE)
                return;
 
+       for (i = start; i <= end; i++)
+               ev_page_cache_schedule_job_if_needed (cache, i);
+
        cache->start_page = start;
        cache->end_page = end;
 
-       for (i = start; i <= end; i++) {
-               EvPageCacheData   *data = &cache->page_list[i];
-               EvJobPageDataFlags flags;
-
-               if (data->flags == cache->flags && !data->dirty && (data->done || data->job))
-                       continue;
-
-               if (data->job)
-                       ev_job_cancel (data->job);
-
-               flags = ev_page_cache_get_flags_for_data (cache, data);
-
-               data->flags = cache->flags;
-               data->job = ev_job_page_data_new (cache->document, i, flags);
-               g_signal_connect (data->job, "finished",
-                                 G_CALLBACK (job_page_data_finished_cb),
-                                 cache);
-               g_signal_connect (data->job, "cancelled",
-                                 G_CALLBACK (job_page_data_cancelled_cb),
-                                 data);
-               ev_job_scheduler_push_job (data->job, EV_JOB_PRIORITY_NONE);
-       }
+        i = 1;
+        pages_to_pre_cache = PRE_CACHE_SIZE * 2;
+        while ((start - i > 0) || (end + i < cache->n_pages)) {
+                if (end + i < cache->n_pages) {
+                        ev_page_cache_schedule_job_if_needed (cache, end + i);
+                        if (--pages_to_pre_cache == 0)
+                                break;
+                }
+
+                if (start - i > 0) {
+                        ev_page_cache_schedule_job_if_needed (cache, start - i);
+                        if (--pages_to_pre_cache == 0)
+                                break;
+                }
+                i++;
+        }
 }
 
 EvJobPageDataFlags