[libchamplain] Fix borders at low zoom levels

[Jiří Techet <jiritechet src gnome org>]

commit 9c7879eb6d3f0108841b21dbea3be2c608ec172f
Author: Jiří Techet <techet gmail com>
Date:   Fri Apr 12 07:38:14 2013 +0200

    Fix borders at low zoom levels

 champlain/champlain-adjustment.c |    4 ++--
 champlain/champlain-view.c       |   19 +++++++++++--------
 2 files changed, 13 insertions(+), 10 deletions(-)
---
diff --git a/champlain/champlain-adjustment.c b/champlain/champlain-adjustment.c
index 2579b71..c0ef459 100644
--- a/champlain/champlain-adjustment.c
+++ b/champlain/champlain-adjustment.c
@@ -295,8 +295,8 @@ champlain_adjustment_set_value (ChamplainAdjustment *adjustment,
   stop_interpolation (adjustment);
 
   if (!priv->elastic)
-    value = CLAMP (value, priv->lower, MAX (priv->lower,
-              priv->upper));
+    value = CLAMP (value, MIN (priv->lower, priv->upper), 
+              MAX (priv->lower, priv->upper));
 
   if (priv->value != value)
     {
diff --git a/champlain/champlain-view.c b/champlain/champlain-view.c
index d62ebef..2cb3da3 100644
--- a/champlain/champlain-view.c
+++ b/champlain/champlain-view.c
@@ -344,14 +344,15 @@ resize_viewport (ChamplainView *view)
 
   if (priv->zoom_level < 8)
     {
-      lower_x = 0.0;
-      lower_y = 0.0;
-      upper_x = champlain_map_source_get_column_count (priv->map_source, priv->zoom_level) *
-        champlain_map_source_get_tile_size (priv->map_source) -
-        priv->viewport_width;
-      upper_y = champlain_map_source_get_row_count (priv->map_source, priv->zoom_level) *
-        champlain_map_source_get_tile_size (priv->map_source) -
-        priv->viewport_height;
+      gdouble map_width = champlain_map_source_get_column_count (priv->map_source, priv->zoom_level) *
+        champlain_map_source_get_tile_size (priv->map_source);
+      gdouble map_height = champlain_map_source_get_row_count (priv->map_source, priv->zoom_level) *
+        champlain_map_source_get_tile_size (priv->map_source);
+      
+      lower_x = MIN (-priv->viewport_width / 2.0, -priv->viewport_width + map_width / 2.0);
+      lower_y = MIN (-priv->viewport_height / 2.0, -priv->viewport_height + map_height / 2.0);
+      upper_x = MAX (map_width - priv->viewport_width / 2.0, map_width / 2.0);
+      upper_y = MAX (map_height - priv->viewport_height / 2.0, map_height / 2.0);
     }
 
   /*
@@ -1289,6 +1290,8 @@ view_update_anchor (ChamplainView *view,
 
   if (priv->zoom_level >= 8)
     need_anchor = TRUE;
+  else if (priv->anchor_x == 0 && priv->anchor_y == 0)
+    return FALSE;
 
   /* update anchor one viewport size before reaching the margin to be sure */
   if (priv->anchor_zoom_level != priv->zoom_level ||