Fix gravitystorm#996 by adding intermittent water bodies support

Author: Penegal

project.mml

@@ -227,7 +227,10 @@ Layer:
             waterway,
             landuse,
             name,
-            way_area/NULLIF(!pixel_width!::real*!pixel_height!::real,0) AS way_pixels
+            way_area/NULLIF(!pixel_width!::real*!pixel_height!::real,0) AS way_pixels,
+            CASE WHEN tags->'intermittent' IN ('yes')
+              OR tags->'seasonal' IN ('yes', 'spring', 'summer', 'autumn', 'winter', 'wet_season', 'dry_season') 
+              THEN 'yes' ELSE 'no' END AS int_intermittent
           FROM planet_osm_polygon
           WHERE
             (waterway IN ('dock', 'riverbank')

symbols/intermittent_water.png

@@ -47,12 +47,23 @@
     [zoom >= 1][zoom < 2][way_pixels >= 16],
     [zoom >= 2][zoom < 8][way_pixels >= 32],
     [zoom >= 8] {
-      polygon-fill: @water-color;
-      [way_pixels >= 4] {
-        polygon-gamma: 0.75;
+      [int_intermittent = 'no'] {
+        polygon-fill: @water-color;
+        [way_pixels >= 4] {
+          polygon-gamma: 0.75;
+        }
+        [way_pixels >= 64] {
+          polygon-gamma: 0.6;
+        }
       }
-      [way_pixels >= 64] {
-        polygon-gamma: 0.6;
+      [int_intermittent = 'yes'] {
+        polygon-pattern-file: url('symbols/intermittent_water.png');
+        [way_pixels >= 4] {
+          polygon-pattern-gamma: 0.75;
+        }
+        [way_pixels >= 64] {
+          polygon-pattern-gamma: 0.6;
+        }
       }
     }
   }