Change initial zoom level for admin-boundaries-text by admin_level at…

… z11 to z16

Add way_pixels limits for admin 1 to 4 same as largest central text label rendering, at 48,000 way_pixels for higher admin_level which have no other text labels

admin.mss

@@ -204,20 +204,30 @@ overlapping borders correctly.
   comp-op: darken;
 }
 
-#admin-text[zoom >= 16] {
-  text-name: "[name]";
-  text-face-name: @book-fonts;
-  text-fill: @admin-boundaries;
-  text-halo-radius: @standard-halo-radius;
-  text-halo-fill: @standard-halo-fill;
-  text-largest-bbox-only: false;
-  text-placement: line;
-  text-spacing: 750;
-  text-repeat-distance: 250;
-  text-margin: 10;
-  text-clip: true;
-  text-vertical-alignment: middle;
-  text-dy: -10;
+#admin-text[zoom >= 11][way_pixels >= 48000] {
+  [admin_level = '1'][way_pixels >= 360000],
+  [admin_level = '2'][way_pixels >= 360000],
+  [admin_level = '3'][way_pixels >= 196000],
+  [admin_level = '4'][way_pixels >= 196000],
+  [zoom >= 12][admin_level = '5'],
+  [zoom >= 13][admin_level = '6'],
+  [zoom >= 14][admin_level = '7'],
+  [zoom >= 15][admin_level = '8'],
+  [zoom >= 16] {
+    text-name: "[name]";
+    text-face-name: @book-fonts;
+    text-fill: @admin-boundaries;
+    text-halo-radius: @standard-halo-radius;
+    text-halo-fill: @standard-halo-fill;
+    text-largest-bbox-only: false;
+    text-placement: line;
+    text-spacing: 750;
+    text-repeat-distance: 250;
+    text-margin: 10;
+    text-clip: true;
+    text-vertical-alignment: middle;
+    text-dy: -10;
+  }
 }
 
 #protected-areas-text[zoom >= 13][way_pixels > 192000] {

project.mml

@@ -2549,15 +2549,16 @@ Layer:
         (SELECT
             way,
             name,
-            admin_level
+            admin_level,
+            way_area/NULLIF(POW(!scale_denominator!*0.001*0.28,2),0) AS way_pixels
           FROM planet_osm_polygon
           WHERE boundary = 'administrative'
-            AND admin_level IN ('0', '1', '2', '3', '4', '5', '6', '7', '8', '9', '10')
+            AND admin_level IN ('1', '2', '3', '4', '5', '6', '7', '8', '9', '10')
             AND name IS NOT NULL
           ORDER BY admin_level::integer ASC, way_area DESC
         ) AS admin_text
     properties:
-      minzoom: 16
+      minzoom: 11
   - id: protected-areas-text
     geometry: linestring
     <<: *extents