[core] Reduce use of RecalculateStyle

* Don't use it to track zoom changes. Instead, Style::update can use the zoom history to check for a change in zoom from the previous frame.
* Don't use it to track active property transitions. Style already knows which layers/light have an active transition, and can re-evaluate only those that do.

This leaves layer property changes as the only use of RecalculateStyle.

1 files changed, 18 insertions, 13 deletions

diff --git a/src/mbgl/map/zoom_history.hpp b/src/mbgl/map/zoom_history.hpp
index 8c88ea6507..308846b1e3 100644
--- a/src/mbgl/map/zoom_history.hpp
+++ b/src/mbgl/map/zoom_history.hpp
@@ -12,25 +12,30 @@ struct ZoomHistory {
     TimePoint lastIntegerZoomTime;
     bool first = true;
 
-    void update(float z, const TimePoint& now) {
+    bool update(float z, const TimePoint& now) {
         if (first) {
             first = false;
-
             lastIntegerZoom = std::floor(z);
             lastIntegerZoomTime = TimePoint(Duration::zero());
             lastZoom = z;
+            return true;
+        } else {
+            if (std::floor(lastZoom) < std::floor(z)) {
+                lastIntegerZoom = std::floor(z);
+                lastIntegerZoomTime = now;
+            } else if (std::floor(lastZoom) > std::floor(z)) {
+                lastIntegerZoom = std::floor(z + 1);
+                lastIntegerZoomTime = now;
+            }
+
+            if (z != lastZoom) {
+                lastZoom = z;
+                return true;
+            }
+
+            return false;
         }
-
-        if (std::floor(lastZoom) < std::floor(z)) {
-            lastIntegerZoom = std::floor(z);
-            lastIntegerZoomTime = now;
-
-        } else if (std::floor(lastZoom) > std::floor(z)) {
-            lastIntegerZoom = std::floor(z + 1);
-            lastIntegerZoomTime = now;
-        }
-
-        lastZoom = z;
     }
 };
+
 } // namespace mbgl