[core] Moved util::log2 to its own header

- Added util::{MIN,MAX}_ZOOM_F to avoid consecutive conversions from
double to float
- Move util::log2 to its own header (part of mbgl/math)

cmake/core-files.cmake

@@ -119,8 +119,10 @@ set(MBGL_CORE_FILES
 
     # math
     include/mbgl/math/clamp.hpp
+    include/mbgl/math/log2.hpp
     include/mbgl/math/minmax.hpp
     include/mbgl/math/wrap.hpp
+    src/mbgl/math/log2.cpp
 
     # mbgl
     include/mbgl/mbgl.hpp
@@ -481,7 +483,6 @@ set(MBGL_CORE_FILES
     src/mbgl/util/mat3.hpp
     src/mbgl/util/mat4.cpp
     src/mbgl/util/mat4.hpp
-    src/mbgl/util/math.cpp
     src/mbgl/util/math.hpp
     src/mbgl/util/offscreen_texture.cpp
     src/mbgl/util/offscreen_texture.hpp

include/mbgl/math/log2.hpp

@@ -0,0 +1,27 @@
+#pragma once
+
+#include <cmath>
+#include <cstdint>
+#include <type_traits>
+
+namespace mbgl {
+namespace util {
+
+// Computes the log2(x) rounded up to the next integer.
+// (== number of bits required to store x)
+uint32_t ceil_log2(uint64_t x);
+
+template <typename T>
+typename std::enable_if_t<std::is_floating_point<T>::value, T> log2(T x)
+{
+// log2() is producing wrong results on ARMv5 binaries
+// running on ARMv7+ CPUs.
+#if defined(__ANDROID__)
+    return std::log(x) / M_LN2;
+#else
+    return std::log2(x);
+#endif
+}
+
+} // namespace util
+} // namespace mbgl

include/mbgl/util/constants.hpp

@@ -35,6 +35,8 @@ constexpr double DEGREES_MAX = 360;
 constexpr double PITCH_MAX = M_PI / 3;
 constexpr double MIN_ZOOM = 0.0;
 constexpr double MAX_ZOOM = 25.5;
+constexpr float  MIN_ZOOM_F = MIN_ZOOM;
+constexpr float  MAX_ZOOM_F = MAX_ZOOM;
 
 constexpr uint64_t DEFAULT_MAX_CACHE_SIZE = 50 * 1024 * 1024;
 

src/mbgl/algorithm/generate_clip_ids_impl.hpp

@@ -1,7 +1,7 @@
 #pragma once
 
 #include <mbgl/algorithm/generate_clip_ids.hpp>
-#include <mbgl/util/math.hpp>
+#include <mbgl/math/log2.hpp>
 #include <mbgl/platform/log.hpp>
 
 namespace mbgl {

src/mbgl/layout/symbol_layout.cpp

@@ -11,12 +11,12 @@
 #include <mbgl/util/constants.hpp>
 #include <mbgl/util/utf.hpp>
 #include <mbgl/util/token.hpp>
-#include <mbgl/util/math.hpp>
 #include <mbgl/util/std.hpp>
 #include <mbgl/util/constants.hpp>
 #include <mbgl/util/string.hpp>
 #include <mbgl/math/clamp.hpp>
 #include <mbgl/math/minmax.hpp>
+#include <mbgl/math/log2.hpp>
 #include <mbgl/platform/platform.hpp>
 #include <mbgl/platform/log.hpp>
 
@@ -418,8 +418,7 @@ std::unique_ptr<SymbolBucket> SymbolLayout::place(CollisionTile& collisionTile)
 
 template <typename Buffer>
 void SymbolLayout::addSymbols(Buffer &buffer, const SymbolQuads &symbols, float scale, const bool keepUpright, const style::SymbolPlacementType placement, const float placementAngle) {
-
-    const float placementZoom = ::fmax(std::log(scale) / std::log(2) + zoom, 0);
+    const float placementZoom = util::max(util::log2(scale) + zoom, 0.0f);
 
     for (const auto& symbol : symbols) {
         const auto &tl = symbol.tl;
@@ -428,9 +427,8 @@ void SymbolLayout::addSymbols(Buffer &buffer, const SymbolQuads &symbols, float
         const auto &br = symbol.br;
         const auto &tex = symbol.tex;
 
-        float minZoom =
-            util::max(static_cast<float>(zoom + log(symbol.minScale) / log(2)), placementZoom);
-        float maxZoom = util::min(static_cast<float>(zoom + log(symbol.maxScale) / log(2)), 25.0f);
+        float minZoom = util::max(zoom + util::log2(symbol.minScale), placementZoom);
+        float maxZoom = util::min(zoom + util::log2(symbol.maxScale), util::MAX_ZOOM_F);
         const auto &anchorPoint = symbol.anchorPoint;
 
         // drop upside down versions of glyphs
@@ -510,8 +508,8 @@ void SymbolLayout::addToDebugBuffers(CollisionTile& collisionTile, SymbolBucket&
                 bl = util::matrixMultiply(collisionTile.reverseRotationMatrix, bl);
                 br = util::matrixMultiply(collisionTile.reverseRotationMatrix, br);
 
-                const float maxZoom = util::clamp(zoom + log(box.maxScale) / log(2), util::MIN_ZOOM, util::MAX_ZOOM);
-                const float placementZoom = util::clamp(zoom + log(box.placementScale) / log(2), util::MIN_ZOOM, util::MAX_ZOOM);
+                const float maxZoom = util::clamp(zoom + util::log2(box.maxScale), util::MIN_ZOOM_F, util::MAX_ZOOM_F);
+                const float placementZoom = util::clamp(zoom + util::log2(box.placementScale), util::MIN_ZOOM_F, util::MAX_ZOOM_F);
 
                 collisionBox.vertices.emplace_back(anchor.x, anchor.y, tl.x, tl.y, maxZoom, placementZoom);
                 collisionBox.vertices.emplace_back(anchor.x, anchor.y, tr.x, tr.y, maxZoom, placementZoom);

src/mbgl/map/map.cpp

@@ -24,6 +24,7 @@
 #include <mbgl/util/tile_coordinate.hpp>
 #include <mbgl/actor/scheduler.hpp>
 #include <mbgl/platform/log.hpp>
+#include <mbgl/math/log2.hpp>
 
 namespace mbgl {
 

src/mbgl/map/transform_state.cpp

@@ -2,7 +2,7 @@
 #include <mbgl/tile/tile_id.hpp>
 #include <mbgl/util/constants.hpp>
 #include <mbgl/util/interpolate.hpp>
-#include <mbgl/util/math.hpp>
+#include <mbgl/math/log2.hpp>
 #include <mbgl/math/clamp.hpp>
 
 namespace mbgl {
@@ -117,7 +117,7 @@ double TransformState::pixel_y() const {
 #pragma mark - Zoom
 
 double TransformState::getZoom() const {
-    return std::log(scale) / M_LN2;
+    return scaleZoom(scale);
 }
 
 int32_t TransformState::getIntegerZoom() const {

src/mbgl/math/log2.cpp

@@ -1,4 +1,4 @@
-#include <mbgl/util/math.hpp>
+#include <mbgl/math/log2.hpp>
 
 namespace mbgl {
 namespace util {
@@ -21,15 +21,5 @@ uint32_t ceil_log2(uint64_t x) {
     return y;
 }
 
-double log2(double x) {
-// log2() is producing wrong results on ARMv5 binaries
-// running on ARMv7+ CPUs.
-#if defined(__ANDROID__)
-    return std::log(x) / 0.6931471805599453; // log(x) / log(2)
-#else
-    return ::log2(x);
-#endif
-}
-
 } // namespace util
 } // namespace mbgl

src/mbgl/text/collision_tile.cpp

@@ -1,5 +1,6 @@
 #include <mbgl/text/collision_tile.hpp>
 #include <mbgl/geometry/feature_index.hpp>
+#include <mbgl/math/log2.hpp>
 #include <mbgl/util/constants.hpp>
 #include <mbgl/util/math.hpp>
 #include <mbgl/math/minmax.hpp>

src/mbgl/util/math.hpp

@@ -106,11 +106,5 @@ T smoothstep(T edge0, T edge1, T x) {
     return t * t * (T(3) - T(2) * t);
 }
 
-// Computes the log2(x) rounded up to the next integer.
-// (== number of bits required to store x)
-uint32_t ceil_log2(uint64_t x);
-
-double log2(double x);
-
 } // namespace util
 } // namespace mbgl