[core] Added padding option to CameraOptions

Moved EdgeInsets to geo.hpp so CameraOptions and Transform can refer to it. Added a padding option to CameraOptions that alters the frame of reference for the center option. Added optional padding parameters to LatLng getters and setters.

Working towards #2600.

8 files changed, 135 insertions, 18 deletions

diff --git a/include/mbgl/map/camera.hpp b/include/mbgl/map/camera.hpp
index 80734b76fd..32ad8f019f 100644
--- a/include/mbgl/map/camera.hpp
+++ b/include/mbgl/map/camera.hpp
@@ -17,6 +17,10 @@ struct CameraOptions {
     /** Coordinate at the center of the map. */
     mapbox::util::optional<LatLng> center;
     
+    /** Padding around the interior of the view that affects the frame of
+        reference for `center`. */
+    mapbox::util::optional<EdgeInsets> padding;
+    
     /** Point of reference for `zoom` and `angle`, assuming an origin at the
         top-left corner of the view. */
     mapbox::util::optional<PrecisionPoint> anchor;
diff --git a/include/mbgl/map/map.hpp b/include/mbgl/map/map.hpp
index 3e52d57d19..3852bb7b6f 100644
--- a/include/mbgl/map/map.hpp
+++ b/include/mbgl/map/map.hpp
@@ -34,13 +34,6 @@ namespace util {
 template <class T> class Thread;
 } // namespace util
 
-struct EdgeInsets {
-    double top = 0;
-    double left = 0;
-    double bottom = 0;
-    double right = 0;
-};
-
 class Map : private util::noncopyable {
     friend class View;
 
@@ -106,8 +99,9 @@ public:
     // Position
     void moveBy(const PrecisionPoint&, const Duration& = Duration::zero());
     void setLatLng(const LatLng&, const PrecisionPoint&, const Duration& = Duration::zero());
+    void setLatLng(const LatLng&, const EdgeInsets&, const Duration& = Duration::zero());
     void setLatLng(const LatLng&, const Duration& = Duration::zero());
-    LatLng getLatLng() const;
+    LatLng getLatLng(const EdgeInsets& = {}) const;
     void resetPosition();
 
     // Scale
diff --git a/include/mbgl/util/geo.hpp b/include/mbgl/util/geo.hpp
index e815456f22..db7d9c792e 100644
--- a/include/mbgl/util/geo.hpp
+++ b/include/mbgl/util/geo.hpp
@@ -108,6 +108,40 @@ enum class NorthOrientation : uint8_t {
     Leftwards,
 };
 
+/// The distance on each side between a rectangle and a rectangle within.
+struct EdgeInsets {
+    double top = 0;     ///< Number of pixels inset from the top edge.
+    double left = 0;    ///< Number of pixels inset from the left edge.
+    double bottom = 0;  ///< Number of pixels inset from the bottom edge.
+    double right = 0;   ///< Number of pixels inset from the right edge.
+    
+    inline EdgeInsets() {}
+    
+    inline EdgeInsets(const double t, const double l, const double b, const double r)
+        : top(t), left(l), bottom(b), right(r) {}
+    
+    inline operator bool() const {
+        return top || left || bottom || right;
+    }
+    
+    inline void operator+=(const EdgeInsets& o) {
+        top += o.top;
+        left += o.left;
+        bottom += o.bottom;
+        right += o.right;
+    }
+
+    inline EdgeInsets operator+(const EdgeInsets& o) const {
+        return {
+            top + o.top, left + o.left, bottom + o.bottom, right + o.right,
+        };
+    }
+    
+    PrecisionPoint getCenter(uint16_t width, uint16_t height) const;
+    
+    void flip();
+};
+
 } // namespace mbgl
 
 #endif
diff --git a/src/mbgl/map/map.cpp b/src/mbgl/map/map.cpp
index 50201ff949..f03915c953 100644
--- a/src/mbgl/map/map.cpp
+++ b/src/mbgl/map/map.cpp
@@ -172,7 +172,11 @@ void Map::moveBy(const PrecisionPoint& point, const Duration& duration) {
 }
 
 void Map::setLatLng(const LatLng& latLng, const Duration& duration) {
-    transform->setLatLng(latLng, duration);
+    setLatLng(latLng, EdgeInsets(), duration);
+}
+
+void Map::setLatLng(const LatLng& latLng, const EdgeInsets& padding, const Duration& duration) {
+    transform->setLatLng(latLng, padding, duration);
     update(Update::Repaint);
 }
 
@@ -181,8 +185,8 @@ void Map::setLatLng(const LatLng& latLng, const PrecisionPoint& point, const Dur
     update(Update::Repaint);
 }
 
-LatLng Map::getLatLng() const {
-    return transform->getLatLng();
+LatLng Map::getLatLng(const EdgeInsets& padding) const {
+    return transform->getLatLng(padding);
 }
 
 void Map::resetPosition() {
@@ -259,7 +263,7 @@ CameraOptions Map::cameraForLatLngs(const std::vector<LatLng>& latLngs, const Ed
     double scaleY = (getHeight() - padding.top - padding.bottom) / height;
     double minScale = ::fmin(scaleX, scaleY);
     double zoom = ::log2(getScale() * minScale);
-    zoom = ::fmax(::fmin(zoom, getMaxZoom()), getMinZoom());
+    zoom = util::clamp(zoom, getMinZoom(), getMaxZoom());
 
     // Calculate the center point of a virtual bounds that is extended in all directions by padding.
     PrecisionPoint paddedNEPixel = {
diff --git a/src/mbgl/map/transform.cpp b/src/mbgl/map/transform.cpp
index 98b0804482..7596d5d543 100644
--- a/src/mbgl/map/transform.cpp
+++ b/src/mbgl/map/transform.cpp
@@ -91,7 +91,12 @@ void Transform::easeTo(const CameraOptions& camera, const AnimationOptions& anim
     }
     
     // Determine endpoints.
-    const LatLng startLatLng = getLatLng();
+    EdgeInsets padding;
+    if (camera.padding) {
+        padding = *camera.padding;
+    }
+    const LatLng startLatLng = getLatLng(padding);
+    padding.flip();
     const PrecisionPoint startPoint = {
         state.lngX(startLatLng.longitude),
         state.latY(startLatLng.latitude),
@@ -141,6 +146,10 @@ void Transform::easeTo(const CameraOptions& camera, const AnimationOptions& anim
         if (pitch != startPitch) {
             state.pitch = util::interpolate(startPitch, pitch, t);
         }
+        
+        if (padding) {
+            state.moveLatLng(frameLatLng, padding.getCenter(state.width, state.height));
+        }
         return update;
     }, duration);
 }
@@ -164,7 +173,12 @@ void Transform::flyTo(const CameraOptions &camera, const AnimationOptions &anima
     }
     
     // Determine endpoints.
-    const LatLng startLatLng = getLatLng();
+    EdgeInsets padding;
+    if (camera.padding) {
+        padding = *camera.padding;
+    }
+    const LatLng startLatLng = getLatLng(padding);
+    padding.flip();
     const PrecisionPoint startPoint = {
         state.lngX(startLatLng.longitude),
         state.latY(startLatLng.latitude),
@@ -189,7 +203,8 @@ void Transform::flyTo(const CameraOptions &camera, const AnimationOptions &anima
     
     /// w₀: Initial visible span, measured in pixels at the initial scale.
     /// Known henceforth as a <i>screenful</i>.
-    double w0 = std::max(state.width, state.height);
+    double w0 = std::max(state.width - padding.left - padding.right,
+                         state.height - padding.top - padding.bottom);
     /// w₁: Final visible span, measured in pixels with respect to the initial
     /// scale.
     double w1 = w0 / state.zoomScale(zoom - startZoom);
@@ -304,6 +319,10 @@ void Transform::flyTo(const CameraOptions &camera, const AnimationOptions &anima
         if (pitch != startPitch) {
             state.pitch = util::interpolate(startPitch, pitch, k);
         }
+        
+        if (padding) {
+            state.moveLatLng(frameLatLng, padding.getCenter(state.width, state.height));
+        }
         return Update::Zoom;
     }, duration);
 }
@@ -340,12 +359,19 @@ void Transform::moveBy(const PrecisionPoint& offset, const Duration& duration) {
 }
 
 void Transform::setLatLng(const LatLng& latLng, const Duration& duration) {
+    setLatLng(latLng, EdgeInsets(), duration);
+}
+
+void Transform::setLatLng(const LatLng& latLng, const EdgeInsets& padding, const Duration& duration) {
     if (!latLng) {
         return;
     }
 
     CameraOptions camera;
     camera.center = latLng;
+    if (padding) {
+        camera.padding = padding;
+    }
     easeTo(camera, duration);
 }
 
@@ -381,6 +407,16 @@ void Transform::setLatLngZoom(const LatLng& latLng, double zoom, const Duration&
     easeTo(camera, duration);
 }
 
+LatLng Transform::getLatLng(const EdgeInsets& padding) const {
+    if (padding) {
+        EdgeInsets flippedPadding = padding;
+        flippedPadding.flip();
+        return state.pointToLatLng(flippedPadding.getCenter(state.width, state.height));
+    } else {
+        return state.getLatLng();
+    }
+}
+
 
 #pragma mark - Zoom
 
diff --git a/src/mbgl/map/transform.hpp b/src/mbgl/map/transform.hpp
index 6be0558f98..77c03e939d 100644
--- a/src/mbgl/map/transform.hpp
+++ b/src/mbgl/map/transform.hpp
@@ -43,9 +43,10 @@ public:
             top to bottom and from left to right. */
     void moveBy(const PrecisionPoint& offset, const Duration& = Duration::zero());
     void setLatLng(const LatLng&, const Duration& = Duration::zero());
+    void setLatLng(const LatLng&, const EdgeInsets&, const Duration& = Duration::zero());
     void setLatLng(const LatLng&, const PrecisionPoint&, const Duration& = Duration::zero());
     void setLatLngZoom(const LatLng&, double zoom, const Duration& = Duration::zero());
-    LatLng getLatLng() const { return state.getLatLng(); }
+    LatLng getLatLng(const EdgeInsets& = {}) const;
 
     // Zoom
 
diff --git a/src/mbgl/util/geo.cpp b/src/mbgl/util/geo.cpp
index e82f4afad2..a0ba44c4a9 100644
--- a/src/mbgl/util/geo.cpp
+++ b/src/mbgl/util/geo.cpp
@@ -28,4 +28,16 @@ LatLngBounds::LatLngBounds(const TileID& id)
       ne(TileID{ id.z, id.x + 1, id.y, id.sourceZ }) {
 }
 
+PrecisionPoint EdgeInsets::getCenter(uint16_t width, uint16_t height) const {
+    return {
+        (width - left - right) / 2.0f + left,
+        (height - top - bottom) / 2.0f + top,
+    };
+}
+
+void EdgeInsets::flip() {
+    std::swap(top, bottom);
+    std::swap(left, right);
+}
+
 } // end namespace mbgl
diff --git a/test/miscellaneous/transform.cpp b/test/miscellaneous/transform.cpp
index f06fb56f14..4a8b685564 100644
--- a/test/miscellaneous/transform.cpp
+++ b/test/miscellaneous/transform.cpp
@@ -2,6 +2,7 @@
 #include "../fixtures/mock_view.hpp"
 
 #include <mbgl/map/transform.hpp>
+#include <mbgl/util/geo.hpp>
 
 using namespace mbgl;
 
@@ -193,8 +194,7 @@ TEST(Transform, Anchor) {
     ASSERT_DOUBLE_EQ(10, transform.getZoom());
     ASSERT_DOUBLE_EQ(0, transform.getAngle());
 
-    const auto size = view.getSize();
-    const PrecisionPoint anchorPoint = { size[0] * 0.8, size[1] * 0.3 };
+    const PrecisionPoint anchorPoint = {0, 0};
     const LatLng anchorLatLng = transform.getState().pointToLatLng(anchorPoint);
     transform.setAngle(M_PI_4, anchorPoint);
 
@@ -202,3 +202,35 @@ TEST(Transform, Anchor) {
     ASSERT_NE(anchorLatLng, transform.getLatLng());
     ASSERT_DOUBLE_EQ(anchorLatLng, transform.getState().pointToLatLng(anchorPoint));
 }
+
+TEST(Transform, Padding) {
+    MockView view;
+    Transform transform(view, ConstrainMode::HeightOnly);
+    transform.resize({{ 1000, 1000 }});
+
+    ASSERT_DOUBLE_EQ(0, transform.getLatLng().latitude);
+    ASSERT_DOUBLE_EQ(0, transform.getLatLng().longitude);
+
+    transform.setLatLngZoom({ 10, -100 }, 10);
+
+    const LatLng trueCenter = transform.getLatLng();
+    ASSERT_DOUBLE_EQ(10, trueCenter.latitude);
+    ASSERT_DOUBLE_EQ(-100, trueCenter.longitude);
+    ASSERT_DOUBLE_EQ(10, transform.getZoom());
+    
+    const LatLng manualShiftedCenter = transform.getState().pointToLatLng({
+        1000.0 / 2.0,
+        1000.0 / 4.0,
+    });
+    
+    EdgeInsets padding;
+    padding.top = 1000.0 / 2.0;
+    ASSERT_GT(padding.top, 0);
+    ASSERT_TRUE(padding);
+    
+    const LatLng shiftedCenter = transform.getLatLng(padding);
+    ASSERT_NE(trueCenter.latitude, shiftedCenter.latitude);
+    ASSERT_DOUBLE_EQ(trueCenter.longitude, shiftedCenter.longitude);
+    ASSERT_DOUBLE_EQ(manualShiftedCenter.latitude, shiftedCenter.latitude);
+    ASSERT_DOUBLE_EQ(manualShiftedCenter.longitude, shiftedCenter.longitude);
+}