[core] Fix collision with content insets

Viewport center offset usage was wrongly submitted in #14664. It was part of alternative approach that used enlarged viewport. Existing and added tests were not sufficient to spot the regression, since the collision check padding is usually larger than the center offset x and y. Annotation picking has tolerance of only 10 pixels but no annotation integration test was using content insets.

Usage of offset is not needed because `posMatrix` in e.g. `CollisionIndex::projectPoint(const mat4& posMatrix, const Point<float>& point)` already incorporates center offset (projection matrix) and the code in current master was just offsetting all by the value.

Modified [ios] MGLAnnotationViewIntegrationTests.testSelectingAnnotationWithCenterOffset to use different insets. It verifies the fix.

Fixes [iOS] Annotations are not selectable (added via iosapp menu) #15106:

In case of #15106, view's original content insets is {top:88, bottom:34}, causing that center offset is {x:0, y:27} and selection with tolerance of 10 wouldn't select annotation.
After tapping the view, so that the header gets removed, view's content insets get changed to {top:44, bottom:34}, center offset is {x:0, y:5} and annotation selection would work, as described in #15106.

Fixes: #15106

platform/ios/Integration Tests/Annotation Tests/MGLAnnotationViewIntegrationTests.m

@@ -401,15 +401,17 @@ - (void)testSelectingAnnotationWithCenterOffset {
     for (CGFloat dx = -100.0; dx <= 100.0; dx += 100.0 ) {
         for (CGFloat dy = -100.0; dy <= 100.0; dy += 100.0 ) {
             CGVector offset = CGVectorMake(dx, dy);
-            [self internalTestSelectingAnnotationWithCenterOffsetWithOffset:offset];
+            UIEdgeInsets edgeInsets = UIEdgeInsetsMake(fmax(-dy, 0.0), fmax(-dy, 0.0), fmax(dy, 0.0), fmax(dx, 0.0));
+            [self internalTestSelectingAnnotationWithCenterOffsetWithOffset:offset edgeInsets:edgeInsets];
         }
     }
 }
 
-- (void)internalTestSelectingAnnotationWithCenterOffsetWithOffset:(CGVector)offset {
+- (void)internalTestSelectingAnnotationWithCenterOffsetWithOffset:(CGVector)offset edgeInsets:(UIEdgeInsets)edgeInsets {
 
     NSString * const MGLTestAnnotationReuseIdentifer = @"MGLTestAnnotationReuseIdentifer";
 
+    self.mapView.contentInset = edgeInsets;
     CGSize size = self.mapView.bounds.size;
 
     CGSize annotationSize = CGSizeMake(40.0, 40.0);
@@ -449,8 +451,8 @@ - (void)internalTestSelectingAnnotationWithCenterOffsetWithOffset:(CGVector)offs
 
     // Check that the annotation is in the center of the view
     CGPoint annotationPoint = [self.mapView convertCoordinate:point.coordinate toPointToView:self.mapView];
-    XCTAssertEqualWithAccuracy(annotationPoint.x, size.width/2.0, 0.25);
-    XCTAssertEqualWithAccuracy(annotationPoint.y, size.height/2.0, 0.25);
+    XCTAssertEqualWithAccuracy(annotationPoint.x, (size.width - edgeInsets.right + edgeInsets.left)/2.0, 0.25);
+    XCTAssertEqualWithAccuracy(annotationPoint.y, (size.height - edgeInsets.bottom + edgeInsets.top)/2.0, 0.25);
 
     // Now test taps around the annotation
     CGPoint tapPoint = CGPointMake(annotationPoint.x + offset.dx, annotationPoint.y + offset.dy);

src/mbgl/map/transform_state.cpp

@@ -226,10 +226,6 @@ double TransformState::getMaxZoom() const {
     return scaleZoom(max_scale);
 }
 
-ScreenCoordinate TransformState::getCenterOffset() const {
-    return { 0.5 * (edgeInsets.left() - edgeInsets.right()), 0.5 * (edgeInsets.top() - edgeInsets.bottom()) };
-}
-
 #pragma mark - Rotation
 
 float TransformState::getBearing() const {
@@ -377,6 +373,10 @@ void TransformState::constrain(double& scale_, double& x_, double& y_) const {
     }
 }
 
+ScreenCoordinate TransformState::getCenterOffset() const {
+    return { 0.5 * (edgeInsets.left() - edgeInsets.right()), 0.5 * (edgeInsets.top() - edgeInsets.bottom()) };
+}
+
 void TransformState::moveLatLng(const LatLng& latLng, const ScreenCoordinate& anchor) {
     auto centerCoord = Projection::project(getLatLng(LatLng::Unwrapped), scale);
     auto latLngCoord = Projection::project(latLng, scale);

src/mbgl/map/transform_state.hpp

@@ -65,10 +65,6 @@ class TransformState {
     void setMaxZoom(double);
     double getMaxZoom() const;
 
-    // Viewport center offset, from [size.width / 2, size.height / 2], defined
-    // by |edgeInsets| in screen coordinates, with top left origin.
-    ScreenCoordinate getCenterOffset() const;
-
     // Rotation
     float getBearing() const;
     float getFieldOfView() const;
@@ -100,6 +96,10 @@ class TransformState {
     bool rotatedNorth() const;
     void constrain(double& scale, double& x, double& y) const;
 
+    // Viewport center offset, from [size.width / 2, size.height / 2], defined
+    // by |edgeInsets| in screen coordinates, with top left origin.
+    ScreenCoordinate getCenterOffset() const;
+
     LatLngBounds bounds;
 
     // Limit the amount of zooming possible on the map.

src/mbgl/text/collision_index.cpp

@@ -348,12 +348,11 @@ std::pair<float,float> CollisionIndex::projectAnchor(const mat4& posMatrix, cons
 std::pair<Point<float>,float> CollisionIndex::projectAndGetPerspectiveRatio(const mat4& posMatrix, const Point<float>& point) const {
     vec4 p = {{ point.x, point.y, 0, 1 }};
     matrix::transformMat4(p, p, posMatrix);
-    auto offset = transformState.getCenterOffset();
     auto size = transformState.getSize();
     return std::make_pair(
         Point<float>(
-            (((p[0] / p[3] + 1) / 2) * size.width) + viewportPadding + offset.x,
-            (((-p[1] / p[3] + 1) / 2) * size.height) + viewportPadding + offset.y
+            (((p[0] / p[3] + 1) / 2) * size.width) + viewportPadding,
+            (((-p[1] / p[3] + 1) / 2) * size.height) + viewportPadding
         ),
         // See perspective ratio comment in symbol_sdf.vertex
         // We're doing collision detection in viewport space so we need
@@ -365,11 +364,10 @@ std::pair<Point<float>,float> CollisionIndex::projectAndGetPerspectiveRatio(cons
 Point<float> CollisionIndex::projectPoint(const mat4& posMatrix, const Point<float>& point) const {
     vec4 p = {{ point.x, point.y, 0, 1 }};
     matrix::transformMat4(p, p, posMatrix);
-    auto offset = transformState.getCenterOffset();
     auto size = transformState.getSize();
     return Point<float> {
-        static_cast<float>((((p[0] / p[3] + 1) / 2) * size.width) + viewportPadding + offset.x),
-        static_cast<float>((((-p[1] / p[3] + 1) / 2) * size.height) + viewportPadding + offset.y) };
+        static_cast<float>((((p[0] / p[3] + 1) / 2) * size.width) + viewportPadding),
+        static_cast<float>((((-p[1] / p[3] + 1) / 2) * size.height) + viewportPadding) };
 }
 
 } // namespace mbgl