[core] Offset viewport center when edge insets are specified

The change is implemented in TransformState::getProjMatrix, the rest of the code is making sure that existing API contracts stay and there are tests verifyingrendering and render query processing only items within screen and given tolerance around screen edges.

MapView: don't bake edge insets into relalculated camera center. Keep edge insets as property of camera in TransformState (similar to pitch, zoom, bearing) independent from specified camera center. Interpolate edge insets in animation.

iOS Demo app: "Turn On/Off Content Insets" pitch the camera and navigate to convenient location in Denver, where streets are parallel to cardinal directions, to illustrate viewport center offset when edge insets are set.

Tests:
ViewFrustumCulling: although Annotations are deprecated, queryRenderedFeatures related tests in Annotations would need to get ported and decided to add the edge insets related query tests next to them. Verify frustum culling (render+queryRenderedFeatures) With different camera and edge insets setups. TODO: port Annotations tests.

Transform.Padding: Verify that coordinates take proper place on screen after applying edge insets.

LocalGlyphRasterizer: verify text rendering when applying padding.

Related to #11882: both use projection matrix elements [8] and [9].

Alternative approach to this was to increase and offset map origin so that the screen would be a sub-rectangle in larger map viewport. This approach has a drawback of unecessary processing the items that are outside screen area.

Fixes #12107, #12728, navigation-sdks/issues/120

1 files changed, 6 insertions, 0 deletions

diff --git a/src/mbgl/map/transform_state.hpp b/src/mbgl/map/transform_state.hpp
index f51660912c..9e501d600f 100644
--- a/src/mbgl/map/transform_state.hpp
+++ b/src/mbgl/map/transform_state.hpp
@@ -62,6 +62,10 @@ public:
     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;
@@ -137,6 +141,8 @@ private:
     double ySkew = 1.0;
     bool axonometric = false;
 
+    EdgeInsets edgeInsets;
+
     // cache values for spherical mercator math
     double Bc = Projection::worldSize(scale) / util::DEGREES_MAX;
     double Cc = Projection::worldSize(scale) / util::M2PI;