Fabric: `pointScaleFactor` is now part of LayoutContext and LayoutMetrics

Summary:
@public
... and we initalize this in Surface.
We need this for requesting images with proper size/pixel-density, setup proper parameters for rasterizing CALayer's and rounding layout metric values.
Then we have to figure out how to wire this up with YGConfig.

Reviewed By: fkgozali

Differential Revision: D8475639

fbshipit-source-id: cec7af581b94efb4595dcf3f232252ce87a1fde3

React/Fabric/RCTSurfacePresenter.mm

@@ -17,6 +17,7 @@
 #import <React/RCTSurfaceRegistry.h>
 #import <React/RCTSurfaceView.h>
 #import <React/RCTSurfaceView+Internal.h>
+#import <React/RCTUtils.h>
 #import <fabric/core/LayoutContext.h>
 #import <fabric/core/LayoutConstraints.h>
 
@@ -106,6 +107,7 @@ using namespace facebook::react;
                           surface:(RCTFabricSurface *)surface
 {
   LayoutContext layoutContext;
+  layoutContext.pointScaleFactor = RCTScreenScale();
   LayoutConstraints layoutConstraints = {};
   layoutConstraints.minimumSize = RCTSizeFromCGSize(minimumSize);
   layoutConstraints.maximumSize = RCTSizeFromCGSize(maximumSize);
@@ -120,6 +122,7 @@ using namespace facebook::react;
                surface:(RCTFabricSurface *)surface
 {
   LayoutContext layoutContext;
+  layoutContext.pointScaleFactor = RCTScreenScale();
   LayoutConstraints layoutConstraints = {};
   layoutConstraints.minimumSize = RCTSizeFromCGSize(minimumSize);
   layoutConstraints.maximumSize = RCTSizeFromCGSize(maximumSize);

React/Fabric/Surface/RCTFabricSurface.mm

@@ -59,7 +59,6 @@
                               moduleName:(NSString *)moduleName
                        initialProperties:(NSDictionary *)initialProperties
 {
-
   if (self = [super init]) {
     _surfacePresenter = surfacePresenter;
     _moduleName = moduleName;

ReactCommon/fabric/core/layout/LayoutContext.h

@@ -21,6 +21,14 @@ struct LayoutContext {
    * Compound absolute position of the node relative to the root node.
    */
   Point absolutePosition {0, 0};
+
+  /*
+   * Reflects the scale factor needed to convert from the logical coordinate
+   * space into the device coordinate space of the physical screen.
+   * Some layout systems *might* use this to round layout metric values
+   * to `pixel value`.
+   */
+  Float pointScaleFactor = {1.0};
 };
 
 } // namespace react

ReactCommon/fabric/core/layout/LayoutMetrics.h

@@ -22,6 +22,7 @@ struct LayoutMetrics {
   EdgeInsets borderWidth {0};
   DisplayType displayType {DisplayType::Flex};
   LayoutDirection layoutDirection {LayoutDirection::Undefined};
+  Float pointScaleFactor {1.0};
 
   Rect getContentFrame() const {
     return Rect {

ReactCommon/fabric/view/yoga/YogaLayoutableShadowNode.cpp

@@ -126,6 +126,7 @@ void YogaLayoutableShadowNode::layoutChildren(LayoutContext layoutContext) {
     auto nonConstYogaLayoutableChild = std::const_pointer_cast<YogaLayoutableShadowNode>(yogaLayoutableChild);
 
     LayoutMetrics childLayoutMetrics = layoutMetricsFromYogaNode(nonConstYogaLayoutableChild->yogaNode_);
+    childLayoutMetrics.pointScaleFactor = layoutContext.pointScaleFactor;
     nonConstYogaLayoutableChild->setLayoutMetrics(childLayoutMetrics);
   }
 }