From 6ad09cc83f9db273cc91ff5277eb310f0671bf4a Mon Sep 17 00:00:00 2001
From: Martin Veillette <martin.veillette@gmail.com>
Date: Thu, 29 Jul 2021 16:38:33 -0400
Subject: [PATCH] hoist projector constant to GeometricOptics (see #129)

---
 js/common/GeometricOpticsConstants.js | 10 ++++++----
 js/lens/model/ProjectorScreen.js      |  4 ++--
 js/lens/view/ProjectorScreenNode.js   | 21 ++++++++++++---------
 3 files changed, 20 insertions(+), 15 deletions(-)

diff --git a/js/common/GeometricOpticsConstants.js b/js/common/GeometricOpticsConstants.js
index 2e742736..55531cbc 100644
--- a/js/common/GeometricOpticsConstants.js
+++ b/js/common/GeometricOpticsConstants.js
@@ -99,12 +99,14 @@ const GeometricOpticsConstants = {
   //                             PROJECTION SCREEN
 
   MASK_CORNERS: {
-    LEFT_TOP: new Vector2( -25, 33 ), // centimeters
-    LEFT_BOTTOM: new Vector2( -25, -56 ),
-    RIGHT_BOTTOM: new Vector2( 25, -88 ),
-    RIGHT_TOP: new Vector2( 25, 67 )
+    LEFT_TOP: new Vector2( -28, 39 ), // centimeters
+    LEFT_BOTTOM: new Vector2( -28, -51 ),
+    RIGHT_BOTTOM: new Vector2( 25, -83 ),
+    RIGHT_TOP: new Vector2( 25, 72 )
   },
 
+  PROJECTOR_INITIAL_POSITION: new Vector2( 200, 0 ),
+  PROJECTOR_SCALE: 0.5, // scaling factor applied to the projector screen image
   FULL_BRIGHT_SPOT_HEIGHT: 7, // centimeters
 
   //----------------------------------------------------------------------------------------
diff --git a/js/lens/model/ProjectorScreen.js b/js/lens/model/ProjectorScreen.js
index efbaab27..5cd897c5 100644
--- a/js/lens/model/ProjectorScreen.js
+++ b/js/lens/model/ProjectorScreen.js
@@ -7,7 +7,6 @@
  */
 
 import Matrix3 from '../../../../dot/js/Matrix3.js';
-import Vector2 from '../../../../dot/js/Vector2.js';
 import Vector2Property from '../../../../dot/js/Vector2Property.js';
 import Line from '../../../../kite/js/segments/Line.js';
 import Shape from '../../../../kite/js/Shape.js';
@@ -17,6 +16,7 @@ import geometricOptics from '../../geometricOptics.js';
 import Spotlight from './Spotlight.js';
 
 const MASK_CORNERS = GeometricOpticsConstants.MASK_CORNERS;
+const INITIAL_POSITION = GeometricOpticsConstants.PROJECTOR_INITIAL_POSITION;
 
 class ProjectorScreen {
 
@@ -37,7 +37,7 @@ class ProjectorScreen {
     assert && assert( tandem instanceof Tandem, 'invalid tandem' );
 
     // @public {Property.<Vector2>} position of the center of the screen
-    this.positionProperty = new Vector2Property( new Vector2( 200, 0 ) );
+    this.positionProperty = new Vector2Property( INITIAL_POSITION );
 
     // @public (read-only) {Property.<Vector2>} position of the optic
     this.opticPositionProperty = optic.positionProperty;
diff --git a/js/lens/view/ProjectorScreenNode.js b/js/lens/view/ProjectorScreenNode.js
index 6de440ae..dacd6fc3 100644
--- a/js/lens/view/ProjectorScreenNode.js
+++ b/js/lens/view/ProjectorScreenNode.js
@@ -18,9 +18,11 @@ import Path from '../../../../scenery/js/nodes/Path.js';
 import Tandem from '../../../../tandem/js/Tandem.js';
 import projectorScreen3dImage from '../../../images/projector-screen-3d_png.js';
 import GeometricOpticsColors from '../../common/GeometricOpticsColors.js';
+import GeometricOpticsConstants from '../../common/GeometricOpticsConstants.js';
 import geometricOptics from '../../geometricOptics.js';
 
 const SPOTLIGHT_FILL = GeometricOpticsColors.projectorScreenSpotlightFillProperty;
+const PROJECTOR_SCALE = GeometricOpticsConstants.PROJECTOR_SCALE;
 
 class ProjectorScreenNode extends Node {
 
@@ -49,24 +51,25 @@ class ProjectorScreenNode extends Node {
     super( options );
 
     // create projectorScreen target
-    const projectorScreenImage = new Image( projectorScreen3dImage, { scale: 0.5 } );
+    const projectorScreenImage = new Image( projectorScreen3dImage, { scale: PROJECTOR_SCALE } );
 
     // add projectorScreen image to scene graph
     this.addChild( projectorScreenImage );
 
-    // difference between the left top position of the image and the "center" of the blackboard
-    const offset = new Vector2( -30, 75 );
+    // TODO: the model should give its size to the view rather than the other way around (see #153)
+    // determine the size of the projector in model coordinates
+    const modelChildHeight = Math.abs( modelViewTransform.viewToModelDeltaY( projectorScreenImage.height ) );
+    const modelChildWidth = modelViewTransform.viewToModelDeltaX( projectorScreenImage.width );
+
+    // difference between the left top position of the image and the "center" of the blackboard in model coordinates
+    const offset = new Vector2( -modelChildWidth, modelChildHeight ).divideScalar( 2 );
 
     // @private {Property.<Vector2} create a property for the left top position of the projectorScreen target
     this.imagePositionProperty = new Vector2Property( projectorScreen.positionProperty.value.plus( offset ) );
 
-    // TODO: the model should give its size to the view rather than the other way around (see #153)
-    // determine the size of the projector in model coordinates
-    const modelChildHeight = Math.abs( modelViewTransform.viewToModelDeltaY( this.height ) );
-    const modelChildWidth = modelViewTransform.viewToModelDeltaX( this.width );
-
     // keep at least half of the projector screen within visible bounds and right of the optic
-    const projectorScreenDragBoundsProperty = new DerivedProperty( [ visibleModelBoundsProperty, projectorScreen.opticPositionProperty ],
+    const projectorScreenDragBoundsProperty = new DerivedProperty(
+      [ visibleModelBoundsProperty, projectorScreen.opticPositionProperty ],
       ( visibleBounds, opticPosition ) => {
         return new Bounds2( opticPosition.x,
           visibleBounds.minY + modelChildHeight / 2,