preattentive symbols

.gitignore

@@ -3,3 +3,8 @@
 dist/
 node_modules
 npm-debug.log
+d3-shape.xcodeproj/xcuserdata/hemanrobinson.xcuserdatad/xcschemes/xcschememanagement.plist
+d3-shape.xcodeproj/project.xcworkspace/xcuserdata/hemanrobinson.xcuserdatad/UserInterfaceState.xcuserstate
+d3-shape.xcodeproj/project.xcworkspace/xcshareddata/IDEWorkspaceChecks.plist
+d3-shape.xcodeproj/project.xcworkspace/contents.xcworkspacedata
+d3-shape.xcodeproj/project.pbxproj

src/pSymbol/asterisk.js

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+/* Asterisk */
+export default {
+    draw: function( g, size ) { if( size > 0 ) {
+        let r = Math.sqrt( size / Math.PI );                // radius
+        let s = Math.max( 1.5, r * Math.PI / 3 + 0.5 );     // +0.5 accounts for overlap.
+        let t = s * Math.sin( Math.PI / 6 ),
+            u = s * Math.cos( Math.PI / 6 );
+        g.moveTo(  0,  s );
+        g.lineTo(  0, -s );
+        g.closePath();
+        g.moveTo( -u, -t );
+        g.lineTo(  u,  t );
+        g.closePath();
+        g.moveTo( -u,  t );
+        g.lineTo(  u, -t );
+        g.closePath();
+    }}
+};

src/pSymbol/circle.js

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+/* Circle */
+export default {
+    draw: function( g, size ) { if( size > 0 ) {
+        let s = Math.sqrt( size / Math.PI );                // radius
+        g.arc( 0, 0, s, 0, 2 * Math.PI );
+        g.closePath();
+    }}
+};

src/pSymbol/diamond.js

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+/* Diamond */
+export default {
+    draw: function( g, size ) { if( size > 0 ) {
+        let r = Math.sqrt( size / Math.PI );                // radius
+        let s = r * Math.PI / ( 2 * Math.SQRT2 ) + 0.5;     // +0.5 accounts for overlap.
+        let t = 1 / ( 2 * Math.SQRT2 );                     // t accounts for line width.
+        g.moveTo(      -t, - s - t );
+        g.lineTo(   s + t,       t );
+        g.closePath();
+        g.moveTo(   s + t,      -t );
+        g.lineTo(      -t,   s + t );
+        g.closePath();
+        g.moveTo(       t,   s + t );
+        g.lineTo( - s - t,      -t );
+        g.closePath();
+        g.moveTo( - s - t,       t );
+        g.lineTo(       t, - s - t );
+        g.closePath();
+    }}
+};

src/pSymbol/pSymbol.js

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+/**
+ * Popular symbols with preattentive features.
+ *
+ * Preattentive features aid pattern detection and reduce overlap.
+ * These symbols are adjusted to have approximately equal weight.
+ *
+ * Symbols are centered at (0,0).  When translating,
+ * round to the center of the pixel to minimize anti-aliasing, e.g.
+ *      .attr( "transform", "translate( " + ( Math.floor( x ) + 0.5 ) + ", " + ( Math.floor( y ) + 0.5 ) + " )" )
+ */
+import circle from "./pSymbol/circle.js";
+import plus from "./pSymbol/plus.js";
+import x from "./pSymbol/x.js";
+import triangle from "./pSymbol/triangle.js";
+import asterisk from "./pSymbol/asterisk.js";
+import square from "./pSymbol/square.js";
+import diamond from "./pSymbol/diamond.js";
+export var pSymbols = [
+  circle,
+  plus,
+  x,
+  triangle,
+  asterisk,
+  square,
+  diamond
+];
+
+/**
+ * Symbol sets.
+ */
+export var symbolSets = [ "geometric": symbols, "preattentive": pSymbols ];

src/pSymbol/plus.js

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+/* Plus */
+export default {
+    draw: function( g, size ) { if( size > 0 ) {
+        let r = Math.sqrt( size / Math.PI );                // radius
+        let s = Math.max( 1.5, r * Math.PI / 2 - 0.25 );    // -0.25 accounts for center pixel.
+        g.moveTo( -s,  0 );
+        g.lineTo(  s,  0 );
+        g.closePath();
+        g.moveTo(  0,  s );
+        g.lineTo(  0, -s );
+        g.closePath();
+    }}
+};

src/pSymbol/square.js

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+/* Square */
+export default {
+    draw: function( g, size ) { if( size > 0 ) {
+        let r = Math.sqrt( size / Math.PI );                // radius
+        let s = r * Math.PI / 4 + 0.25;                     // +0.25 accounts for overlap.
+        g.moveTo(  s,  s );
+        g.lineTo(  s, -s );
+        g.lineTo( -s, -s );
+        g.lineTo( -s,  s );
+        g.closePath();
+    }}
+};

src/pSymbol/triangle.js

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+/* Triangle */
+export default {
+    draw: function( g, size ) { if( size > 0 ) {
+        let r = Math.sqrt( size / Math.PI );                // radius
+        let s = r * Math.PI / 3 + 0.5;                      // +0.5 accounts for overlap.
+        let t = s * Math.sin( Math.PI / 6 ),
+            u = s * Math.cos( Math.PI / 6 );
+        g.moveTo(  0, -s );
+        g.lineTo(  u,  t );
+        g.lineTo( -u,  t );
+        g.closePath();
+    }}
+};

src/pSymbol/x.js

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+/* X */
+export default {
+    draw: function( g, size ) { if( size > 0 ) {
+        let r = Math.sqrt( size / Math.PI );                // radius
+        let s = r * Math.PI / 2 + 0.25;                     // +0.25 accounts for center pixel and line width.
+        let t = Math.max( 1, s / Math.SQRT2 );
+        g.moveTo( -t, -t );
+        g.lineTo(  t,  t );
+        g.closePath();
+        g.moveTo( -t,  t );
+        g.lineTo(  t, -t );
+        g.closePath();
+    }}
+};