Add "touchY" plugin

build.js

@@ -27,6 +27,7 @@ files.push('src/plugins/autoplay/autoplay.js',
            'src/plugins/stop/stop.js',
            'src/plugins/substep/substep.js',
            'src/plugins/touch/touch.js',
+           'src/plugins/touchY/touchY.js',
            'src/plugins/toolbar/toolbar.js')
 var output = files.map((f)=>{
   return fs.readFileSync(f).toString();
@@ -71,4 +72,4 @@ html += '</body>\n</html>'
 
 filename = path.resolve(__dirname, 'examples', 'index.html');
 fs.writeFileSync(filename, html);
-console.log(filename);
+console.log(filename);

src/plugins/touchY/touchY.js

@@ -0,0 +1,67 @@
+/**
+ * Support for swipe and tap on touch devices
+ *
+ * This plugin implements navigation for plugin devices, via swiping up/down,
+ * or tapping on the up/down edges of the screen.
+ *
+ * This is a modified "touch" plugin for impress.js, 2020: Arsenii Lyzenko
+ * (@pticagovorun)
+ *
+ *
+ * MIT License
+ */
+/* global document, window */
+( function( document, window ) {
+    "use strict";
+
+    // Touch handler to detect swiping up and down based on window size.
+    // If the difference in Y change is bigger than 1/20 of the screen height,
+    // we simply call an appropriate API function to complete the transition.
+    var startY = 0;
+    var lastY = 0;
+    var lastDY = 0;
+    var threshold = window.innerHeight / 20;
+
+    document.addEventListener( "touchstart", function( event ) {
+        lastY = startY = event.touches[ 0 ].clientY;
+    } );
+
+    document.addEventListener( "touchmove", function( event ) {
+         var y = event.touches[ 0 ].clientY;
+         var diff = y - startY;
+
+         // To be used in touchend
+         lastDY = lastY - y;
+         lastY = y;
+
+         window.impress().swipe( diff / window.innerHeight );
+     } );
+
+     document.addEventListener( "touchend", function() {
+         var totalDiff = lastY - startY;
+         if ( Math.abs( totalDiff ) > window.innerHeight / 5 && ( totalDiff * lastDY ) <= 0 ) {
+             if ( totalDiff > window.innerHeight / 5 && lastDY <= 0 ) {
+                 window.impress().prev();
+             } else if ( totalDiff < -window.innerHeight / 5 && lastDY >= 0 ) {
+                 window.impress().next();
+             }
+         } else if ( Math.abs( lastDY ) > threshold ) {
+             if ( lastDY < -threshold ) {
+                 window.impress().prev();
+             } else if ( lastDY > threshold ) {
+                 window.impress().next();
+             }
+         } else {
+
+             // No movement - move (back) to the current slide
+             window.impress().goto( document.querySelector( "#impress .step.active" ) );
+         }
+     } );
+
+     document.addEventListener( "touchcancel", function() {
+
+             // Move (back) to the current slide
+             window.impress().goto( document.querySelector( "#impress .step.active" ) );
+     } );
+
+} )( document, window );