implement simple scrolling

src/background/index.js

@@ -2,10 +2,14 @@ import * as tabs from './tabs';
 
 const KEY_MAP = {
   'tabs.prev': 104,
-  'tabs.next': 108
+  'tabs.next': 108,
+  'scroll.up': 107,
+  'scroll.down': 106
 };
 
 browser.runtime.onMessage.addListener((request, sender, sendResponse) => {
+  let response = null;
+
   switch (request.key) {
   case KEY_MAP['tabs.prev']:
     tabs.selectPrevTab(sender.tab.index);
@@ -13,6 +17,12 @@ browser.runtime.onMessage.addListener((request, sender, sendResponse) => {
   case KEY_MAP['tabs.next']:
     tabs.selectNextTab(sender.tab.index);
     break;
+  case KEY_MAP['scroll.up']:
+    response = 'scroll.up'
+    break;
+  case KEY_MAP['scroll.down']:
+    response = 'scroll.down'
+    break;
   }
-  sendResponse();
+  sendResponse(response);
 });

src/content/index.js

@@ -1,3 +1,16 @@
+import * as scrolls from './scrolls';
+
+const invokeEvent = (type) => {
+  switch (type) {
+  case 'scroll.up':
+    scrolls.scrollUp(window);
+    break;
+  case 'scroll.down':
+    scrolls.scrollDown(window);
+    break;
+  }
+}
+
 window.addEventListener("keypress", (e) => {
   browser.runtime.sendMessage({
     key: e.which || e.keyCode,
@@ -5,7 +18,10 @@ window.addEventListener("keypress", (e) => {
     alt: e.alt,
     meta: e.meta,
     ctrl: e.ctrl,
-  }).then(() => {
+  }).then((response) => {
+    if (response) {
+      invokeEvent(response);
+    }
   }, (err) => {
     console.log(`Vim Vixen: ${err}`);
   });

src/content/scrolls.js

@@ -0,0 +1,27 @@
+const SCROLL_DELTA = 48;
+
+const scrollUp = (page) => {
+  let x = page.scrollX;
+  var y = page.scrollY - SCROLL_DELTA;
+  page.scrollTo(x, y);
+};
+
+const scrollDown = (page) => {
+  let x = page.scrollX;
+  var y = page.scrollY + SCROLL_DELTA;
+  page.scrollTo(x, y);
+};
+
+const scrollToTop = (page) => {
+  let x = page.scrollX;
+  var y = page.scrollMaxY;
+  page.scrollTo(x, y);
+};
+
+const scrollToBottom = (page) => {
+  let x = page.scrollX;
+  var y = 0;
+  page.scrollTo(x, y);
+};
+
+export { scrollUp, scrollDown, scrollToTop, scrollToBottom }