Open links when shift-click on link or url

app/less/editor.less

@@ -60,6 +60,13 @@
         .editor-searching();
     }
 
+    .link-clickable {
+        .cm-link:not(.cm-formatting),
+        .cm-url:not(.cm-formatting) {
+            cursor: pointer
+        }
+    }
+
 // Generic editor classes
 // ======================
 

app/renderer/abr-document.js

@@ -207,6 +207,73 @@ function AbrDocument () {
             }
         };
 
+        // Listeners for opening links on shift-click.
+
+        // Helper method to tell us if we should open a link from
+        // the target that has been clicked on. Check the global
+        // link-clickable class first to see if there's some reason
+        // that we shouldn't open a valid link (like selected text),
+        // then check for Markdown indicators.
+        var shouldOpenLink = function(event) {
+            return document.body.classList.contains("link-clickable") &&
+                !event.target.classList.contains("cm-formatting") &&
+                (event.target.classList.contains("cm-link") ||
+                event.target.classList.contains("cm-url"));
+        }
+
+        that.cm.on("mousedown", function(cm, event) { // prevent selection by shift-click
+            if (shouldOpenLink(event)) {
+                event.preventDefault();
+            }
+        });
+
+        document.addEventListener("mouseup", function(event) { // actually open the browser on mouseup
+            if (shouldOpenLink(event)) {
+                event.preventDefault();
+                OpenLinkHandler(event);
+            }
+        });
+
+        // Handle ALT modifier key
+        var ShiftKeyHandler = function(e) {
+            var linkIsClickable = !that.cm.somethingSelected() &&
+                e.type === "keydown" &&
+                e.shiftKey;
+            document.body.classList.toggle("link-clickable", linkIsClickable);
+        }
+
+        window.addEventListener("keydown", ShiftKeyHandler, false);
+        window.addEventListener("keyup", ShiftKeyHandler, false);
+        // when leaving Abricotine to go the browser, the keyup event doesn't trigger
+        window.addEventListener("blur", ShiftKeyHandler, false);
+
+        var OpenLinkHandler = function(e) {
+            if (!document.body.classList.contains("link-clickable")) return;
+
+            var open = null;
+            var url = null;
+            if (e.target.classList.contains("cm-url")) { // link in standard MD format, url part was clicked on
+                open = $(e.target).prevUntil(":not(.cm-url)").andSelf().first();
+                url = open.nextUntil(".cm-formatting-link-string").text();
+            } else if (e.target.classList.contains("cm-link")) {
+                open = $(e.target).prevUntil(":not(.cm-link)");
+                if (open.first().is(".cm-formatting-link")) { // link in standard MD format, link text was clicked on
+                    open = $(e.target).nextAll(".cm-formatting-link-string").first();
+                    url = open.nextUntil(".cm-formatting-link-string").text();
+                } else { // link is a raw url
+                    open = open.andSelf().first();
+                    url = open.nextUntil(":not(.cm-link)").andSelf().text();
+                }
+            }
+
+            if (url === "") return;
+            var hasProtocol = /^[a-z]+:\/\//.test(url);
+            if (!hasProtocol) {
+              url = "http://" + url;
+            }
+            shell.openExternal(url);
+        }
+
         // Handle CTRL+MouseWheel events
         var MouseWheelHandler = function (e) {
             var delta = Math.max(-1, Math.min(1, (e.wheelDelta || -e.detail)));