From d28e51d9b49930b00cec246ca2780fa6332f12be Mon Sep 17 00:00:00 2001
From: John Firebaugh <john.firebaugh@gmail.com>
Date: Fri, 23 Feb 2018 15:13:18 -0800
Subject: [PATCH] Add comments

---
 src/ui/handler/drag_pan.js    | 9 +++++++--
 src/ui/handler/drag_rotate.js | 9 ++++++++-
 2 files changed, 15 insertions(+), 3 deletions(-)

diff --git a/src/ui/handler/drag_pan.js b/src/ui/handler/drag_pan.js
index 8d47b0e6f51..24dc9828f46 100644
--- a/src/ui/handler/drag_pan.js
+++ b/src/ui/handler/drag_pan.js
@@ -91,6 +91,11 @@ class DragPanHandler {
         if (this._map.dragRotate.isActive()) return;
         if (this.isActive()) return;
 
+        // Bind window-level event listeners for move and up/end events. In the absence of
+        // the pointer capture API, which is not supported by all necessary platforms,
+        // window-level event listeners give us the best shot at capturing events that
+        // fall outside the map canvas element. Use `{capture: true}` for the move event
+        // to prevent map move events from being fired during a drag.
         if (e.touches) {
             if ((e.touches: any).length > 1) return;
             window.document.addEventListener('touchmove', this._onMove, {capture: true});
@@ -101,8 +106,8 @@ class DragPanHandler {
             window.document.addEventListener('mouseup', this._onUp);
         }
 
-        // Deactivate DragPan when the window loses focus. Otherwise if a mouseup occurs when the window
-        // isn't in focus, DragPan will still be active even though the mouse is no longer pressed.
+        // Deactivate when the window loses focus. Otherwise if a mouseup occurs when the window
+        // isn't in focus, dragging will continue even though the mouse is no longer pressed.
         window.addEventListener('blur', this._onUp);
 
         this._active = false;
diff --git a/src/ui/handler/drag_rotate.js b/src/ui/handler/drag_rotate.js
index 8c3610e2287..c9b1530b8e0 100644
--- a/src/ui/handler/drag_rotate.js
+++ b/src/ui/handler/drag_rotate.js
@@ -118,9 +118,16 @@ class DragRotateHandler {
 
         DOM.disableDrag();
 
+        // Bind window-level event listeners for move and up/end events. In the absence of
+        // the pointer capture API, which is not supported by all necessary platforms,
+        // window-level event listeners give us the best shot at capturing events that
+        // fall outside the map canvas element. Use `{capture: true}` for the move event
+        // to prevent map move events from being fired during a drag.
         window.document.addEventListener('mousemove', this._onMove, {capture: true});
         window.document.addEventListener('mouseup', this._onUp);
-        /* Deactivate DragRotate when the window looses focus. Otherwise if a mouseup occurs when the window isn't in focus, DragRotate will still be active even though the mouse is no longer pressed. */
+
+        // Deactivate when the window loses focus. Otherwise if a mouseup occurs when the window
+        // isn't in focus, dragging will continue even though the mouse is no longer pressed.
         window.addEventListener('blur', this._onUp);
 
         this._active = false;