From 9658d1372d36220c2ff94242109bdfb7531fefa6 Mon Sep 17 00:00:00 2001
From: Jack Andersen <jackoalan@gmail.com>
Date: Mon, 21 Jan 2019 18:23:22 -1000
Subject: [PATCH] Additional methods for SScrollDelta

---
 include/boo/IWindow.hpp | 15 ++++++++++++---
 1 file changed, 12 insertions(+), 3 deletions(-)

diff --git a/include/boo/IWindow.hpp b/include/boo/IWindow.hpp
index 3a00b4a..03feb8f 100644
--- a/include/boo/IWindow.hpp
+++ b/include/boo/IWindow.hpp
@@ -64,11 +64,11 @@ struct STouchCoord {
 };
 
 struct SScrollDelta {
-  double delta[2];
-  bool isFine;                /* Use system-scale fine-scroll (for scrollable-trackpads) */
+  double delta[2] = {};
+  bool isFine = false;        /* Use system-scale fine-scroll (for scrollable-trackpads) */
   bool isAccelerated = false; /* System performs acceleration computation */
 
-  SScrollDelta operator+(const SScrollDelta& other) {
+  SScrollDelta operator+(const SScrollDelta& other) const {
     SScrollDelta ret;
     ret.delta[0] = delta[0] + other.delta[0];
     ret.delta[1] = delta[1] + other.delta[1];
@@ -76,6 +76,14 @@ struct SScrollDelta {
     ret.isAccelerated = isAccelerated || other.isAccelerated;
     return ret;
   }
+  SScrollDelta operator-(const SScrollDelta& other) const {
+    SScrollDelta ret;
+    ret.delta[0] = delta[0] - other.delta[0];
+    ret.delta[1] = delta[1] - other.delta[1];
+    ret.isFine = isFine || other.isFine;
+    ret.isAccelerated = isAccelerated || other.isAccelerated;
+    return ret;
+  }
   SScrollDelta& operator+=(const SScrollDelta& other) {
     delta[0] += other.delta[0];
     delta[1] += other.delta[1];
@@ -87,6 +95,7 @@ struct SScrollDelta {
     delta[0] = 0.0;
     delta[1] = 0.0;
   }
+  bool isZero() const { return delta[0] == 0.0 && delta[1] == 0.0; }
 };
 
 enum class ESpecialKey {