Add IsPinchZoomEnabled spec

Author: tofuandeve

specs/IsPinchZoomEnabled.md

@@ -0,0 +1,71 @@
+# Background
+
+There are two types of zoom in Chromium: Browser Zoom and Pinch-Zoom:
+- Browser zoom is what you get by using Ctrl + +(plus) or – (minus) or Ctrl + Mousewheel. 
+- Pinch-zoom is activated by using a pinch gesture on a touchscreen. 
+
+Currently, the first type of zoom control is supported in WebView2 and modifying it has no effect on pinch zoom. 
+
+In response to customer requests to be able to change the current functionality of pinch zoon in WebView2: Disable/Enanle pinch zoom, the WebView2 team has introduced Pinch Zoom API which allows users to change setting to disable/enable pinch zoom.
+
+In this document we describe the new setting. We'd appreciate your feedback.
+
+
+# Description
+The default value for IsPinchZoomEnabled is true.
+When this setting is set to false, it disables pinch zoom in WebView.
+
+
+# Examples
+```cpp
+void SettingsComponent::TogglePinchZooomEnabled()
+{
+    BOOL enabled;
+    CHECK_FAILURE(coreWebView2Settings->get_IsPinchZoomEnabled(&enabled));
+    CHECK_FAILURE(coreWebView2Settings->put_IsPinchZoomEnabled(enabled ? FALSE : TRUE));
+}
+```
+
+```c#
+privagte WebView2 _webView;
+void TogglePinchZoomEnabled()
+{
+    var coreWebView2Settings = webView.CoreWebView2.Settings;
+    coreWebView2Settings.IsPinchZoomEnabled = !coreWebView2Settings.IsPinchZoomEnabled;
+}
+```
+# API Notes
+
+See [API Details](#api-details) section below for API reference.
+
+# API Details
+
+## Win32 C++
+```cpp
+[uuid(B625A89E-368F-43F5-BCBA-39AA6234CCF8), object, pointer_default(unique)]
+interface ICoreWebView2StagingSettings : IUnknown {
+  /// The IsPinchZoomEnabled property is used to prevent the default
+  /// pinch zoom control from working in webview. Defaults to TRUE.
+  /// When disabled, user will not be able to pinch zoom.
+  ///
+  /// \snippet SettingsComponent.cpp DisablePinchZoom
+  [propget] HRESULT IsPinchZoomEnabled([out, retval] BOOL* enabled);
+  /// Set the IsPinchZoomEnabled property
+  [propput] HRESULT IsPinchZoomEnabled([in] BOOL enabled);
+}
+```
+
+## .NET and WinRT
+
+```c#
+namespace Microsoft.Web.WebView2.Core
+{
+    public partial class CoreWebView2Settings
+    {
+        /// 
+        public bool IsPinchZoomEnabled { get; set};
+
+    }
+}
+
+```