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| 1 | +Custom Storage Partition |
| 2 | +=== |
| 3 | + |
| 4 | +# Background |
| 5 | +For certain WebView host apps, there is a desire to have different contexts for |
| 6 | +different WebViews using the same profile so that when the same websites run in |
| 7 | +these WebViews, they will have different DOM storages and cookie jars. An example |
| 8 | +is different accounts within an application. |
| 9 | +Previosly, the application can use different profiles for different contexts, but |
| 10 | +that has 2 short comings: |
| 11 | +- WebViews from different profiles are not allowed to have opener/opened window relationship. |
| 12 | +- Using profiles means totally different storage for all files like http caches and less performance. |
| 13 | + |
| 14 | +To help managing different application contexts while using the same profile, we are |
| 15 | +introducing an API to set custom storage parition and an API to clear all data in |
| 16 | +a custom storage partition. |
| 17 | + |
| 18 | +When an application sets custom storage parition for a WebView, the sites and iframes |
| 19 | +running inside the WebView will act as if the site were running in a third party iframe |
| 20 | +inside a top level site uniquelly associated with the custom storage partition id and have |
| 21 | +separate [storage partition](https://developer.chrome.com/docs/privacy-sandbox/storage-partitioning/) |
| 22 | +and [cookie partition](https://developer.chrome.com/docs/privacy-sandbox/chips/). |
| 23 | + |
| 24 | +# Conceptual pages (How To) |
| 25 | +This feature depends on [storage partition](https://developer.chrome.com/docs/privacy-sandbox/storage-partitioning/) |
| 26 | +and [cookie partition](https://developer.chrome.com/docs/privacy-sandbox/chips/) browser |
| 27 | +features which are currently experimental. Before those features are enabled by default, |
| 28 | +the application must enable them by ensuring `--enable-features=ThirdPartyStoragePartitioning,PartitionedCookies` |
| 29 | +is set in [CoreWebView2EnvironmentOptions.AdditionalBrowserArguments](https://learn.microsoft.com/microsoft-edge/webview2/reference/winrt/microsoft_web_webview2_core/corewebview2environmentoptions#additionalbrowserarguments) |
| 30 | +used to create CoreWebView2Environment. If not set, no custom storage partition will be |
| 31 | +created and all data will be treated as unpartitioned and stored in the global default |
| 32 | +location for the profile. |
| 33 | +The custom storage partition APIs will remain experiemental when related browser features |
| 34 | +are still experimental. |
| 35 | + |
| 36 | +# Examples |
| 37 | + |
| 38 | +The example below illustrates how to set partition id on WebView and how to clear all |
| 39 | +data stored in the custom storage partition. |
| 40 | + |
| 41 | +## Win32 C++ |
| 42 | +```cpp |
| 43 | + wil::com_ptr<ICoreWebView2_18> m_webView; |
| 44 | + |
| 45 | + void OnWebViewCreated() |
| 46 | + { |
| 47 | + // ... |
| 48 | + // other WebView setup like add event handlers, update settings. |
| 49 | + |
| 50 | + // Sets custom storage partition identified by the partitionId, which uniquely |
| 51 | + // identifies an application context. |
| 52 | + PCWSTR partitionId = L"Partition 1"; |
| 53 | + CHECK_FAILURE(m_webview->put_CustomStoragePartitionId(partitionId)); |
| 54 | + |
| 55 | + // Navigate to start page |
| 56 | + m_webview->Navigation(startPage); |
| 57 | + } |
| 58 | + |
| 59 | + // Clears all data in custom storage partition identified by the partitionId. |
| 60 | + // Called when the application context is removed. |
| 61 | + HRESULT ClearPartitionData(PCWSTR partitionId) |
| 62 | + { |
| 63 | + wil::com_ptr<ICoreWebView2Profile> webView2Profile; |
| 64 | + CHECK_FAILURE(m_webview->get_Profile(&webView2Profile)); |
| 65 | + auto webView2Profile8 = webView2Profile.try_query<ICoreWebView2Profile8>(); |
| 66 | + CHECK_FEATURE_RETURN(webView2Profile8); |
| 67 | + CHECK_FAILURE(webView2Profile8->ClearCustomStoragePartitionData( |
| 68 | + partitionId, |
| 69 | + Callback<ICoreWebView2StagingClearCustomStoragePartitionDataCompletedHandler>( |
| 70 | + [this](HRESULT result) -> HRESULT |
| 71 | + { |
| 72 | + if (SUCCEEDED(result)) |
| 73 | + { |
| 74 | + AsyncMessageBox(L"Completed", L"Clear Custom Partition Data"); |
| 75 | + } |
| 76 | + else |
| 77 | + { |
| 78 | + std::wstringstream message; |
| 79 | + message << L"Failed: " << std::to_wstring(result) << L"(0x" << std::hex |
| 80 | + << result << L")" << std::endl; |
| 81 | + AsyncMessageBox(message.str(), L"Clear Custom Partition Data"); |
| 82 | + } |
| 83 | + return S_OK; |
| 84 | + }).Get())); |
| 85 | + return S_OK; |
| 86 | + } |
| 87 | + |
| 88 | +``` |
| 89 | +
|
| 90 | +## .NET/WinRT |
| 91 | +```c# |
| 92 | + private CoreWebView2 m_webview; |
| 93 | + |
| 94 | + // Sets custom storage partition identified by the partitionId, which uniquely |
| 95 | + // identifies an application context. |
| 96 | + void CoreWebView_Created() |
| 97 | + { |
| 98 | + // ... |
| 99 | + // other WebView setup like add event handlers, update settings. |
| 100 | + |
| 101 | + // Sets custom storage partition identified by the partitionId, which uniquely |
| 102 | + // identifies an application context. |
| 103 | + string partitionId = "Partition 1"; |
| 104 | + m_webview.CustomStoragePartitionId = partitionId; |
| 105 | + |
| 106 | + // Navigate to start page |
| 107 | + m_webview.Navigation(startPage); |
| 108 | + } |
| 109 | + |
| 110 | + // Clears all data in custom storage partition identified by the partitionId. |
| 111 | + // Called when the application context is removed. |
| 112 | + async void ClearPartitionData(string partitionId) |
| 113 | + { |
| 114 | + await m_webview.Profile.ClearCustomStoragePartitionDataAsync(partitionId); |
| 115 | + MessageBox.Show(this, "Completed", "Clear Custom Partition Data"); |
| 116 | + } |
| 117 | +
|
| 118 | +``` |
| 119 | + |
| 120 | +# API Details |
| 121 | +## Win32 C++ |
| 122 | +``` |
| 123 | +interface ICoreWebView2_18 : ICoreWebView2_17 { |
| 124 | + /// Gets the `CustomStoragePartitionId` property. |
| 125 | + [propget] HRESULT CustomStoragePartitionId([out, retval] LPWSTR* customStoragePartitionId); |
| 126 | +
|
| 127 | + /// Sets the `CustomStoragePartitionId` property. |
| 128 | + /// This feature requires enabling 2 experimental browser features to work properly. |
| 129 | + /// These features will be enabled by default in the future. |
| 130 | + /// Before these features are enabled by default, please enable them by ensuring |
| 131 | + /// `--enable-features=ThirdPartyStoragePartitioning,PartitionedCookies` is set in |
| 132 | + /// `AdditionalBrowserArguments` in `CoreWebView2EnvironmentOptions` used to create |
| 133 | + /// CoreWebView2Environment. If these features are not enabled, all data are treated |
| 134 | + /// as unpartitioned and stored in the global default location for the profile. |
| 135 | + /// When it is set, the page in the WebView will act as if the page were hosted in a |
| 136 | + /// top level site uniquely associated with the `partitionId` and have a separate |
| 137 | + /// storage partition as described in https://developer.chrome.com/docs/privacy-sandbox/storage-partitioning/ |
| 138 | + /// and separete cookie partition as described in https://developer.chrome.com/docs/privacy-sandbox/chips/ |
| 139 | + /// with all cookies partitioned. |
| 140 | + /// If `customStoragePartitionId` is nullptr or empty string, the |
| 141 | + /// `CustomStoragePartitionId` will be reset and the page inside the WebView |
| 142 | + /// will work normally with data treated as unpartitioned. |
| 143 | + /// The `customStoragePartitionId` parameter is case sensitive. The default is |
| 144 | + /// an empty string. There is no restriction on the length or what characters |
| 145 | + /// can be used in partition id. |
| 146 | + /// The change of the custom storage partition id will be applied to new |
| 147 | + /// page or iframe navigations and not impact existing pages and iframes. |
| 148 | + /// To avoid accidentally use new partition id for pending navigations of old page |
| 149 | + /// or iframe, it is recommended to create a new WebView for new partition instead |
| 150 | + /// of changing partition. If you really have to change partition, it is |
| 151 | + /// recommended to navigate to a blank page before setting the new partition |
| 152 | + /// id and navigate to a page for the new partition. |
| 153 | + /// |
| 154 | + /// As setting custom storage partition id does not change DOM security |
| 155 | + /// model, developers should be very careful for WebViews with opener and |
| 156 | + /// opened window relationship, especially when the pages in the WebViews |
| 157 | + /// have same origin, like when the opened window is the same site or |
| 158 | + /// about:blank. The pages in these WebViews can access each other’s DOM and |
| 159 | + /// therefore can potentially access DOM storage and cookies in different |
| 160 | + /// partition for the same site. It is recommended to set the same custom |
| 161 | + /// storage partition id for these WebViews, unless there is an absolute need |
| 162 | + /// to set different partition ids and only trusted code is hosted in them. |
| 163 | + /// |
| 164 | + [propput] HRESULT CustomStoragePartitionId([in] LPCWSTR customStoragePartitionId); |
| 165 | +} |
| 166 | +
|
| 167 | +interface ICoreWebView2Profile8 : ICoreWebView2Profile7 { |
| 168 | + /// Clears all DOM storage and cookies in the custom storage partition |
| 169 | + /// identified by the `customStoragePartitionId`. |
| 170 | + /// As DOM storage and cookies in the custom storage partition is also browsing |
| 171 | + /// data, they will also be cleared when `ClearBrowsingData`, |
| 172 | + /// `ClearBrowsingDataInTimeRange` or `ClearBrowsingDataAll` is called and |
| 173 | + /// the clearing condition is met. |
| 174 | + /// |
| 175 | + HRESULT ClearCustomStoragePartitionData( |
| 176 | + [in] LPCWSTR customStoragePartitionId, |
| 177 | + [in] ICoreWebView2ClearCustomStoragePartitionDataCompletedHandler* handler); |
| 178 | +} |
| 179 | +
|
| 180 | +interface ICoreWebView2ClearCustomStoragePartitionDataCompletedHandler : IUnknown { |
| 181 | +
|
| 182 | + /// Provide the completion status of the corresponding asynchronous method. |
| 183 | + HRESULT Invoke([in] HRESULT errorCode); |
| 184 | +} |
| 185 | +
|
| 186 | +``` |
| 187 | + |
| 188 | +## .NET/WinRT |
| 189 | +```c# |
| 190 | +namespace Microsoft.Web.WebView2.Core |
| 191 | +{ |
| 192 | + |
| 193 | + class CoreWebView2 |
| 194 | + { |
| 195 | + [interface_name("Microsoft.Web.WebView2.Core.ICoreWebView2_18")] |
| 196 | + { |
| 197 | + public string CustomStoragePartitionId { get; set; }; |
| 198 | + } |
| 199 | + } |
| 200 | + |
| 201 | + class CoreWebView2Profile |
| 202 | + { |
| 203 | + [interface_name("Microsoft.Web.WebView2.Core.ICoreWebView2Profile8")] |
| 204 | + { |
| 205 | + public async Task ClearCustomStoragePartitionDataAsync(string customStoragePartitionId); |
| 206 | + } |
| 207 | + } |
| 208 | +``` |
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