CMake: Download SDK when wxUSE_WEBVIEW_EDGE=ON

Automatically download the WebView2 SDK from nuget (official repo for the SDK)
when enabling wxUSE_WEBVIEW_EDGE to simplify usage.
Copying to 3rdparty/webview2 is still supported optionally.

build/cmake/init.cmake

@@ -453,10 +453,6 @@ if(wxUSE_GUI)
                 wx_option_force_value(wxUSE_WEBVIEW OFF)
             endif()
         elseif(WXMSW)
-            if(wxUSE_WEBVIEW_EDGE AND NOT EXISTS "${wxSOURCE_DIR}/3rdparty/webview2")
-                message("WebView2 SDK not found, WebviewEdge won't be available")
-                wx_option_force_value(wxUSE_WEBVIEW_EDGE OFF)
-            endif()
             if(NOT wxUSE_WEBVIEW_IE AND NOT wxUSE_WEBVIEW_EDGE)
                 message(WARNING "WebviewIE and WebviewEdge not found or enabled, wxWebview won't be available")
                 wx_option_force_value(wxUSE_WEBVIEW OFF)

build/cmake/lib/webview/CMakeLists.txt

@@ -37,7 +37,36 @@ if(APPLE)
     wx_lib_link_libraries(wxwebview PUBLIC "-framework WebKit")
 elseif(WXMSW)
     if(wxUSE_WEBVIEW_EDGE)
-        wx_lib_include_directories(wxwebview PRIVATE "${PROJECT_SOURCE_DIR}/3rdparty/webview2/build/native/include")
+        # Update the following variables if updating WebView2 SDK
+        set(WEBVIEW2_VERSION "1.0.705.50")
+        set(WEBVIEW2_URL "https://www.nuget.org/api/v2/package/Microsoft.Web.WebView2/${WEBVIEW2_VERSION}")
+        set(WEBVIEW2_SHA256 "6a34bb553e18cfac7297b4031f3eac2558e439f8d16a45945c22945ac404105d")
+
+        set(WEBVIEW2_DEFAULT_PACKAGE_DIR "${CMAKE_BINARY_DIR}/packages/Microsoft.Web.WebView2.${WEBVIEW2_VERSION}")
+
+        find_path(WEBVIEW2_PACKAGE_DIR
+            NAMES build/native/include/WebView2.h
+            PATHS
+                "${PROJECT_SOURCE_DIR}/3rdparty/webview2"
+                ${WEBVIEW2_DEFAULT_PACKAGE_DIR}
+        )
+        mark_as_advanced(WEBVIEW2_PACKAGE_DIR)
+
+        if (NOT WEBVIEW2_PACKAGE_DIR)
+            message(STATUS "WebView2 SDK not found locally, downloading...")
+            set(WEBVIEW2_PACKAGE_DIR ${WEBVIEW2_DEFAULT_PACKAGE_DIR} CACHE PATH "WebView2 SDK PATH" FORCE)
+            file(DOWNLOAD
+                ${WEBVIEW2_URL}
+                ${CMAKE_BINARY_DIR}/webview2.nuget
+                EXPECTED_HASH SHA256=${WEBVIEW2_SHA256})
+            file(MAKE_DIRECTORY ${WEBVIEW2_PACKAGE_DIR})
+            execute_process(COMMAND
+                ${CMAKE_COMMAND} -E tar x ${CMAKE_BINARY_DIR}/webview2.nuget
+                WORKING_DIRECTORY ${WEBVIEW2_PACKAGE_DIR}
+            )
+        endif()
+
+        wx_lib_include_directories(wxwebview PRIVATE "${WEBVIEW2_PACKAGE_DIR}/build/native/include")
 
         if (CMAKE_SIZEOF_VOID_P EQUAL 4)
             set(WEBVIEW2_ARCH x86)
@@ -47,7 +76,7 @@ elseif(WXMSW)
 
         add_custom_command(TARGET wxwebview POST_BUILD
             COMMAND ${CMAKE_COMMAND} -E copy
-            "${PROJECT_SOURCE_DIR}/3rdparty/webview2/build/native/${WEBVIEW2_ARCH}/WebView2Loader.dll"
+            "${WEBVIEW2_PACKAGE_DIR}/build/native/${WEBVIEW2_ARCH}/WebView2Loader.dll"
             "$<TARGET_FILE_DIR:wxwebview>/WebView2Loader.dll")
     endif()
 elseif(WXGTK)

build/cmake/options.cmake

@@ -445,7 +445,8 @@ if(WIN32)
     else()
         set(wxUSE_WINRT_DEFAULT OFF)
     endif()
-    if(MSVC_VERSION GREATER 1800 AND NOT CMAKE_VS_PLATFORM_TOOLSET MATCHES "_xp$")
+    if(MSVC_VERSION GREATER 1800 AND NOT CMAKE_VS_PLATFORM_TOOLSET MATCHES "_xp$" AND
+        EXISTS "${wxSOURCE_DIR}/3rdparty/webview2")
         set(wxUSE_WEBVIEW_EDGE_DEFAULT ON)
     else()
         set(wxUSE_WEBVIEW_EDGE_DEFAULT OFF)

interface/wx/webview.h

@@ -321,12 +321,14 @@ public:
 
     This backend is not enabled by default, to build it follow these steps:
     - Visual Studio 2015, or newer, is required
-    - Download the <a href="https://aka.ms/webviewnuget">WebView2 SDK</a>
+    - With CMake just enable @c wxUSE_WEBVIEW_EDGE
-      nuget package (Version 1.0.622.22 or newer)
+    - When not using CMake:
-    - Extract the package (it's a zip archive) to @c wxWidgets/3rdparty/webview2
+        - Download the <a href="https://aka.ms/webviewnuget">WebView2 SDK</a>
-      (you should have @c 3rdparty/webview2/build/native/include/WebView2.h
+        nuget package (Version 1.0.622.22 or newer)
-      file after unpacking it)
+        - Extract the package (it's a zip archive) to @c wxWidgets/3rdparty/webview2
-    - Enable @c wxUSE_WEBVIEW_EDGE in CMake or @c setup.h
+        (you should have @c 3rdparty/webview2/build/native/include/WebView2.h
+        file after unpacking it)
+        - Enable @c wxUSE_WEBVIEW_EDGE in @c setup.h
     - Build wxWidgets webview library
     - Copy @c WebView2Loader.dll from the subdirectory corresponding to the
       architecture used (x86 or x64) of @c wxWidgets/3rdparty/webview2/build/