[camera_windows] Fall back to temp dir for capture path.

packages/camera/camera_windows/CHANGELOG.md

@@ -1,3 +1,9 @@
+## 0.2.6+6
+
+* Falls back to the system temp directory for captured pictures and videos when
+  the Pictures / Videos known folder cannot be used, e.g. when blocked by
+  Controlled Folder Access.
+
 ## 0.2.6+5
 
 * Updates pigeon dev_dependency to ^27.3.2 for analyzer 14 compatibility.

packages/camera/camera_windows/pubspec.yaml

@@ -2,7 +2,7 @@ name: camera_windows
 description: A Flutter plugin for getting information about and controlling the camera on Windows.
 repository: https://github.com/flutter/packages/tree/main/packages/camera/camera_windows
 issue_tracker: https://github.com/flutter/flutter/issues?q=is%3Aissue+is%3Aopen+label%3A%22p%3A+camera%22
-version: 0.2.6+5
+version: 0.2.6+6
 
 environment:
   sdk: ^3.10.0

packages/camera/camera_windows/windows/camera_plugin.cpp

@@ -85,33 +85,48 @@ std::string GetCurrentTimeString() {
   return time_start + std::to_string(ms);
 }
 
-// Builds file path for picture capture.
-std::optional<std::string> GetFilePathForPicture() {
+// Returns the directory to write captures into.
+// Falls back to the temp directory if the known folder can't be used, e.g.
+// it's blocked by Controlled Folder Access.
+std::optional<std::string> GetCaptureDirectory(REFKNOWNFOLDERID folder_id) {
   ComHeapPtr<wchar_t> known_folder_path;
-  HRESULT hr = SHGetKnownFolderPath(FOLDERID_Pictures, KF_FLAG_CREATE, nullptr,
+  // KF_FLAG_CREATE opens the folder with write intent even if it already
+  // exists, so this acts also as write permission check.
+  HRESULT hr = SHGetKnownFolderPath(folder_id, KF_FLAG_CREATE, nullptr,
                                     &known_folder_path);
-  if (FAILED(hr)) {
+  if (SUCCEEDED(hr)) {
+    return Utf8FromUtf16(std::wstring(known_folder_path)) + "\\";
+  }
+
+  wchar_t temp_path[MAX_PATH + 1];
+  // The returned length includes the trailing backslash.
+  DWORD length = GetTempPathW(MAX_PATH + 1, temp_path);
+  if (length == 0 || length > MAX_PATH) {
     return std::nullopt;
   }
 
-  std::string path = Utf8FromUtf16(std::wstring(known_folder_path));
+  return Utf8FromUtf16(std::wstring(temp_path, length));
+}
 
-  return path + "\\" + "PhotoCapture_" + GetCurrentTimeString() + "." +
+// Builds file path for picture capture.
+std::optional<std::string> GetFilePathForPicture() {
+  std::optional<std::string> directory = GetCaptureDirectory(FOLDERID_Pictures);
+  if (!directory) {
+    return std::nullopt;
+  }
+
+  return *directory + "PhotoCapture_" + GetCurrentTimeString() + "." +
          kPictureCaptureExtension;
 }
 
 // Builds file path for video capture.
 std::optional<std::string> GetFilePathForVideo() {
-  ComHeapPtr<wchar_t> known_folder_path;
-  HRESULT hr = SHGetKnownFolderPath(FOLDERID_Videos, KF_FLAG_CREATE, nullptr,
-                                    &known_folder_path);
-  if (FAILED(hr)) {
+  std::optional<std::string> directory = GetCaptureDirectory(FOLDERID_Videos);
+  if (!directory) {
     return std::nullopt;
   }
 
-  std::string path = Utf8FromUtf16(std::wstring(known_folder_path));
-
-  return path + "\\" + "VideoCapture_" + GetCurrentTimeString() + "." +
+  return *directory + "VideoCapture_" + GetCurrentTimeString() + "." +
          kVideoCaptureExtension;
 }
 }  // namespace