Add remote stream selection command

BUILD.md

@@ -2,6 +2,25 @@
 
 This file includes quick start recipes. To see general principles, look [here](https://github.com/labstreaminglayer/labstreaminglayer/blob/master/doc/BUILD.md).
 
+## Stream selection regression check
+
+With a GUI build configured, build and run the standalone selection check:
+
+```sh
+cmake --build build --target teststreamselection --config Release
+./build/teststreamselection
+```
+
+For a Visual Studio build, run `build\Release\teststreamselection.exe` instead.
+This target uses the application's Qt and liblsl dependencies and is built only
+when requested. It runs the actual GUI selection code offscreen with temporary
+configuration files and synthetic outlets in a private LSL session. Local stream
+discovery must be available. A failed check returns a nonzero exit code.
+
+The checks cover stream identities after query selection and refresh, missing
+stream deselection and watchlist input, and disappearance/reappearance without
+switching source identities. They do not start a recording or validate XDF contents.
+
 
 ## Windows - CMake - Visual Studio 2017
 

CMakeLists.txt

@@ -198,6 +198,20 @@ if(LABRECORDER_BUILD_GUI)
         LSL::lsl
     )
 
+    # Build explicitly with --target teststreamselection; uses the actual GUI code.
+    add_executable(teststreamselection EXCLUDE_FROM_ALL
+        src/test_stream_selection.cpp
+        src/mainwindow.cpp
+        src/mainwindow.h
+        src/mainwindow.ui
+        src/recording.cpp
+        src/tcpinterface.cpp
+        src/tcpinterface.h
+    )
+    target_link_libraries(teststreamselection PRIVATE
+        xdfwriter Qt6::Core Qt6::Widgets Qt6::Network Threads::Threads LSL::lsl
+    )
+
     # macOS bundle configuration
     if(APPLE)
         set(MACOSX_BUNDLE_GUI_IDENTIFIER "com.labstreaminglayer.${PROJECT_NAME}")

README.md

@@ -87,11 +87,20 @@ If you check the box to EnableRCS then LabRecorder exposes some rudimentary cont
 Currently supported commands include:
 * `select all`
 * `select none`
-* `start`
+* `select <query>` - checks streams matching an LSL resolver predicate such as `name='BioSemi'`, `type='EEG'`, or `name='BioSemi' and hostname='LabPC1'`.
+* `start` - starts recording the current stream selection; returns an error if no streams are selected.
 * `stop`
 * `update`
 * `filename ...`
 
+Commands respond with `OK`, `WARNING ...`, or `ERROR ...`.
+
+Query selection is additive: use `select none` before `select <query>` to select
+only its matches. For a stream with a nonempty source ID, that identity is retained
+during a session if it disappears, so a different source with the same display name
+is not selected or recorded in its place. Unchecked missing streams are not watched
+for recording.
+
 `filename` is followed by a series of space-delimited options enclosed in curly braces. e.g. {root:C:\root_data_dir}
 * `root` - Sets the root data directory.
 * `template` - sets the File Name / Template. Will unselect BIDS option. May contain wildcards.