Find ImageStreamIO in /usr/local/lib/cmake without ImageStreamIO_DIR

README.md

@@ -50,10 +50,10 @@ If you encounter any problems or have questions about this project, please open
 
    `-DINTERFACE_TYPE=` is separate from `-DCONTROLLER=` and selects only which emulator is built. It defaults to `Archon`; `-DINTERFACE_TYPE=AstroCam` skips the emulator, since none is implemented for ARC.
 
-   To enable the shared-memory output (`SHM_ENABLED` in a `.cfg` file, see [Frame Outputs](#frame-outputs) below), add `-DENABLE_SHM_OUTPUT=ON -DImageStreamIO_DIR=<prefix>/lib/cmake`:
+   To enable the shared-memory output (`SHM_ENABLED` in a `.cfg` file, see [Frame Outputs](#frame-outputs) below), add `-DENABLE_SHM_OUTPUT=ON`:
 
     ```bash
-    $ cmake -DENABLE_SHM_OUTPUT=ON -DImageStreamIO_DIR=/usr/local/lib/cmake ..
+    $ cmake -DENABLE_SHM_OUTPUT=ON ..
     ```
 
    This requires [ImageStreamIO](https://github.com/milk-org/ImageStreamIO) to already be built and installed, since it isn't packaged for common distros:
@@ -66,7 +66,7 @@ If you encounter any problems or have questions about this project, please open
     $ sudo make install
     ```
 
-   ImageStreamIO's own `Config.cmake` files install directly under `<prefix>/lib/cmake/` rather than the CMake-conventional `<prefix>/lib/cmake/ImageStreamIO/`, so `-DImageStreamIO_DIR=...` must always be given explicitly, even for a standard system-wide install.
+   ImageStreamIO's own `Config.cmake` files install directly under `<prefix>/lib/cmake/` rather than the CMake-conventional `<prefix>/lib/cmake/ImageStreamIO/`. The build looks in `/usr/local/lib/cmake` for them; for any other prefix pass `-DImageStreamIO_DIR=<prefix>/lib/cmake`.
 
    To build the Python module (see [Python Module](#python-module) below), add `-DBUILD_PYTHON_MODULE=ON`. It is off by default, so builds that don't want it never need pybind11. To install it into an environment rather than build it here, see [Installing with pip](#installing-with-pip) instead, which fetches pybind11 itself:
 

docs/configuration/index.md

@@ -48,7 +48,7 @@ These are CMake options, fixed when the software is compiled, not `.cfg` keys.
 |---|---|---|
 | `CONTROLLER` | none, required | `archon` or `astrocam`. CMake errors out if unset. |
 | `INTERFACE_TYPE` | `Archon` | Selects which emulator is built, independently of `CONTROLLER`. `AstroCam` builds none, since none exists for ARC. |
-| `ENABLE_SHM_OUTPUT` | `OFF` | Build the ImageStreamIO shared-memory output. Also needs `-DImageStreamIO_DIR=<prefix>/lib/cmake`. |
+| `ENABLE_SHM_OUTPUT` | `OFF` | Build the ImageStreamIO shared-memory output. Found in `/usr/local/lib/cmake`; pass `-DImageStreamIO_DIR=<prefix>/lib/cmake` for another prefix. |
 | `BUILD_PYTHON_MODULE` | `OFF` | Build the `camera_interface` Python module. Needs pybind11 at compile time only. |
 | `CMAKE_INSTALL_PREFIX` | `/usr/local` | Where `make install` puts binaries and the module |
 

utils/CMakeLists.txt

@@ -24,7 +24,9 @@ add_library(network STATIC
 target_link_libraries(network nlohmann_json::nlohmann_json)
 
 if(ENABLE_SHM_OUTPUT)
-  find_package(ImageStreamIO CONFIG REQUIRED)
+  # Upstream installs its config straight into lib/cmake, which CMake does not
+  # search on its own
+  find_package(ImageStreamIO CONFIG REQUIRED PATHS /usr/local/lib/cmake)
 
   add_library(shared_memory_writer STATIC
           ${PROJECT_UTILS_DIR}/shared_memory_writer.cpp