From 458015aa90509e4515202c5f15ac76d900b52ef2 Mon Sep 17 00:00:00 2001
From: Mike Langmayr <michael.langmayr@gmail.com>
Date: Tue, 3 Nov 2026 14:19:49 -0800
Subject: [PATCH] Find ImageStreamIO in /usr/local/lib/cmake without
 ImageStreamIO_DIR

---
 .github/workflows/emulator-integration.yml | 2 +-
 README.md                                  | 6 +++---
 docs/configuration/index.md                | 2 +-
 utils/CMakeLists.txt                       | 3 ++-
 4 files changed, 7 insertions(+), 6 deletions(-)

diff --git a/.github/workflows/emulator-integration.yml b/.github/workflows/emulator-integration.yml
index a82c142..a5582a0 100644
--- a/.github/workflows/emulator-integration.yml
+++ b/.github/workflows/emulator-integration.yml
@@ -49,7 +49,7 @@ jobs:
         mkdir -p ${{github.workspace}}/build
         cd ${{github.workspace}}/build
         cmake -DCONTROLLER=archon \
-              -DENABLE_SHM_OUTPUT=ON -DImageStreamIO_DIR=/usr/local/lib/cmake \
+              -DENABLE_SHM_OUTPUT=ON \
               -DBUILD_PYTHON_MODULE=ON ..
         make -j$(nproc)
 
diff --git a/README.md b/README.md
index 7a3fdca..c6cf3e1 100644
--- a/README.md
+++ b/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 `Config.cmake` files install directly under `<prefix>/lib/cmake/` rather than the conventional `<prefix>/lib/cmake/ImageStreamIO/`. The build looks in `/usr/local/lib/cmake`, where the steps above put 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:
 
diff --git a/docs/configuration/index.md b/docs/configuration/index.md
index d0e2e5b..4b4f73f 100644
--- a/docs/configuration/index.md
+++ b/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`; `-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 |
 
diff --git a/utils/CMakeLists.txt b/utils/CMakeLists.txt
index fe1ba83..4d74da7 100644
--- a/utils/CMakeLists.txt
+++ b/utils/CMakeLists.txt
@@ -24,7 +24,8 @@ 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 directly in <prefix>/lib/cmake, which find_package does not search
+  find_package(ImageStreamIO CONFIG REQUIRED PATHS /usr/local/lib/cmake)
 
   add_library(shared_memory_writer STATIC
           ${PROJECT_UTILS_DIR}/shared_memory_writer.cpp