Update to allow running TeX/matplotlib Docker env on arm64

.Dockerfile

@@ -13,9 +13,37 @@ COPY README.md /tmp/README.md
 COPY LICENSE /tmp/LICENSE
 COPY CITATION.cff /tmp/CITATION.cff
 
-RUN mamba env create \
-    -n openflash.openflash-on-branch-tex \
-    -f /tmp/analysis/environment-branch.yml
+# Build the Conda environment in three phases to work around the absence of
+# libquadmath on aarch64: no native libquadmath package exists for arm64, yet
+# gfortran still emits -lquadmath, which breaks capytaine's from-source build
+# (capytaine ships no arm64 wheel).
+#
+# 1. Create the environment with the Conda packages only (strip the pip
+#    section), which installs the compiler toolchain.
+RUN sed '/^[[:space:]]*- pip:/,$d' /tmp/analysis/environment-branch.yml \
+      > /tmp/analysis/environment-nopip.yml \
+ && mamba env create \
+      -n openflash.openflash-on-branch-tex \
+      -f /tmp/analysis/environment-nopip.yml
+
+# 2. If libquadmath is missing (i.e. on aarch64), drop an empty stub into the
+#    env so the linker is satisfied. capytaine references no quadmath symbols,
+#    and Conda links extensions with an rpath to $CONDA_PREFIX/lib, so the stub
+#    resolves at both link and run time.
+RUN mamba run -n openflash.openflash-on-branch-tex bash -c '\
+  if [ ! -e "$CONDA_PREFIX/lib/libquadmath.so" ]; then \
+    echo "void __quadmath_stub(void){}" > /tmp/quadmath_stub.c \
+    && "$CC" -shared -fPIC -Wl,-soname,libquadmath.so.0 \
+         -o "$CONDA_PREFIX/lib/libquadmath.so.0" /tmp/quadmath_stub.c \
+    && ln -sf libquadmath.so.0 "$CONDA_PREFIX/lib/libquadmath.so" \
+    && rm /tmp/quadmath_stub.c; \
+  fi'
+
+# 3. Install the pip packages; capytaine compiles its Fortran extension against
+#    the stub.
+RUN mamba env update \
+      -n openflash.openflash-on-branch-tex \
+      -f /tmp/analysis/environment-branch.yml
 
 ENV PATH=/opt/conda/envs/openflash.openflash-on-branch-tex/bin:$PATH
 
@@ -48,4 +76,4 @@ ENV XDG_CONFIG_HOME=/tmp/home/.config
 ENV MPLCONFIGDIR=/tmp/matplotlib
 ENV JUPYTER_DATA_DIR=/tmp/jupyter
 
-CMD ["bash"]
+CMD ["bash"]

analysis/environment-branch.yml

@@ -15,6 +15,12 @@ dependencies:
   - streamlit
   - ipykernel
   - seaborn
+  # Compiler toolchain so pip can build capytaine's Fortran extension from
+  # source (no prebuilt arm64 wheel exists). Sets CC/FC during env activation.
+  # Note: on aarch64 these don't provide libquadmath, which gfortran still
+  # links against; .Dockerfile supplies an empty stub to satisfy the linker.
+  - c-compiler
+  - fortran-compiler
   - pip:
       - capytaine
       - -e ..