Cache figures between CI builds

Author: llimeht

.github/workflows/test.yml

@@ -58,6 +58,26 @@ jobs:
 
     ### Build sasmodels
 
+
+    - name: Record figure building tools
+      if: env.BUILD_WHEEL
+      id: build-tools
+      run: |
+        echo "details=$(
+          python -m pip index versions matplotlib --json | python -c "import json; print(json.loads(input())['latest'])"
+        )" >> $GITHUB_OUTPUT
+        SASMODELS_BUILD_CACHE=~/.cache/sasmodels-figures
+        mkdir -p $SASMODELS_BUILD_CACHE
+        echo "SASMODELS_BUILD_CACHE=$SASMODELS_BUILD_CACHE" >> $GITHUB_ENV
+
+    - name: Cache figures in documentation
+      if: env.BUILD_WHEEL
+      id: cache-figures
+      uses: actions/cache@v4
+      with:
+        path: ${{ env.SASMODELS_BUILD_CACHE }}
+        key: ${{ steps.build-tools.outputs.details }}-${{ hashFiles('doc/genmodel.py') }}
+
     - name: Build sasmodels
       if: env.BUILD_WHEEL
       run: |