Docs: add how LMFP behaves during QGIS startup

docs/conf.py

@@ -32,6 +32,7 @@
     # 3rd party
     "myst_parser",
     "sphinx_copybutton",
+    "sphinxcontrib.mermaid",
 ]
 
 
@@ -48,7 +49,7 @@
 #
 # This is also used if you do content translation via gettext catalogs.
 # Usually you set "language" from the command line for these cases.
-language = None
+# language = None
 
 # List of patterns, relative to source directory, that match files and
 # directories to ignore when looking for source files.
@@ -82,6 +83,17 @@
     "qgis": ("https://qgis.org/pyqgis/master/", None),
 }
 
+# mermaid
+mermaid_d3_zoom = True
+mermaid_params = [
+    "--theme",
+    "forest",
+    "--backgroundColor",
+    "transparent",
+]
+# TODO: remove next line when the mermaid version shipped with sphinxcontrib-mermaid is 11.4+
+mermaid_version = "11.4.1"
+
 # MyST Parser
 myst_enable_extensions = [
     "amsmath",

docs/how_does_it_works.md

@@ -0,0 +1,24 @@
+# How does it work?
+
+```{mermaid}
+---
+title: "How Layers Menu From Project behaves during QGIS launch"
+---
+flowchart TD
+    A@{ shape: circle, label: "QGIS starts" } -->|splash screen displayed| B(load GUI and plugins)
+
+    subgraph "QGIS UI main thread"
+    B -->|GUI is initialized| C@{ shape: curv-trap, label: "QGIS main UI displayed" }
+    C ==> Q((("QGIS is mainly usable")))
+    end
+
+    subgraph "LMFP thread (QgsTask)"
+    C -.->|threaded LMFP| D[[read projects configuration]]
+    D -.-> E[[check project's cache]]
+    E -.->|cache still valid| F(create menus from caches JSON files)
+    F == menus appear in the main UI ==> Q
+    E -.->|cache has expired or is invalid| G(download/copy remote files)
+    G -.->|store cache|H("{path_to_qgis_profile}/cache/menu_from_project")
+    H --> F
+    end
+```

docs/index.md

@@ -25,6 +25,7 @@ caption: Usage
 ---
 usage/en_use
 usage/fr_use
+how_does_it_works
 ```
 
 ```{toctree}
@@ -33,7 +34,7 @@ maxdepth: 1
 caption: Contributing
 ---
 development/contribute
-development/environment
+development/setup
 development/documentation
 development/translation
 development/packaging

requirements/documentation.txt

@@ -5,3 +5,4 @@ furo>=2024
 myst-parser[linkify]>=2
 sphinx-autobuild>=2024
 sphinx-copybutton>=0.5
+sphinxcontrib-mermaid>=1,<2