Client: diagrams in local folders (setting)

Co-Authored-By: Claude Opus 5.5 <[email protected]>

Client/Diagrams.py

@@ -1,7 +1,8 @@
 """Mermaid diagrams (```mermaid blocks), like the web view's. Flet can't draw
 them, so the server does (POST /api/diagram, Backend/Diagrams.py) and they're
-shown as pictures in this client's theme. In a local folder (no server), or
-if the server can't draw them, they stay code blocks.
+shown as pictures in this client's theme. In a local folder, LocalDiagrams.py
+draws them on this computer instead (Settings > General, on by default). If
+neither can, they stay code blocks.
 
 A DiagramBlock shows its code straight away and swaps in the picture once it
 arrives (fetched on a background thread), so opening a note never waits on
@@ -14,6 +15,7 @@ from typing import Callable, Optional
 
 import flet as ft
 
+import LocalDiagrams
 from Core import CodeStyleSheet, MarkdownCodeTheme, MarkdownSheet, Palette
 from Sources import SourceError
 
@@ -51,8 +53,14 @@ def ThemePalette() -> dict[str, str]:
     }
 
 
+def IsLocal(TheApp) -> bool:
+    return TheApp.Source.Kind != "Server"
+
+
 def CanDraw(TheApp) -> bool:
-    return TheApp.Source.Kind == "Server" and not ServerCantDraw
+    if IsLocal(TheApp):
+        return TheApp.Config.LocalDiagrams
+    return not ServerCantDraw
 
 
 class DiagramBlock(ft.Container):
@@ -83,14 +91,21 @@ class DiagramBlock(ft.Container):
                           alignment=ft.MainAxisAlignment.CENTER, scroll=ft.ScrollMode.AUTO)
         Problem = Problems.get(self.Key)
         if Problem is not None:
-            return ft.Column([self._Code(), ft.Text(f"Diagram error: {Problem}", color=Palette.Red,
-                                                    size=self.FontSize - 2, selectable=True)], spacing=4)
+            return self._WithNote(f"Diagram error: {Problem}", Palette.Red)
+        if self.Fetching and IsLocal(self.TheApp) and not LocalDiagrams.IsSetUp():
+            return self._WithNote("Setting up diagrams (first time only, can take a few minutes)…", Palette.Overlay0)
         return self._Code()
 
+    def _WithNote(self, Note: str, Colour: str) -> ft.Control:
+        return ft.Column([self._Code(), ft.Text(Note, color=Colour, size=self.FontSize - 2, selectable=True)], spacing=4)
+
     def did_mount(self) -> None:
         self.Mounted = True
         if self.Key not in Pictures and self.Key not in Problems and not self.Fetching and CanDraw(self.TheApp):
             self.Fetching = True
+            if IsLocal(self.TheApp) and not LocalDiagrams.IsSetUp():
+                self.content = self._Content()
+                self.update()
             self.page.run_thread(self._Fetch)
 
     def will_unmount(self) -> None:
@@ -99,14 +114,25 @@ class DiagramBlock(ft.Container):
     def _Fetch(self) -> None:
         global ServerCantDraw
         try:
-            Pictures[self.Key] = self.TheApp.Source.Diagram(self.Source, ThemePalette(), self.FontSize)
+            if IsLocal(self.TheApp):
+                Pictures[self.Key] = LocalDiagrams.Render(self.Source, ThemePalette(), self.FontSize)
+            else:
+                Pictures[self.Key] = self.TheApp.Source.Diagram(self.Source, ThemePalette(), self.FontSize)
+        except LocalDiagrams.DiagramError as Error:
+            Problems[self.Key] = str(Error)
         except SourceError as Error:
             if Error.Status == 422:
                 Problems[self.Key] = str(Error)
             elif Error.Status in (404, 503):
                 ServerCantDraw = True  # an older server, or one without Chromium: stay code blocks
+        except Exception as Error:
+            # Can't draw on this computer (setup failed, or it timed out): say why.
+            Problems[self.Key] = f"Can't draw diagrams here: {Error or type(Error).__name__}"
         finally:
-            self.Fetching = False
+            self._Finish()
+
+    def _Finish(self) -> None:
+        self.Fetching = False
         if self.Mounted:
             self.content = self._Content()
             self.update()