Extract dialog, VR, and canvas draw helpers

docs/modernization/roadmap.md

@@ -83,12 +83,12 @@ Current hotspot files:
 - `src/app_layout.cpp`: 1249 lines
 - `src/canvas_modes.cpp`: 1798 lines
 - `src/node.cpp`: 1551 lines
-- `src/main.cpp`: 1218 lines
+- `src/main.cpp`: 1117 lines
 - `src/node_panel_brush.cpp`: 1197 lines
 - `src/node_stroke_preview.cpp`: 933 lines
-- `src/node_canvas.cpp`: 968 lines
+- `src/node_canvas.cpp`: 953 lines
 - `src/app.cpp`: 950 lines
-- `src/app_dialogs.cpp`: 908 lines
+- `src/app_dialogs.cpp`: 789 lines
 
 Current architecture mismatches that must be treated as real blockers:
 
@@ -124,8 +124,11 @@ Current architecture mismatches that must be treated as real blockers:
   per-layer render-path orchestration now also route through retained
   draw-merge helpers even though the broader node draw loop is still inline,
   with the non-`draw_merged` outer layer/plane traversal now also routing
-  through `execute_legacy_canvas_draw_layer_traversal(...)` while the heavier
-  per-layer GL setup and draw lambdas still live in `src/node_canvas.cpp`.
+  through `execute_legacy_canvas_draw_layer_traversal(...)`, while the heavier
+  per-layer GL setup now also routes through
+  `make_legacy_canvas_draw_merge_layer_path_gl_execution(...)` even though the
+  remaining draw lambdas and broader node draw loop still live in
+  `src/node_canvas.cpp`.
 - `app_layout.cpp` and `app_dialogs.cpp` are still mixed shell/controller files
   rather than thin composition/binding surfaces, even though tools-menu binding
   plus nested panels/options submenu wiring now live in
@@ -134,7 +137,9 @@ Current architecture mismatches that must be treated as real blockers:
   live in `src/app_layout_file_menu.cpp` and `App::init_menu_file()` is now a
   thin call-through, while about-menu and layer-menu wiring now also live in
   `src/app_layout_about_layer_menu.cpp` and `App::init_menu_about()` plus
-  `App::init_menu_layer()` are now thin call-throughs.
+  `App::init_menu_layer()` are now thin call-throughs, while the informational
+  overlay opener family now also lives in `src/app_dialogs_info_openers.cpp`
+  and the corresponding `App::dialog_*` entrypoints are thinner.
 - `App`, `Canvas`, `Node`, retained workers, and platform entrypoints still use
   global singleton reach, raw observer pointers, retained static worker
   ownership in several app families, and ad hoc mutex/condition-variable
@@ -161,6 +166,9 @@ Current architecture mismatches that must be treated as real blockers:
   `src/main.cpp`, while Win32 pointer API loading, stylus/ink timer decay,
   Wintab packet reset, and `WM_POINTERUPDATE` pen/touch handling now also live
   in `src/platform_windows/windows_stylus_input.cpp` instead of `src/main.cpp`,
+  while the retained Win32 VR/HMD shell now also routes through
+  `src/platform_windows/windows_vr_shell.h` instead of staying inline in
+  `src/main.cpp`,
   while `App::rec_loop()` now delegates worker-iteration orchestration into
   the retained recording bridge, `App::update_rec_frames()` now delegates
   recording label refresh through that same retained recording path, and the