ifcviewer-web: let host pages choose the mouse nav preset

ViewportCore has had a preset table (blender / rhino / revit / web) since the
nav bindings were shared with the desktop, and the web input handlers already
classify presses against it — but main() hard-coded "web" and nothing could
reach setNavPreset from JS, so every page was stuck on LMB-orbit.

Export ifcv_set_nav_preset_c and wrap it as IfcViewer.create's `navPreset`
option plus a setNavPreset() method. The preset is only the button/modifier
table, so it needs no GPU state: it applies as soon as the module resolves,
which means the first drag already uses the host's scheme rather than
flipping after a frame or two.

Names are validated in JS against the four the core knows. The core silently
falls back to blender for anything unrecognised, which would turn a typo into
a mystery change of scheme rather than an error.

The default stays "web", so existing pages and the smoke tests are unaffected.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

src/ifcviewer-web/CMakeLists.txt

@@ -108,13 +108,15 @@ target_link_options(IfcViewerWeb PRIVATE
     # sidecar via HTTP Range; _ifcv_on_range_done / _ifcv_source_ready are the
     # JS→C completion callbacks for a landed range / a resolved URL size.
     # The _ifcv_{get,set,apply}_* family is the scripting API (camera, selection,
-    # visibility, colour override, object enumeration) that web/ifcviewer.js
-    # wraps; _malloc/_free let it marshal id arrays into the wasm heap.
+    # visibility, colour override, object enumeration, mouse nav preset) that
+    # web/ifcviewer.js wraps; _malloc/_free let it marshal id arrays into the
+    # wasm heap.
     # EMSCRIPTEN_KEEPALIVE alone keeps the symbols in the binary but doesn't
     # add them to Module. ccall lets the host page (web/ifcviewer.js) pass a JS string (the ?model
     # URL) to load_sidecar_from_url_c without manual heap marshalling.
-    "-sEXPORTED_FUNCTIONS=['_main','_malloc','_free','_raf_tick_c','_load_sidecar_from_source_c','_clear_scene_c','_ifcv_on_range_done','_ifcv_chunks_resident_c','_ifcv_chunks_total_c','_ifcv_model_count_c','_ifcv_model_resident_c','_ifcv_model_total_c','_ifcv_bytes_total_c','_ifcv_bytes_needed_c','_ifcv_bytes_loaded_c','_view_all_c','_frame_selection_c','_toggle_projection_c','_projection_is_ortho_c','_standard_view_c','_toggle_fly_c','_fly_is_active_c','_hide_selected_c','_isolate_selected_c','_show_all_c','_hide_all_c','_toggle_xray_c','_xray_is_active_c','_toggle_section_c','_clear_section_c','_section_is_active_c','_ifcv_get_camera_c','_ifcv_set_camera_c','_ifcv_set_ortho_c','_ifcv_get_selection_c','_ifcv_get_active_object_c','_ifcv_apply_selection_c','_ifcv_set_visible_c','_ifcv_get_hidden_c','_ifcv_set_color_c','_ifcv_clear_colors_c','_ifcv_request_objects_c']"
-    # ccall: the host page (web/ifcviewer.js) passes the ?model URL string to load_sidecar_from_url_c.
+    "-sEXPORTED_FUNCTIONS=['_main','_malloc','_free','_raf_tick_c','_load_sidecar_from_source_c','_clear_scene_c','_ifcv_on_range_done','_ifcv_chunks_resident_c','_ifcv_chunks_total_c','_ifcv_model_count_c','_ifcv_model_resident_c','_ifcv_model_total_c','_ifcv_bytes_total_c','_ifcv_bytes_needed_c','_ifcv_bytes_loaded_c','_view_all_c','_frame_selection_c','_toggle_projection_c','_projection_is_ortho_c','_standard_view_c','_toggle_fly_c','_fly_is_active_c','_hide_selected_c','_isolate_selected_c','_show_all_c','_hide_all_c','_toggle_xray_c','_xray_is_active_c','_toggle_section_c','_clear_section_c','_section_is_active_c','_ifcv_get_camera_c','_ifcv_set_camera_c','_ifcv_set_ortho_c','_ifcv_set_nav_preset_c','_ifcv_get_selection_c','_ifcv_get_active_object_c','_ifcv_apply_selection_c','_ifcv_set_visible_c','_ifcv_get_hidden_c','_ifcv_set_color_c','_ifcv_clear_colors_c','_ifcv_request_objects_c']"
+    # ccall: the host page (web/ifcviewer.js) passes the ?model URL string to load_sidecar_from_url_c,
+    # and the nav-preset name to ifcv_set_nav_preset_c.
     # HEAPU8: lets tooling/tests read the wasm heap size (e.g. to verify a large
     # sidecar streams by range instead of loading whole). HEAPU32/HEAPF32: the
     # scripting API marshals object-id arrays and the camera state through them.

src/ifcviewer-web/main_web.cpp

@@ -627,6 +627,17 @@ extern "C" EMSCRIPTEN_KEEPALIVE void ifcv_set_ortho_c(int on) {
     if (bool(on) != g_app->core.projectionOrtho()) g_app->core.toggleProjection();
 }
 
+// Mouse navigation scheme: "blender" | "rhino" | "revit" | "web". The preset
+// only rewrites the button/modifier table classifyPress reads, so unlike the
+// rest of the scripting API it does not need the GPU app to be live — a host
+// page can pick its scheme the moment the module resolves. Unknown names fall
+// back to blender inside the core; web/ifcviewer.js rejects them before they
+// get here so a typo is an error rather than a silent scheme change.
+extern "C" EMSCRIPTEN_KEEPALIVE void ifcv_set_nav_preset_c(const char* name) {
+    if (!g_app || !name) return;
+    g_app->core.setNavPreset(name);
+}
+
 // Selection.
 extern "C" EMSCRIPTEN_KEEPALIVE int ifcv_get_selection_c(std::uint32_t* out, int max) {
     if (!g_app || !g_app->ready) return 0;
@@ -778,6 +789,8 @@ int main(int /*argc*/, char** /*argv*/) {
     Log::info() << "ifcviewer-web: starting";
     g_app = new AppState();
     // Default to the web mouse scheme: LMB orbit, MMB pan, RMB select/marquee.
+    // Host pages override it with ifcv_set_nav_preset_c (IfcViewer.create's
+    // `navPreset` option) — e.g. "blender" for MMB-orbit.
     g_app->core.setNavPreset("web");
     g_app->core.initWgpuAsyncWeb([](bool ok) {
         if (!ok) {

src/ifcviewer-web/web/ifcviewer.js

@@ -5,7 +5,8 @@
 //   <script src="IfcViewerWeb.js"></script>
 //   <script src="ifcviewer.js"></script>
 //   <script>
-//     const viewer = await IfcViewer.create({ canvas: myCanvas });
+//     const viewer = await IfcViewer.create({ canvas: myCanvas,
+//                                             navPreset: 'blender' });
 //     await viewer.ready;                       // GPU app is live
 //     await viewer.addFile(file, { replace: true });
 //     await viewer.addUrl('/model.ifcview');    // appends (federation)
@@ -14,6 +15,7 @@
 //     viewer.setSelection(['3vB2YO$MX4xv5uCqZZG05x']);
 //     viewer.setColor(objects.filter(o => o.type === 'IfcWall'), '#ff8800');
 //     viewer.setCamera({ yaw: 45, pitch: 30 });
+//     viewer.setNavPreset('rhino');             // or switch schemes later
 //   </script>
 //
 // The canvas element MUST have id="viewer-canvas" — the wasm side hard-codes
@@ -41,6 +43,10 @@
     return cr ? parseInt(cr.split('/')[1] || '0', 10) : 0;
   }
 
+  // Mouse navigation schemes the wasm's classifyPress understands. Named so a
+  // typo is an error here rather than a silent fall-back to blender in the core.
+  const NAV_PRESETS = ['blender', 'rhino', 'revit', 'web'];
+
   // Pack a colour into the u32 the shader unpacks: 0xAABBGGRR. Accepts
   // '#rgb' / '#rrggbb' / '#rrggbbaa', or {r, g, b, a} with 0-255 channels
   // (alpha defaulting to opaque). An alpha of 0 is the "no override" sentinel
@@ -314,6 +320,23 @@
         if (c.ortho !== undefined) Module._ifcv_set_ortho_c(c.ortho ? 1 : 0);
       },
 
+      // ---- Navigation ------------------------------------------------------
+
+      // Which mouse buttons orbit / pan / select, as one of NAV_PRESETS:
+      //   blender  MMB orbit · Shift+MMB pan · LMB select
+      //   rhino    RMB orbit · Shift+RMB pan · LMB select
+      //   revit    Shift+MMB orbit · MMB pan · LMB select
+      //   web      LMB orbit · MMB pan · RMB select   (the default)
+      // The wheel zooms under all four. Also settable up-front as the
+      // `navPreset` option to create().
+      setNavPreset: function (name) {
+        if (NAV_PRESETS.indexOf(name) < 0) {
+          throw new Error('unknown nav preset: ' + name +
+                          ' (expected one of ' + NAV_PRESETS.join(', ') + ')');
+        }
+        Module.ccall('ifcv_set_nav_preset_c', null, ['string'], [name]);
+      },
+
       // id: 0 Front, 1 Back, 2 Left, 3 Right, 4 Top, 5 Bottom.
       setStandardView: function (id) { Module._standard_view_c(id | 0); },
       viewAll:        function () { Module._view_all_c(); },
@@ -447,6 +470,13 @@
         Module._load_sidecar_from_source_c(await registerUrl(url));
       },
     };
+
+    // The nav preset is pure button-table state on the wasm side, so it can be
+    // set the moment main() has run (which is by the time `factory` resolved) —
+    // no need to wait on `ready`. Doing it here means the very first drag uses
+    // the host's scheme rather than the "web" default for a frame or two.
+    if (opts.navPreset) api.setNavPreset(opts.navPreset);
+
     return api;
   }