Block Definition dialog: preview, empty-block band, open in editor

The name card draws the selected objects, or the existing definition the
name picks. OK with no objects shows an in-window band offering to select
objects or to define an empty block. A switch opens the new block in the
block editor once it is defined; it is remembered with the other dialog
choices. Automation gains block_def_dialog.

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

src/app/command_driver/entity_commit.rs

@@ -810,6 +810,14 @@ impl OpenCADStudio {
                 self.refresh_properties();
                 self.note_recent_block(&name);
                 self.refresh_block_palette();
+                // The Block Definition dialog asked to edit the new block.
+                if self
+                    .block_definition_open_editor
+                    .take()
+                    .is_some_and(|wanted| wanted.eq_ignore_ascii_case(&name))
+                {
+                    return Some(self.dispatch_command(&format!("BEDIT_OPEN:{name}")));
+                }
             }
             Err(err) => {
                 self.discard_last_undo_entry(i);

src/app/commands/blocks.rs

@@ -61,7 +61,11 @@ impl OpenCADStudio {
             remembered.objects_on_screen = state.objects_specify_onscreen;
             remembered.mode = state.object_mode;
             remembered.allow_exploding = state.allow_exploding;
+            remembered.open_in_editor = state.open_in_editor;
         }
+        self.block_definition_open_editor = state
+            .open_in_editor
+            .then(|| state.name.trim().to_string());
         self.persist_settings_if_changed();
         let i = self.active_tab;
         let base_point = state.parse_base_point();
@@ -122,6 +126,32 @@ impl OpenCADStudio {
         )
     }
 
+    /// Draw the selected objects, or else the existing definition the name
+    /// picks, in the Block Definition dialog's name card.
+    pub(in crate::app) fn refresh_block_definition_preview(&mut self) {
+        let scene = &self.tabs[self.active_tab].scene;
+        let Some(state) = self.block_definition.as_mut() else {
+            return;
+        };
+        state.preview = if state.selected_handles.is_empty() {
+            let name = state.name.trim();
+            state
+                .existing_names
+                .iter()
+                .find(|existing| existing.eq_ignore_ascii_case(name))
+                .map(|existing| scene.block_preview_wires(existing))
+                .unwrap_or_default()
+        } else {
+            state.empty_prompt = false;
+            let entities: Vec<_> = state
+                .selected_handles
+                .iter()
+                .filter_map(|handle| scene.document.get_entity(*handle).cloned())
+                .collect();
+            scene.wires_for_entities(&entities)
+        };
+    }
+
     pub(super) fn dispatch_blocks(&mut self, cmd: &str, i: usize) -> Option<Task<Message>> {
         match cmd {
             // ── BASE — drawing insertion base point ───────────────────────
@@ -469,6 +499,7 @@ impl OpenCADStudio {
                     ),
                 );
                 self.active_modal = Some(crate::app::ModalKind::BlockDefinition);
+                self.refresh_block_definition_preview();
             }
 
             cmd if cmd.starts_with("BLOCK_POINT_PICKED ") => {
@@ -504,6 +535,7 @@ impl OpenCADStudio {
                 }
                 self.tabs[i].active_cmd = None;
                 self.active_modal = Some(crate::app::ModalKind::BlockDefinition);
+                self.refresh_block_definition_preview();
             }
 
             cmd if cmd.starts_with("WBLOCK_POINT_PICKED ") => {

src/app/control/actions.rs

@@ -118,6 +118,7 @@ pub(super) const NAMES: &[&str] = &[
     "ribbon_dropdown",
     "keytips",
     "dialog_ok",
+    "block_def_dialog",
     "attdef_dialog",
     "field_dialog",
     "sheet_set",
@@ -1502,6 +1503,26 @@ impl OpenCADStudio {
                 }
                 return Ok(Task::none());
             }
+            // The open Block Definition dialog: `name=…`, `open_in_editor=0|1`,
+            // `base_on_screen=0|1`, `objects_on_screen=0|1`, `create_empty`,
+            // `select_objects`.
+            "block_def_dialog" => {
+                if self.block_definition.is_none() {
+                    return Err(failure("no_dialog", "The Block Definition dialog is not open"));
+                }
+                let value = string(req, "value")?;
+                let (key, v) = value.split_once('=').unwrap_or((value, ""));
+                let on = v == "1";
+                match key {
+                    "name" => Message::BlockDefNameSelect(v.to_string()),
+                    "open_in_editor" => Message::BlockDefOpenInEditor(on),
+                    "base_on_screen" => Message::BlockDefBaseOnScreen(on),
+                    "objects_on_screen" => Message::BlockDefObjectsOnScreen(on),
+                    "create_empty" => Message::BlockDefCreateEmpty,
+                    "select_objects" => Message::BlockDefSelectObjects,
+                    _ => return Err(failure("invalid_value", "Unknown block definition field")),
+                }
+            }
             // One field of the open attribute definition dialog: `tag=…`,
             // `prompt=…`, `default=…`, `justify=MC`, `style=…`, `height=…`,
             // `rotation=…`, `width=…`, `on_screen=0|1`, `x=…` / `y=…` / `z=…`,

src/app/mod.rs

@@ -577,6 +577,9 @@ pub(super) struct OpenCADStudio {
     drawing_units: Option<crate::ui::window::drawing_units::State>,
     /// Working copy of the Block Definition dialog; `None` while it is closed.
     block_definition: Option<crate::ui::window::block_definition::BlockDefinitionState>,
+    /// The block the Block Definition dialog defines with "Open in block
+    /// editor" on; it opens once the definition is committed.
+    block_definition_open_editor: Option<String>,
     block_edit_picker: Option<crate::ui::window::block_edit_picker::State>,
     block_save_as: Option<crate::ui::window::block_save_as::State>,
     /// PDF dialogs' working copies; `None` while closed.
@@ -3441,6 +3444,10 @@ pub enum Message {
     BlockDefConfirmRedefine(bool),
     BlockDefDismissError,
     BlockDefHelp,
+    /// Block Definition: open the new block in the block editor.
+    BlockDefOpenInEditor(bool),
+    /// Block Definition: define the block with no objects.
+    BlockDefCreateEmpty,
     /// Write Block (WBLOCK) dialog messages
     WblockSourceMode(crate::ui::window::wblock::WblockSourceMode),
     WblockBlockName(String),
@@ -4602,6 +4609,7 @@ impl OpenCADStudio {
             layer_translator: None,
             drawing_units: None,
             block_definition: None,
+            block_definition_open_editor: None,
             block_edit_picker: None,
             block_save_as: None,
             pdf_attach: None,

src/app/update/mod.rs

@@ -5686,6 +5686,7 @@ impl OpenCADStudio {
                     state.error_message = None;
                     state.confirm_redefine = None;
                 }
+                self.refresh_block_definition_preview();
                 Task::none()
             }
             Message::BlockDefNameSelect(chosen) => {
@@ -5701,6 +5702,7 @@ impl OpenCADStudio {
                     );
                     state.set_base_point(glam::DVec3::new(base.x, base.y, base.z));
                 }
+                self.refresh_block_definition_preview();
                 Task::none()
             }
             Message::BlockDefBaseOnScreen(val) => {
@@ -5821,6 +5823,12 @@ impl OpenCADStudio {
                 }
                 Task::none()
             }
+            Message::BlockDefOpenInEditor(on) => {
+                if let Some(state) = self.block_definition.as_mut() {
+                    state.open_in_editor = on;
+                }
+                Task::none()
+            }
             Message::BlockDefHelp => {
                 self.command_line.push_info(
                     crate::t!("BLOCK creates a block definition from objects you select.").as_ref(),
@@ -5836,7 +5844,8 @@ impl OpenCADStudio {
                 }
                 self.commit_block_definition(true)
             }
-            Message::BlockDefApply => {
+            m @ (Message::BlockDefApply | Message::BlockDefCreateEmpty) => {
+                let create_empty = matches!(m, Message::BlockDefCreateEmpty);
                 let Some(state) = self.block_definition.as_mut() else {
                     return Task::none();
                 };
@@ -5859,15 +5868,16 @@ impl OpenCADStudio {
                         Some(crate::t!("Block name cannot start with '*'.").into_owned());
                     return Task::none();
                 }
-                if !state.objects_specify_onscreen && state.selected_handles.is_empty() {
-                    state.error_message = Some(
-                        crate::t!(
-                            "No objects selected. You must select objects to define a block."
-                        )
-                        .into_owned(),
-                    );
+                // No objects: the band offers to select some or to define
+                // an empty block.
+                if !state.objects_specify_onscreen
+                    && state.selected_handles.is_empty()
+                    && !create_empty
+                {
+                    state.empty_prompt = true;
                     return Task::none();
                 }
+                state.empty_prompt = false;
                 let i = self.active_tab;
                 if self.tabs[i]
                     .scene
@@ -7394,6 +7404,7 @@ impl OpenCADStudio {
                         .collect();
                     block_def.error_message = None;
                     self.active_modal = Some(super::ModalKind::BlockDefinition);
+                    self.refresh_block_definition_preview();
                 } else if let Some(ref mut wblock) = self.wblock {
                     wblock.selected_handles = self.tabs[i]
                         .scene

src/app/view/modal.rs

@@ -505,7 +505,7 @@ impl OpenCADStudio {
             }
             super::super::ModalKind::BlockDefinition => {
                 let state = self.block_definition.as_ref()?;
-                sized_flow(ex, 580, 390, |flow| {
+                sized_flow(ex, 600, 560, |flow| {
                     crate::ui::window::block_definition::view_window(state, flow)
                 })
             }