fix: selection bugs — arrow tool click select, box-select on empty drag, preserve selection on tool switch

frontend/src/canvas/SelectionEngine.ts

@@ -294,4 +294,13 @@ export class SelectionEngine {
   isBoxSelecting(): boolean {
     return this.boxStart !== null;
   }
+
+  /**
+   * Returns true when the box selection drag actually moved away from the start point.
+   * Used to distinguish a click (no drag) from a drag-based box selection.
+   */
+  hasBoxMoved(): boolean {
+    if (!this.boxStart || !this.boxEnd) return false;
+    return this.boxStart.x !== this.boxEnd.x || this.boxStart.y !== this.boxEnd.y;
+  }
 }

frontend/src/interaction/index.ts

@@ -131,7 +131,8 @@ export class InteractionEngine {
     this.state.phase = 'idle';
     this.state.points = [];
     this.state.previewElement = null;
-    if (tool !== 'select' && tool !== 'pan') {
+    const drawingTools: ToolType[] = ['line', 'rect', 'circle', 'arc', 'polyline', 'polygon', 'revcloud', 'text', 'dimension', 'leader', 'chair', 'seating-row', 'seating-block', 'table', 'stage', 'seating-template', 'hatch'];
+    if (drawingTools.includes(tool)) {
       this.selectionEngine.clearSelection();
       this.emitSelectionChange();
     }
@@ -368,8 +369,13 @@ export class InteractionEngine {
     }
 
     if (this.state.activeTool === 'select' && this.selectionEngine.isBoxSelecting()) {
+      if (this.selectionEngine.hasBoxMoved()) {
         this.selectionEngine.finishBoxSelect(this.allElements);
         this.emitSelectionChange();
+      } else {
+        // No drag movement — cancel box select (it was just a click, already handled by clickSelect)
+        this.selectionEngine.cancelBoxSelect();
+      }
       this.requestRender();
       return;
     }
@@ -510,8 +516,24 @@ export class InteractionEngine {
     this.selectionEngine.setOptions({ additive, subtractive });
 
     if (!additive && !subtractive) {
-      // Start potential box select
+      // Hit test first: if an object is clicked, select it directly
+      const hit = this.renderEngine.hitTest(world.x, world.y, 5);
+      if (hit) {
+        // Group-aware click selection: if clicked element is in a group, select all group members
+        if (this.groupManager) {
+          const groupElements = this.groupManager.getGroupElements(hit.id);
+          if (groupElements.length > 1) {
+            this.selectionEngine.selectByIds(groupElements, false);
+            this.emitSelectionChange();
+            return;
+          }
+        }
+        this.selectionEngine.clickSelect(world.x, world.y, this.allElements);
+        this.emitSelectionChange();
+      } else {
+        // No object hit: start potential box select for drag
         this.selectionEngine.startBoxSelect(world.x, world.y);
+      }
     } else {
       // Group-aware click selection: if clicked element is in a group, select all group members
       const hit = this.renderEngine.hitTest(world.x, world.y, 5);

frontend/tests/SelectionEngine.test.ts

@@ -272,6 +272,21 @@ describe('SelectionEngine', () => {
       s.selectionEngine.cancelBoxSelect();
       expect(s.selectionEngine.isBoxSelecting()).toBe(false);
     });
+
+    it('hasBoxMoved should return false when box not started', () => {
+      expect(s.selectionEngine.hasBoxMoved()).toBe(false);
+    });
+
+    it('hasBoxMoved should return false when start equals end (no drag)', () => {
+      s.selectionEngine.startBoxSelect(50, 50);
+      expect(s.selectionEngine.hasBoxMoved()).toBe(false);
+    });
+
+    it('hasBoxMoved should return true when box end differs from start', () => {
+      s.selectionEngine.startBoxSelect(50, 50);
+      s.selectionEngine.updateBoxSelect(100, 100, []);
+      expect(s.selectionEngine.hasBoxMoved()).toBe(true);
+    });
   });
 
   describe('clearSelection', () => {