Merge 162c076a145194b80f3275b4f85fbe790d0a332b into a867a25d5f09e410d0c73b7fbeab18b4641f484a

packages/ckeditor5-math/src/ui/mainformview.ts

@@ -48,8 +48,7 @@ export default class MainFormView extends View {
 		this.rawLatexInputView = new RawLatexInputView( locale );
 		this.rawLatexInputView.label = t( 'LaTeX' );
 
-		this.saveButtonView = this._createButton( t( 'Save' ), IconCheck, 'ck-button-save' );
-		this.saveButtonView.type = 'submit';
+		this.saveButtonView = this._createButton( t( 'Save' ), IconCheck, 'ck-button-save', 'submit' );
 
 		this.cancelButtonView = this._createButton( t( 'Cancel' ), IconCancel, 'ck-button-cancel' );
 		this.cancelButtonView.delegate( 'execute' ).to( this, 'cancel' );
@@ -150,58 +149,67 @@ export default class MainFormView extends View {
 	}
 
 	/**
-	 * Sets up split handlers for synchronization.
+	 * Checks if a view currently has focus.
+	 */
+	private _isViewFocused(view: View): boolean {
+		const el = view.element;
+		const active = document.activeElement;
+		return !!(el && active && el.contains(active));
+	}
+
+	/**
+	 * Sets up synchronization with Focus Gating.
 	 */
 	private _setupInputSync(previewEnabled: boolean): void {
-		// Handler 1: MathLive -> Raw LaTeX
+		const updatePreview = (eq: string) => {
+			if (previewEnabled && this.mathView && this.mathView.value !== eq) {
+				this.mathView.value = eq;
+			}
+		};
+
+		// Handler 1: MathLive -> Raw LaTeX + Preview
 		this.mathLiveInputView.on('change:value', () => {
 			let eq = (this.mathLiveInputView.value ?? '').trim();
 
-			// Delimiter Normalization
+			// Strip delimiters if present (e.g. pasted content)
 			if (hasDelimiters(eq)) {
 				const params = extractDelimiters(eq);
 				eq = params.equation;
 				this.displayButtonView.isOn = params.display;
 
-				// UX Fix: If we stripped delimiters, update the source
-				// so the visual editor doesn't show them.
-				if ( this.mathLiveInputView.value !== eq ) {
+				// Only strip delimiters if not actively editing
+				if (!this._isViewFocused(this.mathLiveInputView) && this.mathLiveInputView.value !== eq) {
 					this.mathLiveInputView.value = eq;
 				}
 			}
 
-			// Sync to Raw LaTeX
-			if ( this.rawLatexInputView.value !== eq ) {
+			// Sync to Raw LaTeX only if user isn't typing there
+			if (!this._isViewFocused(this.rawLatexInputView) && this.rawLatexInputView.value !== eq) {
 				this.rawLatexInputView.value = eq;
 			}
 
-			// Sync to Preview
-			if ( previewEnabled && this.mathView && this.mathView.value !== eq ) {
-				this.mathView.value = eq;
-			}
+			updatePreview(eq);
 		});
 
-		// Handler 2: Raw LaTeX -> MathLive
+		// Handler 2: Raw LaTeX -> MathLive + Preview
 		this.rawLatexInputView.on('change:value', () => {
 			const eq = (this.rawLatexInputView.value ?? '').trim();
 			const normalized = eq.length ? eq : null;
 
-			// Sync to MathLive
-			if ( this.mathLiveInputView.value !== normalized ) {
+			// Sync to MathLive only if user isn't interacting with it
+			if (!this._isViewFocused(this.mathLiveInputView) && this.mathLiveInputView.value !== normalized) {
 				this.mathLiveInputView.value = normalized;
 			}
 
-			// Sync to Preview
-			if ( previewEnabled && this.mathView && this.mathView.value !== eq ) {
-				this.mathView.value = eq;
-			}
+			updatePreview(eq);
 		});
 	}
 
-	private _createButton( label: string, icon: string, className: string ): ButtonView {
+	private _createButton( label: string, icon: string, className: string, type?: 'submit' | 'button' ): ButtonView {
 		const btn = new ButtonView( this.locale );
 		btn.set( { label, icon, tooltip: true } );
 		btn.extendTemplate( { attributes: { class: className } } );
+		if (type) btn.type = type;
 		return btn;
 	}
 

packages/ckeditor5-math/src/ui/mathliveinputview.ts

@@ -1,42 +1,19 @@
 import { View, type Locale } from 'ckeditor5';
-import 'mathlive'; // Import side-effects only (registers the <math-field> tag)
 
-/**
- * Interface describing the custom <math-field> element.
- */
 interface MathFieldElement extends HTMLElement {
     value: string;
     readOnly: boolean;
     mathVirtualKeyboardPolicy: string;
-    // Interface includes the shortcuts property
-    inlineShortcuts: Record<string, string>;
+    inlineShortcuts?: Record<string, string>;
 }
 
-/**
- * A wrapper for the MathLive <math-field> component.
- */
 export default class MathLiveInputView extends View {
-    /**
-     * The current LaTeX value.
-     * @observable
-     */
     public declare value: string | null;
-
-    /**
-     * Read-only state.
-     * @observable
-     */
     public declare isReadOnly: boolean;
-
-    /**
-     * Reference to the DOM element.
-     * Typed as MathFieldElement | null for proper TS support.
-     */
     public mathfield: MathFieldElement | null = null;
 
     constructor(locale: Locale) {
         super(locale);
-
         this.set('value', null);
         this.set('isReadOnly', false);
 
@@ -50,43 +27,61 @@ export default class MathLiveInputView extends View {
 
     public override render(): void {
         super.render();
+        this._loadMathLive();
+    }
+
+    private async _loadMathLive(): Promise<void> {
+        try {
+            await import('mathlive');
+            await customElements.whenDefined('math-field');
+
+            // Configure global MathLive settings
+            const MathfieldClass = customElements.get( 'math-field' ) as any;
+            if ( MathfieldClass ) {
+                MathfieldClass.soundsDirectory = null;
+                MathfieldClass.plonkSound = null;
+            }
+
+            if (!this.element) return;
+
+            this._createMathField();
+        } catch (error) {
+            console.error('MathLive load failed:', error);
+            if (this.element) {
+                this.element.textContent = 'Math editor unavailable';
+            }
+        }
+    }
+
+    private _createMathField(): void {
+        if (!this.element) return;
 
-        // 1. Create element with the specific type
         const mathfield = document.createElement('math-field') as MathFieldElement;
 
-        // 2. Configure Options
+        // Instance-level config (no prototype pollution)
         mathfield.mathVirtualKeyboardPolicy = 'manual';
 
-        //Disable differential D
+        // Configure shortcuts after mount
         mathfield.addEventListener('mount', () => {
             mathfield.inlineShortcuts = {
-                ...mathfield.inlineShortcuts, // Safe to read now
+                ...mathfield.inlineShortcuts,
                 dx: 'dx',
                 dy: 'dy',
                 dt: 'dt'
             };
-        } );
+        }, { once: true });
 
-
-        // Disable sounds safely
-        const MathfieldConstructor = customElements.get( 'math-field' );
-        if ( MathfieldConstructor ) {
-            const proto = MathfieldConstructor as any;
-            if ( proto.soundsDirectory !== null ) proto.soundsDirectory = null;
-            if ( proto.plonkSound !== null ) proto.plonkSound = null;
-        }
-
-        // 3. Set Initial State
+        // Initial state
         mathfield.value = this.value ?? '';
         mathfield.readOnly = this.isReadOnly;
 
-        // 4. Bind Events (DOM -> Observable)
+        // DOM -> Observable
         mathfield.addEventListener('input', () => {
             const val = mathfield.value;
             this.value = val.length ? val : null;
         });
 
-        // 5. Bind Events (Observable -> DOM)
+        // Observable -> DOM
         this.on('change:value', (_evt, _name, nextValue) => {
             if (mathfield.value !== nextValue) {
                 mathfield.value = nextValue ?? '';
@@ -97,8 +92,7 @@ export default class MathLiveInputView extends View {
             mathfield.readOnly = nextValue;
         });
 
-        // 6. Mount to the wrapper view
-        this.element?.appendChild( mathfield );
+        this.element.appendChild(mathfield);
         this.mathfield = mathfield;
     }
 

packages/ckeditor5-math/src/ui/mathview.ts

@@ -55,12 +55,22 @@ export default class MathView extends View {
 	}
 
 	public updateMath(): void {
-		if ( this.element ) {
+		if (!this.element) {
+			return;
+		}
 
-			// This prevents the new render from appending to the old one.
+		// Handle empty equations
+		if (!this.value || !this.value.trim()) {
 			this.element.textContent = '';
+			this.element.classList.remove('ck-math-render-error');
+			return;
+		}
 
-			void renderEquation(
+		// Clear previous render
+		this.element.textContent = '';
+		this.element.classList.remove('ck-math-render-error');
+
+		renderEquation(
 			this.value,
 			this.element,
 			this.options.engine,
@@ -70,8 +80,14 @@ export default class MathView extends View {
 			this.options.previewUid,
 			this.options.previewClassName,
 			this.options.katexRenderOptions
-			);
+		).catch(error => {
+			console.error('Math rendering failed:', error);
+
+			if (this.element) {
+				this.element.textContent = 'Error rendering equation';
+				this.element.classList.add('ck-math-render-error');
 			}
+		});
 	}
 
 	public override render(): void {

packages/ckeditor5-math/tests/lazyload.ts

@@ -37,6 +37,7 @@ describe( 'Lazy load', () => {
 		await buildEditor( {
 			math: {
 				engine: 'katex',
+				enablePreview: true,
 				lazyLoad: async () => {
 					lazyLoadInvoked = true;
 				}
@@ -44,6 +45,15 @@ describe( 'Lazy load', () => {
 		} );
 
 		mathUIFeature._showUI();
+
+		// Trigger render with a non-empty value to bypass empty check optimization
+		if ( mathUIFeature.formView ) {
+			mathUIFeature.formView.equation = 'x^2';
+		}
+
+		// Wait for async rendering and lazy loading
+		await new Promise( resolve => setTimeout( resolve, 100 ) );
+
 		expect( lazyLoadInvoked ).to.be.true;
 	} );
 } );

packages/ckeditor5-math/theme/mathform.css

@@ -212,3 +212,13 @@
     outline: none !important;
     box-shadow: none !important;
 }
+
+.ck-math-render-error {
+    color: var(--ck-color-error-text, #db1d1d);
+    padding: var(--ck-spacing-small);
+    font-style: italic;
+    font-size: 0.9em;
+    border: 1px dashed var(--ck-color-error-text, #db1d1d);
+    border-radius: 2px;
+    background: var(--ck-color-base-background, #fff);
+}