fix: do not wrap the inline math equation in a new line (#7035)

* fix: do not wrap the inline math equation in new line

* test: inline equation text and inline text align

frontend/appflowy_flutter/integration_test/desktop/document/document_with_inline_math_equation_test.dart

@@ -147,7 +147,21 @@ void main() {
       const text = 'Hello World';
       await tester.ime.insertText(text);
 
-      expect(find.textContaining(text, findRichText: true), findsOneWidget);
+      final inlineText = find.textContaining(text, findRichText: true);
+      expect(inlineText, findsOneWidget);
+
+      // the text should be in the same line with the math equation
+      final inlineMathEquationPosition = tester.getRect(inlineMathEquation);
+      final textPosition = tester.getRect(inlineText);
+      // allow 5px difference
+      expect(
+        (textPosition.top - inlineMathEquationPosition.top).abs(),
+        lessThan(5),
+      );
+      expect(
+        (textPosition.bottom - inlineMathEquationPosition.bottom).abs(),
+        lessThan(5),
+      );
     });
   });
 }

frontend/appflowy_flutter/lib/plugins/document/presentation/editor_plugins/inline_math_equation/inline_math_equation.dart

@@ -80,20 +80,18 @@ class _InlineMathEquationState extends State<InlineMathEquation> {
         mathFontOptions: const FontOptions(
           fontShape: FontStyle.italic,
         ),
-        fontSize: 14.0,
+        fontSize: widget.textStyle?.fontSize ?? 14.0,
         color: widget.textStyle?.color ?? theme.colorScheme.onSurface,
       ),
       onErrorFallback: (errmsg) {
         return FlowyText(
           errmsg.message,
+          fontSize: widget.textStyle?.fontSize ?? 14.0,
+          color: widget.textStyle?.color ?? theme.colorScheme.onSurface,
         );
       },
     );
-    return Row(
-      children: [
-        longEq,
-      ],
-    );
+    return longEq;
   }
 }
 

frontend/appflowy_flutter/lib/plugins/document/presentation/editor_style.dart

@@ -363,6 +363,7 @@ class EditorStyleCustomizer {
     if (formula is String) {
       return WidgetSpan(
         style: after.style,
+        alignment: PlaceholderAlignment.middle,
         child: InlineMathEquation(
           node: node,
           index: index,