fix: Ensure consistent TextStyle inheritance during button state transitions

packages/flet/lib/src/controls/button.dart

@@ -98,20 +98,22 @@ class _ButtonControlState extends State<ButtonControl> with FletStoreMixin {
     var theme = Theme.of(context);
 
     var style = parseButtonStyle(
-        widget.control.internals?["style"], Theme.of(context),
-        defaultForegroundColor: widget.control
-            .getColor("color", context, theme.colorScheme.primary)!,
-        defaultBackgroundColor: widget.control
-            .getColor("bgcolor", context, theme.colorScheme.surface)!,
-        defaultOverlayColor: theme.colorScheme.primary.withOpacity(0.08),
-        defaultShadowColor: theme.colorScheme.shadow,
-        defaultSurfaceTintColor: theme.colorScheme.surfaceTint,
-        defaultElevation: widget.control.getDouble("elevation", 1)!,
-        defaultPadding: const EdgeInsets.symmetric(horizontal: 8),
-        defaultBorderSide: BorderSide.none,
-        defaultShape: theme.useMaterial3
-            ? const StadiumBorder()
-            : RoundedRectangleBorder(borderRadius: BorderRadius.circular(4)));
+      widget.control.internals?["style"],
+      theme,
+      defaultForegroundColor:
+          widget.control.getColor("color", context, theme.colorScheme.primary)!,
+      defaultBackgroundColor: widget.control
+          .getColor("bgcolor", context, theme.colorScheme.surface)!,
+      defaultOverlayColor: theme.colorScheme.primary.withOpacity(0.08),
+      defaultShadowColor: theme.colorScheme.shadow,
+      defaultSurfaceTintColor: theme.colorScheme.surfaceTint,
+      defaultElevation: widget.control.getDouble("elevation", 1)!,
+      defaultPadding: const EdgeInsets.symmetric(horizontal: 8),
+      defaultBorderSide: BorderSide.none,
+      defaultShape: theme.useMaterial3
+          ? const StadiumBorder()
+          : RoundedRectangleBorder(borderRadius: BorderRadius.circular(4)),
+    );
 
     Widget error = const ErrorControl("Error displaying Button",
         description: "\"icon\" must be specified together with \"content\"");
@@ -203,8 +205,7 @@ class _ButtonControlState extends State<ButtonControl> with FletStoreMixin {
             onLongPress: onLongPressHandler,
             onHover: onHoverHandler,
             clipBehavior: clipBehavior,
-            child:
-                widget.control.buildTextOrWidget("content") ?? const Text(""));
+            child: content ?? const Text(""));
       } else if (isOutlinedButton) {
         button = OutlinedButton(
             autofocus: autofocus,

packages/flet/lib/src/controls/row.dart

@@ -18,12 +18,7 @@ class RowControl extends StatelessWidget {
     debugPrint("Row build: ${control.id}");
 
     var spacing = control.getDouble("spacing", 10)!;
-    var mainAlignment = parseMainAxisAlignment(
-        control.getString("alignment"), MainAxisAlignment.start)!;
-    var tight = control.getBool("tight", false)!;
     var wrap = control.getBool("wrap", false)!;
-    var intrinsicHeight = control.getBool("intrinsic_height", false)!;
-    var verticalAlignment = control.getString("vertical_alignment");
     var controls = control.buildWidgets("controls");
 
     Widget child = wrap
@@ -35,20 +30,23 @@ class RowControl extends StatelessWidget {
                 control.getString("alignment"), WrapAlignment.start)!,
             runAlignment: parseWrapAlignment(
                 control.getString("run_alignment"), WrapAlignment.start)!,
-            crossAxisAlignment: parseWrapCrossAlignment(
-                verticalAlignment, WrapCrossAlignment.center)!,
+            crossAxisAlignment: control.getWrapCrossAlignment(
+                "vertical_alignment", WrapCrossAlignment.center)!,
             children: controls,
           )
         : Row(
             spacing: spacing,
-            mainAxisAlignment: mainAlignment,
-            mainAxisSize: tight ? MainAxisSize.min : MainAxisSize.max,
-            crossAxisAlignment: parseCrossAxisAlignment(
-                verticalAlignment, CrossAxisAlignment.center)!,
+            mainAxisSize: control.getBool("tight", false)!
+                ? MainAxisSize.min
+                : MainAxisSize.max,
+            mainAxisAlignment: control.getMainAxisAlignment(
+                "alignment", MainAxisAlignment.start)!,
+            crossAxisAlignment: control.getCrossAxisAlignment(
+                "vertical_alignment", CrossAxisAlignment.center)!,
             children: controls,
           );
 
-    if (intrinsicHeight) {
+    if (control.getBool("intrinsic_height", false)!) {
       child = IntrinsicHeight(child: child);
     }
 

packages/flet/lib/src/utils/buttons.dart

@@ -29,6 +29,22 @@ ButtonStyle? parseButtonStyle(dynamic value, ThemeData theme,
     TextStyle? defaultTextStyle,
     ButtonStyle? defaultValue}) {
   if (value == null) return defaultValue;
+
+  WidgetStateProperty<TextStyle?>? parseButtonTextStyle(
+      dynamic value, ThemeData theme,
+      {TextStyle? defaultTextStyle}) {
+    final ts = parseWidgetStateTextStyle(value, theme,
+        defaultTextStyle: defaultTextStyle);
+    if (ts == null) return null;
+
+    // Match Material button defaults to avoid TextStyle.lerp assertions when
+    // animating between states.
+    return WidgetStateProperty.resolveWith((Set<WidgetState> states) {
+      final resolved = ts.resolve(states);
+      return resolved?.copyWith(inherit: false);
+    });
+  }
+
   return ButtonStyle(
     foregroundColor: parseWidgetStateColor(value["color"], theme,
         defaultColor: defaultForegroundColor),
@@ -54,7 +70,7 @@ ButtonStyle? parseButtonStyle(dynamic value, ThemeData theme,
         defaultColor: defaultForegroundColor),
     alignment: parseAlignment(value["alignment"]),
     enableFeedback: parseBool(value["enable_feedback"]),
-    textStyle: parseWidgetStateTextStyle(value["text_style"], theme,
+    textStyle: parseButtonTextStyle(value["text_style"], theme,
         defaultTextStyle: defaultTextStyle),
     iconSize: parseWidgetStateDouble(value["icon_size"]),
     visualDensity: parseVisualDensity(value["visual_density"]),

packages/flet/lib/src/utils/text.dart

@@ -140,20 +140,19 @@ TextAffinity? parseTextAffinity(String? value, [TextAffinity? defaultValue]) {
       defaultValue;
 }
 
-TextStyle? parseTextStyle(dynamic value, ThemeData theme,
-    [TextStyle? defaultValue]) {
-  if (value == null) return defaultValue;
-  var fontWeight = value["weight"];
-
-  List<FontVariation>? variations;
-  if (fontWeight != null && fontWeight.startsWith("w")) {
-    variations = [
-      FontVariation('wght', parseDouble(fontWeight.substring(1), 0)!)
-    ];
+List<FontVariation>? parseFontVariations(dynamic fontWeight,
+    [List<FontVariation>? defaultValue]) {
+  if (fontWeight != null &&
+      fontWeight is String &&
+      fontWeight.startsWith("w")) {
+    return [FontVariation('wght', parseDouble(fontWeight.substring(1), 0)!)];
   }
+  return defaultValue;
+}
 
+List<TextDecoration> parseTextDecorations(dynamic decorationValue) {
   List<TextDecoration> decorations = [];
-  var decor = parseInt(value["decoration"], 0)!;
+  var decor = parseInt(decorationValue, 0)!;
   if (decor & 0x1 > 0) {
     decorations.add(TextDecoration.underline);
   }
@@ -163,6 +162,16 @@ TextStyle? parseTextStyle(dynamic value, ThemeData theme,
   if (decor & 0x4 > 0) {
     decorations.add(TextDecoration.lineThrough);
   }
+  return decorations;
+}
+
+TextStyle? parseTextStyle(dynamic value, ThemeData theme,
+    [TextStyle? defaultValue]) {
+  if (value == null) return defaultValue;
+
+  var fontWeight = value["weight"];
+  List<FontVariation>? variations = parseFontVariations(fontWeight);
+  List<TextDecoration> decorations = parseTextDecorations(value["decoration"]);
 
   return TextStyle(
     fontSize: parseDouble(value["size"]),

sdk/python/examples/apps/timer/declarative.py

@@ -0,0 +1,135 @@
+import asyncio
+import time
+from dataclasses import dataclass
+
+import flet as ft
+
+
+def format_hhmmss(seconds: int) -> str:
+    """Format elapsed seconds as HH:MM:SS."""
+    h = seconds // 3600
+    m = (seconds % 3600) // 60
+    s = seconds % 60
+    return f"{h:02}:{m:02}:{s:02}"
+
+
+@ft.observable
+@dataclass
+class TimerState:
+    """
+    Declarative timer state.
+
+    This class is the single source of truth for the UI.
+    Any mutation of its public fields automatically triggers a re-render.
+    """
+
+    running: bool = False
+    paused: bool = False
+    elapsed: int = 0  # seconds shown in UI
+
+    # Internals
+    _base_elapsed: int = 0  # accumulated time before the current run
+    _started_at: float = 0.0  # wall-clock start time
+    _task: asyncio.Task | None = None  # background ticker task
+
+    async def _ticker(self):
+        """
+        Background task that updates elapsed time once per second
+        while the timer is running.
+        """
+        while self.running:
+            if not self.paused:
+                self.elapsed = self._base_elapsed + int(time.time() - self._started_at)
+            await asyncio.sleep(1)
+
+        # Task cleanup when stopped
+        self._task = None
+
+    def toggle(self):
+        """
+        Toggle button handler:
+        - stopped → start
+        - running → pause
+        - paused → resume
+        """
+        # stopped → start
+        if not self.running:
+            self.running = True
+            self.paused = False
+            self._base_elapsed = self.elapsed
+            self._started_at = time.time()
+
+            # Ensure only one ticker task runs
+            if self._task is None or self._task.done():
+                self._task = asyncio.create_task(self._ticker())
+            return
+
+        # running → pause
+        if not self.paused:
+            self._base_elapsed += int(time.time() - self._started_at)
+            self.elapsed = self._base_elapsed
+            self.paused = True
+            return
+
+        # paused → resume
+        self.paused = False
+        self._started_at = time.time()
+
+    def stop(self):
+        """Stop the timer and reset all state."""
+        self.running = False
+        self.paused = False
+        self.elapsed = 0
+        self._base_elapsed = 0
+        self._started_at = 0.0
+
+
+@ft.component
+def App():
+    state, _ = ft.use_state(TimerState())
+
+    # Button appearance derived entirely from state
+    label = "Pause" if state.running and not state.paused else "Start"
+    icon = ft.Icons.PAUSE if state.running and not state.paused else ft.Icons.PLAY_ARROW
+
+    return ft.SafeArea(
+        ft.Column(
+            spacing=20,
+            horizontal_alignment=ft.CrossAxisAlignment.CENTER,
+            alignment=ft.MainAxisAlignment.CENTER,
+            controls=[
+                ft.Text(
+                    format_hhmmss(state.elapsed),
+                    size=30,
+                    weight=ft.FontWeight.BOLD,
+                ),
+                ft.Row(
+                    alignment=ft.MainAxisAlignment.CENTER,
+                    controls=[
+                        ft.FilledButton(
+                            label,
+                            icon=icon,
+                            on_click=state.toggle,
+                        ),
+                        ft.TextButton(
+                            "Stop",
+                            icon=ft.Icons.STOP,
+                            on_click=state.stop,
+                            disabled=not state.running and state.elapsed == 0,
+                        ),
+                    ],
+                ),
+            ],
+        )
+    )
+
+
+def main(page: ft.Page):
+    """Application entry point."""
+    page.vertical_alignment = ft.MainAxisAlignment.CENTER
+    page.horizontal_alignment = ft.CrossAxisAlignment.CENTER
+
+    page.render(App)
+
+
+ft.run(main)