android: restore vertical centering for content-hugging custom top-bar buttons (#8332)

* fix(android): size custom top-bar buttons to content height for vertical centering

* test(android): assert content-height (AT_MOST) for custom top-bar buttons

Author: Yoavpagir

android/src/main/java/com/reactnativenavigation/views/stack/topbar/titlebar/TitleBarReactButtonView.java

@@ -50,10 +50,12 @@ protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
         // before the content has laid out that width is collapsed (~1px), Fabric lays the content into
         // it and the button never recovers (#8320/#8326 did this and regressed under the New Arch).
         //
-        // Height: EXACTLY the available bar height. Giving the surface a filled height (rather than a
-        // content-hugging AT_MOST height) lets content that centers itself (e.g. a flex container with
-        // justifyContent: 'center') sit vertically centered in the bar, matching the legacy layout.
-        // It does not cause the width collapse — only a forced width does.
+        // Height: bounded (AT_MOST) so the surface sizes to its content height. The view is then
+        // centered vertically by the toolbar's action-view layout and the CENTER_VERTICAL gravity set
+        // in onViewAdded(). Forcing EXACTLY the full bar height (as #8328 did) made the surface fill
+        // the bar, so content-hugging buttons that don't self-center (plain text like "Publish", a
+        // fixed-size avatar image) were pinned to the top. AT_MOST height does NOT cause the width
+        // collapse — only a forced EXACTLY *width* does.
         int widthSpec = component.width.hasValue()
                 ? createExactSpec(component.width)
                 : makeMeasureSpec(resolveAvailableWidth(widthMeasureSpec), AT_MOST);
@@ -66,7 +68,7 @@ private int createHeightSpec(int measureSpec, Number dimension) {
             return createExactSpec(dimension);
         }
         int availableSize = MeasureSpec.getSize(measureSpec);
-        return makeMeasureSpec(availableSize > 0 ? availableSize : Math.max(resolveActionBarSize(), 1), EXACTLY);
+        return makeMeasureSpec(availableSize > 0 ? availableSize : Math.max(resolveActionBarSize(), 1), AT_MOST);
     }
 
     private int resolveAvailableWidth(int measureSpec) {

android/src/test/java/com/reactnativenavigation/views/TitleBarReactButtonViewTest.java

@@ -34,12 +34,14 @@ public class TitleBarReactButtonViewTest extends BaseTest {
 
     // Without explicit dimensions the button measures the hosted React surface ONCE:
     //  - width  AT_MOST  → the surface sizes itself to its content (max-of-children under Fabric).
-    //  - height EXACTLY the available bar height → the surface gets a filled box so content that
-    //    centers itself (flex justifyContent: 'center') stays vertically centered in the bar.
+    //  - height AT_MOST  → the surface sizes to its content height; the view is then centered
+    //    vertically in the bar by the toolbar's action-view layout + the CENTER_VERTICAL gravity from
+    //    onViewAdded(). A forced EXACTLY full-bar height would pin content-hugging buttons (plain
+    //    text, a fixed-size avatar) to the top.
     // It deliberately does not push a forced EXACTLY *width*; under the New Architecture that re-pushes
     // a (initially collapsed) width to the async Fabric layout and the button never recovers.
     @Test
-    public void missingDimensionsSizeWidthToContentAndFillHeight() {
+    public void missingDimensionsSizeToContent() {
         Activity activity = newActivity();
         TitleBarReactButtonView uut = createView(activity, new ComponentOptions());
         RecordingContentView child = new RecordingContentView(activity);
@@ -48,11 +50,11 @@ public void missingDimensionsSizeWidthToContentAndFillHeight() {
         uut.measure(makeMeasureSpec(PARENT_WIDTH, AT_MOST), makeMeasureSpec(PARENT_HEIGHT, AT_MOST));
 
         assertThat(uut.getMeasuredWidth()).isEqualTo(CHILD_WIDTH);
-        assertThat(uut.getMeasuredHeight()).isEqualTo(PARENT_HEIGHT);
+        assertThat(uut.getMeasuredHeight()).isEqualTo(CHILD_HEIGHT);
         assertThat(child.widthMeasureSpecs.size()).isEqualTo(1);
         assertThat(getMode(child.widthMeasureSpecs.get(0))).isEqualTo(AT_MOST);
         assertThat(getSize(child.widthMeasureSpecs.get(0))).isEqualTo(PARENT_WIDTH);
-        assertThat(getMode(child.heightMeasureSpecs.get(0))).isEqualTo(EXACTLY);
+        assertThat(getMode(child.heightMeasureSpecs.get(0))).isEqualTo(AT_MOST);
         assertThat(getSize(child.heightMeasureSpecs.get(0))).isEqualTo(PARENT_HEIGHT);
     }
 
@@ -78,7 +80,7 @@ public void explicitDimensionsMeasureExactly() {
     }
 
     @Test
-    public void zeroParentSpecsFallBackToScreenWidthAndActionBarHeight() {
+    public void zeroParentSpecsFallBackToScreenWidthAndBoundedActionBarHeight() {
         Activity activity = newActivity();
         TitleBarReactButtonView uut = createView(activity, new ComponentOptions());
         RecordingContentView child = new RecordingContentView(activity);
@@ -90,12 +92,12 @@ public void zeroParentSpecsFallBackToScreenWidthAndActionBarHeight() {
         assertThat(getMode(child.widthMeasureSpecs.get(0))).isEqualTo(AT_MOST);
         assertThat(getSize(child.widthMeasureSpecs.get(0)))
                 .isEqualTo(Math.max(activity.getResources().getDisplayMetrics().widthPixels, 1));
-        assertThat(getMode(child.heightMeasureSpecs.get(0))).isEqualTo(EXACTLY);
+        assertThat(getMode(child.heightMeasureSpecs.get(0))).isEqualTo(AT_MOST);
         assertThat(getSize(child.heightMeasureSpecs.get(0))).isEqualTo(Math.max(resolveActionBarSize(activity), 1));
     }
 
     @Test
-    public void rtlMissingDimensionsUseBoundedWidthAndFilledHeight() {
+    public void rtlMissingDimensionsUseBoundedWidthAndHeight() {
         Activity activity = newActivity();
         TitleBarReactButtonView uut = createView(activity, new ComponentOptions());
         RecordingContentView child = new RecordingContentView(activity);
@@ -107,7 +109,7 @@ public void rtlMissingDimensionsUseBoundedWidthAndFilledHeight() {
         assertThat(child.widthMeasureSpecs.size()).isEqualTo(1);
         assertThat(getMode(child.widthMeasureSpecs.get(0))).isEqualTo(AT_MOST);
         assertThat(getSize(child.widthMeasureSpecs.get(0))).isEqualTo(PARENT_WIDTH);
-        assertThat(getMode(child.heightMeasureSpecs.get(0))).isEqualTo(EXACTLY);
+        assertThat(getMode(child.heightMeasureSpecs.get(0))).isEqualTo(AT_MOST);
         assertThat(getSize(child.heightMeasureSpecs.get(0))).isEqualTo(PARENT_HEIGHT);
     }