[Button] Support icon gravity with text alignments other than centered

Resolves #1371

PiperOrigin-RevId: 421605261

Author: drchen

lib/java/com/google/android/material/button/MaterialButton.java

@@ -35,8 +35,10 @@
 import android.os.Parcelable;
 import androidx.appcompat.content.res.AppCompatResources;
 import androidx.appcompat.widget.AppCompatButton;
+import android.text.Layout.Alignment;
 import android.util.AttributeSet;
 import android.util.Log;
+import android.view.Gravity;
 import android.view.accessibility.AccessibilityEvent;
 import android.view.accessibility.AccessibilityNodeInfo;
 import android.widget.Button;
@@ -493,28 +495,89 @@ public void refreshDrawableState() {
     }
   }
 
+  @RequiresApi(VERSION_CODES.JELLY_BEAN_MR1)
+  @Override
+  public void setTextAlignment(int textAlignment) {
+    super.setTextAlignment(textAlignment);
+    updateIconPosition(getMeasuredWidth(), getMeasuredHeight());
+  }
+
+  /**
+   * This method and {@link #getActualTextAlignment()} is modified from Android framework TextView's
+   * private method getLayoutAlignment(). Please note that the logic here assumes the actual text
+   * direction is the same as the layout direction, which is not always the case, especially when
+   * the text mixes different languages. However, this is probably the best we can do for now,
+   * unless we have a good way to detect the final text direction being used by TextView.
+   */
+  private Alignment getGravityTextAlignment() {
+    switch (getGravity() & Gravity.RELATIVE_HORIZONTAL_GRAVITY_MASK) {
+      case Gravity.CENTER_HORIZONTAL:
+        return Alignment.ALIGN_CENTER;
+      case Gravity.END:
+      case Gravity.RIGHT:
+        return Alignment.ALIGN_OPPOSITE;
+      case Gravity.START:
+      case Gravity.LEFT:
+      default:
+        return Alignment.ALIGN_NORMAL;
+    }
+  }
+
+  /**
+   * This method and {@link #getGravityTextAlignment()} is modified from Android framework
+   * TextView's private method getLayoutAlignment(). Please note that the logic here assumes
+   * the actual text direction is the same as the layout direction, which is not always the case,
+   * especially when the text mixes different languages. However, this is probably the best we can
+   * do for now, unless we have a good way to detect the final text direction being used by
+   * TextView.
+   */
+  private Alignment getActualTextAlignment() {
+    if (VERSION.SDK_INT < VERSION_CODES.JELLY_BEAN_MR1) {
+      return getGravityTextAlignment();
+    }
+    switch (getTextAlignment()) {
+      case TEXT_ALIGNMENT_GRAVITY:
+        return getGravityTextAlignment();
+      case TEXT_ALIGNMENT_CENTER:
+        return Alignment.ALIGN_CENTER;
+      case TEXT_ALIGNMENT_TEXT_END:
+      case TEXT_ALIGNMENT_VIEW_END:
+        return Alignment.ALIGN_OPPOSITE;
+      case TEXT_ALIGNMENT_TEXT_START:
+      case TEXT_ALIGNMENT_VIEW_START:
+      case TEXT_ALIGNMENT_INHERIT:
+      default:
+        return Alignment.ALIGN_NORMAL;
+    }
+  }
+
   private void updateIconPosition(int buttonWidth, int buttonHeight) {
     if (icon == null || getLayout() == null) {
       return;
     }
 
     if (isIconStart() || isIconEnd()) {
       iconTop = 0;
-      if (iconGravity == ICON_GRAVITY_START || iconGravity == ICON_GRAVITY_END) {
+
+      Alignment textAlignment = getActualTextAlignment();
+      if (iconGravity == ICON_GRAVITY_START
+          || iconGravity == ICON_GRAVITY_END
+          || (iconGravity == ICON_GRAVITY_TEXT_START && textAlignment == Alignment.ALIGN_NORMAL)
+          || (iconGravity == ICON_GRAVITY_TEXT_END && textAlignment == Alignment.ALIGN_OPPOSITE)) {
         iconLeft = 0;
         updateIcon(/* needsIconReset = */ false);
         return;
       }
 
       int localIconSize = iconSize == 0 ? icon.getIntrinsicWidth() : iconSize;
+      int availableWidth = buttonWidth
+          - getTextWidth()
+          - ViewCompat.getPaddingEnd(this)
+          - localIconSize
+          - iconPadding
+          - ViewCompat.getPaddingStart(this);
       int newIconLeft =
-          (buttonWidth
-              - getTextWidth()
-              - ViewCompat.getPaddingEnd(this)
-              - localIconSize
-              - iconPadding
-              - ViewCompat.getPaddingStart(this))
-              / 2;
+          textAlignment == Alignment.ALIGN_CENTER ? availableWidth / 2 : availableWidth;
 
       // Only flip the bound value if either isLayoutRTL() or iconGravity is textEnd, but not both
       if (isLayoutRTL() != (iconGravity == ICON_GRAVITY_TEXT_END)) {