[TopAppBar] Correctly set letter spacing when expanding titles

We recreated title text layout when expanding from the collapsed state but didn't correctly set the letter spacing to the expanded one. The letter spacing being used will be a interpolated value between collapsed and expanded letter spacing (close to the collapsed one due to the implementation). This will cause the text layout incorrectly calculate the line count from the wrong letter spacing and result in a broken layout.

Correctly sets the letter spacing to fix the issue.

Resolves #2463

PiperOrigin-RevId: 408910555

Author: drchen

lib/java/com/google/android/material/internal/CollapsingTextHelper.java

@@ -153,6 +153,7 @@ public final class CollapsingTextHelper {
 
   private float collapsedLetterSpacing;
   private float expandedLetterSpacing;
+  private float currentLetterSpacing;
 
   private StaticLayout textLayout;
   private float collapsedTextWidth;
@@ -907,10 +908,12 @@ private void calculateUsingTextSize(final float textSize, boolean forceRecalcula
 
     float availableWidth;
     float newTextSize;
+    float newLetterSpacing;
     boolean updateDrawText = false;
 
     if (isClose(textSize, collapsedTextSize)) {
       newTextSize = collapsedTextSize;
+      newLetterSpacing = collapsedLetterSpacing;
       scale = 1f;
       if (currentTypeface != collapsedTypeface) {
         currentTypeface = collapsedTypeface;
@@ -919,6 +922,7 @@ private void calculateUsingTextSize(final float textSize, boolean forceRecalcula
       availableWidth = collapsedWidth;
     } else {
       newTextSize = expandedTextSize;
+      newLetterSpacing = expandedLetterSpacing;
       if (currentTypeface != expandedTypeface) {
         currentTypeface = expandedTypeface;
         updateDrawText = true;
@@ -953,14 +957,20 @@ private void calculateUsingTextSize(final float textSize, boolean forceRecalcula
     }
 
     if (availableWidth > 0) {
-      updateDrawText = (currentTextSize != newTextSize) || boundsChanged || updateDrawText;
+      boolean textSizeChanged = currentTextSize != newTextSize;
+      boolean letterSpacingChanged = currentLetterSpacing != newLetterSpacing;
+      updateDrawText = textSizeChanged || letterSpacingChanged || boundsChanged || updateDrawText;
       currentTextSize = newTextSize;
+      currentLetterSpacing = newLetterSpacing;
       boundsChanged = false;
     }
 
     if (textToDraw == null || updateDrawText) {
       textPaint.setTextSize(currentTextSize);
       textPaint.setTypeface(currentTypeface);
+      if (VERSION.SDK_INT >= VERSION_CODES.LOLLIPOP) {
+        textPaint.setLetterSpacing(currentLetterSpacing);
+      }
       // Use linear text scaling if we're scaling the canvas
       textPaint.setLinearText(scale != 1f);