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[Internal] Make letter spacing dependent on text size in CollapsingTextHelper #4640

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[Internal] Make letter spacing dependent on text size in CollapsingTextHelper #4640

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39 changes: 24 additions & 15 deletions lib/java/com/google/android/material/internal/CollapsingTextHelper.java
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Original file line number Diff line number Diff line change
Expand Up @@ -712,17 +712,6 @@ private void calculateOffsets(final float fraction) {
textPaint.setColor(getCurrentCollapsedTextColor());
}

if (collapsedLetterSpacing != expandedLetterSpacing) {
textPaint.setLetterSpacing(
lerp(
expandedLetterSpacing,
collapsedLetterSpacing,
fraction,
AnimationUtils.FAST_OUT_SLOW_IN_INTERPOLATOR));
} else {
textPaint.setLetterSpacing(collapsedLetterSpacing);
}

Comment on lines -715 to -725
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@hunterstich hunterstich Dec 30, 2025

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Instead of removing this block, could it be moved into the else statement of if (fadeModeEnabled)?

if (fadeModeEnabled) {
   ...
} else {
   lerp letter spacing
}

// Calculates paint parameters for shadow layer.
currentShadowRadius = lerp(expandedShadowRadius, collapsedShadowRadius, fraction, null);
currentShadowDx = lerp(expandedShadowDx, collapsedShadowDx, fraction, null);
Expand Down Expand Up @@ -1099,7 +1088,6 @@ private void calculateUsingTextSize(final float fraction, boolean forceRecalcula
newTypeface = collapsedTypeface;
} else {
newTextSize = expandedTextSize;
newLetterSpacing = expandedLetterSpacing;
newTypeface = expandedTypeface;
if (isClose(fraction, /* targetValue= */ 0)) {
// If we're close to the expanded text size, snap to it and use a scale of 1
Expand All @@ -1111,6 +1099,11 @@ private void calculateUsingTextSize(final float fraction, boolean forceRecalcula
/ expandedTextSize;
}

newLetterSpacing = lerp(
expandedLetterSpacing, collapsedLetterSpacing,
1f, collapsedTextSize / expandedTextSize,
scale);

Comment on lines +1102 to +1106
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@hunterstich hunterstich Dec 30, 2025

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No longer needed if letter spacing lerping is replaced inside calculateOffsets

float textSizeRatio = collapsedTextSize / expandedTextSize;
// This is the size of the expanded bounds when it is scaled to match the
// collapsed text size
Expand Down Expand Up @@ -1320,11 +1313,11 @@ public void setStaticLayoutBuilderConfigurer(
}

/**
* Returns true if {@code value} is 'close' to it's closest decimal value. Close is currently
* Returns true if {@code value1} is 'close' to {@code value2}. Close is currently
* defined as it's difference being < 0.00001.
*/
private static boolean isClose(float value, float targetValue) {
return Math.abs(value - targetValue) < 0.00001f;
private static boolean isClose(float value1, float value2) {
return Math.abs(value1 - value2) < 0.00001f;
}

public ColorStateList getExpandedTextColor() {
Expand Down Expand Up @@ -1367,6 +1360,22 @@ private static float lerp(
return AnimationUtils.lerp(startValue, endValue, fraction);
}

private static float lerp(
float outputStart, float outputEnd,
float inputStart, float inputEnd,
float inputValue) {
if (isClose(inputEnd, inputStart)) {
if (isClose(outputEnd, outputStart)) {
return outputStart;
} else {
throw new RuntimeException("\"input\" range is empty, but \"output\" is not");
}
}

float value = (inputValue - inputStart) / (inputEnd - inputStart);
return outputStart + (outputEnd - outputStart) * value;
}

private static boolean rectEquals(@NonNull Rect r, int left, int top, int right, int bottom) {
return !(r.left != left || r.top != top || r.right != right || r.bottom != bottom);
}
Expand Down