Merge "fix(non linear font scaling): fix crash with certain negative SP values"

core/java/android/content/res/FontScaleConverter.java

@@ -36,11 +36,6 @@ import java.util.Arrays;
  * @hide
  */
 public class FontScaleConverter {
-    /**
-     * How close the given SP should be to a canonical SP in the array before they are considered
-     * the same for lookup purposes.
-     */
-    private static final float THRESHOLD_FOR_MATCHING_SP = 0.02f;
 
     @VisibleForTesting
     final float[] mFromSpValues;
@@ -78,10 +73,11 @@ public class FontScaleConverter {
     public float convertSpToDp(float sp) {
         final float spPositive = Math.abs(sp);
         // TODO(b/247861374): find a match at a higher index?
-        final int spRounded = Math.round(spPositive);
         final float sign = Math.signum(sp);
-        final int index = Arrays.binarySearch(mFromSpValues, spRounded);
-        if (index >= 0 && Math.abs(spRounded - spPositive) < THRESHOLD_FOR_MATCHING_SP) {
+        // We search for exact matches only, even if it's just a little off. The interpolation will
+        // handle any non-exact matches.
+        final int index = Arrays.binarySearch(mFromSpValues, spPositive);
+        if (index >= 0) {
             // exact match, return the matching dp
             return sign * mToDpValues[index];
         } else {

core/tests/coretests/src/android/content/res/FontScaleConverterFactoryTest.kt

@@ -18,8 +18,12 @@ package android.content.res
 
 import androidx.core.util.forEach
 import androidx.test.ext.junit.runners.AndroidJUnit4
+import androidx.test.filters.LargeTest
 import androidx.test.filters.SmallTest
 import com.google.common.truth.Truth.assertThat
+import com.google.common.truth.Truth.assertWithMessage
+import kotlin.math.ceil
+import kotlin.math.floor
 import org.junit.Test
 import org.junit.runner.RunWith
 
@@ -72,7 +76,70 @@ class FontScaleConverterFactoryTest {
         }
     }
 
+    @LargeTest
+    @Test
+    fun allFeasibleScalesAndConversionsDoNotCrash() {
+        generateSequenceOfFractions(-10000f..10000f, step = 0.01f)
+            .mapNotNull{ FontScaleConverterFactory.forScale(it) }
+            .flatMap{ table ->
+                generateSequenceOfFractions(-10000f..10000f, step = 0.01f)
+                    .map{ Pair(table, it) }
+            }
+            .forEach { (table, sp) ->
+                try {
+                    assertWithMessage(
+                        "convertSpToDp(%s) on table: %s",
+                        sp.toString(),
+                        table.toString()
+                    )
+                        .that(table.convertSpToDp(sp))
+                        .isFinite()
+                } catch (e: Exception) {
+                    throw AssertionError("Exception during convertSpToDp($sp) on table: $table", e)
+                }
+            }
+    }
+
+    @Test
+    fun testGenerateSequenceOfFractions() {
+        val fractions = generateSequenceOfFractions(-1000f..1000f, step = 0.1f)
+            .toList()
+        fractions.forEach {
+            assertThat(it).isAtLeast(-1000f)
+            assertThat(it).isAtMost(1000f)
+        }
+
+        assertThat(fractions).isInStrictOrder()
+        assertThat(fractions).hasSize(1000 * 2 * 10 + 1) // Don't forget the 0 in the middle!
+
+        assertThat(fractions).contains(100f)
+        assertThat(fractions).contains(500.1f)
+        assertThat(fractions).contains(500.2f)
+        assertThat(fractions).contains(0.2f)
+        assertThat(fractions).contains(0f)
+        assertThat(fractions).contains(-10f)
+        assertThat(fractions).contains(-10f)
+        assertThat(fractions).contains(-10.3f)
+
+        assertThat(fractions).doesNotContain(-10.31f)
+        assertThat(fractions).doesNotContain(0.35f)
+        assertThat(fractions).doesNotContain(0.31f)
+        assertThat(fractions).doesNotContain(-.35f)
+    }
+
     companion object {
         private const val CONVERSION_TOLERANCE = 0.05f
     }
 }
+
+fun generateSequenceOfFractions(
+    range: ClosedFloatingPointRange<Float>,
+    step: Float
+): Sequence<Float> {
+    val multiplier = 1f / step
+    val start = floor(range.start * multiplier).toInt()
+    val endInclusive = ceil(range.endInclusive * multiplier).toInt()
+    return generateSequence(start) { it + 1 }
+        .takeWhile { it <= endInclusive }
+        .map{ it.toFloat() / multiplier }
+}