fix(high contrast text): draw contrasting backgrounds when text changes color via Spans (48a980e1) · Commits · e / os / android_frameworks_base

core/java/android/text/Layout.java

+72 −9

Original line number	Diff line number	Diff line
		@@ -18,9 +18,10 @@ package android.text;

		import static com.android.graphics.hwui.flags.Flags.highContrastTextLuminance;
		import static com.android.text.flags.Flags.FLAG_FIX_LINE_HEIGHT_FOR_LOCALE;
		import static com.android.text.flags.Flags.FLAG_USE_BOUNDS_FOR_WIDTH;
		import static com.android.text.flags.Flags.FLAG_LETTER_SPACING_JUSTIFICATION;
		import static com.android.text.flags.Flags.FLAG_USE_BOUNDS_FOR_WIDTH;

		import android.annotation.ColorInt;
		import android.annotation.FlaggedApi;
		import android.annotation.FloatRange;
		import android.annotation.IntDef;
		@@ -398,6 +399,20 @@ public abstract class Layout {
		mUseBoundsForWidth = useBoundsForWidth;
		mShiftDrawingOffsetForStartOverhang = shiftDrawingOffsetForStartOverhang;
		mMinimumFontMetrics = minimumFontMetrics;

		initSpanColors();
		}

		private void initSpanColors() {
		if (mSpannedText && Flags.highContrastTextSmallTextRect()) {
		if (mSpanColors == null) {
		mSpanColors = new SpanColors();
		} else {
		mSpanColors.recycle();
		}
		} else {
		mSpanColors = null;
		}
		}

		/**
		@@ -417,6 +432,7 @@ public abstract class Layout {
		mSpacingMult = spacingmult;
		mSpacingAdd = spacingadd;
		mSpannedText = text instanceof Spanned;
		initSpanColors();
		}

		/**
		@@ -643,20 +659,20 @@ public abstract class Layout {
		return null;
		}

		return isHighContrastTextDark() ? BlendMode.MULTIPLY : BlendMode.DIFFERENCE;
		return isHighContrastTextDark(mPaint.getColor()) ? BlendMode.MULTIPLY
		: BlendMode.DIFFERENCE;
		}

		private boolean isHighContrastTextDark() {
		private boolean isHighContrastTextDark(@ColorInt int color) {
		// High-contrast text mode
		// Determine if the text is black-on-white or white-on-black, so we know what blendmode will
		// give the highest contrast and most realistic text color.
		// This equation should match the one in libs/hwui/hwui/DrawTextFunctor.h
		if (highContrastTextLuminance()) {
		var lab = new double[3];
		ColorUtils.colorToLAB(mPaint.getColor(), lab);
		return lab[0] < 0.5;
		ColorUtils.colorToLAB(color, lab);
		return lab[0] < 50.0;
		} else {
		var color = mPaint.getColor();
		int channelSum = Color.red(color) + Color.green(color) + Color.blue(color);
		return channelSum < (128 * 3);
		}
		@@ -1010,15 +1026,22 @@ public abstract class Layout {
		var padding = Math.max(HIGH_CONTRAST_TEXT_BORDER_WIDTH_MIN_PX,
		mPaint.getTextSize() * HIGH_CONTRAST_TEXT_BORDER_WIDTH_FACTOR);

		var originalTextColor = mPaint.getColor();
		var bgPaint = mWorkPlainPaint;
		bgPaint.reset();
		bgPaint.setColor(isHighContrastTextDark() ? Color.WHITE : Color.BLACK);
		bgPaint.setColor(isHighContrastTextDark(originalTextColor) ? Color.WHITE : Color.BLACK);
		bgPaint.setStyle(Paint.Style.FILL);

		int start = getLineStart(firstLine);
		int end = getLineEnd(lastLine);
		// Draw a separate background rectangle for each line of text, that only surrounds the
		// characters on that line.
		// characters on that line. But we also have to check the text color for each character, and
		// make sure we are drawing the correct contrasting background. This is because Spans can
		// change colors throughout the text and we'll need to match our backgrounds.
		if (mSpannedText && mSpanColors != null) {
		mSpanColors.init(mWorkPaint, ((Spanned) mText), start, end);
		}

		forEachCharacterBounds(
		start,
		end,
		@@ -1028,13 +1051,24 @@ public abstract class Layout {
		int mLastLineNum = -1;
		final RectF mLineBackground = new RectF();

		@ColorInt int mLastColor = originalTextColor;

		@Override
		public void onCharacterBounds(int index, int lineNum, float left, float top,
		float right, float bottom) {
		if (lineNum != mLastLineNum) {

		var newBackground = determineContrastingBackgroundColor(index);
		var hasBgColorChanged = newBackground != bgPaint.getColor();

		if (lineNum != mLastLineNum \|\| hasBgColorChanged) {
		// Draw what we have so far, then reset the rect and update its color
		drawRect();
		mLineBackground.set(left, top, right, bottom);
		mLastLineNum = lineNum;

		if (hasBgColorChanged) {
		bgPaint.setColor(newBackground);
		}
		} else {
		mLineBackground.union(left, top, right, bottom);
		}
		@@ -1051,8 +1085,36 @@ public abstract class Layout {
		canvas.drawRect(mLineBackground, bgPaint);
		}
		}

		private int determineContrastingBackgroundColor(int index) {
		if (!mSpannedText \|\| mSpanColors == null) {
		// The text is not Spanned. it's all one color.
		return bgPaint.getColor();
		}

		// Sometimes the color will change, but not enough to warrant a background
		// color change. e.g. from black to dark grey still gets clamped to black,
		// so the background stays white and we don't need to draw a fresh
		// background.
		var textColor = mSpanColors.getColorAt(index);
		if (textColor == SpanColors.NO_COLOR_FOUND) {
		textColor = originalTextColor;
		}
		var hasColorChanged = textColor != mLastColor;
		if (hasColorChanged) {
		mLastColor = textColor;

		return isHighContrastTextDark(textColor) ? Color.WHITE : Color.BLACK;
		}

		return bgPaint.getColor();
		}
		}
		);

		if (mSpanColors != null) {
		mSpanColors.recycle();
		}
		}

		/**
		@@ -3580,6 +3642,7 @@ public abstract class Layout {
		private float mSpacingAdd;
		private static final Rect sTempRect = new Rect();
		private boolean mSpannedText;
		@Nullable private SpanColors mSpanColors;
		private TextDirectionHeuristic mTextDir;
		private SpanSet<LineBackgroundSpan> mLineBackgroundSpans;
		private boolean mIncludePad;

core/java/android/text/SpanColors.java

0 → 100644

+89 −0

Original line number	Diff line number	Diff line
		/*
		* Copyright (C) 2024 The Android Open Source Project
		*
		* Licensed under the Apache License, Version 2.0 (the "License");
		* you may not use this file except in compliance with the License.
		* You may obtain a copy of the License at
		*
		* http://www.apache.org/licenses/LICENSE-2.0
		*
		* Unless required by applicable law or agreed to in writing, software
		* distributed under the License is distributed on an "AS IS" BASIS,
		* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
		* See the License for the specific language governing permissions and
		* limitations under the License.
		*/

		package android.text;

		import android.annotation.ColorInt;
		import android.annotation.Nullable;
		import android.graphics.Color;
		import android.text.style.CharacterStyle;

		/**
		* Finds the foreground text color for the given Spanned text so you can iterate through each color
		* change.
		*
		* @hide
		*/
		public class SpanColors {
		public static final @ColorInt int NO_COLOR_FOUND = Color.TRANSPARENT;

		private final SpanSet<CharacterStyle> mCharacterStyleSpanSet =
		new SpanSet<>(CharacterStyle.class);
		@Nullable private TextPaint mWorkPaint;

		public SpanColors() {}

		/**
		* Init for the given text
		*
		* @param workPaint A temporary TextPaint object that will be used to calculate the colors. The
		* paint properties will be mutated on calls to {@link #getColorAt(int)} so
		* make sure to reset it before you use it for something else.
		* @param spanned the text to examine
		* @param start index to start at
		* @param end index of the end
		*/
		public void init(TextPaint workPaint, Spanned spanned, int start, int end) {
		mWorkPaint = workPaint;
		mCharacterStyleSpanSet.init(spanned, start, end);
		}

		/**
		* Removes all internal references to the spans to avoid memory leaks.
		*/
		public void recycle() {
		mWorkPaint = null;
		mCharacterStyleSpanSet.recycle();
		}

		/**
		* Calculates the foreground color of the text at the given character index.
		*
		* <p>You must call {@link #init(TextPaint, Spanned, int, int)} before calling this
		*/
		public @ColorInt int getColorAt(int index) {
		var finalColor = NO_COLOR_FOUND;
		// Reset the paint so if we get a CharacterStyle that doesn't actually specify color,
		// (like UnderlineSpan), we still return no color found.
		mWorkPaint.setColor(finalColor);
		for (int k = 0; k < mCharacterStyleSpanSet.numberOfSpans; k++) {
		if ((index >= mCharacterStyleSpanSet.spanStarts[k])
		&& (index <= mCharacterStyleSpanSet.spanEnds[k])) {
		final CharacterStyle span = mCharacterStyleSpanSet.spans[k];
		span.updateDrawState(mWorkPaint);

		finalColor = calculateFinalColor(mWorkPaint);
		}
		}
		return finalColor;
		}

		private @ColorInt int calculateFinalColor(TextPaint workPaint) {
		// TODO: can we figure out what the getColorFilter() will do?
		// if so, we also need to reset colorFilter before the loop in getColorAt()
		return workPaint.getColor();
		}
		}

core/tests/coretests/src/android/text/LayoutTest.java

+78 −0

Original line number	Diff line number	Diff line
		@@ -39,6 +39,7 @@ import android.platform.test.annotations.RequiresFlagsEnabled;
		import android.platform.test.flag.junit.CheckFlagsRule;
		import android.platform.test.flag.junit.DeviceFlagsValueProvider;
		import android.text.Layout.Alignment;
		import android.text.style.ForegroundColorSpan;
		import android.text.style.StrikethroughSpan;

		import androidx.test.filters.SmallTest;
		@@ -933,6 +934,83 @@ public class LayoutTest {
		expect.that(numBackgroundsFound).isEqualTo(backgroundRectsDrawn);
		}

		@Test
		@RequiresFlagsEnabled(FLAG_HIGH_CONTRAST_TEXT_SMALL_TEXT_RECT)
		public void highContrastTextEnabled_testDrawMulticolorText_drawsBlackAndWhiteBackgrounds() {
		/*
		Here's what the final render should look like:

		Text \| Background
		========================
		al \| BW
		w \| WW
		ei \| WW
		\t; \| WW
		s \| BB
		df \| BB
		s \| BB
		df \| BB
		@ \| BB
		------------------------
		*/

		mTextPaint.setColor(Color.WHITE);

		mSpannedText.setSpan(
		// Can't use DKGREY because it is right on the cusp of clamping white
		new ForegroundColorSpan(0xFF332211),
		/* start= */ 1,
		/* end= */ 6,
		Spanned.SPAN_INCLUSIVE_EXCLUSIVE
		);
		mSpannedText.setSpan(
		new ForegroundColorSpan(Color.LTGRAY),
		/* start= */ 8,
		/* end= */ 11,
		Spanned.SPAN_INCLUSIVE_EXCLUSIVE
		);
		Layout layout = new StaticLayout(mSpannedText, mTextPaint, mWidth,
		mAlign, mSpacingMult, mSpacingAdd, /* includePad= */ false);

		final int width = 256;
		final int height = 256;
		MockCanvas c = new MockCanvas(width, height);
		c.setHighContrastTextEnabled(true);
		layout.draw(
		c,
		/* highlightPaths= */ null,
		/* highlightPaints= */ null,
		/* selectionPath= */ null,
		/* selectionPaint= */ null,
		/* cursorOffsetVertical= */ 0
		);
		List<MockCanvas.DrawCommand> drawCommands = c.getDrawCommands();
		var highlightsDrawn = 0;
		var numColorChangesWithinOneLine = 1;
		var textsDrawn = STATIC_LINE_COUNT + numColorChangesWithinOneLine;
		var backgroundRectsDrawn = STATIC_LINE_COUNT + numColorChangesWithinOneLine;
		expect.withMessage("wrong number of drawCommands: " + drawCommands)
		.that(drawCommands.size())
		.isEqualTo(textsDrawn + backgroundRectsDrawn + highlightsDrawn);

		var backgroundCommands = drawCommands.stream()
		.filter(it -> it.rect != null)
		.toList();

		expect.that(backgroundCommands.get(0).paint.getColor()).isEqualTo(Color.BLACK);
		expect.that(backgroundCommands.get(1).paint.getColor()).isEqualTo(Color.WHITE);
		expect.that(backgroundCommands.get(2).paint.getColor()).isEqualTo(Color.WHITE);
		expect.that(backgroundCommands.get(3).paint.getColor()).isEqualTo(Color.WHITE);
		expect.that(backgroundCommands.get(4).paint.getColor()).isEqualTo(Color.WHITE);
		expect.that(backgroundCommands.get(5).paint.getColor()).isEqualTo(Color.BLACK);
		expect.that(backgroundCommands.get(6).paint.getColor()).isEqualTo(Color.BLACK);
		expect.that(backgroundCommands.get(7).paint.getColor()).isEqualTo(Color.BLACK);
		expect.that(backgroundCommands.get(8).paint.getColor()).isEqualTo(Color.BLACK);
		expect.that(backgroundCommands.get(9).paint.getColor()).isEqualTo(Color.BLACK);

		expect.that(backgroundCommands.size()).isEqualTo(backgroundRectsDrawn);
		}

		private static final class MockCanvas extends Canvas {

		static class DrawCommand {

core/tests/coretests/src/android/text/SpanColorsTest.java

0 → 100644

+78 −0

Original line number	Diff line number	Diff line
		/*
		* Copyright (C) 2024 The Android Open Source Project
		*
		* Licensed under the Apache License, Version 2.0 (the "License");
		* you may not use this file except in compliance with the License.
		* You may obtain a copy of the License at
		*
		* http://www.apache.org/licenses/LICENSE-2.0
		*
		* Unless required by applicable law or agreed to in writing, software
		* distributed under the License is distributed on an "AS IS" BASIS,
		* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
		* See the License for the specific language governing permissions and
		* limitations under the License.
		*/

		package android.text;

		import static com.google.common.truth.Truth.assertThat;

		import android.graphics.Color;
		import android.graphics.drawable.ShapeDrawable;
		import android.platform.test.annotations.Presubmit;
		import android.text.style.ForegroundColorSpan;
		import android.text.style.ImageSpan;
		import android.text.style.UnderlineSpan;

		import androidx.test.filters.SmallTest;
		import androidx.test.runner.AndroidJUnit4;

		import org.junit.Before;
		import org.junit.Test;
		import org.junit.runner.RunWith;

		@Presubmit
		@SmallTest
		@RunWith(AndroidJUnit4.class)
		public class SpanColorsTest {
		private final TextPaint mWorkPaint = new TextPaint();
		private SpanColors mSpanColors;
		private SpannableString mSpannedText;

		@Before
		public void setup() {
		mSpanColors = new SpanColors();
		mSpannedText = new SpannableString("Hello world! This is a test.");
		mSpannedText.setSpan(new ForegroundColorSpan(Color.RED), 0, 4,
		Spanned.SPAN_INCLUSIVE_EXCLUSIVE);
		mSpannedText.setSpan(new ForegroundColorSpan(Color.GREEN), 6, 11,
		Spanned.SPAN_INCLUSIVE_EXCLUSIVE);
		mSpannedText.setSpan(new UnderlineSpan(), 5, 10, Spanned.SPAN_INCLUSIVE_EXCLUSIVE);
		mSpannedText.setSpan(new ImageSpan(new ShapeDrawable()), 1, 2,
		Spanned.SPAN_EXCLUSIVE_EXCLUSIVE);
		mSpannedText.setSpan(new ForegroundColorSpan(Color.BLUE), 12, 16,
		Spanned.SPAN_INCLUSIVE_EXCLUSIVE);
		}

		@Test
		public void testNoColorFound() {
		mSpanColors.init(mWorkPaint, mSpannedText, 25, 30); // Beyond the spans
		assertThat(mSpanColors.getColorAt(27)).isEqualTo(SpanColors.NO_COLOR_FOUND);
		}

		@Test
		public void testSingleColorSpan() {
		mSpanColors.init(mWorkPaint, mSpannedText, 1, 4);
		assertThat(mSpanColors.getColorAt(3)).isEqualTo(Color.RED);
		}

		@Test
		public void testMultipleColorSpans() {
		mSpanColors.init(mWorkPaint, mSpannedText, 0, mSpannedText.length());
		assertThat(mSpanColors.getColorAt(2)).isEqualTo(Color.RED);
		assertThat(mSpanColors.getColorAt(5)).isEqualTo(SpanColors.NO_COLOR_FOUND);
		assertThat(mSpanColors.getColorAt(8)).isEqualTo(Color.GREEN);
		assertThat(mSpanColors.getColorAt(13)).isEqualTo(Color.BLUE);
		}
		}