1 /* 2 * Copyright (C) 2023 The Android Open Source Project 3 * 4 * Licensed under the Apache License, Version 2.0 (the "License"); 5 * you may not use this file except in compliance with the License. 6 * You may obtain a copy of the License at 7 * 8 * http://www.apache.org/licenses/LICENSE-2.0 9 * 10 * Unless required by applicable law or agreed to in writing, software 11 * distributed under the License is distributed on an "AS IS" BASIS, 12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 13 * See the License for the specific language governing permissions and 14 * limitations under the License. 15 */ 16 17 package android.content.res; 18 19 20 import android.annotation.AnyThread; 21 import android.annotation.FlaggedApi; 22 import android.annotation.Nullable; 23 import android.ravenwood.annotation.RavenwoodKeepWholeClass; 24 25 /** 26 * A converter for non-linear font scaling. Converts font sizes given in "sp" dimensions to a 27 * "dp" dimension according to a non-linear curve. 28 * 29 * <p>This is meant to improve readability at larger font scales: larger fonts will scale up more 30 * slowly than smaller fonts, so we don't get ridiculously huge fonts that don't fit on the screen. 31 * 32 * <p>The thinking here is that large fonts are already big enough to read, but we still want to 33 * scale them slightly to preserve the visual hierarchy when compared to smaller fonts. 34 */ 35 @FlaggedApi(Flags.FLAG_FONT_SCALE_CONVERTER_PUBLIC) 36 @RavenwoodKeepWholeClass 37 public interface FontScaleConverter { 38 /** 39 * Converts a dimension in "sp" to "dp". 40 */ convertSpToDp(float sp)41 float convertSpToDp(float sp); 42 43 /** 44 * Converts a dimension in "dp" back to "sp". 45 */ convertDpToSp(float dp)46 float convertDpToSp(float dp); 47 48 /** 49 * Returns true if non-linear font scaling curves would be in effect for the given scale, false 50 * if the scaling would follow a linear curve or for no scaling. 51 * 52 * <p>Example usage: {@code 53 * isNonLinearFontScalingActive(getResources().getConfiguration().fontScale)} 54 */ 55 @AnyThread isNonLinearFontScalingActive(float fontScale)56 static boolean isNonLinearFontScalingActive(float fontScale) { 57 return FontScaleConverterFactory.isNonLinearFontScalingActive(fontScale); 58 } 59 60 /** 61 * Finds a matching FontScaleConverter for the given fontScale factor. 62 * 63 * Generally you shouldn't need this; you can use {@link 64 * android.util.TypedValue#applyDimension(int, float, DisplayMetrics)} directly and it will do 65 * the scaling conversion for you. Dimens and resources loaded from XML will also be 66 * automatically converted. But for UI frameworks or other situations where you need to do the 67 * conversion without an Android Context, you can use this method. 68 * 69 * @param fontScale the scale factor, usually from {@link Configuration#fontScale}. 70 * 71 * @return a converter for the given scale, or null if non-linear scaling should not be used. 72 */ 73 @Nullable 74 @AnyThread forScale(float fontScale)75 static FontScaleConverter forScale(float fontScale) { 76 return FontScaleConverterFactory.forScale(fontScale); 77 } 78 } 79