15c4dd610eace399c47eb0418d617aa05701f9ab9Chris Banes/* 25c4dd610eace399c47eb0418d617aa05701f9ab9Chris Banes * Copyright (C) 2017 The Android Open Source Project 35c4dd610eace399c47eb0418d617aa05701f9ab9Chris Banes * 45c4dd610eace399c47eb0418d617aa05701f9ab9Chris Banes * Licensed under the Apache License, Version 2.0 (the "License"); 55c4dd610eace399c47eb0418d617aa05701f9ab9Chris Banes * you may not use this file except in compliance with the License. 65c4dd610eace399c47eb0418d617aa05701f9ab9Chris Banes * You may obtain a copy of the License at 75c4dd610eace399c47eb0418d617aa05701f9ab9Chris Banes * 85c4dd610eace399c47eb0418d617aa05701f9ab9Chris Banes * http://www.apache.org/licenses/LICENSE-2.0 95c4dd610eace399c47eb0418d617aa05701f9ab9Chris Banes * 105c4dd610eace399c47eb0418d617aa05701f9ab9Chris Banes * Unless required by applicable law or agreed to in writing, software 115c4dd610eace399c47eb0418d617aa05701f9ab9Chris Banes * distributed under the License is distributed on an "AS IS" BASIS, 125c4dd610eace399c47eb0418d617aa05701f9ab9Chris Banes * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 135c4dd610eace399c47eb0418d617aa05701f9ab9Chris Banes * See the License for the specific language governing permissions and 145c4dd610eace399c47eb0418d617aa05701f9ab9Chris Banes * limitations under the License. 155c4dd610eace399c47eb0418d617aa05701f9ab9Chris Banes */ 165c4dd610eace399c47eb0418d617aa05701f9ab9Chris Banes 17ac5fe7c617c66850fff75a9fce9979c6e5674b0fAurimas Liutikaspackage androidx.core.graphics; 185c4dd610eace399c47eb0418d617aa05701f9ab9Chris Banes 195c4dd610eace399c47eb0418d617aa05701f9ab9Chris Banesimport android.graphics.Paint; 2077baef49563f9910641a797d9a9b8dd01c807564Aurimas Liutikasimport android.graphics.Rect; 215c4dd610eace399c47eb0418d617aa05701f9ab9Chris Banesimport android.os.Build; 229dede51868bbbe16aadcd65e04860bea8ea50e05Aurimas Liutikas 23ac5fe7c617c66850fff75a9fce9979c6e5674b0fAurimas Liutikasimport androidx.annotation.NonNull; 24ac5fe7c617c66850fff75a9fce9979c6e5674b0fAurimas Liutikasimport androidx.core.util.Pair; 255c4dd610eace399c47eb0418d617aa05701f9ab9Chris Banes 265c4dd610eace399c47eb0418d617aa05701f9ab9Chris Banes/** 27645e5c8aa6b31961c5f73f3d30bb5261d5e04aebKirill Grouchnikov * Helper for accessing features in {@link Paint}. 285c4dd610eace399c47eb0418d617aa05701f9ab9Chris Banes */ 295c4dd610eace399c47eb0418d617aa05701f9ab9Chris Banespublic final class PaintCompat { 3077baef49563f9910641a797d9a9b8dd01c807564Aurimas Liutikas // U+DFFFD which is very end of unassigned plane. 3177baef49563f9910641a797d9a9b8dd01c807564Aurimas Liutikas private static final String TOFU_STRING = "\uDB3F\uDFFD"; 3277baef49563f9910641a797d9a9b8dd01c807564Aurimas Liutikas private static final String EM_STRING = "m"; 3377baef49563f9910641a797d9a9b8dd01c807564Aurimas Liutikas 3477baef49563f9910641a797d9a9b8dd01c807564Aurimas Liutikas private static final ThreadLocal<Pair<Rect, Rect>> sRectThreadLocal = new ThreadLocal<>(); 355c4dd610eace399c47eb0418d617aa05701f9ab9Chris Banes 365c4dd610eace399c47eb0418d617aa05701f9ab9Chris Banes /** 375c4dd610eace399c47eb0418d617aa05701f9ab9Chris Banes * Determine whether the typeface set on the paint has a glyph supporting the 385c4dd610eace399c47eb0418d617aa05701f9ab9Chris Banes * string in a backwards compatible way. 395c4dd610eace399c47eb0418d617aa05701f9ab9Chris Banes * 405c4dd610eace399c47eb0418d617aa05701f9ab9Chris Banes * @param paint the paint instance to check 415c4dd610eace399c47eb0418d617aa05701f9ab9Chris Banes * @param string the string to test whether there is glyph support 425c4dd610eace399c47eb0418d617aa05701f9ab9Chris Banes * @return true if the typeface set on the given paint has a glyph for the string 435c4dd610eace399c47eb0418d617aa05701f9ab9Chris Banes */ 445c4dd610eace399c47eb0418d617aa05701f9ab9Chris Banes public static boolean hasGlyph(@NonNull Paint paint, @NonNull String string) { 455c4dd610eace399c47eb0418d617aa05701f9ab9Chris Banes if (Build.VERSION.SDK_INT >= 23) { 467347bef5c2512cbd809773a0cb5f247c23b3392dAurimas Liutikas return paint.hasGlyph(string); 475c4dd610eace399c47eb0418d617aa05701f9ab9Chris Banes } 4877baef49563f9910641a797d9a9b8dd01c807564Aurimas Liutikas final int length = string.length(); 4977baef49563f9910641a797d9a9b8dd01c807564Aurimas Liutikas 5077baef49563f9910641a797d9a9b8dd01c807564Aurimas Liutikas if (length == 1 && Character.isWhitespace(string.charAt(0))) { 5177baef49563f9910641a797d9a9b8dd01c807564Aurimas Liutikas // measureText + getTextBounds skips whitespace so we need to special case it here 5277baef49563f9910641a797d9a9b8dd01c807564Aurimas Liutikas return true; 5377baef49563f9910641a797d9a9b8dd01c807564Aurimas Liutikas } 5477baef49563f9910641a797d9a9b8dd01c807564Aurimas Liutikas 5577baef49563f9910641a797d9a9b8dd01c807564Aurimas Liutikas final float missingGlyphWidth = paint.measureText(TOFU_STRING); 5677baef49563f9910641a797d9a9b8dd01c807564Aurimas Liutikas final float emGlyphWidth = paint.measureText(EM_STRING); 5777baef49563f9910641a797d9a9b8dd01c807564Aurimas Liutikas 5877baef49563f9910641a797d9a9b8dd01c807564Aurimas Liutikas final float width = paint.measureText(string); 5977baef49563f9910641a797d9a9b8dd01c807564Aurimas Liutikas 6077baef49563f9910641a797d9a9b8dd01c807564Aurimas Liutikas if (width == 0f) { 6177baef49563f9910641a797d9a9b8dd01c807564Aurimas Liutikas // If the string width is 0, it can't be rendered 6277baef49563f9910641a797d9a9b8dd01c807564Aurimas Liutikas return false; 6377baef49563f9910641a797d9a9b8dd01c807564Aurimas Liutikas } 6477baef49563f9910641a797d9a9b8dd01c807564Aurimas Liutikas 6577baef49563f9910641a797d9a9b8dd01c807564Aurimas Liutikas if (string.codePointCount(0, string.length()) > 1) { 6677baef49563f9910641a797d9a9b8dd01c807564Aurimas Liutikas // Heuristic to detect fallback glyphs for ligatures like flags and ZWJ sequences 6777baef49563f9910641a797d9a9b8dd01c807564Aurimas Liutikas // Return false if string is rendered too widely 6877baef49563f9910641a797d9a9b8dd01c807564Aurimas Liutikas if (width > 2 * emGlyphWidth) { 6977baef49563f9910641a797d9a9b8dd01c807564Aurimas Liutikas return false; 7077baef49563f9910641a797d9a9b8dd01c807564Aurimas Liutikas } 7177baef49563f9910641a797d9a9b8dd01c807564Aurimas Liutikas 7277baef49563f9910641a797d9a9b8dd01c807564Aurimas Liutikas // Heuristic to detect fallback glyphs for ligatures like flags and ZWJ sequences (2). 7377baef49563f9910641a797d9a9b8dd01c807564Aurimas Liutikas // If width is greater than or equal to the sum of width of each code point, it is very 7477baef49563f9910641a797d9a9b8dd01c807564Aurimas Liutikas // likely that the system is using fallback fonts to draw {@code string} in two or more 7577baef49563f9910641a797d9a9b8dd01c807564Aurimas Liutikas // glyphs instead of a single ligature glyph. (hasGlyph returns false in this case.) 7677baef49563f9910641a797d9a9b8dd01c807564Aurimas Liutikas // False detections are possible (the ligature glyph may happen to have the same width 7777baef49563f9910641a797d9a9b8dd01c807564Aurimas Liutikas // as the sum width), but there are no good way to avoid them. 7877baef49563f9910641a797d9a9b8dd01c807564Aurimas Liutikas // NOTE: This heuristic does not work with proportional glyphs. 7977baef49563f9910641a797d9a9b8dd01c807564Aurimas Liutikas // NOTE: This heuristic does not work when a ZWJ sequence is partially combined. 8077baef49563f9910641a797d9a9b8dd01c807564Aurimas Liutikas // E.g. If system has a glyph for "A ZWJ B" and not for "A ZWJ B ZWJ C", this heuristic 8177baef49563f9910641a797d9a9b8dd01c807564Aurimas Liutikas // returns true for "A ZWJ B ZWJ C". 8277baef49563f9910641a797d9a9b8dd01c807564Aurimas Liutikas float sumWidth = 0; 8377baef49563f9910641a797d9a9b8dd01c807564Aurimas Liutikas int i = 0; 8477baef49563f9910641a797d9a9b8dd01c807564Aurimas Liutikas while (i < length) { 8577baef49563f9910641a797d9a9b8dd01c807564Aurimas Liutikas int charCount = Character.charCount(string.codePointAt(i)); 8677baef49563f9910641a797d9a9b8dd01c807564Aurimas Liutikas sumWidth += paint.measureText(string, i, i + charCount); 8777baef49563f9910641a797d9a9b8dd01c807564Aurimas Liutikas i += charCount; 8877baef49563f9910641a797d9a9b8dd01c807564Aurimas Liutikas } 8977baef49563f9910641a797d9a9b8dd01c807564Aurimas Liutikas if (width >= sumWidth) { 9077baef49563f9910641a797d9a9b8dd01c807564Aurimas Liutikas return false; 9177baef49563f9910641a797d9a9b8dd01c807564Aurimas Liutikas } 9277baef49563f9910641a797d9a9b8dd01c807564Aurimas Liutikas } 9377baef49563f9910641a797d9a9b8dd01c807564Aurimas Liutikas 9477baef49563f9910641a797d9a9b8dd01c807564Aurimas Liutikas if (width != missingGlyphWidth) { 9577baef49563f9910641a797d9a9b8dd01c807564Aurimas Liutikas // If the widths are different then its not tofu 9677baef49563f9910641a797d9a9b8dd01c807564Aurimas Liutikas return true; 9777baef49563f9910641a797d9a9b8dd01c807564Aurimas Liutikas } 9877baef49563f9910641a797d9a9b8dd01c807564Aurimas Liutikas 9977baef49563f9910641a797d9a9b8dd01c807564Aurimas Liutikas // If the widths are the same, lets check the bounds. The chance of them being 10077baef49563f9910641a797d9a9b8dd01c807564Aurimas Liutikas // different chars with the same bounds is extremely small 10177baef49563f9910641a797d9a9b8dd01c807564Aurimas Liutikas final Pair<Rect, Rect> rects = obtainEmptyRects(); 10277baef49563f9910641a797d9a9b8dd01c807564Aurimas Liutikas paint.getTextBounds(TOFU_STRING, 0, TOFU_STRING.length(), rects.first); 10377baef49563f9910641a797d9a9b8dd01c807564Aurimas Liutikas paint.getTextBounds(string, 0, length, rects.second); 10477baef49563f9910641a797d9a9b8dd01c807564Aurimas Liutikas return !rects.first.equals(rects.second); 10577baef49563f9910641a797d9a9b8dd01c807564Aurimas Liutikas } 10677baef49563f9910641a797d9a9b8dd01c807564Aurimas Liutikas 10777baef49563f9910641a797d9a9b8dd01c807564Aurimas Liutikas private static Pair<Rect, Rect> obtainEmptyRects() { 10877baef49563f9910641a797d9a9b8dd01c807564Aurimas Liutikas Pair<Rect, Rect> rects = sRectThreadLocal.get(); 10977baef49563f9910641a797d9a9b8dd01c807564Aurimas Liutikas if (rects == null) { 11077baef49563f9910641a797d9a9b8dd01c807564Aurimas Liutikas rects = new Pair<>(new Rect(), new Rect()); 11177baef49563f9910641a797d9a9b8dd01c807564Aurimas Liutikas sRectThreadLocal.set(rects); 11277baef49563f9910641a797d9a9b8dd01c807564Aurimas Liutikas } else { 11377baef49563f9910641a797d9a9b8dd01c807564Aurimas Liutikas rects.first.setEmpty(); 11477baef49563f9910641a797d9a9b8dd01c807564Aurimas Liutikas rects.second.setEmpty(); 11577baef49563f9910641a797d9a9b8dd01c807564Aurimas Liutikas } 11677baef49563f9910641a797d9a9b8dd01c807564Aurimas Liutikas return rects; 1175c4dd610eace399c47eb0418d617aa05701f9ab9Chris Banes } 1185c4dd610eace399c47eb0418d617aa05701f9ab9Chris Banes 1195c4dd610eace399c47eb0418d617aa05701f9ab9Chris Banes private PaintCompat() {} 1205c4dd610eace399c47eb0418d617aa05701f9ab9Chris Banes} 121