| /* |
| * Copyright 2018 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 androidx.ui.text.font |
| |
| /** |
| * Given a [FontFamily], [FontWeight] and [FontStyle], matches the best font in the [FontFamily] |
| * that satisfies the requirements of [FontWeight] and [FontStyle]. |
| * |
| * For the case without font synthesis, applies the rules at |
| * [CSS 4 Font Matching](https://www.w3.org/TR/css-fonts-4/#font-style-matching). |
| */ |
| internal open class FontMatcher { |
| |
| /** |
| * Given a [FontFamily], [FontWeight] and [FontStyle], matches the best font in the |
| * [FontFamily] that satisfies the requirements of [FontWeight] and [FontStyle]. If there is |
| * not a font that exactly satisfies the given constraints of [FontWeight] and [FontStyle], the |
| * best match will be returned. The rules for the best match are defined in |
| * [CSS 4 Font Matching](https://www.w3.org/TR/css-fonts-4/#font-style-matching). |
| * |
| * @param fontList iterable of fonts to choose the [Font] from |
| * @param fontWeight desired [FontWeight] |
| * @param fontStyle desired [FontStyle] |
| */ |
| open fun matchFont( |
| fontList: Iterable<Font>, |
| fontWeight: FontWeight, |
| fontStyle: FontStyle |
| ): Font { |
| // check for exact match first |
| fontList.filter { it.weight == fontWeight && it.style == fontStyle }.let { |
| // TODO(b/130797349): IR compiler bug was here |
| if (it.isNotEmpty()) { |
| return it[0] |
| } |
| } |
| |
| // if no exact match, filter with style |
| val fonts = fontList.filter { it.style == fontStyle }.let { |
| if (it.isNotEmpty()) it else fontList |
| } |
| |
| val result = if (fontWeight < FontWeight.W400) { |
| // If the desired weight is less than 400 |
| // - weights less than or equal to the desired weight are checked in descending order |
| // - followed by weights above the desired weight in ascending order |
| fonts.filter { it.weight <= fontWeight }.maxByOrNull { it.weight } |
| ?: fonts.filter { it.weight > fontWeight }.minByOrNull { it.weight } |
| } else if (fontWeight > FontWeight.W500) { |
| // If the desired weight is greater than 500 |
| // - weights greater than or equal to the desired weight are checked in ascending order |
| // - followed by weights below the desired weight in descending order |
| fonts.filter { it.weight >= fontWeight }.minByOrNull { it.weight } |
| ?: fonts.filter { it.weight < fontWeight }.maxByOrNull { it.weight } |
| } else { |
| // If the desired weight is inclusively between 400 and 500 |
| // - weights greater than or equal to the target weight are checked in ascending order |
| // until 500 is hit and checked, |
| // - followed by weights less than the target weight in descending order, |
| // - followed by weights greater than 500 |
| fonts.filter { it.weight >= fontWeight && it.weight <= FontWeight.W500 } |
| .minByOrNull { it.weight } |
| ?: fonts.filter { it.weight < fontWeight }.maxByOrNull { it.weight } |
| ?: fonts.filter { it.weight > FontWeight.W500 }.minByOrNull { it.weight } |
| } |
| |
| return result ?: throw IllegalStateException("Cannot match any font") |
| } |
| } |