Add a way to use fonts installed on the system (#898)

## Proposed Changes

- Add `SystemFont` class to be able to use fonts installed on the
system.

## API Change

```diff
+androidx.compose.ui.text.platform.SystemFont
```

## Testing

Usage looks like this:
```kt
FontFamily(SystemFont("Menlo")),
FontFamily(SystemFont("Times New Roman", FontWeight.Bold)),
FontFamily(SystemFont("Webdings")),
```
<img width="1003" alt="Screenshot 2023-11-09 at 12 18 02"
src="https://github.com/JetBrains/compose-multiplatform-core/assets/1836384/0c36d4aa-6bc9-47e2-94dd-edb09fd242ac">

compose/ui/ui-text/api/desktop/ui-text.api

@@ -1384,6 +1384,16 @@ public final class androidx/compose/ui/text/platform/SkiaParagraph_skikoKt {
 	public static final fun toSkPlaceholderAlignment-do9X-Gg (I)Lorg/jetbrains/skia/paragraph/PlaceholderAlignment;
 }
 
+public final class androidx/compose/ui/text/platform/SystemFont : androidx/compose/ui/text/platform/PlatformFont {
+	public static final field $stable I
+	public synthetic fun <init> (Ljava/lang/String;Landroidx/compose/ui/text/font/FontWeight;IILkotlin/jvm/internal/DefaultConstructorMarker;)V
+	public synthetic fun <init> (Ljava/lang/String;Landroidx/compose/ui/text/font/FontWeight;ILkotlin/jvm/internal/DefaultConstructorMarker;)V
+	public fun getIdentity ()Ljava/lang/String;
+	public fun getStyle-_-LCdwA ()I
+	public fun getWeight ()Landroidx/compose/ui/text/font/FontWeight;
+	public fun toString ()Ljava/lang/String;
+}
+
 public final class androidx/compose/ui/text/style/BaselineShift {
 	public static final field Companion Landroidx/compose/ui/text/style/BaselineShift$Companion;
 	public static final synthetic fun box-impl (F)Landroidx/compose/ui/text/style/BaselineShift;

compose/ui/ui-text/src/desktopMain/kotlin/androidx/compose/ui/text/platform/DesktopFont.desktop.kt

@@ -16,12 +16,13 @@
 package androidx.compose.ui.text.platform
 
 import org.jetbrains.skia.Typeface as SkTypeface
+import org.jetbrains.skia.FontStyle as SkFontStyle
 import androidx.compose.ui.text.ExperimentalTextApi
 import androidx.compose.ui.text.font.*
-import androidx.compose.ui.util.fastForEach
 import java.io.File
-import java.security.MessageDigest
 import org.jetbrains.skia.Data
+import org.jetbrains.skia.FontSlant
+import org.jetbrains.skia.FontWidth
 import org.jetbrains.skia.makeFromFile
 
 actual sealed class PlatformFont : Font {
@@ -163,6 +164,7 @@ internal actual fun loadTypeface(font: Font): SkTypeface {
         is ResourceFont -> typefaceResource(font.name)
         is FileFont -> SkTypeface.makeFromFile(font.file.toString())
         is LoadedFont -> SkTypeface.makeFromData(Data.makeFromBytes(font.data))
+        is SystemFont -> SkTypeface.makeFromName(font.identity, font.skFontStyle)
     }
 }
 
@@ -176,6 +178,12 @@ private fun typefaceResource(resourceName: String): SkTypeface {
     return SkTypeface.makeFromData(Data.makeFromBytes(bytes))
 }
 
+private val Font.skFontStyle: SkFontStyle get() = SkFontStyle(
+    weight = weight.weight,
+    width = FontWidth.NORMAL,
+    slant = if (style == FontStyle.Italic) FontSlant.ITALIC else FontSlant.UPRIGHT
+)
+
 internal actual fun currentPlatform(): Platform {
     val name = System.getProperty("os.name")
     return when {

compose/ui/ui-text/src/desktopTest/kotlin/androidx/compose/ui/text/DesktopFontTest.kt

@@ -21,8 +21,8 @@ import androidx.compose.ui.text.font.FontFamily
 import androidx.compose.ui.text.font.FontStyle
 import androidx.compose.ui.text.font.SkiaFontLoader
 import androidx.compose.ui.text.platform.Font
-import androidx.compose.ui.text.platform.GenericFontFamiliesMapping
 import androidx.compose.ui.text.platform.Typeface
+import androidx.compose.ui.text.platform.aliases
 import com.google.common.truth.Truth
 import org.jetbrains.skia.Data
 import org.jetbrains.skia.Typeface
@@ -66,10 +66,10 @@ class DesktopFontTest {
     @Test
     fun ensureRegistered() {
         Truth.assertThat(fontLoader.loadPlatformTypes(FontFamily.Cursive).aliases)
-            .isEqualTo(GenericFontFamiliesMapping[FontFamily.Cursive.name])
+            .isEqualTo(FontFamily.Cursive.aliases)
 
         Truth.assertThat(fontLoader.loadPlatformTypes(FontFamily.Default).aliases)
-            .isEqualTo(GenericFontFamiliesMapping[FontFamily.SansSerif.name])
+            .isEqualTo(FontFamily.SansSerif.aliases)
 
         Truth.assertThat(fontLoader.loadPlatformTypes(loadedFontFamily).aliases)
             .isEqualTo(listOf("Sample Font"))

compose/ui/ui-text/src/skikoMain/kotlin/androidx/compose/ui/text/platform/PlatformFont.skiko.kt

@@ -19,9 +19,17 @@ import org.jetbrains.skia.Typeface as SkTypeface
 import androidx.compose.ui.text.Cache
 import androidx.compose.ui.text.ExperimentalTextApi
 import androidx.compose.ui.text.ExpireAfterAccessCache
-import androidx.compose.ui.text.WeakKeysCache
-import androidx.compose.ui.text.font.*
+import androidx.compose.ui.text.font.DefaultFontFamily
+import androidx.compose.ui.text.font.Font
+import androidx.compose.ui.text.font.FontFamily
+import androidx.compose.ui.text.font.FontListFontFamily
+import androidx.compose.ui.text.font.FontLoadingStrategy
+import androidx.compose.ui.text.font.FontStyle
+import androidx.compose.ui.text.font.FontWeight
+import androidx.compose.ui.text.font.GenericFontFamily
+import androidx.compose.ui.text.font.LoadedFontFamily
 import androidx.compose.ui.text.font.Typeface
+import androidx.compose.ui.text.font.createFontFamilyResolver
 import org.jetbrains.skia.FontMgr
 import org.jetbrains.skia.paragraph.FontCollection
 import org.jetbrains.skia.paragraph.TypefaceFontProvider
@@ -31,6 +39,20 @@ expect sealed class PlatformFont() : Font {
     internal val cacheKey: String
 }
 
+/**
+ * A Font that already installed in system.
+ */
+@ExperimentalTextApi
+class SystemFont(
+    override val identity: String,
+    override val weight: FontWeight = FontWeight.Normal,
+    override val style: FontStyle = FontStyle.Normal
+) : PlatformFont() {
+    override fun toString(): String {
+        return "SystemInstalledFont(identity='$identity', weight=$weight, style=$style)"
+    }
+}
+
 /**
  * Defines a Font using byte array with loaded font data.
  *
@@ -91,10 +113,11 @@ fun Font(
     style: FontStyle = FontStyle.Normal
 ): Font = LoadedFont(identity, data, weight, style)
 
-internal class SkiaBackedTypeface(
-    val alias: String?,
+private class SkiaBackedTypeface(
+    alias: String?,
     val nativeTypeface: SkTypeface
 ) : Typeface {
+    val alias = alias ?: nativeTypeface.familyName
     override val fontFamily: FontFamily? = null
 }
 
@@ -150,11 +173,6 @@ internal class FontCache {
         fonts.setAssetFontManager(fontProvider)
     }
 
-    private fun mapGenericFontFamily(generic: GenericFontFamily): List<String> {
-        return GenericFontFamiliesMapping[generic.name]
-            ?: error("Unknown generic font family ${generic.name}")
-    }
-
     internal fun load(font: PlatformFont): FontLoadResult {
         val typeface = typefacesCache.get(font.cacheKey) {
             loadTypeface(font)
@@ -183,19 +201,23 @@ internal class FontCache {
     private fun ensureRegistered(fontFamily: FontFamily): List<String> =
         when (fontFamily) {
             is FontListFontFamily -> {
-                // not supported
-                throw IllegalArgumentException(
-                    "Don't load FontListFontFamily through ensureRegistered: $fontFamily"
-                )
+                val fonts = fontFamily.fonts.filterIsInstance<SystemFont>()
+                if (fonts.size == fontFamily.fonts.size) {
+                    fonts.map { it.identity }
+                } else {
+                    // not supported
+                    throw IllegalArgumentException(
+                        "Don't load FontListFontFamily through ensureRegistered: $fontFamily"
+                    )
+                }
             }
             is LoadedFontFamily -> {
                 val typeface = fontFamily.typeface as SkiaBackedTypeface
-                val alias = typeface.alias ?: typeface.nativeTypeface.familyName
-                ensureRegistered(typeface.nativeTypeface, alias)
-                listOf(alias)
+                ensureRegistered(typeface.nativeTypeface, typeface.alias)
+                listOf(typeface.alias)
             }
-            is GenericFontFamily -> mapGenericFontFamily(fontFamily)
-            FontFamily.Default -> mapGenericFontFamily(FontFamily.SansSerif)
+            is GenericFontFamily -> fontFamily.aliases
+            is DefaultFontFamily -> FontFamily.SansSerif.aliases
             else -> throw IllegalArgumentException("Unknown font family type: $fontFamily")
         }
 }
@@ -214,7 +236,11 @@ internal enum class Platform {
 internal expect fun currentPlatform(): Platform
 internal expect fun loadTypeface(font: Font): SkTypeface
 
-internal val GenericFontFamiliesMapping: Map<String, List<String>> by lazy {
+internal val GenericFontFamily.aliases
+    get() = GenericFontFamiliesMapping[name]
+        ?: error("Unknown generic font family $name")
+
+private val GenericFontFamiliesMapping: Map<String, List<String>> by lazy {
     when (currentPlatform()) {
         Platform.Linux ->
             mapOf(