feat(compose): add a font family picker with bundled open-source fonts

Bundle four SIL OFL 1.1 fonts in res/font (no build-time downloads, F-Droid
safe): Inter, Lora, and JetBrains Mono as weight-variable TTFs plus a static
Merriweather Regular cut (its variable font is 4.4 MB) — ~1.5 MB total. Each
family's OFL license text is committed under THIRD_PARTY_LICENSES/, and *.ttf/
*.otf are marked binary in .gitattributes so the bytes commit intact.

Add FontRegistry: display name <-> email-safe CSS stack <-> Compose FontFamily,
with three generic Sans/Serif/Monospace entries that need no bundled file. Each
bundled stack names the family first then falls back to a generic (e.g.
'Lora', Georgia, serif), so a recipient whose client lacks the face still gets
a sensible one. resolveFontFamily maps a stored CSS stack back to a FontFamily
for in-editor rendering, and is now passed into RichTextBodyField from
ComposeScreen so styled runs actually render in their font.

Add FontPicker (ui/compose/format): a toolbar dropdown applying
RichStyle.FontFamily(css) via the generalized applyStyle/clearStyle path, with a
leading "Default" entry that clears it; each menu entry previews itself in its
own face. Appended at the END of the toolbar (with the size/alignment controls),
after the block and link buttons — per the #73/#76 lesson, nothing may shift the
bullet/numbered/quote buttons that the compose E2E taps without scrolling.

Tests: FontRegistryTest (JVM) proves every CSS stack survives an html
round-trip, the resolver maps known/unknown stacks, and bundled stacks end in a
generic fallback; a compile-only FontPickerTest drives the picker in isolation
(default label, current-font label, menu lists every font, picking reports the
css / Default clears).

Closes #72

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

.gitattributes

@@ -9,6 +9,8 @@ gradlew text eol=lf
 
 # Treat these as binary.
 *.jar binary
+*.ttf binary
+*.otf binary
 *.png binary
 *.jpg binary
 *.jpeg binary

THIRD_PARTY_LICENSES/Inter-OFL.txt

@@ -0,0 +1,93 @@
+Copyright 2020 The Inter Project Authors (https://github.com/rsms/inter)
+
+This Font Software is licensed under the SIL Open Font License, Version 1.1.
+This license is copied below, and is also available with a FAQ at:
+https://scripts.sil.org/OFL
+
+
+-----------------------------------------------------------
+SIL OPEN FONT LICENSE Version 1.1 - 26 February 2007
+-----------------------------------------------------------
+
+PREAMBLE
+The goals of the Open Font License (OFL) are to stimulate worldwide
+development of collaborative font projects, to support the font creation
+efforts of academic and linguistic communities, and to provide a free and
+open framework in which fonts may be shared and improved in partnership
+with others.
+
+The OFL allows the licensed fonts to be used, studied, modified and
+redistributed freely as long as they are not sold by themselves. The
+fonts, including any derivative works, can be bundled, embedded, 
+redistributed and/or sold with any software provided that any reserved
+names are not used by derivative works. The fonts and derivatives,
+however, cannot be released under any other type of license. The
+requirement for fonts to remain under this license does not apply
+to any document created using the fonts or their derivatives.
+
+DEFINITIONS
+"Font Software" refers to the set of files released by the Copyright
+Holder(s) under this license and clearly marked as such. This may
+include source files, build scripts and documentation.
+
+"Reserved Font Name" refers to any names specified as such after the
+copyright statement(s).
+
+"Original Version" refers to the collection of Font Software components as
+distributed by the Copyright Holder(s).
+
+"Modified Version" refers to any derivative made by adding to, deleting,
+or substituting -- in part or in whole -- any of the components of the
+Original Version, by changing formats or by porting the Font Software to a
+new environment.
+
+"Author" refers to any designer, engineer, programmer, technical
+writer or other person who contributed to the Font Software.
+
+PERMISSION & CONDITIONS
+Permission is hereby granted, free of charge, to any person obtaining
+a copy of the Font Software, to use, study, copy, merge, embed, modify,
+redistribute, and sell modified and unmodified copies of the Font
+Software, subject to the following conditions:
+
+1) Neither the Font Software nor any of its individual components,
+in Original or Modified Versions, may be sold by itself.
+
+2) Original or Modified Versions of the Font Software may be bundled,
+redistributed and/or sold with any software, provided that each copy
+contains the above copyright notice and this license. These can be
+included either as stand-alone text files, human-readable headers or
+in the appropriate machine-readable metadata fields within text or
+binary files as long as those fields can be easily viewed by the user.
+
+3) No Modified Version of the Font Software may use the Reserved Font
+Name(s) unless explicit written permission is granted by the corresponding
+Copyright Holder. This restriction only applies to the primary font name as
+presented to the users.
+
+4) The name(s) of the Copyright Holder(s) or the Author(s) of the Font
+Software shall not be used to promote, endorse or advertise any
+Modified Version, except to acknowledge the contribution(s) of the
+Copyright Holder(s) and the Author(s) or with their explicit written
+permission.
+
+5) The Font Software, modified or unmodified, in part or in whole,
+must be distributed entirely under this license, and must not be
+distributed under any other license. The requirement for fonts to
+remain under this license does not apply to any document created
+using the Font Software.
+
+TERMINATION
+This license becomes null and void if any of the above conditions are
+not met.
+
+DISCLAIMER
+THE FONT SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
+EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTIES OF
+MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT
+OF COPYRIGHT, PATENT, TRADEMARK, OR OTHER RIGHT. IN NO EVENT SHALL THE
+COPYRIGHT HOLDER BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY,
+INCLUDING ANY GENERAL, SPECIAL, INDIRECT, INCIDENTAL, OR CONSEQUENTIAL
+DAMAGES, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
+FROM, OUT OF THE USE OR INABILITY TO USE THE FONT SOFTWARE OR FROM
+OTHER DEALINGS IN THE FONT SOFTWARE.

THIRD_PARTY_LICENSES/JetBrainsMono-OFL.txt

@@ -0,0 +1,93 @@
+Copyright 2020 The JetBrains Mono Project Authors (https://github.com/JetBrains/JetBrainsMono)
+
+This Font Software is licensed under the SIL Open Font License, Version 1.1.
+
+This license is copied below, and is also available with a FAQ at: https://scripts.sil.org/OFL
+
+
+-----------------------------------------------------------
+SIL OPEN FONT LICENSE Version 1.1 - 26 February 2007
+-----------------------------------------------------------
+
+PREAMBLE
+The goals of the Open Font License (OFL) are to stimulate worldwide
+development of collaborative font projects, to support the font creation
+efforts of academic and linguistic communities, and to provide a free and
+open framework in which fonts may be shared and improved in partnership
+with others.
+
+The OFL allows the licensed fonts to be used, studied, modified and
+redistributed freely as long as they are not sold by themselves. The
+fonts, including any derivative works, can be bundled, embedded,
+redistributed and/or sold with any software provided that any reserved
+names are not used by derivative works. The fonts and derivatives,
+however, cannot be released under any other type of license. The
+requirement for fonts to remain under this license does not apply
+to any document created using the fonts or their derivatives.
+
+DEFINITIONS
+"Font Software" refers to the set of files released by the Copyright
+Holder(s) under this license and clearly marked as such. This may
+include source files, build scripts and documentation.
+
+"Reserved Font Name" refers to any names specified as such after the
+copyright statement(s).
+
+"Original Version" refers to the collection of Font Software components as
+distributed by the Copyright Holder(s).
+
+"Modified Version" refers to any derivative made by adding to, deleting,
+or substituting -- in part or in whole -- any of the components of the
+Original Version, by changing formats or by porting the Font Software to a
+new environment.
+
+"Author" refers to any designer, engineer, programmer, technical
+writer or other person who contributed to the Font Software.
+
+PERMISSION & CONDITIONS
+Permission is hereby granted, free of charge, to any person obtaining
+a copy of the Font Software, to use, study, copy, merge, embed, modify,
+redistribute, and sell modified and unmodified copies of the Font
+Software, subject to the following conditions:
+
+1) Neither the Font Software nor any of its individual components,
+in Original or Modified Versions, may be sold by itself.
+
+2) Original or Modified Versions of the Font Software may be bundled,
+redistributed and/or sold with any software, provided that each copy
+contains the above copyright notice and this license. These can be
+included either as stand-alone text files, human-readable headers or
+in the appropriate machine-readable metadata fields within text or
+binary files as long as those fields can be easily viewed by the user.
+
+3) No Modified Version of the Font Software may use the Reserved Font
+Name(s) unless explicit written permission is granted by the corresponding
+Copyright Holder. This restriction only applies to the primary font name as
+presented to the users.
+
+4) The name(s) of the Copyright Holder(s) or the Author(s) of the Font
+Software shall not be used to promote, endorse or advertise any
+Modified Version, except to acknowledge the contribution(s) of the
+Copyright Holder(s) and the Author(s) or with their explicit written
+permission.
+
+5) The Font Software, modified or unmodified, in part or in whole,
+must be distributed entirely under this license, and must not be
+distributed under any other license. The requirement for fonts to
+remain under this license does not apply to any document created
+using the Font Software.
+
+TERMINATION
+This license becomes null and void if any of the above conditions are
+not met.
+
+DISCLAIMER
+THE FONT SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
+EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTIES OF
+MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT
+OF COPYRIGHT, PATENT, TRADEMARK, OR OTHER RIGHT. IN NO EVENT SHALL THE
+COPYRIGHT HOLDER BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY,
+INCLUDING ANY GENERAL, SPECIAL, INDIRECT, INCIDENTAL, OR CONSEQUENTIAL
+DAMAGES, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
+FROM, OUT OF THE USE OR INABILITY TO USE THE FONT SOFTWARE OR FROM
+OTHER DEALINGS IN THE FONT SOFTWARE.

THIRD_PARTY_LICENSES/Lora-OFL.txt

@@ -0,0 +1,93 @@
+Copyright 2011 The Lora Project Authors (https://github.com/cyrealtype/Lora-Cyrillic), with Reserved Font Name "Lora".
+
+This Font Software is licensed under the SIL Open Font License, Version 1.1.
+This license is copied below, and is also available with a FAQ at:
+https://scripts.sil.org/OFL
+
+
+-----------------------------------------------------------
+SIL OPEN FONT LICENSE Version 1.1 - 26 February 2007
+-----------------------------------------------------------
+
+PREAMBLE
+The goals of the Open Font License (OFL) are to stimulate worldwide
+development of collaborative font projects, to support the font creation
+efforts of academic and linguistic communities, and to provide a free and
+open framework in which fonts may be shared and improved in partnership
+with others.
+
+The OFL allows the licensed fonts to be used, studied, modified and
+redistributed freely as long as they are not sold by themselves. The
+fonts, including any derivative works, can be bundled, embedded, 
+redistributed and/or sold with any software provided that any reserved
+names are not used by derivative works. The fonts and derivatives,
+however, cannot be released under any other type of license. The
+requirement for fonts to remain under this license does not apply
+to any document created using the fonts or their derivatives.
+
+DEFINITIONS
+"Font Software" refers to the set of files released by the Copyright
+Holder(s) under this license and clearly marked as such. This may
+include source files, build scripts and documentation.
+
+"Reserved Font Name" refers to any names specified as such after the
+copyright statement(s).
+
+"Original Version" refers to the collection of Font Software components as
+distributed by the Copyright Holder(s).
+
+"Modified Version" refers to any derivative made by adding to, deleting,
+or substituting -- in part or in whole -- any of the components of the
+Original Version, by changing formats or by porting the Font Software to a
+new environment.
+
+"Author" refers to any designer, engineer, programmer, technical
+writer or other person who contributed to the Font Software.
+
+PERMISSION & CONDITIONS
+Permission is hereby granted, free of charge, to any person obtaining
+a copy of the Font Software, to use, study, copy, merge, embed, modify,
+redistribute, and sell modified and unmodified copies of the Font
+Software, subject to the following conditions:
+
+1) Neither the Font Software nor any of its individual components,
+in Original or Modified Versions, may be sold by itself.
+
+2) Original or Modified Versions of the Font Software may be bundled,
+redistributed and/or sold with any software, provided that each copy
+contains the above copyright notice and this license. These can be
+included either as stand-alone text files, human-readable headers or
+in the appropriate machine-readable metadata fields within text or
+binary files as long as those fields can be easily viewed by the user.
+
+3) No Modified Version of the Font Software may use the Reserved Font
+Name(s) unless explicit written permission is granted by the corresponding
+Copyright Holder. This restriction only applies to the primary font name as
+presented to the users.
+
+4) The name(s) of the Copyright Holder(s) or the Author(s) of the Font
+Software shall not be used to promote, endorse or advertise any
+Modified Version, except to acknowledge the contribution(s) of the
+Copyright Holder(s) and the Author(s) or with their explicit written
+permission.
+
+5) The Font Software, modified or unmodified, in part or in whole,
+must be distributed entirely under this license, and must not be
+distributed under any other license. The requirement for fonts to
+remain under this license does not apply to any document created
+using the Font Software.
+
+TERMINATION
+This license becomes null and void if any of the above conditions are
+not met.
+
+DISCLAIMER
+THE FONT SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
+EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTIES OF
+MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT
+OF COPYRIGHT, PATENT, TRADEMARK, OR OTHER RIGHT. IN NO EVENT SHALL THE
+COPYRIGHT HOLDER BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY,
+INCLUDING ANY GENERAL, SPECIAL, INDIRECT, INCIDENTAL, OR CONSEQUENTIAL
+DAMAGES, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
+FROM, OUT OF THE USE OR INABILITY TO USE THE FONT SOFTWARE OR FROM
+OTHER DEALINGS IN THE FONT SOFTWARE.

THIRD_PARTY_LICENSES/Merriweather-OFL.txt

@@ -0,0 +1,93 @@
+Copyright 2020 The Merriweather Project Authors (https://github.com/EbenSorkin/Merriweather4) with Reserved Font Name "Merriweather".
+
+This Font Software is licensed under the SIL Open Font License, Version 1.1.
+This license is copied below, and is also available with a FAQ at:
+https://openfontlicense.org
+
+
+-----------------------------------------------------------
+SIL OPEN FONT LICENSE Version 1.1 - 26 February 2007
+-----------------------------------------------------------
+
+PREAMBLE
+The goals of the Open Font License (OFL) are to stimulate worldwide
+development of collaborative font projects, to support the font creation
+efforts of academic and linguistic communities, and to provide a free and
+open framework in which fonts may be shared and improved in partnership
+with others.
+
+The OFL allows the licensed fonts to be used, studied, modified and
+redistributed freely as long as they are not sold by themselves. The
+fonts, including any derivative works, can be bundled, embedded, 
+redistributed and/or sold with any software provided that any reserved
+names are not used by derivative works. The fonts and derivatives,
+however, cannot be released under any other type of license. The
+requirement for fonts to remain under this license does not apply
+to any document created using the fonts or their derivatives.
+
+DEFINITIONS
+"Font Software" refers to the set of files released by the Copyright
+Holder(s) under this license and clearly marked as such. This may
+include source files, build scripts and documentation.
+
+"Reserved Font Name" refers to any names specified as such after the
+copyright statement(s).
+
+"Original Version" refers to the collection of Font Software components as
+distributed by the Copyright Holder(s).
+
+"Modified Version" refers to any derivative made by adding to, deleting,
+or substituting -- in part or in whole -- any of the components of the
+Original Version, by changing formats or by porting the Font Software to a
+new environment.
+
+"Author" refers to any designer, engineer, programmer, technical
+writer or other person who contributed to the Font Software.
+
+PERMISSION & CONDITIONS
+Permission is hereby granted, free of charge, to any person obtaining
+a copy of the Font Software, to use, study, copy, merge, embed, modify,
+redistribute, and sell modified and unmodified copies of the Font
+Software, subject to the following conditions:
+
+1) Neither the Font Software nor any of its individual components,
+in Original or Modified Versions, may be sold by itself.
+
+2) Original or Modified Versions of the Font Software may be bundled,
+redistributed and/or sold with any software, provided that each copy
+contains the above copyright notice and this license. These can be
+included either as stand-alone text files, human-readable headers or
+in the appropriate machine-readable metadata fields within text or
+binary files as long as those fields can be easily viewed by the user.
+
+3) No Modified Version of the Font Software may use the Reserved Font
+Name(s) unless explicit written permission is granted by the corresponding
+Copyright Holder. This restriction only applies to the primary font name as
+presented to the users.
+
+4) The name(s) of the Copyright Holder(s) or the Author(s) of the Font
+Software shall not be used to promote, endorse or advertise any
+Modified Version, except to acknowledge the contribution(s) of the
+Copyright Holder(s) and the Author(s) or with their explicit written
+permission.
+
+5) The Font Software, modified or unmodified, in part or in whole,
+must be distributed entirely under this license, and must not be
+distributed under any other license. The requirement for fonts to
+remain under this license does not apply to any document created
+using the Font Software.
+
+TERMINATION
+This license becomes null and void if any of the above conditions are
+not met.
+
+DISCLAIMER
+THE FONT SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
+EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTIES OF
+MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT
+OF COPYRIGHT, PATENT, TRADEMARK, OR OTHER RIGHT. IN NO EVENT SHALL THE
+COPYRIGHT HOLDER BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY,
+INCLUDING ANY GENERAL, SPECIAL, INDIRECT, INCIDENTAL, OR CONSEQUENTIAL
+DAMAGES, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
+FROM, OUT OF THE USE OR INABILITY TO USE THE FONT SOFTWARE OR FROM
+OTHER DEALINGS IN THE FONT SOFTWARE.

app/src/androidTest/kotlin/org/libremail/ui/compose/format/FontPickerTest.kt

@@ -0,0 +1,81 @@
+// SPDX-License-Identifier: GPL-3.0-or-later
+package org.libremail.ui.compose.format
+
+import androidx.activity.ComponentActivity
+import androidx.compose.ui.test.assertIsDisplayed
+import androidx.compose.ui.test.junit4.createAndroidComposeRule
+import androidx.compose.ui.test.onNodeWithText
+import androidx.compose.ui.test.performClick
+import androidx.test.ext.junit.runners.AndroidJUnit4
+import org.junit.Assert.assertEquals
+import org.junit.Rule
+import org.junit.Test
+import org.junit.runner.RunWith
+import org.libremail.R
+import org.libremail.ui.theme.LibreMailTheme
+
+/**
+ * UI tests for the compose formatting toolbar's font-family picker (#72). [FontPicker] is
+ * presentational, so it is driven in isolation - independent of the surrounding
+ * [org.libremail.ui.compose.RichTextBodyField] editor - mirroring how `FontSizePickerTest`
+ * exercises its dropdown.
+ */
+@RunWith(AndroidJUnit4::class)
+class FontPickerTest {
+
+    @get:Rule
+    val composeTestRule = createAndroidComposeRule<ComponentActivity>()
+
+    private fun string(resId: Int) = composeTestRule.activity.getString(resId)
+
+    private fun setContent(selectedCss: String?, onSelect: (String?) -> Unit = {}) {
+        composeTestRule.setContent {
+            LibreMailTheme(darkTheme = false, dynamicColor = false) {
+                FontPicker(selectedCss = selectedCss, onSelect = onSelect)
+            }
+        }
+    }
+
+    @Test
+    fun noFontSelected_buttonShowsDefaultLabel() {
+        setContent(selectedCss = null)
+        composeTestRule.onNodeWithText(string(R.string.format_font_default)).assertIsDisplayed()
+    }
+
+    @Test
+    fun aFontSelected_buttonShowsItsDisplayName() {
+        val inter = FontRegistry.choices.first { it.name == "Inter" }
+        setContent(selectedCss = inter.css)
+        composeTestRule.onNodeWithText("Inter").assertIsDisplayed()
+    }
+
+    @Test
+    fun tappingTheButton_opensAMenuListingEveryRegistryFont() {
+        setContent(selectedCss = null)
+        composeTestRule.onNodeWithText(string(R.string.format_font_default)).performClick()
+        FontRegistry.choices.forEach { choice ->
+            composeTestRule.onNodeWithText(choice.name).assertIsDisplayed()
+        }
+    }
+
+    @Test
+    fun pickingAFontFromTheMenu_reportsItsCssStack() {
+        var picked: String? = "unset"
+        val lora = FontRegistry.choices.first { it.name == "Lora" }
+        setContent(selectedCss = null) { picked = it }
+        composeTestRule.onNodeWithText(string(R.string.format_font_default)).performClick()
+        composeTestRule.onNodeWithText("Lora").performClick()
+        assertEquals(lora.css, picked)
+    }
+
+    @Test
+    fun pickingDefaultFromTheMenu_clearsBySelectingNull() {
+        var picked: String? = "unset"
+        val inter = FontRegistry.choices.first { it.name == "Inter" }
+        // The button reads "Inter" here, so the menu's own "Default" entry is the only such match.
+        setContent(selectedCss = inter.css) { picked = it }
+        composeTestRule.onNodeWithText("Inter").performClick()
+        composeTestRule.onNodeWithText(string(R.string.format_font_default)).performClick()
+        assertEquals(null, picked)
+    }
+}

app/src/main/kotlin/org/libremail/ui/compose/ComposeScreen.kt

@@ -74,6 +74,7 @@ import kotlinx.coroutines.flow.collect
 import org.libremail.R
 import org.libremail.domain.model.Account
 import org.libremail.domain.model.OutgoingAttachment
+import org.libremail.ui.compose.format.FontRegistry
 
 @OptIn(ExperimentalMaterial3Api::class)
 @Composable
@@ -186,6 +187,7 @@ fun ComposeScreen(onBack: () -> Unit, viewModel: ComposeViewModel = hiltViewMode
                     onBodyChange = viewModel::onBodyChange,
                     label = stringResource(R.string.compose_body),
                     modifier = Modifier.fillMaxWidth().weight(1f),
+                    resolveFont = FontRegistry::resolveFontFamily,
                 )
             }
 

app/src/main/kotlin/org/libremail/ui/compose/RichTextEditor.kt

@@ -58,6 +58,7 @@ import org.libremail.richtext.RichTextEditing
 import org.libremail.richtext.RichTextHtml
 import org.libremail.ui.compose.format.ColorSwatch
 import org.libremail.ui.compose.format.ColorSwatchRow
+import org.libremail.ui.compose.format.FontPicker
 import org.libremail.ui.compose.format.FontSizePicker
 import org.libremail.ui.compose.format.ParagraphAlignmentControl
 
@@ -76,9 +77,9 @@ internal const val IMAGE_TAG = "libremail:image"
 
 /**
  * A rich-text body editor: a formatting toolbar (bold / italic / underline / strikethrough, font
- * size, font color and highlight, bulleted + numbered lists, block quote, link, and paragraph
+ * family + size, font color and highlight, bulleted + numbered lists, block quote, link, and
- * alignment) above a rounded [OutlinedTextField]. It converts its [AnnotatedString] to the app's
+ * paragraph alignment) above a rounded [OutlinedTextField]. It converts its [AnnotatedString] to the
- * [RichTextContent] model and reports both the plaintext form and its HTML — or null HTML when
+ * app's [RichTextContent] model and reports both the plaintext form and its HTML — or null HTML when
  * nothing is formatted, so an unformatted message stays plaintext-only and feels exactly like the
  * old editor.
  *
@@ -149,6 +150,15 @@ fun RichTextBodyField(
                 )
             },
             onAlignment = { align -> emit(applyAlignment(value, align, linkColor, resolveFont)) },
+            onFont = { css ->
+                emit(
+                    if (css != null) {
+                        applyStyle(value, RichStyle.FontFamily(css), linkColor, resolveFont)
+                    } else {
+                        clearStyle(value, RichStyle.FontFamily::class.java, linkColor, resolveFont)
+                    },
+                )
+            },
         )
         OutlinedTextField(
             value = value,
@@ -234,6 +244,7 @@ private fun FormattingToolbar(
     onHighlight: () -> Unit,
     onFontSize: (Int?) -> Unit,
     onAlignment: (RichAlign) -> Unit,
+    onFont: (String?) -> Unit,
 ) {
     val content = value.annotatedString.toRichContent()
     val start = value.selection.min
@@ -320,6 +331,8 @@ private fun FormattingToolbar(
         // so its click lands on the button's on-screen center. Any control inserted *before* the block
         // buttons shifts them right and can push the bullet past the viewport, making that tap miss —
         // so these wider controls are appended last, leaving every pre-existing button in its tested spot.
+        val fontCss = RichTextEditing.styleAt(content, start, end, RichStyle.FontFamily::class.java)?.css
+        FontPicker(selectedCss = fontCss, onSelect = onFont)
         val fontSizePt = RichTextEditing.styleAt(content, start, end, RichStyle.FontSize::class.java)?.pt
         FontSizePicker(selectedPt = fontSizePt, onSelect = onFontSize)
         ParagraphAlignmentControl(

app/src/main/kotlin/org/libremail/ui/compose/format/FontPicker.kt

@@ -0,0 +1,93 @@
+// SPDX-License-Identifier: GPL-3.0-or-later
+package org.libremail.ui.compose.format
+
+import androidx.compose.foundation.background
+import androidx.compose.foundation.clickable
+import androidx.compose.foundation.layout.Arrangement
+import androidx.compose.foundation.layout.Box
+import androidx.compose.foundation.layout.Row
+import androidx.compose.foundation.layout.padding
+import androidx.compose.foundation.layout.size
+import androidx.compose.material.icons.Icons
+import androidx.compose.material.icons.filled.ArrowDropDown
+import androidx.compose.material3.DropdownMenu
+import androidx.compose.material3.DropdownMenuItem
+import androidx.compose.material3.Icon
+import androidx.compose.material3.LocalTextStyle
+import androidx.compose.material3.MaterialTheme
+import androidx.compose.material3.Text
+import androidx.compose.runtime.Composable
+import androidx.compose.runtime.getValue
+import androidx.compose.runtime.mutableStateOf
+import androidx.compose.runtime.remember
+import androidx.compose.runtime.setValue
+import androidx.compose.ui.Alignment
+import androidx.compose.ui.Modifier
+import androidx.compose.ui.draw.clip
+import androidx.compose.ui.graphics.Color
+import androidx.compose.ui.res.stringResource
+import androidx.compose.ui.semantics.Role
+import androidx.compose.ui.unit.dp
+import org.libremail.R
+
+/**
+ * A toolbar dropdown for [org.libremail.richtext.RichStyle.FontFamily]. The anchor shows the
+ * selection's current font by display name (via [FontRegistry]), or "Default" when [selectedCss] is
+ * null (no font applied, or a mixed selection). The menu lists a leading "Default" entry that clears
+ * the style, then every [FontRegistry] choice rendered in its own face as a preview. Mirrors
+ * [FontSizePicker]'s "Default" convention: [onSelect] receives null to clear and a CSS stack
+ * otherwise, so the caller routes the choice straight through the generalized `applyStyle`/`clearStyle`
+ * path with no font-specific branching.
+ */
+@Composable
+fun FontPicker(selectedCss: String?, onSelect: (String?) -> Unit, modifier: Modifier = Modifier) {
+    var expanded by remember { mutableStateOf(false) }
+    val colors = MaterialTheme.colorScheme
+    val label = when {
+        selectedCss == null -> stringResource(R.string.format_font_default)
+        else -> FontRegistry.displayNameFor(selectedCss) ?: selectedCss
+    }
+    val contentColor = if (selectedCss != null) colors.onSecondaryContainer else colors.onSurfaceVariant
+    Box(modifier = modifier) {
+        Row(
+            modifier = Modifier
+                .clip(MaterialTheme.shapes.small)
+                .background(if (selectedCss != null) colors.secondaryContainer else Color.Transparent)
+                .clickable(
+                    onClick = { expanded = true },
+                    role = Role.Button,
+                    onClickLabel = stringResource(R.string.format_font),
+                )
+                .padding(horizontal = 12.dp, vertical = 8.dp),
+            horizontalArrangement = Arrangement.spacedBy(2.dp),
+            verticalAlignment = Alignment.CenterVertically,
+        ) {
+            Text(text = label, color = contentColor)
+            Icon(
+                Icons.Filled.ArrowDropDown,
+                contentDescription = null,
+                modifier = Modifier.size(18.dp),
+                tint = contentColor,
+            )
+        }
+        DropdownMenu(expanded = expanded, onDismissRequest = { expanded = false }) {
+            DropdownMenuItem(
+                text = { Text(stringResource(R.string.format_font_default)) },
+                onClick = {
+                    expanded = false
+                    onSelect(null)
+                },
+            )
+            FontRegistry.choices.forEach { choice ->
+                DropdownMenuItem(
+                    // Each entry previews itself in its own face so the picker reads like a font menu.
+                    text = { Text(choice.name, style = LocalTextStyle.current.copy(fontFamily = choice.fontFamily)) },
+                    onClick = {
+                        expanded = false
+                        onSelect(choice.css)
+                    },
+                )
+            }
+        }
+    }
+}

app/src/main/kotlin/org/libremail/ui/compose/format/FontRegistry.kt

@@ -0,0 +1,40 @@
+// SPDX-License-Identifier: GPL-3.0-or-later
+package org.libremail.ui.compose.format
+
+import androidx.compose.ui.text.font.Font
+import androidx.compose.ui.text.font.FontFamily
+import org.libremail.R
+
+/** One selectable font: a display [name], its email-safe CSS stack, and the Compose family to render it. */
+data class FontChoice(val name: String, val css: String, val fontFamily: FontFamily)
+
+/**
+ * The fonts the [FontPicker] offers and the resolver the editor renders them with. Three generic
+ * families need no bundled file (they map to the platform defaults and to bare CSS generics); four
+ * bundled open-source families (all SIL OFL 1.1 — Inter, Lora, Merriweather, JetBrains Mono, whose
+ * license texts live under `THIRD_PARTY_LICENSES/`) each name the family first in their CSS stack and
+ * fall back to a generic, so a recipient whose mail client lacks the bundled face still renders a
+ * sensible one. The stored [RichStyle.FontFamily] carries only the CSS string, so nothing here leaks
+ * into the wire format — [resolveFontFamily] just maps that string back to a Compose [FontFamily] for
+ * in-editor display (null → leave the system default).
+ */
+object FontRegistry {
+
+    val choices: List<FontChoice> = listOf(
+        FontChoice("Sans-serif", "sans-serif", FontFamily.SansSerif),
+        FontChoice("Serif", "serif", FontFamily.Serif),
+        FontChoice("Monospace", "monospace", FontFamily.Monospace),
+        FontChoice("Inter", "'Inter', sans-serif", FontFamily(Font(R.font.inter))),
+        FontChoice("Lora", "'Lora', Georgia, serif", FontFamily(Font(R.font.lora))),
+        FontChoice("Merriweather", "'Merriweather', Georgia, serif", FontFamily(Font(R.font.merriweather))),
+        FontChoice("JetBrains Mono", "'JetBrains Mono', monospace", FontFamily(Font(R.font.jetbrains_mono))),
+    )
+
+    private val byCss: Map<String, FontChoice> = choices.associateBy { it.css }
+
+    /** The Compose family for a stored CSS stack, or null when it isn't one of ours (→ system font). */
+    fun resolveFontFamily(css: String): FontFamily? = byCss[css]?.fontFamily
+
+    /** The display name for a stored CSS stack, or null when it isn't one of ours. */
+    fun displayNameFor(css: String): String? = byCss[css]?.name
+}

app/src/main/res/values/strings.xml

@@ -127,6 +127,8 @@
     <string name="format_align_start">Align start</string>
     <string name="format_align_center">Align center</string>
     <string name="format_align_end">Align end</string>
+    <string name="format_font">Font</string>
+    <string name="format_font_default">Default</string>
 
     <!-- Drafts -->
     <string name="drafts_title">Drafts</string>

app/src/test/kotlin/org/libremail/ui/compose/format/FontRegistryTest.kt

@@ -0,0 +1,62 @@
+// SPDX-License-Identifier: GPL-3.0-or-later
+package org.libremail.ui.compose.format
+
+import org.junit.Test
+import org.libremail.richtext.RichSpan
+import org.libremail.richtext.RichStyle
+import org.libremail.richtext.RichTextContent
+import org.libremail.richtext.RichTextHtml
+import kotlin.test.assertEquals
+import kotlin.test.assertNotNull
+import kotlin.test.assertNull
+import kotlin.test.assertTrue
+
+/**
+ * Unit tests for [FontRegistry] — the font-family picker's source of truth. These run on the JVM:
+ * the registry's CSS stacks and lookups are plain data, so no emulator is needed to prove the wire
+ * format (the stored CSS) round-trips and that recipients fall back down the stack.
+ */
+class FontRegistryTest {
+
+    private val generics = setOf("sans-serif", "serif", "monospace")
+
+    @Test
+    fun `every css stack survives an html round-trip`() {
+        FontRegistry.choices.forEach { choice ->
+            val content = RichTextContent("x", spans = listOf(RichSpan(0, 1, RichStyle.FontFamily(choice.css))))
+            val restored = RichTextHtml.fromHtml(RichTextHtml.toHtml(content))
+            assertEquals(content.spans, restored.spans, "round-trip of ${choice.name}")
+        }
+    }
+
+    @Test
+    fun `resolveFontFamily maps a known css stack and rejects an unknown one`() {
+        FontRegistry.choices.forEach { choice ->
+            assertNotNull(FontRegistry.resolveFontFamily(choice.css), "resolve ${choice.name}")
+        }
+        assertNull(FontRegistry.resolveFontFamily("'Nonexistent', fantasy"))
+    }
+
+    @Test
+    fun `bundled stacks name the family first then end in a generic fallback`() {
+        // A recipient whose client lacks the bundled face falls back down the CSS stack to a generic.
+        FontRegistry.choices.filter { it.css !in generics }.forEach { choice ->
+            val parts = choice.css.split(",").map { it.trim() }
+            assertTrue(parts.size >= 2, "${choice.name} needs at least one fallback")
+            assertTrue(parts.first().startsWith("'"), "${choice.name} must name the family first")
+            assertTrue(parts.last().lowercase() in generics, "${choice.name} must end in a generic family")
+        }
+    }
+
+    @Test
+    fun `the three generic families need no bundled file`() {
+        assertEquals(generics, FontRegistry.choices.map { it.css }.filter { it in generics }.toSet())
+    }
+
+    @Test
+    fun `displayNameFor resolves a known stack and is null otherwise`() {
+        val choice = FontRegistry.choices.last()
+        assertEquals(choice.name, FontRegistry.displayNameFor(choice.css))
+        assertNull(FontRegistry.displayNameFor("'Nonexistent', fantasy"))
+    }
+}