FontPicker

FontPicker — a drop-in font-family selector.

A ComboBox preset that lists every installed font family and lets the user pick one, in the tradition of Qt's QFontComboBox, GTK's FontChooser, and UIKit's UIFontPickerViewController. It

• self-populates from the app's shared typesetter (ctx.app_state::<SharedTypesetter>() → families()), so no font list is passed in;
• previews each font: every row shows the family name in a legible system font next to a tiny sample rendered in that font (FontPreviewMode::NameThenSample, the default), and the closed trigger shows the selected family in its own typeface;
• is searchable (type to filter hundreds of fonts) and filterable by spacing (FontSpacingFilter) and by writing system (WritingSystem);
• binds the choice to a Signal<Option<String>> (the family name), which plugs straight into TextStyle.family / RichTextEditor::set_font_family.

let family: Signal<Option<String>> = Signal::new(None);
VStack::new()
    .child(TextWidget::new(tr!(font())).style(TextStyleRole::BodyBold))
    .child(FontPicker::new(family.clone())
        .on_select(|name, _ctx| editor.set_font_family(name)));

Writing-system detection is off-thread

Classifying which scripts a font covers parses its OS/2 table, i.e. reads the font file — hundreds of reads for a full system. The picker therefore builds the coverage index on a background thread the first time it mounts and polls readiness on the frame tick; until the index is ready the writing-system filter shows the unfiltered list and samples fall back to a Latin default. Spacing (monospaced / proportional) filtering is instant (it uses only font metadata, no bytes).

Only family selection is offered, matching Qt's QFontComboBox. Face / weight / size selection belongs to a larger font dialog and is out of scope.

Builder methods at a glance

families, families_with_meta, spacing_filter, writing_system, preview_mode, preview_in_own_font, sample_text, sample_text_for, sample_text_for_family, show_selected_in_own_font, placeholder, label, enabled, variant, style, max_visible_items, searchable, search_query, on_select, tooltip, rich_tooltip, rich_tooltip_content, composite_tooltip

API reference

📖 Full rustdoc API for this module

pub enum FontSpacingFilter

Spacing filter, mirroring the monospaced / proportional axis of Qt's QFontComboBox::FontFilters. Cheap — it reads only font metadata.

#![allow(unused)]
fn main() {
pub enum FontSpacingFilter { /* variants */ }
}

Variants

• Any — Show all fonts (default).
• Monospaced — Only monospaced fonts.
• Proportional — Only proportional (non-monospaced) fonts.

pub enum FontPreviewMode

How each row — and the closed trigger — previews a font.

#![allow(unused)]
fn main() {
pub enum FontPreviewMode { /* variants */ }
}

Variants

• NameThenSample — Family name in a legible system font, then a tiny sample rendered in the font itself (the default). The sample text is chosen for the font's writing system.
• NameInOwnFont — Family name rendered in its own typeface (the Qt / UIKit default).
• NameInSystemFont — Family name in the system font, no in-font sample (UIKit displayUsingSystemFont). Maximum legibility.

pub struct FontMeta

Per-family metadata for headless testing / restricted font sets via FontPicker::families_with_meta. In a real app this data comes from the shared typesetter instead.

#![allow(unused)]
fn main() {
pub struct FontMeta { /* fields */ }
}

pub struct FontPicker

A font-family selector built on ComboBox. See the module docs.

#![allow(unused)]
fn main() {
pub struct FontPicker { /* fields */ }
}

Methods

pub fn new(selected: Signal<Option<String>>) -> Self

Create a picker bound to selected (the chosen family name). The list is enumerated from the app's shared typesetter at build time.

pub fn families(mut self, families: impl IntoIterator<Item = impl Into<String>>) -> Self

Override the family list instead of enumerating from the typesetter. Family names only — spacing is treated as proportional and writing-system coverage is unknown (the writing-system filter shows all). For deterministic filter tests, prefer families_with_meta.

pub fn families_with_meta(mut self, families: Vec<(String, FontMeta)>) -> Self

Override the family list and its metadata (monospaced + writing systems). Enables headless testing of the spacing / writing-system filters and the script-aware sample without a font backend.

pub fn spacing_filter(mut self, filter: impl Into<Prop<FontSpacingFilter>>) -> Self

Restrict the list by spacing (monospaced / proportional). Accepts a static value or a Signal for a reactive filter toolbar.

pub fn writing_system(mut self, ws: impl Into<Prop<Option<WritingSystem>>>) -> Self

Restrict the list to fonts covering a writing system. None shows all. Accepts a static value or a Signal. The first time a non-None value is applied, the coverage index is built off-thread; until it is ready the list is unfiltered.

pub fn preview_mode(mut self, mode: FontPreviewMode) -> Self

Choose how rows (and the trigger) preview each font. Default FontPreviewMode::NameThenSample.

pub fn preview_in_own_font(mut self, on: bool) -> Self

Convenience: true keeps the default preview; false switches to FontPreviewMode::NameInSystemFont (UIKit displayUsingSystemFont).

pub fn sample_text(mut self, text: impl Into<String>) -> Self

Global sample text override (used when the font's writing system has no more specific sample). Mirrors GTK's preview text.

pub fn sample_text_for(mut self, ws: WritingSystem, text: impl Into<String>) -> Self

Per-writing-system sample override (Qt setSampleTextForSystem).

pub fn sample_text_for_family( mut self, family: impl Into<String>, text: impl Into<String>, ) -> Self

Per-family sample override (Qt setSampleTextForFont) — for fonts whose script the generic sample doesn't suit (icon fonts, etc.).

pub fn show_selected_in_own_font(mut self, on: bool) -> Self

Whether the closed trigger renders the selected family in its own typeface (default true; Qt behaviour). No effect in FontPreviewMode::NameInSystemFont.

pub fn placeholder(mut self, text: impl Into<LocalizedString>) -> Self

Placeholder shown when nothing is selected. Defaults to a localized "Select a font…".

pub fn label(mut self, label: impl Into<LocalizedString>) -> Self

Accessible / control label. Defaults to a localized "Font".

pub fn enabled(mut self, enabled: impl Into<Prop<bool>>) -> Self

Enable / disable the control, statically or reactively.

pub fn variant(mut self, variant: ComboBoxVariant) -> Self

Design-language variant, forwarded to the inner ComboBox.

pub fn style(mut self, style: impl ComboBoxStyle) -> Self

Per-call ComboBoxStyle override, forwarded to the inner combo.

pub fn max_visible_items(mut self, n: usize) -> Self

Maximum rows shown before the dropdown scrolls (default 8).

pub fn searchable(mut self, on: bool) -> Self

Enable / disable the in-dropdown search field (default true).

pub fn search_query(mut self, query: Signal<String>) -> Self

Drive the search field from an external query signal (implies searchable).

pub fn on_select(mut self, f: impl Fn(&str, &mut EventContext) + 'static) -> Self

React to a commit with a live EventContext — the place to apply the chosen font (e.g. editor.set_font_family(name)).

pub fn tooltip(mut self, text: impl Into<LocalizedString>) -> Self

Attach a plain tooltip, forwarded to the inner ComboBox. Mutually exclusive with the rich / composite variants — last-call-wins.

pub fn rich_tooltip(mut self, key: impl Into<String>) -> Self

Attach a registry-keyed rich tooltip, forwarded to the inner combo.

pub fn rich_tooltip_content(mut self, content: crate::tooltip::TooltipContent) -> Self

Attach an inline rich tooltip, forwarded to the inner combo.

pub fn composite_tooltip(mut self, content: impl Widget + 'static) -> Self

Attach a composite tooltip hosting an arbitrary widget tree, forwarded to the inner combo.