T25a Generative: prompt and settings

PromptEnhancer offers a fuller prompt with the words it adds washed,
split at punctuation; Use this takes it into the field, Keep mine
lets it go. StylePresetPicker and AspectRatioPicker are rows of Tab
stops, the chosen one in accent; a ratio chip draws its shape.
SeedInput keeps digits up to u32::MAX and rolls one with a die.
NegativePromptInput and ImageGenerationPanel point to forms::TagInput
and forms::Form. theme.generative() holds the chapter's sizes. The
gallery's preset pictures are the atrium photo in five styles.

src/generative/style.rs

@@ -0,0 +1,148 @@
+use std::rc::Rc;
+
+use gpui::{
+    App, ElementId, InteractiveElement, IntoElement, MouseButton, ParentElement, RenderOnce,
+    SharedString, StatefulInteractiveElement, Styled, Window, div, transparent_black,
+};
+
+use crate::{
+    documents::source,
+    forms::OnValue,
+    primitives::{Icon, IconName, Image, tab_stop},
+    theme::{ActiveTheme, IconSize, Radius, TextSize},
+    typography::Ellipsis,
+};
+
+/// A style to generate in: its key, its name, and a picture of it; one with no picture draws a plain tile.
+#[derive(Clone, Debug, PartialEq)]
+pub struct StylePreset {
+    pub key: SharedString,
+    pub name: SharedString,
+    pub picture: Option<SharedString>,
+}
+
+/// Styles to generate in, a tile each with its picture and name. The chosen tile takes accent; each is a Tab stop.
+#[derive(IntoElement)]
+pub struct StylePresetPicker {
+    id: ElementId,
+    presets: Vec<StylePreset>,
+    selected: SharedString,
+    on_select: Option<OnValue>,
+}
+
+impl StylePresetPicker {
+    /// `selected` names one of `presets` by key.
+    pub fn new(
+        id: impl Into<ElementId>,
+        presets: impl IntoIterator<Item = StylePreset>,
+        selected: impl Into<SharedString>,
+    ) -> Self {
+        let (presets, selected): (Vec<StylePreset>, SharedString) =
+            (presets.into_iter().collect(), selected.into());
+        assert!(
+            presets.iter().any(|preset| preset.key == selected),
+            "style {selected} is not among the presets"
+        );
+        Self {
+            id: id.into(),
+            presets,
+            selected,
+            on_select: None,
+        }
+    }
+
+    pub fn on_select(
+        mut self,
+        handler: impl Fn(&SharedString, &mut Window, &mut App) + 'static,
+    ) -> Self {
+        self.on_select = Some(Rc::new(handler));
+        self
+    }
+}
+
+impl RenderOnce for StylePresetPicker {
+    fn render(self, window: &mut Window, cx: &mut App) -> impl IntoElement {
+        let tiles: Vec<_> = self
+            .presets
+            .into_iter()
+            .map(|preset| {
+                let id: ElementId = (self.id.clone(), format!("preset-{}", preset.key)).into();
+                let focus = tab_stop((id.clone(), "focus").into(), true, window, cx);
+                (id, focus.is_focused(window), focus, preset)
+            })
+            .collect();
+        let theme = cx.theme();
+        let colors = theme.colors.clone();
+        let side = theme.generative().preset;
+        div()
+            .w_full()
+            .flex()
+            .flex_wrap()
+            .gap_3()
+            .children(tiles.into_iter().map(|(id, focused, focus, preset)| {
+                let chosen = preset.key == self.selected;
+                let ring = if focused {
+                    colors.focus
+                } else if chosen {
+                    colors.accent
+                } else {
+                    transparent_black()
+                };
+                let (key, pick) = (preset.key.clone(), self.on_select.clone());
+                let inner = theme.radius(Radius::Md);
+                let picture = match &preset.picture {
+                    Some(path) => Image::new((id.clone(), "picture"), source(path))
+                        .size_full()
+                        .rounded(inner)
+                        .into_any_element(),
+                    None => div()
+                        .size_full()
+                        .rounded(inner)
+                        .flex()
+                        .items_center()
+                        .justify_center()
+                        .bg(colors.sunken)
+                        .child(
+                            Icon::new(IconName::Ban)
+                                .size(IconSize::Md)
+                                .color(colors.fg_subtle),
+                        )
+                        .into_any_element(),
+                };
+                div()
+                    .id(id)
+                    .track_focus(&focus)
+                    .w(side)
+                    .flex()
+                    .flex_col()
+                    .gap_1p5()
+                    .cursor_pointer()
+                    .on_mouse_down(MouseButton::Left, |_, window, _| window.prevent_default())
+                    .on_click(move |_, window, cx| {
+                        if chosen {
+                            return;
+                        }
+                        log::info!("style preset: {key}");
+                        if let Some(pick) = &pick {
+                            pick(&key, window, cx);
+                        }
+                    })
+                    .child(
+                        div()
+                            .size(side)
+                            .p_0p5()
+                            .rounded(theme.radius(Radius::Lg))
+                            .border_1()
+                            .border_color(ring)
+                            .child(picture),
+                    )
+                    .child(
+                        div()
+                            .px_0p5()
+                            .text_size(theme.text_size(TextSize::Xs))
+                            .text_color(if chosen { colors.fg } else { colors.fg_muted })
+                            .child(Ellipsis::new(preset.name)),
+                    )
+            }))
+    }
+}