ui: move note and profile rendering to notedeck_ui

We want to render notes in other apps like dave, so lets move
our note rendering to notedeck_ui. We rework NoteAction so it doesn't
have anything specific to notedeck_columns

Signed-off-by: William Casarin <jb55@jb55.com>

crates/notedeck_ui/src/lib.rs

@@ -1,10 +1,55 @@
-mod anim;
+pub mod anim;
 pub mod colors;
 pub mod constants;
 pub mod gif;
 pub mod icons;
 pub mod images;
+pub mod mention;
+pub mod note;
 pub mod profile;
+mod username;
+pub mod widgets;
 
 pub use anim::{AnimationHelper, ImagePulseTint};
-pub use profile::ProfilePic;
+pub use mention::Mention;
+pub use note::{NoteContents, NoteOptions, NoteView};
+pub use profile::{ProfilePic, ProfilePreview};
+pub use username::Username;
+
+use egui::Margin;
+
+/// This is kind of like the Widget trait but is meant for larger top-level
+/// views that are typically stateful.
+///
+/// The Widget trait forces us to add mutable
+/// implementations at the type level, which screws us when generating Previews
+/// for a Widget. I would have just Widget instead of making this Trait otherwise.
+///
+/// There is some precendent for this, it looks like there's a similar trait
+/// in the egui demo library.
+pub trait View {
+    fn ui(&mut self, ui: &mut egui::Ui);
+}
+
+pub fn padding<R>(
+    amount: impl Into<Margin>,
+    ui: &mut egui::Ui,
+    add_contents: impl FnOnce(&mut egui::Ui) -> R,
+) -> egui::InnerResponse<R> {
+    egui::Frame::new()
+        .inner_margin(amount)
+        .show(ui, add_contents)
+}
+
+pub fn hline(ui: &egui::Ui) {
+    // pixel perfect horizontal line
+    let rect = ui.available_rect_before_wrap();
+    #[allow(deprecated)]
+    let resize_y = ui.painter().round_to_pixel(rect.top()) - 0.5;
+    let stroke = ui.style().visuals.widgets.noninteractive.bg_stroke;
+    ui.painter().hline(rect.x_range(), resize_y, stroke);
+}
+
+pub fn show_pointer(ui: &egui::Ui) {
+    ui.ctx().set_cursor_icon(egui::CursorIcon::PointingHand);
+}