Add retained paints and shared text selection

src/widget/text/mod.rs

@@ -1,9 +1,11 @@
 mod build;
 mod edit;
+mod selection;
 
 pub use build::*;
 pub use edit::*;
 use iris_core::util::MutDetect;
+pub use selection::*;
 
 use crate::prelude::*;
 use std::ops::{Deref, DerefMut};
@@ -19,6 +21,7 @@ pub struct TextView {
     tex: Option<RenderedText>,
     width: Option<f32>,
     pub hint: Option<StrongWidget>,
+    selection: TextSelection,
 }
 
 impl TextView {
@@ -37,6 +40,7 @@ impl TextView {
             tex: None,
             width: None,
             hint,
+            selection: TextSelection::default(),
         }
     }
 
@@ -94,6 +98,39 @@ impl TextView {
         Size::abs(tex.size)
     }
 
+    pub(super) fn draw_selectable(&mut self, painter: &mut Painter, caret: bool) -> Size {
+        let base = painter.layer;
+        painter.child_layer();
+        let used = self.draw(painter);
+        painter.layer = base;
+        let region = self.region();
+
+        let Some(selection) = self.selection.range else {
+            return used;
+        };
+        let layout = self.buf.layout();
+        for (rect, _) in selection.geometry(layout) {
+            let size = vec2(rect.width() as f32, rect.height() as f32);
+            let top_left = vec2(rect.x0 as f32, rect.y0 as f32);
+            let paint = painter.paint(&PaintId::SKY);
+            painter.primitive_within(
+                RectPrimitive::color(paint),
+                size.align(Align::TOP_LEFT).offset(top_left).within(&region),
+            );
+        }
+        if caret {
+            let caret = selection.focus().geometry(layout, CARET_WIDTH);
+            let size = vec2(caret.width() as f32, caret.height() as f32);
+            let top_left = vec2(caret.x0 as f32, caret.y0 as f32);
+            let paint = painter.paint(&PaintId::WHITE);
+            painter.primitive_within(
+                RectPrimitive::color(paint),
+                size.align(Align::TOP_LEFT).offset(top_left).within(&region),
+            );
+        }
+        used
+    }
+
     pub fn content(&self) -> String {
         self.buf.text().to_string()
     }
@@ -111,14 +148,36 @@ impl Text {
         if self.content.changed {
             self.content.changed = false;
             self.view.buf.set_text(self.content.as_str());
+            self.view.selection.deselect();
         }
     }
+
+    pub fn selected_text(&self) -> Option<String> {
+        self.view.selection.selected_text(self.view.buf.text())
+    }
+
+    pub fn selection_range(&self) -> Option<std::ops::Range<usize>> {
+        self.view.selection.range()
+    }
+
+    pub fn set_with_spans(&mut self, content: impl Into<String>, spans: Vec<SpanStyle>) {
+        let content = content.into();
+        *self.content = content.clone();
+        self.content.changed = false;
+        self.view.buf.set_text(content);
+        self.view.buf.set_spans(spans);
+        self.view.selection.deselect();
+    }
 }
 
 impl Widget for Text {
     fn draw(&mut self, painter: &mut Painter) {
         self.update_buf();
-        let size = self.view.draw(painter);
+        let size = if self.view.selection.range.is_some() {
+            self.view.draw_selectable(painter, false)
+        } else {
+            self.view.draw(painter)
+        };
         painter.set_size(size);
     }
 
@@ -127,6 +186,8 @@ impl Widget for Text {
     }
 }
 
+pub(super) const CARET_WIDTH: f32 = 1.0;
+
 impl Deref for Text {
     type Target = TextAttrs;
 
@@ -160,6 +221,89 @@ mod tests {
     use crate::layout_tests::TestRsc;
     use crate::prelude::*;
 
+    fn rendered_text(content: &str) -> (TestRsc, UiRenderState, WeakWidget<Text>, StrongWidget) {
+        let mut rsc = TestRsc {
+            ui: UiData::default(),
+        };
+        let text = wtext(content).add_strong(&mut rsc);
+        let id = text.weak();
+        let root = text.any();
+        let mut render = UiRenderState::new();
+        render.resize((800.0, 600.0));
+        render.update(&root, &mut rsc);
+        (rsc, render, id, root)
+    }
+
+    #[test]
+    fn display_text_and_edit_text_use_the_same_selection_engine() {
+        let (mut rsc, _render, text, _root) = rendered_text("hello there");
+        text.selection(&mut rsc).select_all();
+
+        let view = TextView::new(TextBuffer::new("hello there"), TextAttrs::default(), None);
+        let mut edit = TextEdit::new(view, EditMode::MultiLine);
+        let mut data = TextData::default();
+        TextEditCtx {
+            text: &mut edit,
+            data: &mut data,
+        }
+        .select_all();
+
+        assert_eq!(
+            rsc.ui.widgets[text].selection_range(),
+            edit.selection_range()
+        );
+        assert_eq!(rsc.ui.widgets[text].selected_text(), edit.selected_text());
+    }
+
+    #[test]
+    fn changing_display_text_clears_its_now_stale_selection() {
+        let (mut rsc, mut render, text, root) = rendered_text("before");
+        text.selection(&mut rsc).select_all();
+        assert_eq!(
+            rsc.ui.widgets[text].selected_text().as_deref(),
+            Some("before")
+        );
+
+        *rsc.ui.widgets[text].content = "after".to_string();
+        render.update(&root, &mut rsc);
+
+        assert_eq!(rsc.ui.widgets[text].selected_text(), None);
+        assert_eq!(rsc.ui.widgets[text].selection_range(), None);
+    }
+
+    #[test]
+    fn display_text_draws_the_shared_highlight_without_an_editing_caret() {
+        let (mut rsc, mut render, text, root) = rendered_text("selected");
+        let plain = render.active[&text.id()].primitives.len();
+        text.selection(&mut rsc).select_all();
+        render.update(&root, &mut rsc);
+        let selected = render.active[&text.id()].primitives.len();
+
+        let view = TextView::new(TextBuffer::new("selected"), TextAttrs::default(), None);
+        let edit = rsc
+            .ui
+            .widgets
+            .add_strong(TextEdit::new(view, EditMode::MultiLine));
+        let edit_id = edit.weak();
+        let edit_root = edit.any();
+        let mut edit_render = UiRenderState::new();
+        edit_render.resize((800.0, 600.0));
+        edit_render.update(&edit_root, &mut rsc);
+        edit_id.edit(&mut rsc).select_all();
+        edit_render.update(&edit_root, &mut rsc);
+        let editable = edit_render.active[&edit_id.id()].primitives.len();
+
+        assert!(
+            selected > plain,
+            "the selection added no highlight primitive"
+        );
+        assert_eq!(
+            editable,
+            selected + 1,
+            "editable text should add exactly its caret to the shared highlight"
+        );
+    }
+
     #[test]
     fn clearing_the_atlas_re_renders_cached_text_instead_of_reusing_it() {
         let mut rsc = TestRsc {
@@ -167,7 +311,7 @@ mod tests {
         };
         let root = wtext("hello there")
             .size(18)
-            .color(UiColor::WHITE)
+            .color(PaintId::WHITE)
             .add_strong(&mut rsc)
             .any();
         let mut render = UiRenderState::new();