Make signature_help more like hover, fix overflow and lack of scrolling in signature_help (#13566)

Co-authored-by: Michael Davis <mcarsondavis@gmail.com>

helix-term/src/ui/lsp/signature_help.rs

@@ -94,7 +94,8 @@ impl Component for SignatureHelp {
     }
 
     fn render(&mut self, area: Rect, surface: &mut Buffer, cx: &mut Context) {
-        let margin = Margin::horizontal(1);
+        let margin = Margin::all(1);
+        let area = area.inner(margin);
 
         let signature = self
             .signatures
@@ -127,13 +128,15 @@ impl Component for SignatureHelp {
             let signature_index = self.signature_index();
             let text = Text::from(signature_index);
             let paragraph = Paragraph::new(&text).alignment(Alignment::Right);
-            paragraph.render(area.clip_top(1).with_height(1).clip_right(1), surface);
+            paragraph.render(area.with_height(1).clip_right(1), surface);
         }
 
-        let (_, sig_text_height) = crate::ui::text::required_size(&sig_text, area.width);
-        let sig_text_area = area.clip_top(1).with_height(sig_text_height);
-        let sig_text_area = sig_text_area.inner(margin).intersection(surface.area);
-        let sig_text_para = Paragraph::new(&sig_text).wrap(Wrap { trim: false });
+        let sig_text_para = Paragraph::new(&sig_text)
+            .wrap(Wrap { trim: false })
+            .scroll((cx.scroll.unwrap_or_default() as u16, 0));
+        let (_, sig_text_height) = sig_text_para.required_size(area.width);
+        let sig_text_area = area.with_height(sig_text_height.min(area.height));
+        let sig_text_area = sig_text_area.intersection(surface.area);
         sig_text_para.render(sig_text_area, surface);
 
         if signature.signature_doc.is_none() {
@@ -159,7 +162,7 @@ impl Component for SignatureHelp {
         let sig_doc_para = Paragraph::new(&sig_doc)
             .wrap(Wrap { trim: false })
             .scroll((cx.scroll.unwrap_or_default() as u16, 0));
-        sig_doc_para.render(sig_doc_area.inner(margin), surface);
+        sig_doc_para.render(sig_doc_area, surface);
     }
 
     fn required_size(&mut self, viewport: (u16, u16)) -> Option<(u16, u16)> {
@@ -180,8 +183,8 @@ impl Component for SignatureHelp {
             &self.config_loader.load(),
             None,
         );
-        let (sig_width, sig_height) =
-            crate::ui::text::required_size(&signature_text, max_text_width);
+        let sig_text_para = Paragraph::new(&signature_text).wrap(Wrap { trim: false });
+        let (sig_width, sig_height) = sig_text_para.required_size(max_text_width);
 
         let (width, height) = match signature.signature_doc {
             Some(ref doc) => {

helix-tui/src/widgets/paragraph.rs

@@ -127,6 +127,38 @@ impl<'a> Paragraph<'a> {
         self.alignment = alignment;
         self
     }
+
+    pub fn required_size(&self, max_text_width: u16) -> (u16, u16) {
+        let style = self.style;
+        let mut styled = self.text.lines.iter().flat_map(|spans| {
+            spans
+                .0
+                .iter()
+                .flat_map(|span| span.styled_graphemes(style))
+                // Required given the way composers work but might be refactored out if we change
+                // composers to operate on lines instead of a stream of graphemes.
+                .chain(iter::once(StyledGrapheme {
+                    symbol: "\n",
+                    style: self.style,
+                }))
+        });
+        let mut line_composer: Box<dyn LineComposer> = if let Some(Wrap { trim }) = self.wrap {
+            Box::new(WordWrapper::new(&mut styled, max_text_width, trim))
+        } else {
+            let mut line_composer = Box::new(LineTruncator::new(&mut styled, max_text_width));
+            if self.alignment == Alignment::Left {
+                line_composer.set_horizontal_offset(self.scroll.1);
+            }
+            line_composer
+        };
+        let mut text_width = 0;
+        let mut text_height = 0;
+        while let Some((_, line_width)) = line_composer.next_line() {
+            text_width = line_width.max(text_width);
+            text_height += 1;
+        }
+        (text_width, text_height)
+    }
 }
 
 impl Widget for Paragraph<'_> {