Improve popup position

Make the popup positions more consistent.
Improvements:
1. if the signature popup content is bigger than the available space,
   then the popup is always shown under the cursor, even if there more
   space above the cursor than below
2. There is no mutation anymore inside required_size. Maybe in the future
   we can update all widgets to have no mutations and change the trait

Signed-off-by: Ben Fekih, Hichem <hichem.f@live.de>

helix-term/src/ui/completion.rs

@@ -493,12 +493,7 @@ impl Component for Completion {
             None => return,
         };
 
-        let popup_area = {
-            let (popup_x, popup_y) = self.popup.get_rel_position(area, cx.editor);
-            let (popup_width, popup_height) = self.popup.get_size();
-            Rect::new(popup_x, popup_y, popup_width, popup_height)
-        };
-
+        let popup_area = self.popup.area(area, cx.editor);
         let doc_width_available = area.width.saturating_sub(popup_area.right());
         let doc_area = if doc_width_available > 30 {
             let mut doc_width = doc_width_available;

helix-term/src/ui/editor.rs

@@ -1034,7 +1034,6 @@ impl EditorView {
         self.last_insert.1.push(InsertEvent::TriggerCompletion);
 
         // TODO : propagate required size on resize to completion too
-        completion.required_size((size.width, size.height));
         self.completion = Some(completion);
         Some(area)
     }

helix-term/src/ui/mod.rs

@@ -13,7 +13,7 @@ mod spinner;
 mod statusline;
 mod text;
 
-use crate::compositor::{Component, Compositor};
+use crate::compositor::Compositor;
 use crate::filter_picker_entry;
 use crate::job::{self, Callback};
 pub use completion::{Completion, CompletionItem};
@@ -143,14 +143,12 @@ pub fn raw_regex_prompt(
                                         move |_editor: &mut Editor, compositor: &mut Compositor| {
                                             let contents = Text::new(format!("{}", err));
                                             let size = compositor.size();
-                                            let mut popup = Popup::new("invalid-regex", contents)
+                                            let popup = Popup::new("invalid-regex", contents)
                                                 .position(Some(helix_core::Position::new(
                                                     size.height as usize - 2, // 2 = statusline + commandline
                                                     0,
                                                 )))
                                                 .auto_close(true);
-                                            popup.required_size((size.width, size.height));
-
                                             compositor.replace_or_push("invalid-regex", popup);
                                         },
                                     ));

helix-term/src/ui/popup.rs

@@ -15,6 +15,8 @@ use helix_view::{
     Editor,
 };
 
+const MIN_HEIGHT: u16 = 4;
+
 // TODO: share logic with Menu, it's essentially Popup(render_fn), but render fn needs to return
 // a width/height hint. maybe Popup(Box<Component>)
 
@@ -22,11 +24,9 @@ pub struct Popup<T: Component> {
     contents: T,
     position: Option<Position>,
     margin: Margin,
-    size: (u16, u16),
-    child_size: (u16, u16),
     area: Rect,
     position_bias: Open,
-    scroll: usize,
+    scroll_half_pages: usize,
     auto_close: bool,
     ignore_escape_key: bool,
     id: &'static str,
@@ -39,11 +39,9 @@ impl<T: Component> Popup<T> {
             contents,
             position: None,
             margin: Margin::none(),
-            size: (0, 0),
             position_bias: Open::Below,
-            child_size: (0, 0),
             area: Rect::new(0, 0, 0, 0),
-            scroll: 0,
+            scroll_half_pages: 0,
             auto_close: false,
             ignore_escape_key: false,
             id,
@@ -95,15 +93,43 @@ impl<T: Component> Popup<T> {
         self
     }
 
-    /// Calculate the position where the popup should be rendered and return the coordinates of the
-    /// top left corner.
-    pub fn get_rel_position(&mut self, viewport: Rect, editor: &Editor) -> (u16, u16) {
+    pub fn scroll_half_page_down(&mut self) {
+        self.scroll_half_pages += 1;
+    }
+
+    pub fn scroll_half_page_up(&mut self) {
+        self.scroll_half_pages = self.scroll_half_pages.saturating_sub(1);
+    }
+
+    /// Toggles the Popup's scrollbar.
+    /// Consider disabling the scrollbar in case the child
+    /// already has its own.
+    pub fn with_scrollbar(mut self, enable_scrollbar: bool) -> Self {
+        self.has_scrollbar = enable_scrollbar;
+        self
+    }
+
+    pub fn contents(&self) -> &T {
+        &self.contents
+    }
+
+    pub fn contents_mut(&mut self) -> &mut T {
+        &mut self.contents
+    }
+
+    pub fn area(&mut self, viewport: Rect, editor: &Editor) -> Rect {
+        // trigger required_size so we recalculate if the child changed
+        let (width, height) = self
+            .required_size((viewport.width, viewport.height))
+            .expect("Component needs required_size implemented in order to be embedded in a popup");
+
+        let width = width.min(viewport.width);
+        let height = height.min(viewport.height.saturating_sub(2)); // add some spacing in the viewport
+
         let position = self
             .position
             .get_or_insert_with(|| editor.cursor().0.unwrap_or_default());
 
-        let (width, height) = self.size;
-
         // if there's a orientation preference, use that
         // if we're on the top part of the screen, do below
         // if we're on the bottom part, do above
@@ -115,8 +141,8 @@ impl<T: Component> Popup<T> {
             rel_x = rel_x.saturating_sub((rel_x + width).saturating_sub(viewport.width));
         }
 
-        let can_put_below = viewport.height > rel_y + height;
-        let can_put_above = rel_y.checked_sub(height).is_some();
+        let can_put_below = viewport.height > rel_y + MIN_HEIGHT;
+        let can_put_above = rel_y.checked_sub(MIN_HEIGHT).is_some();
         let final_pos = match self.position_bias {
             Open::Below => match can_put_below {
                 true => Open::Below,
@@ -128,61 +154,19 @@ impl<T: Component> Popup<T> {
             },
         };
 
-        rel_y = match final_pos {
-            Open::Above => rel_y.saturating_sub(height),
-            Open::Below => rel_y + 1,
-        };
-
-        (rel_x, rel_y)
-    }
-
-    pub fn get_size(&self) -> (u16, u16) {
-        (self.size.0, self.size.1)
-    }
-
-    pub fn scroll(&mut self, offset: usize, direction: bool) {
-        if direction {
-            let max_offset = self.child_size.1.saturating_sub(self.size.1);
-            self.scroll = (self.scroll + offset).min(max_offset as usize);
-        } else {
-            self.scroll = self.scroll.saturating_sub(offset);
+        match final_pos {
+            Open::Above => {
+                rel_y = rel_y.saturating_sub(height);
+                Rect::new(rel_x, rel_y, width, position.row as u16 - rel_y)
+            }
+            Open::Below => {
+                rel_y += 1;
+                let y_max = viewport.bottom().min(height + rel_y);
+                Rect::new(rel_x, rel_y, width, y_max - rel_y)
+            }
         }
     }
 
-    pub fn scroll_half_page_down(&mut self) {
-        self.scroll(self.size.1 as usize / 2, true)
-    }
-
-    pub fn scroll_half_page_up(&mut self) {
-        self.scroll(self.size.1 as usize / 2, false)
-    }
-
-    /// Toggles the Popup's scrollbar.
-    /// Consider disabling the scrollbar in case the child
-    /// already has its own.
-    pub fn with_scrollbar(mut self, enable_scrollbar: bool) -> Self {
-        self.has_scrollbar = enable_scrollbar;
-        self
-    }
-
-    pub fn contents(&self) -> &T {
-        &self.contents
-    }
-
-    pub fn contents_mut(&mut self) -> &mut T {
-        &mut self.contents
-    }
-
-    pub fn area(&mut self, viewport: Rect, editor: &Editor) -> Rect {
-        // trigger required_size so we recalculate if the child changed
-        self.required_size((viewport.width, viewport.height));
-
-        let (rel_x, rel_y) = self.get_rel_position(viewport, editor);
-
-        // clip to viewport
-        viewport.intersection(Rect::new(rel_x, rel_y, self.size.0, self.size.1))
-    }
-
     fn handle_mouse_event(
         &mut self,
         &MouseEvent {
@@ -266,38 +250,41 @@ impl<T: Component> Component for Popup<T> {
         // tab/enter/ctrl-k or whatever will confirm the selection/ ctrl-n/ctrl-p for scroll.
     }
 
-    fn required_size(&mut self, viewport: (u16, u16)) -> Option<(u16, u16)> {
-        let max_width = 120.min(viewport.0);
-        let max_height = 26.min(viewport.1.saturating_sub(2)); // add some spacing in the viewport
+    fn required_size(&mut self, _viewport: (u16, u16)) -> Option<(u16, u16)> {
+        const MAX_WIDTH: u16 = 120;
+        const MAX_HEIGHT: u16 = 26;
 
-        let inner = Rect::new(0, 0, max_width, max_height).inner(&self.margin);
+        let inner = Rect::new(0, 0, MAX_WIDTH, MAX_HEIGHT).inner(&self.margin);
 
         let (width, height) = self
             .contents
             .required_size((inner.width, inner.height))
             .expect("Component needs required_size implemented in order to be embedded in a popup");
 
-        self.child_size = (width, height);
-        self.size = (
-            (width + self.margin.width()).min(max_width),
-            (height + self.margin.height()).min(max_height),
+        let size = (
+            (width + self.margin.width()).min(MAX_WIDTH),
+            (height + self.margin.height()).min(MAX_HEIGHT),
         );
 
-        Some(self.size)
+        Some(size)
     }
 
     fn render(&mut self, viewport: Rect, surface: &mut Surface, cx: &mut Context) {
         let area = self.area(viewport, cx.editor);
         self.area = area;
 
-        // required_size() calculates the popup size without taking account of self.position
-        // so we need to correct the popup height to correctly calculate the scroll
-        self.size.1 = area.height;
+        let child_size = self
+            .contents
+            .required_size((area.width, area.height))
+            .expect("Component needs required_size implemented in order to be embedded in a popup");
 
-        // re-clamp scroll offset
-        let max_offset = self.child_size.1.saturating_sub(self.size.1);
-        self.scroll = self.scroll.min(max_offset as usize);
-        cx.scroll = Some(self.scroll);
+        let max_offset = child_size.1.saturating_sub(area.height) as usize;
+        let half_page_size = (area.height / 2) as usize;
+        let scroll = max_offset.min(self.scroll_half_pages * half_page_size);
+        if half_page_size > 0 {
+            self.scroll_half_pages = scroll / half_page_size;
+        }
+        cx.scroll = Some(scroll);
 
         // clear area
         let background = cx.editor.theme.get("ui.popup");
@@ -325,9 +312,8 @@ impl<T: Component> Component for Popup<T> {
         // render scrollbar if contents do not fit
         if self.has_scrollbar {
             let win_height = (inner.height as usize).saturating_sub(2 * border);
-            let len = (self.child_size.1 as usize).saturating_sub(2 * border);
+            let len = (child_size.1 as usize).saturating_sub(2 * border);
             let fits = len <= win_height;
-            let scroll = self.scroll;
             let scroll_style = cx.editor.theme.get("ui.menu.scroll");
 
             const fn div_ceil(a: usize, b: usize) -> usize {