Refactor new Rect construction (#575)

* Refactor new Rect construction

Introduces methods that can be chained to construct new Rects
out of pre-existing ones

* Clamp x and y to edges in Rect chop methods

* Rename Rect clipping functions

2 files changed, 87 insertions, 7 deletions

diff --git a/helix-view/src/graphics.rs b/helix-view/src/graphics.rs
index 9a7a86c3..66013ee5 100644
--- a/helix-view/src/graphics.rs
+++ b/helix-view/src/graphics.rs
@@ -24,7 +24,7 @@ pub struct Margin {
 }

 

 /// A simple rectangle used in the computation of the layout and to give widgets an hint about the

-/// area they are supposed to render to.

+/// area they are supposed to render to. (x, y) = (0, 0) is at the top left corner of the screen.

 #[derive(Debug, Clone, Copy, Hash, PartialEq, Eq)]

 pub struct Rect {

     pub x: u16,

@@ -92,6 +92,57 @@ impl Rect {
         self.y.saturating_add(self.height)

     }

 

+    // Returns a new Rect with width reduced from the left side.

+    // This changes the `x` coordinate and clamps it to the right

+    // edge of the original Rect.

+    pub fn clip_left(self, width: u16) -> Rect {

+        let width = std::cmp::min(width, self.width);

+        Rect {

+            x: self.x.saturating_add(width),

+            width: self.width.saturating_sub(width),

+            ..self

+        }

+    }

+

+    // Returns a new Rect with width reduced from the right side.

+    // This does _not_ change the `x` coordinate.

+    pub fn clip_right(self, width: u16) -> Rect {

+        Rect {

+            width: self.width.saturating_sub(width),

+            ..self

+        }

+    }

+

+    // Returns a new Rect with height reduced from the top.

+    // This changes the `y` coordinate and clamps it to the bottom

+    // edge of the original Rect.

+    pub fn clip_top(self, height: u16) -> Rect {

+        let height = std::cmp::min(height, self.height);

+        Rect {

+            y: self.y.saturating_add(height),

+            height: self.height.saturating_sub(height),

+            ..self

+        }

+    }

+

+    // Returns a new Rect with height reduced from the bottom.

+    // This does _not_ change the `y` coordinate.

+    pub fn clip_bottom(self, height: u16) -> Rect {

+        Rect {

+            height: self.height.saturating_sub(height),

+            ..self

+        }

+    }

+

+    pub fn with_height(self, height: u16) -> Rect {

+        // new height may make area > u16::max_value, so use new()

+        Self::new(self.x, self.y, self.width, height)

+    }

+

+    pub fn with_width(self, width: u16) -> Rect {

+        Self::new(self.x, self.y, width, self.height)

+    }

+

     pub fn inner(self, margin: &Margin) -> Rect {

         if self.width < 2 * margin.horizontal || self.height < 2 * margin.vertical {

             Rect::default()

@@ -495,6 +546,40 @@ mod tests {
         assert_eq!(rect.height, 100);

     }

 

+    #[test]

+    fn test_rect_chop_from_left() {

+        let rect = Rect::new(0, 0, 20, 30);

+        assert_eq!(Rect::new(10, 0, 10, 30), rect.clip_left(10));

+        assert_eq!(

+            Rect::new(20, 0, 0, 30),

+            rect.clip_left(40),

+            "x should be clamped to original width if new width is bigger"

+        );

+    }

+

+    #[test]

+    fn test_rect_chop_from_right() {

+        let rect = Rect::new(0, 0, 20, 30);

+        assert_eq!(Rect::new(0, 0, 10, 30), rect.clip_right(10));

+    }

+

+    #[test]

+    fn test_rect_chop_from_top() {

+        let rect = Rect::new(0, 0, 20, 30);

+        assert_eq!(Rect::new(0, 10, 20, 20), rect.clip_top(10));

+        assert_eq!(

+            Rect::new(0, 30, 20, 0),

+            rect.clip_top(50),

+            "y should be clamped to original height if new height is bigger"

+        );

+    }

+

+    #[test]

+    fn test_rect_chop_from_bottom() {

+        let rect = Rect::new(0, 0, 20, 30);

+        assert_eq!(Rect::new(0, 0, 20, 20), rect.clip_bottom(10));

+    }

+

     fn styles() -> Vec<Style> {

         vec![

             Style::default(),

diff --git a/helix-view/src/view.rs b/helix-view/src/view.rs
index b707c092..01f18c71 100644
--- a/helix-view/src/view.rs
+++ b/helix-view/src/view.rs
@@ -83,12 +83,7 @@ impl View {
     pub fn inner_area(&self) -> Rect {
         // TODO: not ideal
         const OFFSET: u16 = 7; // 1 diagnostic + 5 linenr + 1 gutter
-        Rect::new(
-            self.area.x + OFFSET,
-            self.area.y,
-            self.area.width - OFFSET,
-            self.area.height.saturating_sub(1), // -1 for statusline
-        )
+        self.area.clip_left(OFFSET).clip_bottom(1) // -1 for statusline
     }
 
     pub fn ensure_cursor_in_view(&mut self, doc: &Document, scrolloff: usize) {