Fix message bar not damaged when the same size

The regression was added due to `y` coordinate in OpenGL differs to
`y` inside the damage rectangles.

Fixes: 40160c5d (Damage only terminal inside `alacritty_terminal`)

alacritty/src/display/damage.rs

@@ -164,11 +164,19 @@ impl FrameDamage {
         self.full = true;
     }
 
-    /// Add a damage rectangle.
+    /// Add viewport rectangle to damage.
     ///
     /// This allows covering elements outside of the terminal viewport, like message bar.
     #[inline]
-    pub fn add_rect(&mut self, x: i32, y: i32, width: i32, height: i32) {
+    pub fn add_viewport_rect(
+        &mut self,
+        size_info: &SizeInfo,
+        x: i32,
+        y: i32,
+        width: i32,
+        height: i32,
+    ) {
+        let y = viewport_y_to_damage_y(size_info, y, height);
         self.rects.push(Rect { x, y, width, height });
     }
 
@@ -183,6 +191,16 @@ impl FrameDamage {
     }
 }
 
+/// Convert viewport `y` coordinate to [`Rect`] damage coordinate.
+pub fn viewport_y_to_damage_y(size_info: &SizeInfo, y: i32, height: i32) -> i32 {
+    size_info.height() as i32 - y - height
+}
+
+/// Convert viewport `y` coordinate to [`Rect`] damage coordinate.
+pub fn damage_y_to_viewport_y(size_info: &SizeInfo, rect: &Rect) -> i32 {
+    size_info.height() as i32 - rect.y - rect.height
+}
+
 /// Iterator which converts `alacritty_terminal` damage information into renderer damaged rects.
 struct RenderDamageIterator<'a> {
     damaged_lines: Peekable<TermDamageIterator<'a>>,
@@ -316,4 +334,24 @@ mod tests {
             rect
         );
     }
+
+    #[test]
+    fn add_viewport_damage() {
+        let mut frame_damage = FrameDamage::default();
+        let viewport_height = 100.;
+        let x = 0;
+        let y = 40;
+        let height = 5;
+        let width = 10;
+        let size_info = SizeInfo::new(viewport_height, viewport_height, 5., 5., 0., 0., true);
+        frame_damage.add_viewport_rect(&size_info, x, y, width, height);
+        assert_eq!(frame_damage.rects[0], Rect {
+            x,
+            y: viewport_height as i32 - y - height,
+            width,
+            height
+        });
+        assert_eq!(frame_damage.rects[0].y, viewport_y_to_damage_y(&size_info, y, height));
+        assert_eq!(damage_y_to_viewport_y(&size_info, &frame_damage.rects[0]), y);
+    }
 }

alacritty/src/display/mod.rs

@@ -43,7 +43,7 @@ use crate::display::bell::VisualBell;
 use crate::display::color::{List, Rgb};
 use crate::display::content::{RenderableContent, RenderableCursor};
 use crate::display::cursor::IntoRects;
-use crate::display::damage::DamageTracker;
+use crate::display::damage::{damage_y_to_viewport_y, DamageTracker};
 use crate::display::hint::{HintMatch, HintState};
 use crate::display::meter::Meter;
 use crate::display::window::Window;
@@ -935,7 +935,7 @@ impl Display {
             rects.push(message_bar_rect);
 
             // Always damage message bar, since it could have messages of the same size in it.
-            self.damage_tracker.frame().add_rect(x, y as i32, width, height);
+            self.damage_tracker.frame().add_viewport_rect(&size_info, x, y as i32, width, height);
 
             // Draw rectangles.
             self.renderer.draw_rects(&size_info, &metrics, rects);
@@ -1327,7 +1327,7 @@ impl Display {
             let x = damage_rect.x as f32;
             let height = damage_rect.height as f32;
             let width = damage_rect.width as f32;
-            let y = self.size_info.height() - damage_rect.y as f32 - height;
+            let y = damage_y_to_viewport_y(&self.size_info, damage_rect) as f32;
             let render_rect = RenderRect::new(x, y, width, height, DAMAGE_RECT_COLOR, 0.5);
 
             render_rects.push(render_rect);