Apply transparent background colors to "UI" cells

CHANGELOG.md

@@ -34,6 +34,7 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/).
 - IME popup now tries to not obscure the current cursor line
 - The double click threshold was raised to `400ms`
 - OSC 52 paste ability is now **disabled by default**; use `terminal.osc52` to adjust it
+- Apply `colors.transparent_background_colors` for selections, hints, and search matches
 
 ### Fixed
 

alacritty/src/display/content.rs

@@ -256,6 +256,11 @@ impl RenderableCell {
             Self::compute_cell_rgb(&mut fg, &mut bg, &mut bg_alpha, config_fg, config_bg);
         }
 
+        // Apply transparency to all renderable cells if `transparent_background_colors` is set
+        if bg_alpha > 0. && content.config.colors.transparent_background_colors {
+            bg_alpha = content.config.window_opacity();
+        }
+
         // Convert cell point to viewport position.
         let cell_point = cell.point;
         let point = term::point_to_viewport(display_offset, cell_point).unwrap();