fix(webkitgtk): normalize u8 color values to 0.0–1.0 for gdk::RGBA (#1692)

gdk::RGBA::new() expects values in the 0.0–1.0 range, but the u8
color components (0–255) were cast directly to f64 without dividing
by 255.0. GDK clamps values >1.0 to 1.0, so any non-zero color
ended up as white.

Fixes #1690

Author: Sbenazar

.changes/fix-webkitgtk-background-color.md

@@ -0,0 +1,5 @@
+---
+"wry": patch
+---
+
+fix(webkitgtk): normalize background color values to 0.0–1.0

src/webkitgtk/mod.rs

@@ -292,7 +292,10 @@ impl InnerWebView {
       // background color
       if let Some((red, green, blue, alpha)) = attributes.background_color {
         webview.set_background_color(&gtk::gdk::RGBA::new(
-          red as _, green as _, blue as _, alpha as _,
+          red as f64 / 255.0,
+          green as f64 / 255.0,
+          blue as f64 / 255.0,
+          alpha as f64 / 255.0,
         ));
       }
     }
@@ -763,7 +766,10 @@ impl InnerWebView {
 
   pub fn set_background_color(&self, (red, green, blue, alpha): RGBA) -> Result<()> {
     self.webview.set_background_color(&gtk::gdk::RGBA::new(
-      red as _, green as _, blue as _, alpha as _,
+      red as f64 / 255.0,
+      green as f64 / 255.0,
+      blue as f64 / 255.0,
+      alpha as f64 / 255.0,
     ));
     Ok(())
   }