GTK3,4: Improve ComboBox visuals

src/gtk3/widgets/_button.scss

@@ -389,6 +389,24 @@ combobox {
 		padding-top: 4px;
 		padding-bottom: 4px;
 	}
+
+	> box > button.combo:only-child {
+
+		//Force shadow for single combobox buttons
+		@include neobutton(normal)
+
+		arrow {
+			min-width: 14px;
+
+			&:dir(rtl) {
+				margin-left: -3px;
+			}
+
+			&:dir(ltr) {
+				margin-right: -3px;
+			}
+		}
+	}
 }
 
 %needs_attention {

src/gtk3/widgets/_entry.scss

@@ -207,3 +207,21 @@ treeview entry {
 		}
 	}
 }
+
+combobox > box > button.combo {
+	background: none;
+	@include entry(normal)
+
+	&:focus {
+		@include entry(focus);
+	}
+	&:disabled {
+		@include entry(insensitive);
+	}
+	&:backdrop {
+		@include entry(backdrop);
+	}
+	&:backdrop:disabled {
+		@include entry(backdrop-insensitive);
+	}
+}

src/gtk3/widgets/_headerbar.scss

@@ -41,6 +41,9 @@ headerbar {
 	}
 	button {
 		@include neobutton(toolbutton);
+
+		//ensure we don't have a shadow on headerbar buttons at all
+		box-shadow: none;
 		color: gtk("@theme_titlebar_foreground");
 
 		&:hover {

src/gtk4/widgets/_button.scss

@@ -342,6 +342,24 @@ combobox {
 		padding-top: 4px;
 		padding-bottom: 4px;
 	}
+
+	> box > button.combo:only-child {
+
+		//Force shadow for single combobox buttons
+		@include neobutton(normal)
+
+		arrow {
+			min-width: 14px;
+
+			&:dir(rtl) {
+				margin-left: -3px;
+			}
+
+			&:dir(ltr) {
+				margin-right: -3px;
+			}
+		}
+	}
 }
 
 %needs_attention {

src/gtk4/widgets/_entry.scss

@@ -207,3 +207,22 @@ treeview entry {
 		}
 	}
 }
+
+combobox > box > button.combo {
+	background: none;
+	@include entry(normal)
+
+	&:focus {
+		@include entry(focus);
+	}
+	&:disabled {
+		@include entry(insensitive);
+	}
+	&:backdrop {
+		@include entry(backdrop);
+	}
+	&:backdrop:disabled {
+		@include entry(backdrop-insensitive);
+	}
+}
+

src/gtk4/widgets/_headerbar.scss

@@ -41,6 +41,9 @@ headerbar {
 	}
 	button {
 		@include neobutton(toolbutton);
+
+		//ensure we don't have a shadow on headerbar buttons at all
+		box-shadow: none;
 		color: gtk("@theme_titlebar_foreground");
 
 		&:hover {