Gtk3Backend: Fix Alert styling, Gtk3 styling is a nightmare...

Author: stackotter

Examples/Package.resolved

@@ -2,10 +2,14 @@ import CGtk3
 
 /// Swift representation of a Gtk CSS provider
 public class CSSProvider {
-    var pointer: UnsafeMutablePointer<GtkCssProvider>
-    var context: UnsafeMutablePointer<GtkStyleContext>
+    public var pointer: UnsafeMutablePointer<GtkCssProvider>
+    var context: UnsafeMutablePointer<GtkStyleContext>?
 
-    init(
+    public init() {
+        pointer = gtk_css_provider_new()
+    }
+
+    public init(
         forContext context: UnsafeMutablePointer<GtkStyleContext>,
         priority: UInt32 = UInt32(GTK_STYLE_PROVIDER_PRIORITY_APPLICATION)
     ) {
@@ -16,6 +20,10 @@ public class CSSProvider {
     }
 
     deinit {
+        guard let context else {
+            return
+        }
+
         gtk_style_context_remove_provider(context, OpaquePointer(pointer))
         g_object_unref(context)
     }

Sources/Gtk3/Utility/CSS/CSSProvider.swift

@@ -62,6 +62,21 @@ public final class Gtk3Backend: AppBackend {
         gtkApp.run { window in
             self.precreatedWindow = window
             callback()
+
+            let provider = CSSProvider()
+            provider.loadCss(
+                from: """
+                .dialog-vbox .horizontal .vertical {
+                    padding-top: 20px;
+                    margin-bottom: -10px;
+                }
+                """
+            )
+            gtk_style_context_add_provider_for_screen(
+                gdk_screen_get_default(),
+                OpaquePointer(provider.pointer),
+                guint(GTK_STYLE_PROVIDER_PRIORITY_APPLICATION)
+            )
         }
     }