apprt/gtk-ng: hovered url overlay (#8010)

I was going to do more overlays but this introduced enough new
complexity that I want to PR this on its own.

Valgrind clean!

src/Surface.zig

@@ -1316,9 +1316,7 @@ fn mouseRefreshLinks(
                     break :link .{ null, false };
                 };
                 break :link .{
-                    .{
+                    .{ .url = try alloc.dupeZ(u8, uri) },
-                        .url = uri,
-                    },
                     self.config.link_previews != .false,
                 };
             },

src/apprt/action.zig

@@ -507,7 +507,7 @@ pub const MouseVisibility = enum(c_int) {
 };
 
 pub const MouseOverLink = struct {
-    url: []const u8,
+    url: [:0]const u8,
 
     // Sync with: ghostty_action_mouse_over_link_s
     pub const C = extern struct {

src/apprt/gtk-ng/build/gresource.zig

@@ -16,6 +16,9 @@ pub const app_id = "com.mitchellh.ghostty";
 /// minimum adwaita version.
 pub const ui_path = "src/apprt/gtk-ng/ui";
 
+/// The path to the CSS files.
+pub const css_path = "src/apprt/gtk-ng/css";
+
 /// The possible icon sizes we'll embed into the gresource file.
 /// If any size doesn't exist then it will be an error. We could
 /// infer this completely from available files but we wouldn't be
@@ -36,6 +39,14 @@ pub const blueprints: []const Blueprint = &.{
     .{ .major = 1, .minor = 5, .name = "window" },
 };
 
+/// CSS files in css_path
+pub const css = [_][]const u8{
+    "style.css",
+    // "style-dark.css",
+    // "style-hc.css",
+    // "style-hc-dark.css",
+};
+
 pub const Blueprint = struct {
     major: u16,
     minor: u16,
@@ -45,7 +56,7 @@ pub const Blueprint = struct {
 /// The list of filepaths that we depend on. Used for the build
 /// system to have proper caching.
 pub const file_inputs = deps: {
-    const total = (icon_sizes.len * 2) + blueprints.len;
+    const total = (icon_sizes.len * 2) + blueprints.len + css.len;
     var deps: [total][]const u8 = undefined;
     var index: usize = 0;
     for (icon_sizes) |size| {
@@ -62,6 +73,10 @@ pub const file_inputs = deps: {
         });
         index += 1;
     }
+    for (css) |name| {
+        deps[index] = std.fmt.comptimePrint("{s}/{s}", .{ css_path, name });
+        index += 1;
+    }
     break :deps deps;
 };
 
@@ -120,6 +135,7 @@ pub fn main() !void {
         \\
     );
 
+    try genRoot(writer);
     try genIcons(writer);
     try genUi(alloc, writer, &ui_files);
 
@@ -173,6 +189,34 @@ fn genIcons(writer: anytype) !void {
     );
 }
 
+/// Generate the resources at the root prefix.
+fn genRoot(writer: anytype) !void {
+    try writer.print(
+        \\  <gresource prefix="{s}">
+        \\
+    , .{prefix});
+
+    const cwd = std.fs.cwd();
+    inline for (css) |name| {
+        const source = std.fmt.comptimePrint(
+            "{s}/{s}",
+            .{ css_path, name },
+        );
+        try cwd.access(source, .{});
+        try writer.print(
+            \\    <file compressed="true" alias="{s}">{s}</file>
+            \\
+        ,
+            .{ name, source },
+        );
+    }
+
+    try writer.writeAll(
+        \\  </gresource>
+        \\
+    );
+}
+
 /// Generate all the UI resources. This works by looking up all the
 /// blueprint files in `${ui_path}/{major}.{minor}/{name}.blp` and
 /// assuming these will be

src/apprt/gtk-ng/class/application.zig

@@ -463,6 +463,7 @@ pub const Application = extern struct {
                 value.config,
             ),
 
+            .mouse_over_link => Action.mouseOverLink(target, value),
             .mouse_shape => Action.mouseShape(target, value),
             .mouse_visibility => Action.mouseVisibility(target, value),
 
@@ -484,6 +485,8 @@ pub const Application = extern struct {
 
             .set_title => Action.setTitle(target, value),
 
+            .show_gtk_inspector => Action.showGtkInspector(),
+
             // Unimplemented but todo on gtk-ng branch
             .close_window,
             .toggle_maximize,
@@ -499,12 +502,10 @@ pub const Application = extern struct {
             .open_config,
             .reload_config,
             .inspector,
-            .show_gtk_inspector,
             .desktop_notification,
             .present_terminal,
             .initial_size,
             .size_limit,
-            .mouse_over_link,
             .toggle_tab_overview,
             .toggle_split_zoom,
             .toggle_window_decorations,
@@ -1014,6 +1015,25 @@ const Action = struct {
         }
     }
 
+    pub fn mouseOverLink(
+        target: apprt.Target,
+        value: apprt.action.MouseOverLink,
+    ) void {
+        switch (target) {
+            .app => log.warn("mouse over link to app is unexpected", .{}),
+            .surface => |surface| {
+                var v = gobject.ext.Value.new([:0]const u8);
+                if (value.url.len > 0) gobject.ext.Value.set(&v, value.url);
+                defer v.unset();
+                gobject.Object.setProperty(
+                    surface.rt_surface.gobj().as(gobject.Object),
+                    "mouse-hover-url",
+                    &v,
+                );
+            },
+        }
+    }
+
     pub fn mouseShape(
         target: apprt.Target,
         shape: terminal.MouseShape,
@@ -1115,6 +1135,10 @@ const Action = struct {
             },
         }
     }
+
+    pub fn showGtkInspector() void {
+        gtk.Window.setInteractiveDebugging(@intFromBool(true));
+    }
 };
 
 /// This sets various GTK-related environment variables as necessary

src/apprt/gtk-ng/class/surface.zig

@@ -94,6 +94,23 @@ pub const Surface = extern struct {
             );
         };
 
+        pub const @"mouse-hover-url" = struct {
+            pub const name = "mouse-hover-url";
+            pub const get = impl.get;
+            pub const set = impl.set;
+            const impl = gobject.ext.defineProperty(
+                name,
+                Self,
+                ?[:0]const u8,
+                .{
+                    .nick = "Mouse Hover URL",
+                    .blurb = "The URL the mouse is currently hovering over (if any).",
+                    .default = null,
+                    .accessor = C.privateStringFieldAccessor("mouse_hover_url"),
+                },
+            );
+        };
+
         pub const pwd = struct {
             pub const name = "pwd";
             pub const get = impl.get;
@@ -162,6 +179,9 @@ pub const Surface = extern struct {
         /// Whether the mouse should be hidden or not as requested externally.
         mouse_hidden: bool = false,
 
+        /// The URL that the mouse is currently hovering over.
+        mouse_hover_url: ?[:0]const u8 = null,
+
         /// The current working directory. This has to be reported externally,
         /// usually by shell integration which then talks to libghostty
         /// which triggers this property.
@@ -170,10 +190,18 @@ pub const Surface = extern struct {
         /// The title of this surface, if any has been set.
         title: ?[:0]const u8 = null,
 
+        /// The overlay we use for things such as the URL hover label
+        /// or resize box. Bound from the template.
+        overlay: *gtk.Overlay = undefined,
+
         /// The GLAarea that renders the actual surface. This is a binding
         /// to the template so it doesn't have to be unrefed manually.
         gl_area: *gtk.GLArea = undefined,
 
+        /// The labels for the left/right sides of the URL hover tooltip.
+        url_left: *gtk.Label = undefined,
+        url_right: *gtk.Label = undefined,
+
         /// The apprt Surface.
         rt_surface: ApprtSurface = undefined,
 
@@ -809,6 +837,13 @@ pub const Surface = extern struct {
         );
 
         // Some property signals
+        _ = gobject.Object.signals.notify.connect(
+            self,
+            ?*anyopaque,
+            &propMouseHoverUrl,
+            null,
+            .{ .detail = "mouse-hover-url" },
+        );
         _ = gobject.Object.signals.notify.connect(
             self,
             ?*anyopaque,
@@ -823,6 +858,41 @@ pub const Surface = extern struct {
             null,
             .{ .detail = "mouse-shape" },
         );
+
+        // Some other initialization steps
+        self.initUrlOverlay();
+    }
+
+    fn initUrlOverlay(self: *Self) void {
+        const priv = self.private();
+        const overlay = priv.overlay;
+        const url_left = priv.url_left.as(gtk.Widget);
+        const url_right = priv.url_right.as(gtk.Widget);
+
+        // Add the url label to the overlay
+        overlay.addOverlay(url_left);
+        overlay.addOverlay(url_right);
+
+        // Setup a motion controller to handle moving the label
+        // to avoid the mouse.
+        const ec_motion = gtk.EventControllerMotion.new();
+        errdefer ec_motion.unref();
+        url_left.addController(ec_motion.as(gtk.EventController));
+        errdefer url_left.removeController(ec_motion.as(gtk.EventController));
+        _ = gtk.EventControllerMotion.signals.enter.connect(
+            ec_motion,
+            *Self,
+            ecUrlMouseEnter,
+            self,
+            .{},
+        );
+        _ = gtk.EventControllerMotion.signals.leave.connect(
+            ec_motion,
+            *Self,
+            ecUrlMouseLeave,
+            self,
+            .{},
+        );
     }
 
     fn dispose(self: *Self) callconv(.C) void {
@@ -863,6 +933,10 @@ pub const Surface = extern struct {
             priv.core_surface = null;
         }
 
+        if (priv.mouse_hover_url) |v| {
+            glib.free(@constCast(@ptrCast(v)));
+            priv.mouse_hover_url = null;
+        }
         if (priv.pwd) |v| {
             glib.free(@constCast(@ptrCast(v)));
             priv.pwd = null;
@@ -886,6 +960,16 @@ pub const Surface = extern struct {
         return self.private().title;
     }
 
+    fn propMouseHoverUrl(
+        self: *Self,
+        _: *gobject.ParamSpec,
+        _: ?*anyopaque,
+    ) callconv(.c) void {
+        const priv = self.private();
+        const visible = if (priv.mouse_hover_url) |v| v.len > 0 else false;
+        priv.url_left.as(gtk.Widget).setVisible(if (visible) 1 else 0);
+    }
+
     fn propMouseHidden(
         self: *Self,
         _: *gobject.ParamSpec,
@@ -1539,6 +1623,26 @@ pub const Surface = extern struct {
         priv.core_surface = surface;
     }
 
+    fn ecUrlMouseEnter(
+        _: *gtk.EventControllerMotion,
+        _: f64,
+        _: f64,
+        self: *Self,
+    ) callconv(.c) void {
+        const priv = self.private();
+        const right = priv.url_right.as(gtk.Widget);
+        right.setVisible(1);
+    }
+
+    fn ecUrlMouseLeave(
+        _: *gtk.EventControllerMotion,
+        self: *Self,
+    ) callconv(.c) void {
+        const priv = self.private();
+        const right = priv.url_right.as(gtk.Widget);
+        right.setVisible(0);
+    }
+
     const C = Common(Self, Private);
     pub const as = C.as;
     pub const ref = C.ref;
@@ -1561,13 +1665,17 @@ pub const Surface = extern struct {
             );
 
             // Bindings
+            class.bindTemplateChildPrivate("overlay", .{});
             class.bindTemplateChildPrivate("gl_area", .{});
+            class.bindTemplateChildPrivate("url_left", .{});
+            class.bindTemplateChildPrivate("url_right", .{});
 
             // Properties
             gobject.ext.registerProperties(class, &.{
                 properties.config.impl,
                 properties.@"mouse-shape".impl,
                 properties.@"mouse-hidden".impl,
+                properties.@"mouse-hover-url".impl,
                 properties.pwd.impl,
                 properties.title.impl,
             });

src/apprt/gtk-ng/css/style.css

@@ -0,0 +1,24 @@
+/* Application CSS that applies to the entire application.
+ *
+ * This is automatically loaded by AdwApplication:
+ * https://gnome.pages.gitlab.gnome.org/libadwaita/doc/1.3/styles-and-appearance.html#custom-styles
+ */
+
+label.url-overlay {
+  padding: 4px 8px 4px 8px;
+  outline-style: solid;
+  outline-color: #555555;
+  outline-width: 1px;
+}
+
+label.url-overlay:hover {
+  opacity: 0;
+}
+
+label.url-overlay.left {
+  border-radius: 0px 6px 0px 0px;
+}
+
+label.url-overlay.right {
+  border-radius: 6px 0px 0px 0px;
+}

src/apprt/gtk-ng/ui/1.2/surface.blp

@@ -2,7 +2,14 @@ using Gtk 4.0;
 using Adw 1;
 
 template $GhosttySurface: Adw.Bin {
-  Overlay {
+  // We need to wrap our Overlay one more time because if you bind a
+  // direct child of your widget to a property, it will double free:
+  // https://gitlab.gnome.org/GNOME/gtk/-/blob/847571a1e314aba79260e4ef282e2ed9ba91a0d9/gtk/gtkwidget.c#L11423-11425
+  Adw.Bin {
+    Overlay overlay {
+      focusable: false;
+      focus-on-click: false;
+
       GLArea gl_area {
         hexpand: true;
         vexpand: true;
@@ -10,4 +17,28 @@ template $GhosttySurface: Adw.Bin {
         focus-on-click: true;
       }
     }
+  }
+}
+
+// The label that shows the currently hovered URL.
+Label url_left {
+  styles [
+    "url-overlay",
+  ]
+
+  visible: false;
+  halign: start;
+  valign: end;
+  label: bind template.mouse-hover-url;
+}
+
+Label url_right {
+  styles [
+    "url-overlay",
+  ]
+
+  visible: false;
+  halign: end;
+  valign: end;
+  label: bind template.mouse-hover-url;
 }