fix(gtk): detect modifier keys without cursor movement

src/apprt/gtk/key.zig

@@ -49,6 +49,22 @@ pub fn translateMods(state: c.GdkModifierType) input.Mods {
     return mods;
 }
 
+pub fn deviceMods(device: ?*c.GdkDevice, gtk_mods: c.GdkModifierType) ?input.Mods {
+    if (device) |dev| {
+        const device_mods = c.gdk_device_get_modifier_state(dev);
+        if (device_mods != gtk_mods) {
+            return input.Mods{
+                .shift = (device_mods & c.GDK_SHIFT_MASK) != 0,
+                .ctrl = (device_mods & c.GDK_CONTROL_MASK) != 0,
+                .alt = (device_mods & c.GDK_ALT_MASK) != 0,
+                .super = (device_mods & c.GDK_SUPER_MASK) != 0,
+                .caps_lock = (device_mods & c.GDK_LOCK_MASK) != 0,
+            };
+        }
+    }
+    return null;
+}
+
 // Get the unshifted unicode value of the keyval. This is used
 // by the Kitty keyboard protocol.
 pub fn keyvalUnicodeUnshifted(

src/apprt/gtk/winproto/wayland.zig

@@ -5,6 +5,7 @@ const Allocator = std.mem.Allocator;
 const c = @import("../c.zig").c;
 const Config = @import("../../../config.zig").Config;
 const input = @import("../../../input.zig");
+const key = @import("../key.zig");
 
 const wl = wayland.client.wl;
 const org = wayland.client.org;
@@ -76,11 +77,11 @@ pub const App = struct {
     }
 
     pub fn eventMods(
-        _: *App,
-        _: ?*c.GdkDevice,
-        _: c.GdkModifierType,
+        _: App,
+        device: ?*c.GdkDevice,
+        gtk_mods: c.GdkModifierType,
     ) ?input.Mods {
-        return null;
+        return key.deviceMods(device, gtk_mods);
     }
 
     fn registryListener(

src/apprt/gtk/winproto/x11.zig

@@ -7,6 +7,7 @@ const c = @import("../c.zig").c;
 const input = @import("../../../input.zig");
 const Config = @import("../../../config.zig").Config;
 const adwaita = @import("../adwaita.zig");
+const key = @import("../key.zig");
 
 const log = std.log.scoped(.gtk_x11);
 
@@ -122,8 +123,9 @@ pub const App = struct {
         device: ?*c.GdkDevice,
         gtk_mods: c.GdkModifierType,
     ) ?input.Mods {
-        _ = device;
-        _ = gtk_mods;
+        if (key.deviceMods(device, gtk_mods)) |mods| {
+            return mods;
+        }
 
         // Shoutout to Mozilla for figuring out a clean way to do this, this is
         // paraphrased from Firefox/Gecko in widget/gtk/nsGtkKeyUtils.cpp.