wxSplashScreen shows titlebar on Wayland compositors that prefer server-side decorations (Issue #26357)

[akelmanson]

akelmanson created an issue (wxWidgets/wxWidgets#26357)

Description

wxSplashScreen created with wxBORDER_NONE (or wxSIMPLE_BORDER) displays a window titlebar on Wayland compositors that prefer server-side decorations (SSD) via the xdg-decoration protocol.

The existing code in src/gtk/toplevel.cpp correctly calls gtk_window_set_decorated(GTK_WINDOW(m_widget), false) when wxNO_BORDER is in the style flags. However, this only removes client-side decorations (CSD). Wayland compositors that default to SSD — such as Sway (wlroots), Cosmic (smithay), Hyprland, and others — still add their own titlebar because the client never explicitly opted into CSD mode via the xdg-decoration negotiation.

Steps to reproduce

1. Create a wxSplashScreen with wxBORDER_NONE style
2. Run on a Wayland session with a compositor that prefers SSD (e.g., Sway, Cosmic DE)
3. Observe: the splash screen has a compositor-drawn titlebar

Expected behavior

Splash screen should appear as a borderless, undecorated floating window — identical to X11 behavior.

Platform

• wxWidgets 3.3.2 (wxGTK3)
• Tested on: Sway (wlroots), Cosmic DE (smithay)
• Does not reproduce on GNOME (Mutter uses CSD-only)
• Does not reproduce on X11

Proposed fix

Before the window is realized, set an empty GtkFixed widget as the titlebar via gtk_window_set_titlebar(). This forces GTK to request CSD mode from the compositor via xdg-decoration, after which gtk_window_set_decorated(false) removes the CSD titlebar entirely. Net result: zero decorations on all compositors.

diff --git a/src/generic/splash.cpp b/src/generic/splash.cpp
index 2e55a6e..a8150de 100644
--- a/src/generic/splash.cpp
+++ b/src/generic/splash.cpp
@@ -64,6 +64,19 @@ wxSplashScreen::wxSplashScreen(const wxBitmap& bitmap, long splashStyle, int mil
 #if defined(__WXGTK__)
     gtk_window_set_type_hint(GTK_WINDOW(m_widget),
                              GDK_WINDOW_TYPE_HINT_SPLASHSCREEN);
+    // On Wayland, compositors that prefer server-side decorations (SSD)
+    // via the xdg-decoration protocol may add a titlebar even when
+    // gtk_window_set_decorated(false) was called (which only removes CSD).
+    // Setting a custom titlebar widget forces GTK to request client-side
+    // decoration mode from the compositor, then set_decorated(false)
+    // removes the CSD titlebar entirely.
+    if (style & (wxSIMPLE_BORDER | wxNO_BORDER))
+    {
+        GtkWidget *empty = gtk_fixed_new();
+        gtk_widget_set_size_request(empty, 0, 0);
+        gtk_window_set_titlebar(GTK_WINDOW(m_widget), empty);
+        gtk_window_set_decorated(GTK_WINDOW(m_widget), false);
+    }
 #endif
 
     m_splashStyle = splashStyle;

Note

This issue likely affects any wxFrame created with wxNO_BORDER on Wayland with SSD-preferring compositors, not just wxSplashScreen. The fix in src/gtk/toplevel.cpp (where gtk_window_set_decorated is called for wxNO_BORDER) might be the better location for a general fix. The splash.cpp patch above is a minimal targeted fix.

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[VZ]

vadz left a comment (wxWidgets/wxWidgets#26357)

Thanks for the report and the fix suggestion! This very much looks like a hack, but if it works, I think we should do it — and, indeed, do it at wxFrame level.

@paulcor Would you have any comments about this?

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[paulcor]

paulcor left a comment (wxWidgets/wxWidgets#26357)

@akelmanson Can you check that #26359 fixes the issue for you?

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[akelmanson]

akelmanson left a comment (wxWidgets/wxWidgets#26357)

@paulcor Confirmed — #26359 fixes the issue. Tested on Cosmic DE (smithay) and Sway (wlroots), splash screen now renders borderless on both. X11 unaffected.

Thanks for the quick fix!

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[paulcor]

Closed #26357 as completed.

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