[PATCH v2 0/1] MR10915: winex11: Ignore expected WM rects for shaped maximized windows

[Ivan Lyugaev (＠valy)]

I encountered a problem with flickering of a maximized window. I was able to determine that the issue arises from an extra call to NtUserSetWindowPos with incorrect rects. When SetWindowRgn is called, it triggers a call to NtUserSetWindowPos with SWP_NOSIZE | SWP_NOMOVE. Later, execution reaches the window_update_client_config function, where swp_flags are formed without SWP_NOSIZE | SWP_NOMOVE. These flags are formed because the rects in winex11 and win32u diverge:

Win32u rect: (-4,-4)-(1924,1175)
X11 desired rect: (0,0)-(1920,1171)
X11 current rect: (0,0)-(1920,1171)

In win32u, the rects are used after offset handling for the maximized window in the adjust_window_rect function. The formed swp_flags are passed to NtUserSetWindowPos, which causes the flickering.

--
  v2: winex11: Ignore expected WM rects for shaped maximized windows
 
https://gitlab.winehq.org/wine/wine/-/merge_requests/10915

[PATCH v2 1/1] winex11: Ignore expected WM rects for shaped maximized windows

[Ivan Lyugaev]

From: Ivan Lyugaev <[e-mail]>

---
 dlls/user32/tests/msg.c   | 72 +++++++++++++++++++++++++++++++++++++++
 dlls/winex11.drv/window.c |  9 +++++
 2 files changed, 81 insertions(+)

diff --git a/dlls/user32/tests/msg.c b/dlls/user32/tests/msg.c
index 6fd76d28533..ef67aae0cea 100644
--- a/dlls/user32/tests/msg.c
+++ b/dlls/user32/tests/msg.c
@@ -15410,6 +15410,77 @@ static const struct message WmSetWindowRgn_clear[] = {
     { 0 }
 };
 
+#define SET_WINDOW_RGN_FEEDBACK_LIMIT 10
+static unsigned int set_window_rgn_feedback_count;
+static BOOL set_window_rgn_feedback_armed;
+
+static void set_window_rgn_feedback_update_region(HWND hwnd)
+{
+    RECT rect;
+    HRGN rgn;
+    int width, height;
+    BOOL ret;
+
+    GetClientRect(hwnd, &rect);
+    width = rect.right - rect.left;
+    height = rect.bottom - rect.top;
+
+    rgn = CreateRectRgn(0, 0, width, height);
+    ret = SetWindowRgn(hwnd, rgn, TRUE);
+    if (!ret) DeleteObject(rgn);
+}
+
+static LRESULT CALLBACK set_window_rgn_feedback_proc(HWND hwnd, UINT msg, WPARAM wparam, LPARAM lparam)
+{
+    switch(msg)
+    {
+    case WM_WINDOWPOSCHANGED:
+        {
+            WINDOWPOS *pos = (WINDOWPOS *)lparam;
+            if (set_window_rgn_feedback_armed && ((pos->flags & (SWP_NOSIZE | SWP_NOMOVE)) != (SWP_NOSIZE | SWP_NOMOVE)))
+            {
+                set_window_rgn_feedback_count++;
+                if (set_window_rgn_feedback_count < SET_WINDOW_RGN_FEEDBACK_LIMIT)
+                    set_window_rgn_feedback_update_region(hwnd);
+            }
+            break;
+        }
+    }
+    return DefWindowProcA(hwnd, msg, wparam, lparam);
+}
+
+static void test_SetWindowRgn_Feedback(void)
+{
+    HWND hwnd;
+    HINSTANCE instance = GetModuleHandleA(0);
+    WNDCLASSA cls = {
+        .lpfnWndProc = set_window_rgn_feedback_proc,
+        .hInstance = GetModuleHandleA(0),
+        .hCursor = LoadCursorA(0, (LPCSTR)IDC_ARROW),
+        .hbrBackground = GetStockObject(WHITE_BRUSH),
+        .lpszClassName = "TestSetWindowRgnFeedback"
+    };
+
+    register_class(&cls);
+    hwnd = CreateWindowExA(WS_EX_APPWINDOW, "TestSetWindowRgnFeedback", "TestSetWindowRgnFeedback",
+                                 WS_MAXIMIZE, CW_USEDEFAULT, CW_USEDEFAULT, CW_USEDEFAULT, CW_USEDEFAULT,
+                                 NULL, NULL, instance, NULL);
+    ok(hwnd != 0, "CreateWindowExA failed\n");
+    ShowWindow(hwnd, SW_SHOWMAXIMIZED);
+    ok(IsZoomed(hwnd), "window should be maximized\n");
+
+    flush_events();
+    set_window_rgn_feedback_count = 0;
+    set_window_rgn_feedback_armed = TRUE;
+    set_window_rgn_feedback_update_region(hwnd);
+    flush_events();
+
+    set_window_rgn_feedback_armed = FALSE;
+    DestroyWindow(hwnd) ;
+    flush_events();
+    ok(!set_window_rgn_feedback_count, "got window region feedback loop, count %u (expected 0)\n", set_window_rgn_feedback_count);
+}
+
 static void test_SetWindowRgn(void)
 {
     HRGN hrgn;
@@ -21536,6 +21607,7 @@ START_TEST(msg)
         test_TrackMouseEvent();
 
     test_SetWindowRgn();
+    test_SetWindowRgn_Feedback();
     test_sys_menu();
     test_dialog_messages();
     test_EndDialog();
diff --git a/dlls/winex11.drv/window.c b/dlls/winex11.drv/window.c
index d2d53a40be3..bc4b2665dbd 100644
--- a/dlls/winex11.drv/window.c
+++ b/dlls/winex11.drv/window.c
@@ -1763,6 +1763,15 @@ static UINT window_update_client_config( struct x11drv_win_data *data )
             return 0;
     }
 
+    /* Ignore shaped window config changes when a maximized window is still at the desired
+     * rect. This is needed because when calling SetWindowRgn for a maximized window in X11,
+     * the rect after adjustment is mistakenly taken as an actual window resize. Syncing back X11 rects
+     * that do not include the adjustment causes SetWindowRgn to be called again, leading to visual flickering
+     * of the application window.*/
+    if (data->shaped && (data->current_state.net_wm_state & (1 << NET_WM_STATE_MAXIMIZED)) &&
+        EqualRect( &data->current_state.rect, &data->desired_state.rect ))
+        return 0;
+
     flags = SWP_NOACTIVATE | SWP_NOZORDER;
     rect = new_rect = window_rect_from_visible( &data->rects, data->current_state.rect );
     if (new_rect.left == old_rect.left && new_rect.top == old_rect.top) flags |= SWP_NOMOVE;
-- 
GitLab

https://gitlab.winehq.org/wine/wine/-/merge_requests/10915

[Ivan Lyugaev (＠valy)]

@rbernon Sorry to bother you — I assume you can help me with winex11.drv. My merge request has had 0 reviewers for a month now. Will it be reviewed?

-- 
https://gitlab.winehq.org/wine/wine/-/merge_requests/10915#note_143598

[Rémi Bernon (＠rbernon)]

Rémi Bernon (@rbernon) commented about dlls/winex11.drv/window.c:
> return 0;
>      }
>
> +    /* Ignore shaped window config changes when a maximized window is still at the desired
> +     * rect. This is needed because when calling SetWindowRgn for a maximized window in X11,
> +     * the rect after adjustment is mistakenly taken as an actual window resize. Syncing back X11 rects
> +     * that do not include the adjustment causes SetWindowRgn to be called again, leading to visual flickering
> +     * of the application window.*/
> +    if (data->shaped && (data->current_state.net_wm_state & (1 << NET_WM_STATE_MAXIMIZED)) &&
> +        EqualRect( &data->current_state.rect, &data->desired_state.rect ))
> +        return 0;

I'm thinking we could perhaps just return early if `EqualRect( &data->current_state.rect, &data->desired_state.rect )`, and I'm not even completely sure why we get there if it's the case already. There's perhaps some corner case I'm missing, I'll need to look into it.

-- 
https://gitlab.winehq.org/wine/wine/-/merge_requests/10915#note_143789