win32: adjust top border offset when title bar is disabled

Windows 11 draws border regardless, so we are 1px off on window size,
blending border with one line of video. Fix that by adding the border to
our internal windows size calculation.

Windows 10 on the other hand has a bug where specifying left and top NC
area will trigger title bar drawn in full height always. Keep old
behaviour in this case. Also while there is similar "visible" border
there, it seems to be transparent on Windows 10.

For high contrast themes, don't adjust title bar height and instead
remove WS_CAPTION to have the same border all around the window, as DWM
doesn't make borders invisible in this case.

1 files changed, 52 insertions, 18 deletions

diff --git a/video/out/w32_common.c b/video/out/w32_common.c
index 51e40d1166..a4e61a3db5 100644
--- a/video/out/w32_common.c
+++ b/video/out/w32_common.c
@@ -217,13 +217,43 @@ static void adjust_window_rect(struct vo_w32_state *w32, HWND hwnd, RECT *rc)
     }
 }
 
+// Get adjusted title bar height, only relevant for --title-bar=no
+static int get_title_bar_height(struct vo_w32_state *w32)
+{
+    assert(!w32->opts->title_bar && w32->opts->border);
+    UINT visible_border = 0;
+    // Only available on Windows 11
+    DwmGetWindowAttribute(w32->window, DWMWA_VISIBLE_FRAME_BORDER_THICKNESS,
+                          &visible_border, sizeof(visible_border));
+    int top_bar = IsMaximized(w32->window)
+                      ? get_system_metrics(w32, SM_CYFRAME) +
+                        get_system_metrics(w32, SM_CXPADDEDBORDER)
+                      : visible_border;
+    return top_bar;
+}
+
 static void add_window_borders(struct vo_w32_state *w32, HWND hwnd, RECT *rc)
 {
     RECT win = *rc;
     adjust_window_rect(w32, hwnd, rc);
     // Adjust for title bar height that will be hidden in WM_NCCALCSIZE
-    if (w32->opts->border && !w32->opts->title_bar && !w32->current_fs)
-        rc->top -= rc->top - win.top;
+    // Keep the frame border. On Windows 10 the top border is not retained.
+    // It appears that DWM draws the title bar with its full height, extending
+    // outside the window area. Essentially, there is a bug in DWM, preventing
+    // the adjustment of the title bar height. This issue occurs when both the
+    // top and left client areas are non-zero in WM_NCCALCSIZE. If the left NC
+    // area is set to 0, the title bar is drawn correctly with the adjusted
+    // height. To mitigate this problem, set the top NC area to zero. The issue
+    // doesn't happen on Windows 11 or when DWM NC drawing is disabled with
+    // DWMWA_NCRENDERING_POLICY. We aim to avoid the manual drawing the border
+    // and want the DWM look and feel, so skip the top border on Windows 10.
+    // Also DWMWA_VISIBLE_FRAME_BORDER_THICKNESS is available only on Windows 11,
+    // so it would be hard to guess this size correctly on Windows 10 anyway.
+    if (w32->opts->border && !w32->opts->title_bar && !w32->current_fs &&
+       (GetWindowLongPtrW(w32->window, GWL_STYLE) & WS_CAPTION))
+    {
+        rc->top = win.top - get_title_bar_height(w32);
+    }
 }
 
 // basically a reverse AdjustWindowRect (win32 doesn't appear to have this)
@@ -874,6 +904,13 @@ static bool snap_to_screen_edges(struct vo_w32_state *w32, RECT *rc)
     return true;
 }
 
+static bool is_high_contrast(void)
+{
+    HIGHCONTRAST hc = {sizeof(hc)};
+    SystemParametersInfo(SPI_GETHIGHCONTRAST, sizeof(hc), &hc, 0);
+    return hc.dwFlags & HCF_HIGHCONTRASTON;
+}
+
 static DWORD update_style(struct vo_w32_state *w32, DWORD style)
 {
     const DWORD NO_FRAME = WS_OVERLAPPED | WS_MINIMIZEBOX | WS_THICKFRAME;
@@ -885,17 +922,12 @@ static DWORD update_style(struct vo_w32_state *w32, DWORD style)
         style |= FULLSCREEN;
     } else {
         style |= w32->opts->border ? FRAME : NO_FRAME;
+        if (!w32->opts->title_bar && is_high_contrast())
+            style &= ~WS_CAPTION;
     }
     return style;
 }
 
-static LONG get_title_bar_height(struct vo_w32_state *w32)
-{
-    RECT rc = {0};
-    adjust_window_rect(w32, w32->window, &rc);
-    return -rc.top;
-}
-
 static void update_window_style(struct vo_w32_state *w32)
 {
     if (w32->parent)
@@ -1210,13 +1242,9 @@ static void update_dark_mode(const struct vo_w32_state *w32)
     if (w32->api.pSetPreferredAppMode)
         w32->api.pSetPreferredAppMode(1); // allow dark mode
 
-    HIGHCONTRAST hc = {sizeof(hc)};
-    SystemParametersInfo(SPI_GETHIGHCONTRAST, sizeof(hc), &hc, 0);
-    bool high_contrast = hc.dwFlags & HCF_HIGHCONTRASTON;
-
     // if pShouldAppsUseDarkMode is not available, just assume it to be true
-    const BOOL use_dark_mode = !high_contrast && (!w32->api.pShouldAppsUseDarkMode ||
-                                                  w32->api.pShouldAppsUseDarkMode());
+    const BOOL use_dark_mode = !is_high_contrast() && (!w32->api.pShouldAppsUseDarkMode ||
+                                                       w32->api.pShouldAppsUseDarkMode());
 
     SetWindowTheme(w32->window, use_dark_mode ? L"DarkMode_Explorer" : L"", NULL);
 
@@ -1591,6 +1619,8 @@ static LRESULT CALLBACK WndProc(HWND hWnd, UINT message, WPARAM wParam,
         break;
     case WM_SETTINGCHANGE:
         update_dark_mode(w32);
+        update_window_style(w32);
+        update_window_state(w32);
         break;
     case WM_NCCALCSIZE:
         if (!w32->opts->border)
@@ -1598,10 +1628,14 @@ static LRESULT CALLBACK WndProc(HWND hWnd, UINT message, WPARAM wParam,
         // Apparently removing WS_CAPTION disables some window animation, instead
         // just reduce non-client size to remove title bar.
         if (wParam && lParam && w32->opts->border && !w32->opts->title_bar &&
-            !w32->current_fs && !w32->parent)
+            !w32->current_fs && !w32->parent &&
+            (GetWindowLongPtrW(w32->window, GWL_STYLE) & WS_CAPTION))
         {
-            ((LPNCCALCSIZE_PARAMS) lParam)->rgrc[0].top -= get_title_bar_height(w32);
-        }
+            RECT r = {0};
+            adjust_window_rect(w32, w32->window, &r);
+            NCCALCSIZE_PARAMS *p = (LPNCCALCSIZE_PARAMS)lParam;
+            p->rgrc[0].top += r.top + get_title_bar_height(w32);
+       }
         break;
     case WM_IME_STARTCOMPOSITION: {
         HIMC imc = ImmGetContext(w32->window);