Add debugging code to w32fns.c.

 src/w32fns.c (w32_wnd_proc) [ENABLE_CHECKING]: Add code to help
 identify the reasons for assertion violations in bug#14062 and
 similar ones.

2 files changed, 22 insertions, 0 deletions

diff --git a/src/ChangeLog b/src/ChangeLog
index d4edb2c3267..1e47fa0e1b6 100644
--- a/src/ChangeLog
+++ b/src/ChangeLog
@@ -1,5 +1,9 @@
 2013-03-28  Eli Zaretskii  <eliz@gnu.org>
 
+        * w32fns.c (w32_wnd_proc) [ENABLE_CHECKING]: Add code to help
+        identify the reasons for assertion violations in bug#14062 and
+        similar ones.
+
         * image.c (g_error_free) [WINDOWSNT]: Add DEF_IMGLIB_FN.
         Reported by <rzl24ozi@gmail.com>.
 
diff --git a/src/w32fns.c b/src/w32fns.c
index 88141893445..02cc2a00338 100644
--- a/src/w32fns.c
+++ b/src/w32fns.c
@@ -3155,8 +3155,26 @@ w32_wnd_proc (HWND hwnd, UINT msg, WPARAM wParam, LPARAM lParam)
           form.ptCurrentPos.y = w32_system_caret_y;
 
           form.rcArea.left = WINDOW_TEXT_TO_FRAME_PIXEL_X (w, 0);
+
+#ifdef ENABLE_CHECKING
+          /* Temporary code to catch crashes in computing form.rcArea.top.  */
+          {
+            int wmbp = WINDOW_MENU_BAR_P (w);
+            int wtbp = WINDOW_TOOL_BAR_P (w);
+            struct frame *wf = WINDOW_XFRAME (w);
+            int fibw = FRAME_INTERNAL_BORDER_WIDTH (wf);
+            int wtel = WINDOW_TOP_EDGE_LINE (w);
+            int wflh = FRAME_LINE_HEIGHT (wf);
+            int wwhlp= WINDOW_WANTS_HEADER_LINE_P (w);
+            int chlh = CURRENT_HEADER_LINE_HEIGHT (w);
+            int whlh = (wwhlp ? chlh : 0);
+
+            form.rcArea.top = ((wmbp || wtbp) ? 0 : fibw) + wtel * wflh + whlh;
+          }
+#else
           form.rcArea.top = (WINDOW_TOP_EDGE_Y (w)
                              + WINDOW_HEADER_LINE_HEIGHT (w));
+#endif
           form.rcArea.right = (WINDOW_BOX_RIGHT_EDGE_X (w)
                                - WINDOW_RIGHT_MARGIN_WIDTH (w)
                                - WINDOW_RIGHT_FRINGE_WIDTH (w));