[EXPLORER] Show time and date when two lines are available in the taskbar clock area (#5410)

- Add registry key to show the time and date when two lines are available
in the taskbar clock area.
- Keep old behavior when `PreferDateOverWeekday` registry key in
`HKCU\Software\Microsoft\Windows\CurrentVersion\Explorer\Advanced`
is set to 0 or not present.

When three or more lines are available, the clock will continue to show
the time, day of the week, and the date. When only one line is visible,
the clock will continue to only display the time.

CORE-19018

base/shell/explorer/precomp.h

···
     BOOL bLock;
     BOOL bGroupButtons;
     BOOL bShowSeconds;
+    BOOL bPreferDate;
     BOOL bHideInactiveIcons;
     TW_STRUCKRECTS2 sr;
 

base/shell/explorer/settings.cpp

···
 BOOL TaskbarSettings::Save()
 {
     SHSetValueW(hkExplorer, NULL, L"EnableAutotray", REG_DWORD, &bHideInactiveIcons, sizeof(bHideInactiveIcons));
+    SHSetValueW(hkExplorer, L"Advanced", L"PreferDateOverWeekday", REG_DWORD, &bPreferDate, sizeof(bPreferDate));
     SHSetValueW(hkExplorer, L"Advanced", L"ShowSeconds", REG_DWORD, &bShowSeconds, sizeof(bShowSeconds));
     SHSetValueW(hkExplorer, L"Advanced", L"TaskbarGlomming", REG_DWORD, &bGroupButtons, sizeof(bGroupButtons));
     BOOL bAllowSizeMove = !bLock;
···
     cbSize = sizeof(dwValue);
     dwRet = SHGetValueW(hkExplorer, L"Advanced", L"TaskbarSizeMove", NULL, &dwValue, &cbSize);
     bLock = (dwRet == ERROR_SUCCESS) ? (dwValue == 0) : TRUE;
+
+    dwRet = SHGetValueW(hkExplorer, L"Advanced", L"PreferDateOverWeekday", NULL, &dwValue, &cbSize);
+    bPreferDate = (dwRet == ERROR_SUCCESS) ? (dwValue != 0) : FALSE; /* This is opt-in setting */
 
     dwRet = SHGetValueW(hkExplorer, L"Advanced", L"ShowSeconds", NULL, &dwValue, &cbSize);
     bShowSeconds = (dwRet == ERROR_SUCCESS) ? (dwValue != 0) : FALSE;

base/shell/explorer/trayclock.cpp

···
 const UINT ClockWndFormatsCount = _ARRAYSIZE(ClockWndFormats);
 
 #define CLOCKWND_FORMAT_COUNT ClockWndFormatsCount
+#define CLOCKWND_FORMAT_TIME 0
+#define CLOCKWND_FORMAT_DAY  1
+#define CLOCKWND_FORMAT_DATE 2
 
 static const WCHAR szTrayClockWndClass[] = L"TrayClockWClass";
 
···
     LRESULT OnSize(UINT uMsg, WPARAM wParam, LPARAM lParam, BOOL& bHandled);
     LRESULT OnTaskbarSettingsChanged(UINT uMsg, WPARAM wParam, LPARAM lParam, BOOL& bHandled);
     LRESULT OnLButtonDblClick(UINT uMsg, WPARAM wParam, LPARAM lParam, BOOL& bHandled);
+    VOID PaintLine(IN HDC hDC, IN OUT RECT *rcClient, IN UINT LineNumber, IN UINT szLinesIndex);
 
 public:
 
···
         rcClient.top = (rcClient.bottom - CurrentSize.cy) / 2;
         rcClient.bottom = rcClient.top + CurrentSize.cy;
 
-        for (i = 0, line = 0;
-                i < CLOCKWND_FORMAT_COUNT && line < VisibleLines;
-                i++)
+        if (VisibleLines == 2)
+        {
+            /* Display either time and weekday (by default), or time and date (opt-in) */
+            PaintLine(hDC, &rcClient, 0, CLOCKWND_FORMAT_TIME);
+            PaintLine(hDC, &rcClient, 1,
+                      g_TaskbarSettings.bPreferDate ? CLOCKWND_FORMAT_DATE : CLOCKWND_FORMAT_DAY);
+        }
+        else
         {
-            if (LineSizes[i].cx != 0)
+            for (i = 0, line = 0;
+                 i < CLOCKWND_FORMAT_COUNT && line < VisibleLines;
+                 i++)
             {
-                TextOut(hDC,
-                    (rcClient.right - LineSizes[i].cx) / 2,
-                    rcClient.top + TRAY_CLOCK_WND_SPACING_Y,
-                    szLines[i],
-                    wcslen(szLines[i]));
-
-                rcClient.top += LineSizes[i].cy + LineSpacing;
+                PaintLine(hDC, &rcClient, i, i);
                 line++;
             }
         }
···
         EndPaint(&ps);
 
     return TRUE;
+}
+
+VOID CTrayClockWnd::PaintLine(IN HDC hDC, IN OUT RECT *rcClient, IN UINT LineNumber, IN UINT szLinesIndex)
+{
+    if (LineSizes[LineNumber].cx == 0)
+        return;
+
+    TextOut(hDC,
+            (rcClient->right - LineSizes[szLinesIndex].cx) / 2,
+            rcClient->top + TRAY_CLOCK_WND_SPACING_Y,
+            szLines[szLinesIndex],
+            wcslen(szLines[szLinesIndex]));
+
+    rcClient->top += LineSizes[LineNumber].cy + LineSpacing;
 }
 
 VOID CTrayClockWnd::SetFont(IN HFONT hNewFont, IN BOOL bRedraw)
···
         {
             ResetTime();
         }
+    }
+
+    if (newSettings->bPreferDate != g_TaskbarSettings.bPreferDate)
+    {
+        g_TaskbarSettings.bPreferDate = newSettings->bPreferDate;
+        bRealign = TRUE;
     }
 
     if (bRealign)

boot/bootdata/hivedef.inf

···
 HKCU,"SOFTWARE\Microsoft\Windows\CurrentVersion\Explorer\CLSID\{20D04FE0-3AEA-1069-A2D8-08002B30309D}",,0x00000012
 HKCU,"SOFTWARE\Microsoft\Windows\CurrentVersion\Explorer\Advanced","ListviewShadow",0x00010003,0x00000001
 HKCU,"SOFTWARE\Microsoft\Windows\CurrentVersion\Explorer\Advanced","HideFileExt",0x00010003,0x00000000
+HKCU,"SOFTWARE\Microsoft\Windows\CurrentVersion\Explorer\Advanced","PreferDateOverWeekday",0x00010003,0x00000001
 HKCU,"SOFTWARE\Microsoft\Windows\CurrentVersion\Explorer\Advanced","StartMenuLogoff",0x00010003,0x00000001
 ; "Hidden" to be changed to 2 if we later want to have "Hide hidden files by default"
 HKCU,"SOFTWARE\Microsoft\Windows\CurrentVersion\Explorer\Advanced","Hidden",0x00010003,1