[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

@@ -208,6 +208,7 @@ struct TaskbarSettings
     BOOL bLock;
     BOOL bGroupButtons;
     BOOL bShowSeconds;
+    BOOL bPreferDate;
     BOOL bHideInactiveIcons;
     TW_STRUCKRECTS2 sr;
 

base/shell/explorer/settings.cpp

@@ -25,6 +25,7 @@ TaskbarSettings g_TaskbarSettings;
 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;
@@ -44,6 +45,9 @@ BOOL TaskbarSettings::Load()
     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

@@ -38,6 +38,9 @@ const struct
 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";
 
@@ -98,6 +101,7 @@ private:
     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:
 
@@ -529,19 +533,20 @@ LRESULT CTrayClockWnd::OnPaint(UINT uMsg, WPARAM wParam, LPARAM lParam, BOOL& bH
         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)
         {
-            if (LineSizes[i].cx != 0)
+            /* 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
+        {
+            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++;
             }
         }
@@ -557,6 +562,20 @@ LRESULT CTrayClockWnd::OnPaint(UINT uMsg, WPARAM wParam, LPARAM lParam, BOOL& bH
     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)
 {
     hFont = hNewFont;
@@ -704,6 +723,12 @@ LRESULT CTrayClockWnd::OnTaskbarSettingsChanged(UINT uMsg, WPARAM wParam, LPARAM
         }
     }
 
+    if (newSettings->bPreferDate != g_TaskbarSettings.bPreferDate)
+    {
+        g_TaskbarSettings.bPreferDate = newSettings->bPreferDate;
+        bRealign = TRUE;
+    }
+
     if (bRealign)
     {
         /* Ask the parent to resize */

boot/bootdata/hivedef.inf

@@ -1894,6 +1894,7 @@ HKCU,"SOFTWARE\Microsoft\Windows\CurrentVersion\Explorer\HideDesktopIcons\Classi
 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