Avoid drawing wxListCtrl items when we need to just measure them

In dark mode we redrew all the items when setting the column width to
"automatic" size which made it very slow compared to light mode.

Just don't do it in this case, as it's completely unnecessary.

This brings the time for autosizing 10 columns with 500 items down from
~9s to ~250ms which is almost the same as in light mode.

Closes #24011.

include/wx/msw/listctrl.h

@@ -481,6 +481,9 @@ private:
     // another WM_SIZE to be generated.
     int m_inResize = 0;
 
+    // Non-zero while the native control is auto-sizing a column, which it does
+    // by sending NM_CUSTOMDRAW notifications for all of its items.
+    int m_inAutoSize = 0;
 
     wxDECLARE_DYNAMIC_CLASS(wxListCtrl);
     wxDECLARE_EVENT_TABLE();

src/msw/listctrl.cpp

@@ -843,7 +843,18 @@ bool wxListCtrl::SetColumnWidth(int col, int width)
         return true;
     }
 
-    if ( !ListView_SetColumnWidth(GetHwnd(), col, width) )
+    // See the comment in OnCustomDraw() for why we need to know about this.
+    const bool autoSize = width == LVSCW_AUTOSIZE ||
+                            width == LVSCW_AUTOSIZE_USEHEADER;
+    if ( autoSize )
+        m_inAutoSize++;
+
+    const bool ok = ListView_SetColumnWidth(GetHwnd(), col, width) != FALSE;
+
+    if ( autoSize )
+        m_inAutoSize--;
+
+    if ( !ok )
         return false;
 
     // Failure to explicitly refresh the control with horizontal rules results
@@ -3540,7 +3551,11 @@ WXLPARAM wxListCtrl::OnCustomDraw(WXLPARAM lParam)
             //
             // for virtual controls, always suppose that we have attributes as
             // there is no way to check for this
-            if ( IsVirtual() || m_hasAnyAttr || wxMSWDarkMode::IsActive() )
+            //
+            // in dark mode we also need to draw all items ourselves, but not
+            // when auto-sizing the columns, see CDDS_ITEMPREPAINT case below
+            if ( IsVirtual() || m_hasAnyAttr ||
+                    (wxMSWDarkMode::IsActive() && !m_inAutoSize) )
                 return CDRF_NOTIFYITEMDRAW;
             break;
 
@@ -3552,7 +3567,15 @@ WXLPARAM wxListCtrl::OnCustomDraw(WXLPARAM lParam)
             // repeat the same drawing once per column, which is not only
             // wasteful but also results in visible delays when scrolling
             // lists with many columns.
-            if ( wxMSWDarkMode::IsActive() && InReportView() )
+            //
+            // Don't do it while auto-sizing a column however: in this case the
+            // native control sends us this notification for every item, but
+            // only to allow us to select a different font for measuring it, so
+            // painting the entire row here would be useless and would make
+            // setting the column width very slow for big controls (see
+            // #24011). Just fall through to the default handling below, which
+            // takes care of the custom fonts, if any, instead.
+            if ( wxMSWDarkMode::IsActive() && InReportView() && !m_inAutoSize )
             {
                 const int item = nmcd.dwItemSpec;