Add ability to delete from Find combobox history

When any of the Find window comboboxes are dropped and an entry is highlighted, pressing the Delete key will remove the highlighted entry from the following comboboxes:

1. Find what combobox
2. Replace with combobox
3. Directory combobox
4. Filters combobox

No method is provided for clearing all entries at once, but as the "depth" of the comboboxes is limited to a small amount, clearing one entry at a time (when one wants to clear all) is not overly burdensome.

Fix #9366, close #9396

PowerEditor/src/ScitillaComponent/FindReplaceDlg.cpp

@@ -443,10 +443,9 @@ int FindReplaceDlg::saveComboHistory(int id, int maxcount, vector<generic_string
 	int count = static_cast<int32_t>(::SendMessage(hCombo, CB_GETCOUNT, 0, 0));
 	count = min(count, maxcount);
 
-    if (count == CB_ERR) return 0;
+	if (count == CB_ERR) return 0;
 
-    if (count)
-        strings.clear();
+	strings.clear();
 
 	if (saveEmpty)
 	{
@@ -456,7 +455,7 @@ int FindReplaceDlg::saveComboHistory(int id, int maxcount, vector<generic_string
 		}
 	}
 
-    for (int i = 0 ; i < count ; ++i)
+	for (int i = 0 ; i < count ; ++i)
 	{
 		auto cbTextLen = ::SendMessage(hCombo, CB_GETLBTEXTLEN, i, 0);
 		if (cbTextLen <= FINDREPLACE_MAXLENGTH - 1)
@@ -465,7 +464,7 @@ int FindReplaceDlg::saveComboHistory(int id, int maxcount, vector<generic_string
 			strings.push_back(generic_string(text));
 		}
 	}
-    return count;
+	return count;
 }
 
 void FindReplaceDlg::updateCombos()
@@ -865,12 +864,16 @@ INT_PTR CALLBACK FindReplaceDlg::run_dlgProc(UINT message, WPARAM wParam, LPARAM
 			COMBOBOXINFO cbinfo = { sizeof(COMBOBOXINFO) };
 			GetComboBoxInfo(hFindCombo, &cbinfo);
 			originalComboEditProc = SetWindowLongPtr(cbinfo.hwndItem, GWLP_WNDPROC, reinterpret_cast<LONG_PTR>(comboEditProc));
+			SetWindowLongPtr(cbinfo.hwndItem, GWLP_USERDATA, reinterpret_cast<LONG_PTR>(cbinfo.hwndCombo));
 			GetComboBoxInfo(hReplaceCombo, &cbinfo);
 			SetWindowLongPtr(cbinfo.hwndItem, GWLP_WNDPROC, reinterpret_cast<LONG_PTR>(comboEditProc));
+			SetWindowLongPtr(cbinfo.hwndItem, GWLP_USERDATA, reinterpret_cast<LONG_PTR>(cbinfo.hwndCombo));
 			GetComboBoxInfo(hFiltersCombo, &cbinfo);
 			SetWindowLongPtr(cbinfo.hwndItem, GWLP_WNDPROC, reinterpret_cast<LONG_PTR>(comboEditProc));
+			SetWindowLongPtr(cbinfo.hwndItem, GWLP_USERDATA, reinterpret_cast<LONG_PTR>(cbinfo.hwndCombo));
 			GetComboBoxInfo(hDirCombo, &cbinfo);
 			SetWindowLongPtr(cbinfo.hwndItem, GWLP_WNDPROC, reinterpret_cast<LONG_PTR>(comboEditProc));
+			SetWindowLongPtr(cbinfo.hwndItem, GWLP_USERDATA, reinterpret_cast<LONG_PTR>(cbinfo.hwndCombo));
 
 			if ((NppParameters::getInstance()).getNppGUI()._monospacedFontFindDlg)
 			{
@@ -3245,7 +3248,31 @@ LRESULT FAR PASCAL FindReplaceDlg::finderProc(HWND hwnd, UINT message, WPARAM wP
 
 LRESULT FAR PASCAL FindReplaceDlg::comboEditProc(HWND hwnd, UINT message, WPARAM wParam, LPARAM lParam)
 {
-	if (message == WM_CHAR && wParam == 0x7F) // ASCII "DEL" (Ctrl+Backspace)
+	HWND hwndCombo = reinterpret_cast<HWND>(GetWindowLongPtr(hwnd, GWLP_USERDATA));
+
+	bool isDropped = ::SendMessage(hwndCombo, CB_GETDROPPEDSTATE, 0, 0) != 0;
+
+	if (isDropped && (message == WM_KEYDOWN) && (wParam == VK_DELETE))
+	{
+		int curSel = static_cast<int>(::SendMessage(hwndCombo, CB_GETCURSEL, 0, 0));
+		if (curSel != CB_ERR)
+		{
+			int itemsRemaining = static_cast<int>(::SendMessage(hwndCombo, CB_DELETESTRING, curSel, 0));
+			// if we close the dropdown and reopen it, it will be correctly-sized for remaining items
+			::SendMessage(hwndCombo, CB_SHOWDROPDOWN, FALSE, 0);
+			if (itemsRemaining > 0)
+			{
+				if (itemsRemaining == curSel)
+				{
+					--curSel;
+				}
+				::SendMessage(hwndCombo, CB_SETCURSEL, curSel, 0);
+				::SendMessage(hwndCombo, CB_SHOWDROPDOWN, TRUE, 0);
+			}
+			return 0;
+		}
+	}
+	else if (message == WM_CHAR && wParam == 0x7F) // ASCII "DEL" (Ctrl+Backspace)
 	{
 		delLeftWordInEdit(hwnd);
 		return 0;