如何实现右键点击TRichEdit控件单词时光标定位至单词内部？

Absolutely! You can totally get your TRichEdit control to position the cursor inside a clicked word when you right-click—just like a left-click does. Here's a straightforward way to make this work in Delphi:

Step 1: Handle the OnMouseDown Event #

Hook into the TRichEdit's OnMouseDown event to capture right-clicks and adjust the cursor position before the context menu pops up.

Step 2: Add the Implementation Code #

Drop this code into your form's unit. It converts the mouse position to a character index, then moves the cursor to that exact spot:

procedure TYourForm.RichEdit1MouseDown(Sender: TObject; Button: TMouseButton;
  Shift: TShiftState; X, Y: Integer);
var
  ClickPoint: TPoint;
  CharIndex: Integer;
begin
  // Only act on right-clicks
  if Button = mbRight then
  begin
    // Convert screen cursor position to the RichEdit's client coordinates
    ClickPoint := RichEdit1.ScreenToClient(Mouse.CursorPos);
    
    // Use the native Windows message to get the character index at the clicked spot
    CharIndex := RichEdit1.Perform(EM_CHARFROMPOS, 0, LPARAM(@ClickPoint));
    
    // Make sure we're within valid text bounds
    if (CharIndex >= 0) and (CharIndex < RichEdit1.GetTextLen) then
    begin
      // Position the cursor at the clicked character (match left-click behavior)
      RichEdit1.SelStart := CharIndex;
      RichEdit1.SelLength := 0;
      
      // If you have a custom popup menu, uncomment this to show it
      // YourPopupMenu.Popup(Mouse.CursorPos.X, Mouse.CursorPos.Y);
    end;
  end;
end;

Key Details: #

• EM_CHARFROMPOS: This native Windows message tells the TRichEdit to return the 0-based index of the character under the specified mouse position—perfect for pinpointing where the user clicked.
• Cursor Positioning: Setting SelStart to the character index and SelLength to 0 moves the cursor to that exact spot, matching left-click behavior exactly.
• Custom Menus: If you’re using a custom popup menu, call its Popup method after adjusting the cursor to ensure it behaves as expected.

Optional: Ensure Cursor Lands on a Word #

If you want to only adjust the cursor when clicking actual words (not blank spaces), add a check to verify the character is part of a word:

// Add this right after getting CharIndex
if (CharIndex >= 0) and (CharIndex < RichEdit1.GetTextLen) then
begin
  // Check if the character is alphanumeric (part of a word)
  if IsCharAlphaNumeric(RichEdit1.Text[CharIndex + 1]) then // Delphi strings are 1-based
  begin
    RichEdit1.SelStart := CharIndex;
    RichEdit1.SelLength := 0;
  end;
end;

This way, right-clicking on blank space won’t move the cursor—only clicks on words will trigger the positioning.

内容的提问来源于stack exchange，提问作者Max Smith