comctl32/edit: Don't use WM_TIMER to update caret position.

An application subclasses edit control and crashes on unexpected WM_TIMER messages. A timer was added a long time ago and it was for auto scrolling the view when the cursor is outside of the client area. However, with a EDIT_EM_ScrollCaret() call in EDIT_WM_MouseMove(), the view can be scrolled to the correct position automatically. So the timer is not necessary at all. This is tested manually with a long text in the edit control with notepad on XP, Win7 and Win10. Before this patch, the caret will move backwards every 100ms when the clicking the left mouse button on the bottom of the text and then dragging the cursor upwards and outside of the client area. After this, the behavior is the same as native.

comctl32/edit: Don't use WM_TIMER to update caret position.
753ddd3a · Zhiyi Zhang · Alexandre Julliard · 03d6a867 · 753ddd3a
Commit 753ddd3a authored Dec 13, 2022 by Zhiyi Zhang Committed by Alexandre Julliard Sep 06, 2023
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edit.c dlls/comctl32/edit.c +1 -39

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--- a/dlls/comctl32/edit.c
+++ b/dlls/comctl32/edit.c
@@ -113,8 +113,6 @@ typedef struct
 	RECT format_rect;
 	INT text_width;			/* width of the widest line in pixels for multi line controls
 					   and just line width for single line controls	*/
-	INT region_posx;		/* Position of cursor relative to region: */
-	INT region_posy;		/* -1: to left, 0: within, 1: to right */
 	EDITWORDBREAKPROCW word_break_proc;
 	INT line_count;			/* number of lines */
 	INT y_offset;			/* scroll offset in number of lines */
@@ -3438,8 +3436,6 @@ static LRESULT EDIT_WM_LButtonDblClk(EDITSTATE *es)
 	e = li + EDIT_CallWordBreakProc(es, li, e - li, ll, WB_RIGHT);
 	EDIT_EM_SetSel(es, s, e, FALSE);
 	EDIT_EM_ScrollCaret(es);
-	es->region_posx = es->region_posy = 0;
-	SetTimer(es->hwndSelf, 0, 100, NULL);
 	return 0;
 }

@@ -3460,8 +3456,6 @@ static LRESULT EDIT_WM_LButtonDown(EDITSTATE *es, DWORD keys, INT x, INT y)
 	e = EDIT_CharFromPos(es, x, y, &after_wrap);
 	EDIT_EM_SetSel(es, (keys & MK_SHIFT) ? es->selection_start : e, e, after_wrap);
 	EDIT_EM_ScrollCaret(es);
-	es->region_posx = es->region_posy = 0;
-	SetTimer(es->hwndSelf, 0, 100, NULL);

 	if (!(es->flags & EF_FOCUSED))
            SetFocus(es->hwndSelf);
@@ -3478,7 +3472,6 @@ static LRESULT EDIT_WM_LButtonDown(EDITSTATE *es, DWORD keys, INT x, INT y)
 static LRESULT EDIT_WM_LButtonUp(EDITSTATE *es)
 {
 	if (es->bCaptureState) {
-		KillTimer(es->hwndSelf, 0);
 		if (GetCapture() == es->hwndSelf) ReleaseCapture();
 	}
 	es->bCaptureState = FALSE;
@@ -3507,7 +3500,6 @@ static LRESULT EDIT_WM_MouseMove(EDITSTATE *es, INT x, INT y)
 {
 	INT e;
 	BOOL after_wrap;
-	INT prex, prey;

        /* If the mouse has been captured by process other than the edit control itself,
         * the windows edit controls will not select the strings with mouse move.
@@ -3515,17 +3507,10 @@ static LRESULT EDIT_WM_MouseMove(EDITSTATE *es, INT x, INT y)
        if (!es->bCaptureState || GetCapture() != es->hwndSelf)
 		return 0;

-	/*
-	 *	FIXME: gotta do some scrolling if outside client
-	 *		area.  Maybe reset the timer ?
-	 */
-	prex = x; prey = y;
-	EDIT_ConfinePoint(es, &x, &y);
-	es->region_posx = (prex < x) ? -1 : ((prex > x) ? 1 : 0);
-	es->region_posy = (prey < y) ? -1 : ((prey > y) ? 1 : 0);
 	e = EDIT_CharFromPos(es, x, y, &after_wrap);
 	EDIT_EM_SetSel(es, es->selection_start, e, after_wrap);
 	EDIT_SetCaretPos(es,es->selection_end,es->flags & EF_AFTER_WRAP);
+	EDIT_EM_ScrollCaret(es);
 	return 0;
 }

@@ -3924,25 +3909,6 @@ static LRESULT EDIT_WM_SysKeyDown(EDITSTATE *es, INT key, DWORD key_data)
 	return DefWindowProcW(es->hwndSelf, WM_SYSKEYDOWN, key, key_data);
 }

-
-/*********************************************************************
- *
- *	WM_TIMER
- *
- */
-static void EDIT_WM_Timer(EDITSTATE *es)
-{
-	if (es->region_posx < 0) {
-		EDIT_MoveBackward(es, TRUE);
-	} else if (es->region_posx > 0) {
-		EDIT_MoveForward(es, TRUE);
-	}
-/*
- *	FIXME: gotta do some vertical scrolling here, like
- *		EDIT_EM_LineScroll(hwnd, 0, 1);
- */
-}
-
 /*********************************************************************
 *
 *	WM_HSCROLL
@@ -4915,10 +4881,6 @@ static LRESULT CALLBACK EDIT_WindowProc(HWND hwnd, UINT msg, WPARAM wParam, LPAR
        result = EDIT_WM_SysKeyDown(es, (INT)wParam, (DWORD)lParam);
        break;

-    case WM_TIMER:
-        EDIT_WM_Timer(es);
-        break;
-
    case WM_VSCROLL:
        result = EDIT_WM_VScroll(es, LOWORD(wParam), (short)HIWORD(wParam));
        break;