user32: Improve mouse wheel scrolling in edit control.

Allow fractions of WHEEL_DELTA to scroll fractions of SPI_GETWHEELSCROLLLINES, although still only whole lines. Keep the remainder and apply it to next event if in same direction.

user32: Improve mouse wheel scrolling in edit control.
1642d312 · Ken Thomases · Alexandre Julliard · 8f1a3604 · 1642d312
Commit 1642d312 authored Feb 10, 2013 by Ken Thomases Committed by Alexandre Julliard Feb 11, 2013
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Showing with 17 additions and 6 deletions

edit.c dlls/user32/edit.c +17 -6

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--- a/dlls/user32/edit.c
+++ b/dlls/user32/edit.c
@@ -140,6 +140,7 @@ typedef struct
 				           Even if parent will change, EN_* messages
 					   should be sent to the first parent. */
 	HWND hwndListBox;		/* handle of ComboBox's listbox or NULL */
+	INT wheelDeltaRemainder;        /* scroll wheel delta left over after scrolling whole lines */
 	/*
 	 *	only for multi line controls
 	 */
@@ -3551,6 +3552,8 @@ static LRESULT EDIT_WM_KillFocus(EDITSTATE *es)
 	if(!(es->style & ES_NOHIDESEL))
 		EDIT_InvalidateText(es, es->selection_start, es->selection_end);
 	EDIT_NOTIFY_PARENT(es, EN_KILLFOCUS);
+	/* throw away left over scroll when we lose focus */
+	es->wheelDeltaRemainder = 0;
 	return 0;
 }

@@ -5108,7 +5111,7 @@ LRESULT EditWndProc_common( HWND hwnd, UINT msg, WPARAM wParam, LPARAM lParam, B

        case WM_MOUSEWHEEL:
                {
-                    int gcWheelDelta = 0;
+                    int wheelDelta;
                    UINT pulScrollLines = 3;
                    SystemParametersInfoW(SPI_GETWHEELSCROLLLINES,0, &pulScrollLines, 0);

@@ -5116,12 +5119,20 @@ LRESULT EditWndProc_common( HWND hwnd, UINT msg, WPARAM wParam, LPARAM lParam, B
                        result = DefWindowProcW(hwnd, msg, wParam, lParam);
                        break;
                    }
-                    gcWheelDelta -= GET_WHEEL_DELTA_WPARAM(wParam);
-                    if (abs(gcWheelDelta) >= WHEEL_DELTA && pulScrollLines)
+                    wheelDelta = GET_WHEEL_DELTA_WPARAM(wParam);
+                    /* if scrolling changes direction, ignore left overs */
+                    if ((wheelDelta < 0 && es->wheelDeltaRemainder < 0) ||
+                        (wheelDelta > 0 && es->wheelDeltaRemainder > 0))
+                        es->wheelDeltaRemainder += wheelDelta;
+                    else
+                        es->wheelDeltaRemainder = wheelDelta;
+                    if (es->wheelDeltaRemainder && pulScrollLines)
                    {
-                        int cLineScroll= (int) min((UINT) es->line_count, pulScrollLines);
-                        cLineScroll *= (gcWheelDelta / WHEEL_DELTA);
-			result = EDIT_EM_LineScroll(es, 0, cLineScroll);
+                        int cLineScroll;
+                        pulScrollLines = (int) min((UINT) es->line_count, pulScrollLines);
+                        cLineScroll = pulScrollLines * (float)es->wheelDeltaRemainder / WHEEL_DELTA;
+                        es->wheelDeltaRemainder -= WHEEL_DELTA * cLineScroll / (int)pulScrollLines;
+                        result = EDIT_EM_LineScroll(es, 0, -cLineScroll);
                    }
                }
                break;