[reactos] 01/01: [NTUSER] Scrollbar.c, improve co_IntSetScrollInfo() CORE-17769

[Joachim Henze]

https://git.reactos.org/?p=reactos.git;a=commitdiff;h=dda9c3979e87223b66e61…

commit dda9c3979e87223b66e61f0f936f46920221e509
Author:     Joachim Henze <Joachim.Henze(a)reactos.org>
AuthorDate: Sun Sep 19 22:35:37 2021 +0200
Commit:     Joachim Henze <Joachim.Henze(a)reactos.org>
CommitDate: Sun Sep 19 22:35:37 2021 +0200

    [NTUSER] Scrollbar.c, improve co_IntSetScrollInfo() CORE-17769
    
    Fixes CORE-17769 'Rapps Listview manual resize may erroneously not draw the
triangles sometimes'
    This could happen for both: themed and unthemed.
    
    CORE-17769 was a regression introduced by 0.4.14-dev-1134-g
00adb1a3f967ac7f5cd56b4c39df72a7b3814603
    
    We don't really like the added state in form of the static variables,
    but the patch works good from a pure testing-perspective.
    
    Many Thanks to the patches author: Doug Lyons
---
 win32ss/user/ntuser/scrollbar.c | 18 ++++++++++++++++--
 1 file changed, 16 insertions(+), 2 deletions(-)

diff --git a/win32ss/user/ntuser/scrollbar.c b/win32ss/user/ntuser/scrollbar.c
index 52d5f38c377..eba1b41f666 100644
--- a/win32ss/user/ntuser/scrollbar.c
+++ b/win32ss/user/ntuser/scrollbar.c
@@ -495,6 +495,8 @@ co_IntSetScrollInfo(PWND Window, INT nBar, LPCSCROLLINFO lpsi, BOOL
bRedraw)
    /* [0] = HORZ, [1] = VERT */
    static PWND PrevHwnd[2] = { 0 };
    static DWORD PrevPos[2] = { 0 };
+   static DWORD PrevMax[2] = { 0 };
+   static INT PrevAction[2] = { 0 };
 
    ASSERT_REFS_CO(Window);
 
@@ -637,6 +639,16 @@ co_IntSetScrollInfo(PWND Window, INT nBar, LPCSCROLLINFO lpsi, BOOL
bRedraw)
    }
 
 //done:
+   if ((Window != PrevHwnd[nBar]) || (action != PrevAction[nBar]))
+   {
+      if ((action == SA_SSI_SHOW) && (PrevAction[nBar] == SA_SSI_HIDE))
+      {
+         co_UserShowScrollBar(Window, nBar, TRUE, TRUE);
+      }
+   }
+   if ((action != PrevAction[nBar]) && action != 0)
+      PrevAction[nBar] = action;
+
    if ( action & SA_SSI_HIDE )
    {
       co_UserShowScrollBar(Window, nBar, FALSE, FALSE);
@@ -690,12 +702,14 @@ co_IntSetScrollInfo(PWND Window, INT nBar, LPCSCROLLINFO lpsi, BOOL
bRedraw)
                }
             }
             CurrentPos = lpsi->fMask & SIF_PREVIOUSPOS ? OldPos :
pSBData->pos;
-            /* Check for changes to Window or CurrentPos */
-            if ((Window != PrevHwnd[nBar]) || (CurrentPos != PrevPos[nBar]))
+            /* Check for changes to Window or CurrentPos or lpsi->nMax */
+            if ((Window != PrevHwnd[nBar]) || (CurrentPos != PrevPos[nBar]) ||
+               (lpsi->nMax != PrevMax[nBar]))
             {
                 co_UserRedrawWindow(Window, &UpdateRect, 0, RDW_INVALIDATE |
RDW_FRAME);
                 PrevHwnd[nBar] = Window;
                 PrevPos[nBar] = CurrentPos;
+                PrevMax[nBar] = lpsi->nMax;
             }
          }
       } // FIXME: Arrows