01/01: [MSPAINT] Fix scrollbar presence on canvas/view fitting (#878)

[Ștefan Fulea]

https://git.reactos.org/?p=reactos.git;a=commitdiff;h=3d48aa2992d8c9c20d6cf7...

commit 3d48aa2992d8c9c20d6cf72065dc02fc07d3553b
Author:     Ștefan Fulea [e-mail]
AuthorDate: Sat Nov 17 00:05:51 2018 +0200
Commit:     Hermès BÉLUSCA - MAÏTO [e-mail]
CommitDate: Fri Nov 16 23:05:51 2018 +0100

[MSPAINT] Fix scrollbar presence on canvas/view fitting (#878)

* [MSPAINT] Fix scrollbar presence on canvas/view fitting

This is a small fix for a scrollbar related edge case functionality exhibited in mspaint (and in a lesser degree also elsewhere in instances of) scrollbar controlled content. As known, the scrollbars presence is given by the size ratio between the accommodating outer frame and the scroll-controlled contents inside it, and it works for the most part. There is, however, a case where the presence of both toolbars is kept even when the contents would fit the frame (if not for the scrollba [...]

* [MSPAINT] Fix a small mistake and improve readability in UpdateScrollbox()

Although with no visible impact on testing, I've used a wrong constant related to vertical scrollbox width in one instance (SM_CXHSCROLL instead of SM_CXVSCROLL), and this fixes it. Also, prefer using constants, to improve a bit readability and performance (by avoiding repeated function calls).
---
 base/applications/mspaint/scrollbox.cpp | 84 ++++++++++++++++++++++++++++-----
 1 file changed, 71 insertions(+), 13 deletions(-)

diff --git a/base/applications/mspaint/scrollbox.cpp b/base/applications/mspaint/scrollbox.cpp
index b0ef7373c7..351c59c717 100644
--- a/base/applications/mspaint/scrollbox.cpp
+++ b/base/applications/mspaint/scrollbox.cpp
@@ -9,31 +9,89 @@
 /* INCLUDES *********************************************************/

#include "precomp.h"
+#include <atltypes.h>
+
+/*
+ * Scrollbar functional modes:
+ * 0  view < canvas
+ * 1  view < canvas + scroll width
+ * 2  view >= canvas + scroll width
+ *
+ * Matrix of scrollbar presence (VERTICAL,HORIZONTAL) given by
+ * vertical & horizontal scrollbar modes (view:canvas ratio):
+ *
+ *           horizontal mode
+ *             |      0      |      1      |      2
+ * vertical ---+-------------+-------------+------------
+ *   mode    0 |  TRUE,TRUE  |  TRUE,TRUE  |  TRUE,FALSE
+ *          ---+-------------+-------------+------------
+ *           1 |  TRUE,TRUE  | FALSE,FALSE | FALSE,FALSE
+ *          ---+-------------+-------------+------------
+ *           2 | FALSE,TRUE  | FALSE,FALSE | FALSE,FALSE
+ */
+
+struct ScrollbarPresence
+{
+    BOOL bVert;
+    BOOL bHoriz;
+};
+
+CONST ScrollbarPresence sp_mx[3][3] =
+{
+    { {  TRUE,TRUE  }, {  TRUE,TRUE  }, {  TRUE,FALSE } },
+    { {  TRUE,TRUE  }, { FALSE,FALSE }, { FALSE,FALSE } },
+    { { FALSE,TRUE  }, { FALSE,FALSE }, { FALSE,FALSE } }
+};
+
+CONST INT HSCROLL_WIDTH = ::GetSystemMetrics(SM_CYHSCROLL);
+CONST INT VSCROLL_WIDTH = ::GetSystemMetrics(SM_CXVSCROLL);
+

/* FUNCTIONS ********************************************************/

void
 UpdateScrollbox()
 {
-    RECT clientRectScrollbox;
-    RECT clientRectImageArea;
+    CONST INT EXTRASIZE = 5; /* 3 px of selection markers + 2 px of border */
+
+    CRect tempRect;
+    CSize sizeImageArea;
+    CSize sizeScrollBox;
+    INT vmode, hmode;
     SCROLLINFO si;
-    scrollboxWindow.GetClientRect(&clientRectScrollbox);
-    imageArea.GetClientRect(&clientRectImageArea);
+
+    scrollboxWindow.GetWindowRect(&tempRect);
+    sizeScrollBox = CSize(tempRect.Width(), tempRect.Height());
+
+    imageArea.GetClientRect(&tempRect);
+    sizeImageArea = CSize(tempRect.Width(), tempRect.Height());
+    sizeImageArea += CSize(EXTRASIZE * 2, EXTRASIZE * 2);
+
+    /* show/hide the scrollbars */
+    vmode = (sizeScrollBox.cy < sizeImageArea.cy ? 0 :
+                (sizeScrollBox.cy < sizeImageArea.cy + HSCROLL_WIDTH ? 1 : 2));
+    hmode = (sizeScrollBox.cx < sizeImageArea.cx ? 0 :
+                (sizeScrollBox.cx < sizeImageArea.cx + VSCROLL_WIDTH ? 1 : 2));
+    scrollboxWindow.ShowScrollBar(SB_VERT, sp_mx[vmode][hmode].bVert);
+    scrollboxWindow.ShowScrollBar(SB_HORZ, sp_mx[vmode][hmode].bHoriz);
+
     si.cbSize = sizeof(SCROLLINFO);
     si.fMask  = SIF_PAGE | SIF_RANGE;
-    si.nMax   = clientRectImageArea.right + 6 - 1;
     si.nMin   = 0;
-    si.nPage  = clientRectScrollbox.right;
+
+    si.nMax   = sizeImageArea.cx +
+                    (sp_mx[vmode][hmode].bVert == TRUE ? HSCROLL_WIDTH : 0);
+    si.nPage  = sizeScrollBox.cx;
     scrollboxWindow.SetScrollInfo(SB_HORZ, &si);
-    scrollboxWindow.GetClientRect(&clientRectScrollbox);
-    si.nMax   = clientRectImageArea.bottom + 6 - 1;
-    si.nPage  = clientRectScrollbox.bottom;
+
+    si.nMax   = sizeImageArea.cy +
+                    (sp_mx[vmode][hmode].bHoriz == TRUE ? VSCROLL_WIDTH : 0);
+    si.nPage  = sizeScrollBox.cy;
     scrollboxWindow.SetScrollInfo(SB_VERT, &si);
-    scrlClientWindow.MoveWindow(
-        -scrollboxWindow.GetScrollPos(SB_HORZ), -scrollboxWindow.GetScrollPos(SB_VERT),
-        max(clientRectImageArea.right + 6, clientRectScrollbox.right),
-        max(clientRectImageArea.bottom + 6, clientRectScrollbox.bottom), TRUE);
+
+    scrlClientWindow.MoveWindow(-scrollboxWindow.GetScrollPos(SB_HORZ),
+                                -scrollboxWindow.GetScrollPos(SB_VERT),
+                                sizeImageArea.cx, sizeImageArea.cy, TRUE);
 }

LRESULT CScrollboxWindow::OnSize(UINT nMsg, WPARAM wParam, LPARAM lParam, BOOL& bHandled)