Simple splitter with CWnd-derived panes

• Download demo project - 14.2 Kb
• Download source - 3.65 Kb

Introduction

Yes, it's yet another splitter window class. So why I release a new class, when there are a plenty of similar classes? The answer is simple. All splitter window classes at CodeProject can be IMHO divided into two parts:

• These derived from original MFC CSplitterWnd. They look nice and give a lot of advantages to classical CSplitterWnd, but deriving from CSplitterWnd restrict you to use only CView-derived windows in it.
• The others, which I can use in various windows - but when I compiled and tested them, they didn't look as pretty as the CSplitterWnd.

In this article I offer a class, which is not derived from CSplitterWnd. It allows you to use simple CWnd-derived windows. But it's combined with professional looking of the original CSplitterWnd. Some routines I took from MFC source code. Please be forbearing while reading this article. It's my first article at CodeProject :).

Features

My goal in CSimpleSplitterWnd design was to simulate the basic features of CSplitterWnd. With this class you can make several panes arranged either horizontally or vertically. It doesn't offer automatic splitting, shared scroll bars and intersection trackers. I didn't find it very useful - but if there are enough people, who did, I can add some of these features :) The idea of CSimpleSplitter (compared to CSplitterWnd) is that pane windows are independent to each other, hence they are also responsible for their scrolling and borders.

Using the code

The layout of splitter is set in constructor:

CSimpleSplitter(int nPanes, UINT nOrientation = SSP_HORZ,   
 int nMinSize = 30, int nBarThickness = 3);

nPanes is number of the panes, nOrientation should be either SSP_HORZ or SSP_VERT. nMinSize is the minimal height (or width) of any pane - it is important in recalculating layout algorithm, when you resize the splitter. nBarThickness is height or width of bars between panes. All of these properties remain fixed during lifetime of the splitter instance. The creation of splitter and its panes is straightforward:

BOOL Create(CWnd* pParent, UINT nID = AFX_IDW_PANE_FIRST);
BOOL CreatePane(int nIndex, CWnd* pPaneWnd, DWORD dwStyle,   
 DWORD dwExStyle, LPCTSTR lpszClassName = NULL);

Panes are indexed from 0 to nPanes - 1. The parameters dwStyle, dwExStyle and lpszClassName are passed to pPaneWnd->CreateEx() (If you want to bind a created window with a pane, use SetPane instead). You can specify for example the borders of panes there. In demo app, the "large" panes have a WS_EX_CLIENTEDGE extended style, while the three "flat" panes have WS_EX_STATICEDGE extended style. The splitter bar alone is only a gray rectangle, so if you don't specify any edge and set the gray background to pane windows, you can use the splitter in dialogs too.

The following five methods are analogous to CSplitterWnd methods, so they don't require a special documentation.

int GetPaneCount() const;void SetPane(int nIndex, CWnd* pPaneWnd);
CWnd* GetPane(int nIndex) const;
virtual void SetActivePane(int nIndex);
CWnd* GetActivePane(int* pIndex) const;

However, setting the pane widths or heights uses different technique:

void SetPaneSizes(const int* sizes);

You pass an array of nPanes integers. They specify relative sizes of panes. You can use any scale, the panes are resized proportionally to the sum of the array members. When you resize the whole splitter, the sizes of panes are changed proportionally to their actual sizes. If necessary, they're adjusted to m_nMinSize.

void GetPaneRect(int nIndex, CRect& rcPane) const;
void GetBarRect(int nIndex, CRect& rcBar) const;

With these functions you can retrieve the position of panes in splitter client coordinates. Bars are indexed from 1 to nPanes - 1.

And that's all. Look at the SimpleSplitterApp demo, especially the CMainFrame::OnCreate code, you will know everything!

Points of Interest

When I programmed the splitter, I was confused, how the framework redraws resized window. If you resize the top or left border, the framework first only move the window content in corresponding direction, and then it calls OnPaint(). So the window was redrawn twice and in the splitter this looked ugly.

Fortunately, there is a message handler CWnd::OnWindowPosChanging. You can avoid the initial moving of content, if you see SWP_NOCOPYBITS as you see in CSimpleSplitter and CChildWnd code. I think that this is useful in many other cases that splitters.

History

• 11. 2. 2004 - First version released
• 24. 3. 2004 - Some bugs fixed (see the messages below). In the SetPaneSizes function now you should pass only relative sizes, not absolute.