5.7.1 Keyboard Events

Microsoft Windows sends keyboard events to the active window. MFC will call the message method OnKeyDown() for the active window. Objective Grid will call the method CGXGridCore::ProcessKeys().

ProcessKeys() is called both from the current cell control and the grid itself, depending on active state of the current cell. ProcessKeys() needs to know which window is calling it. For this reason, the calling window passes the this pointer to ProcessKeys().

If you want to process keyboard events, you should override ProcessKeys() in a derived grid class. The return value of ProcessKeys() specifies if the event has been processed.

The following example illustrates how to override ProcessKeys() to process the F1 and TAB keys. If the user presses TAB at the bottom-right cell, a new row will be added to the table.

It is important to realize that ProcessKeys() is called from both OnKeyDown and OnKeyUp message handlers. You should keep this in mind when overriding ProcessKeys(), as it may be necessary to distinguish between WM_KEYDOWN and WM_KEYUP messages.

BOOL CGSampleView::ProcessKeys(CWnd* pSender, UINT nMessage, UINT nChar, UINT nRepCnt, UINT flags) { // check if user pressed <CTRL>-Key BOOL bCtl = GetKeyState(VK_CONTROL) & 0x8000; // check if user pressed <SHIFT>-Key BOOL bShift = GetKeyState(VK_SHIFT) & 0x8000; if (nMessage == WM_KEYDOWN) { switch (nChar) { case VK_HELP: // user pressed <F1>-Key // display a message box with help if (bShift) { MessageBox("Help!"); return TRUE; } case VK_TAB: // user pressed <TAB>-Key { ROWCOL nRow = 1, nCol = 1; GetCurrentCell(nRow, nCol); if (!bShift) { // Jump to the right cell if (nCol < GetColCount()) MoveCurrentCell(GX_RIGHT); else if (nRow < GetRowCount()) { // if current cell is at last column, // move down a row and to the first column. if (MoveCurrentCell(GX_MOSTLEFT)) MoveCurrentCell(GX_DOWN); } else { // if current cell is at last row, // add a new row SetRowCount(GetRowCount()+1); // move to the first column in the new row if (MoveCurrentCell(GX_MOSTLEFT)) MoveCurrentCell(GX_DOWN); } } else { // Jump to the left cell or move up a row if (nCol > 1) MoveCurrentCell(GX_LEFT); else if (nRow > 1) { if (MoveCurrentCell(GX_MOSTRIGHT)) MoveCurrentCell(GX_UP); } else { MoveCurrentCell(GX_BOTTOMRIGHT); } } return TRUE; } } } // call base class version return CGXGridView::ProcessKeys(pSender,nMessage,nChar,nRepCnt,flags); }

5.7.2 Keyboard Shortcuts

Table 4: Keyboard shortcuts