CODEWITHSUNDEEP
c++mfcclistctrlclistbox
mrdecompilator
mrdecompilator

Reputation: 165

MFC - CListCtrl rows with optional checkboxes

In runtime, I'm trying to create a single-column custom CListCtrl (or CMFCListCtrl, but not CheckListBox - I want to be able to add multiple columns in the future) using MFC. Using LVS_EX_CHECKBOXES style forces all items to have the checkbox. The desired control should look like this (item1 and item3 have checkboxes, item2 doesn't):

enter image description here

From the user's point of view, the desired list control should be created like this:

int main() {
    MyCListCtrl list_control;
    list_control.AddItem("item1", true) // true indicates checkbox presence
    list_control.AddItem("item2", false) // false - item without checkbox
    list_control.AddItem("item3", true) // true indicates checkbox presence
}

So far I was able to create a control like this, but adding LVS_OWNERDRAWFIXED triggers a failed assertion, when calling base class CListCtrl::DrawItem method:

enter image description here

    // MyCListCtrl.h
    class MyCListCtrl : public CListCtrl {
    public:
        virtual void DrawItem(LPDRAWITEMSTRUCT lpDrawItemStruct) override {
            // if the item should be without a checkbox, here I want to move it a few pixels
            // to the left so that the checkbox is hidden
            ...
            CListCtrl::DrawItem(lpDrawItemStruct); // call base's DrawItem - without this
                                  // there's no exception but the listbox appears empty
        }
    };

    BOOL MyCDialogEx::OnInitDialog() {
        CDialogEx::OnInitDialog();
        ...
        // list being defined somewhere in the header file
        list->Create(WS_CHILD | WS_VISIBLE | WS_BORDER | LVS_REPORT | LVS_NOCOLUMNHEADER |
                                            LVS_OWNERDRAWFIXED, // for DrawItem invocation
                                            rect, this, SOME_ID);
        list->SetExtendedStyle(list->GetExtendedStyle() | LVS_EX_CHECKBOXES);

        // add 1 mandatory column because of LVS_REPORT style
        LVCOLUMN lvColumn;
        lvColumn.mask = LVCF_FMT | LVCF_TEXT | LVCF_WIDTH;
        lvColumn.fmt = LVCFMT_LEFT;
        lvColumn.cx = rect.Width() - 20; // also, how to make this column fit the width exactly?
        lvColumn.pszText = nullptr;
        list->InsertColumn(0, &lvColumn);

        // for now only add 1 testing item and make his checkbox disappear by moving the
        // whole item to the left in DrawItem method (called by the system), so that the text
        // is aligned to the left list border
        list->InsertItem(0, "item1");
        ...
    }

This is how my (not working) solution looks like, if you know how to solve this, maybe even in an easier way, please let me know. Thanks.

EDIT

With @Landstalker 's help, I'm now able to erase the checkbox with the custom drawing, but I still need to move the text to the left (so it takes the place of a non-existing checkbox, like on the picture above). Current solution results in this result:

enter image description here

This is achieved by handling the NM_CUSTOMDRAW message like this:

    void MyCListCtrl::OnCustomDraw(NMHDR* pNMHDR, LRESULT* pResult)
    {
        *pResult = CDRF_DODEFAULT; // default windows painting
        LPNMLVCUSTOMDRAW lpn = (LPNMLVCUSTOMDRAW)pNMHDR;

        if (CDDS_PREPAINT == lpn->nmcd.dwDrawStage)
        {
            *pResult = CDRF_NOTIFYITEMDRAW; // notify on every item
        }
        else if (CDDS_ITEMPREPAINT == lpn->nmcd.dwDrawStage)
        {
            int row = lpn->nmcd.dwItemSpec;
            if (row == 1) {
                lpn->nmcd.rc.left -= 16; // not working
                lpn->rcText.left -= 16; // not working

                SetItemState(row, INDEXTOSTATEIMAGEMASK(0), 
                                  LVIS_STATEIMAGEMASK); // erase checkbox
            }
        }
    }

Upvotes: 0

Views: 1644

Answers (1)

Landstalker
Landstalker

Reputation: 1368

After long investigations ... I found a solution for you: use SetItemState () magic function :

enter image description here

Remarque : Having multiple columns is not a problem

MyCListCtrl.h 

class MyCListCtrl : public CListCtrl 
{
    DECLARE_DYNAMIC(MyCListCtrl)

public:
    afx_msg void DrawItem(NMHDR* pNMHDR, LRESULT* pResult);
    DECLARE_MESSAGE_MAP()
};

MyCListCtrl.cpp 

IMPLEMENT_DYNAMIC(MyCListCtrl, CListCtrl)

BEGIN_MESSAGE_MAP(MyCListCtrl, CListCtrl)
    ON_NOTIFY_REFLECT(NM_CUSTOMDRAW, DrawItem)
END_MESSAGE_MAP()

void MyCListCtrl::DrawItem(NMHDR* pNMHDR, LRESULT* pResult)
{
    *pResult = 0;
    LPNMLVCUSTOMDRAW  pLPN = (LPNMLVCUSTOMDRAW)pNMHDR;
    int iRow = pLPN->nmcd.dwItemSpec;

    // Get item flag : true or false (true we show checkbox, false we hide it)
    // Here i simulate, i disable rows 1 and 3
    SetItemState(1, INDEXTOSTATEIMAGEMASK(0), LVIS_STATEIMAGEMASK);
    SetItemState(3, INDEXTOSTATEIMAGEMASK(0), LVIS_STATEIMAGEMASK);

    switch(pLPN->nmcd.dwDrawStage)
    {
    case CDDS_PREPAINT | CDDS_ITEM | CDDS_SUBITEM :
        {
            *pResult = CDRF_DODEFAULT | CDRF_DOERASE; return;
        }
    case CDDS_PREPAINT :
        {
            *pResult = CDRF_NOTIFYITEMDRAW; return;
        }
    case CDDS_ITEMPREPAINT:
        {
            pLPN->clrText = RGB(0,0,0);
            *pResult = CDRF_NOTIFYSUBITEMDRAW;  return;
        }
    }
}

MainDlg.cpp 

CRect rect (30, 30, 180, 180);
list_control.Create(WS_CHILD | WS_VISIBLE | LVS_REPORT | LVS_NOCOLUMNHEADER |LBS_OWNERDRAWVARIABLE , rect, this, IDC_LIST2);
list_control.SetExtendedStyle(list_control.GetExtendedStyle() | LVS_EX_FLATSB | LVS_EX_CHECKBOXES | LVS_EX_GRIDLINES);

LVCOLUMN lvColumn;
lvColumn.mask = LVCF_FMT | LVCF_TEXT | LVCF_WIDTH;
lvColumn.fmt = LVCFMT_LEFT;
lvColumn.cx = 70; 
lvColumn.pszText = "Column 1";
list_control.InsertColumn(0, &lvColumn);  

lvColumn.pszText = "Column 2";
list_control.InsertColumn(1, &lvColumn);

//// add 1 test item
LVITEM lvItem;
lvItem.mask = LVIF_TEXT;
lvItem.iItem = 0;
lvItem.iSubItem = 0;
lvItem.pszText = "Test";
list_control.InsertItem(&lvItem);

lvItem.pszText = "Stack";
list_control.InsertItem(&lvItem);

lvItem.pszText = "Over";
list_control.InsertItem(&lvItem);

lvItem.pszText = "Flow";
list_control.InsertItem(&lvItem);

Upvotes: 2

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