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CGridListCtrlEx - Grid Control Based on CListCtrlBy SnakefootA custom draw CListCtrl with subitem editing and formatting |
C++, Windows, MFC, Dev
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Microsoft's CListCtrl has support for displaying data in a grid using the report style, but we have to make several changes to implement features like:
This article demonstrates how to use CGridListCtrlEx, which implements all the above features while maintaining the Windows XP/Vista look.
The Google Code - CGridListCtrlEx can be used if wanting SubVersion access, and there is also Doxygen Documentation.
There are lots of advanced grid controls that extend the CListCtrl, and one of those is the Enhanced List Control (CGfxListCtrl). This wonderful control provides all the above features, but fails to handle Windows XP and Vista. Finding a good replacement for this control is not very easy:
CListCtrl so it is not restricted by it, but it will not benefit from any improvements that Microsoft adds to the CListCtrl. CListCtrl. Originally one had to buy it, but now it is free to use. LVS_OWNERDATA that makes sorting a little harder. CListCtrl, but hard to add new ways to display data, and it fails to support LVS_OWNERDATA. One now has to buy a license, to get the latest version. CEdit, and also misses subitem navigation. LVS_OWNERDRAWFIXED, and now evolved into using custom draw. The combination of both custom draw and owner draw causes the code to be a little complicated, and it also doesn't support LVS_OWNERDATA. The CGridListCtrlEx tries to be simple, while still providing the ability to customize how a cell should be displayed and edited. In case Microsoft extends their CListCtrl again, then hopefully, the core of CGridListCtrlEx will continue to function.
The CGridListCtrlEx tries to stay true to the CListCtrl, and doesn't try to replace anything the CListCtrl already provides. This means we can replace a CListCtrl with CGridListCtrlEx without needing to do anything more.
It is recommended that we don't use the CGridListCtrlEx directly, but create a new class that inherits/derives from CGridListCtrlEx. This will make it easier to migrate any updates there will be to the CGridListCtrlEx class later on.
By default, when inserting columns in the CGridListCtrlEx, they will be configured as read-only, without the ability to be edited. By using CGridListCtrlEx::InsertColumnTrait(), we can provide a CGridColumnTrait class which specifies what type of editor it should use.
CGridColumnTrait* pTrait = new CGridColumnTraitEdit;
m_ListCtrl.InsertColumnTrait(nCol, title.c_str(), LVCFMT_LEFT, 100, nCol, pTrait);
When having edited an item, a standard LVN_ENDLABELEDIT message will be sent to the CListCtrl. When the CGridListCtrlEx receives this message, it will automatically call the virtual method CGridListCtrlEx::OnTraitEditComplete(), allowing a derived class to validate the input and maybe update an underlying data model.
By using CGridListCtrlEx::InsertColumnTrait(), we can also provide a CGridColumnTrait class which works as a CComboBox.
CGridColumnTraitCombo* pTrait = new CGridColumnTraitCombo;
pTrait->AddItem(0, "Hello");
pTrait->AddItem(1, "Goodbye");
m_ListCtrl.InsertColumnTrait(nCol, title.c_str(), LVCFMT_LEFT, 100, nCol, pTrait);
We can specify the items of the CComboBox when inserting the columns (as shown above). If we want to provide the CComboBox items dynamically, then we can override the CGridListCtrlEx::OnTraitEditBegin(), and then either use dynamic_cast<> or use the CGridColumnTraitVisitor to modify the items in the CComboBox.
By default, the GridListCtrlEx will have sorting enabled for all columns, where it will perform a simple text-comparison. If we want a more advanced sorting, then we can override the CGridListCtrlEx::SortColumn() method. Then, it is just a matter of choosing the right way to perform the sorting. See CListCtrl and Sorting Rows.
By default, the CGridListCtrlEx will just display the cell contents as tooltip. If we want to display something different in the tooltip, then we can override the CGridListCtrlEx::OnDisplayCellTooltip() method.
If we want to change the foreground/background color or the font style (bold, italic, underline), then we can override the methods CGridListCtrlEx::OnDisplayCellColor() and CGridListCtrlEx::OnDisplayCellFont().
The CGridListCtrlEx enables the extended style LVS_EX_SUBITEMIMAGES by default, but one is still required to attach a CImageList using CListCtrl::SetImageList().
After having attached the images, one can bind a cell/subitem with an index in the CImageList. This can be done with CGridListCtrlEx::SetCellImage(), or if using I_IMAGECALLBACK then return the image index by overriding CGridListCtrlEx::OnDisplayCellImage().
The CGridListCtrlEx also enables the extended style LVS_EX_GRIDLINES by default, which can cause subitem images to overlap the grid border. This can be solved by making sure that the image only uses 15 of the 16 pixels (first pixel transparent).
When using subitem images and running the application on Windows XP or using classic style, it will show a white background when a row is selected. This can be fixed by using CGridRowTraitXP:
m_ListCtrl.SetDefaultRowTrait(new CGridRowTraitXP);
The CGridListCtrlEx uses customdraw, so there are only these available solutions:
CImageList where the image has the height wanted for the row. CGridListCtrlEx::SetCellMargin() uses this trick to increase the font of the grid control, while keeping the row font intact. When the CGridListCtrlEx doesn't contain any items, it will display markup text to indicate the list is empty.
Use CGridListCtrlEx::SetEmptyMarkupText() to change this markup text. If providing empty text, then it will behave like a normal CListCtrl.
If using CGridListCtrlGroups, it will instead react to LVN_GETEMPTYMARKUP if running on Windows Vista.
CGridColumnManagerProfile provides the ability to store the width, position and whether columns are shown. After having added all available columns to the CGridListCtrlEx, assign an instance of CGridColumnManagerProfile using CGridListCtrlEx::SetupColumnConfig() and it will restore the last saved column configuration through CWinApp.
m_ListCtrl.SetupColumnConfig(new CGridColumnManagerProfile("MyList"));
If using CGridListCtrlEx several places in your application, then one should ensure creation of a unique CGridColumnManagerProfile for each place.
CGridListCtrlEx can both work as an OLE drag source and an OLE drop target. This allows drag operations between the CGridListCtrlEx and other windows and applications.
CGridListCtrlEx supports reordering of rows when doing internal drag and drop. This is implemented using a special sort operation, so items are not deleted/inserted.
To implement your own special behavior for a drop operation, either override OnDropSelf() or OnDropExternal() depending on what situation you want to handle.
To control what is placed in the drag-source when a drag is initiated, override OnDisplayToDragDrop().
CGridListCtrlEx tries to keep away from all the nasty details about how to display and edit data. These things are instead handled by the CGridColumnTrait class, and if we want to modify how data is displayed, then it is "just" a matter of creating a new CGridColumnTrait class.
When inserting a column, we can assign a CGridColumnTrait to the column. The CGridListCtrlEx will activate the appropriate CGridColumnTrait when we need to draw a cell in that column, or edit a cell in the column.
The CGridColumnTrait includes some special members known as meta-data. These members can be used by your own class when it derives from CGridListCtrlEx, so we can easily add extra properties to a column.
When inheriting from CGridColumnTrait, we must consider the following:
LVN_ENDLABELEDIT message when the edit is complete. It is based on the same idea as CGridColumnTrait but operates at row level instead of column level. This is useful for situations where one has to modify the display behavior of all columns.
The source code includes the following classes:
CGridListCtrlEx - The specialized CListCtrl CGridListCtrlGroups - CGridListCtrlEx extended with support for grouping CGridColumnTrait - Specifies the interface of a column-trait
CGridColumnTraitText - Implements cell formatting
CGridColumnTraitEdit - Implements cell editing with CEdit CGridColumnTraitCombo - Implements cell editing with CComboBox CGridColumnTraitDateTime - Implements cell editing with CDateTimeCtrl CGridRowTrait - Specifies the interface of a row trait
CGridRowTraitText - Implements row formatting CGridRowTraitXP - Implements drawing of subitem image background when using classic- or XP-style CGridColumnnManager - Specifies the interface for managing column persistence
CGridColumnManagerProfile - Implements the interface for working with multiple column configurations. The CGridListCtrlEx tries to stay away from performing any drawing itself. This means that the following features/bugs will not get that much attention:
checkboxes - Requires a CGridColumnTrait class that draws the entire cell. Maybe consider some misuse of the iImage property of LV_ITEM to store the checkbox state. CGridColumnTrait class that draws the entire cell. Implementing a CGridColumnTrait class that draws the entire cell could probably be done by stealing/borrowing some code from ListCtrl - A WTL List Control with Windows Vista Style Item Selection.
Contributions to this project are very welcome.
CGridListCtrlGroups CDateTimeCtrl editor CComboBox editor, so it automatically resizes dropdown width to its contents CGridListCtrlXP with CGridRowTraitXP CView Callback"-functions to "OnDisplay", as it resembles the MFC naming convention CGridColumnManager checkbox style LVS_EX_CHECKBOX when using LVS_OWNERDATA LVS_OWNERDATA 
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Last Updated: 16 Sep 2009 Editor: Deeksha Shenoy |
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