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Posted 4 Apr 2004


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CDiagramEditor - DIY vector and dialog editor

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4.96/5 (165 votes)
23 Jun 2006Public Domain11 min read
A feature rich vector editor skeleton.

Sample Image - diagrameditor.gif

The DialogEditorDemo app

Sample Image - diagrameditor2.gif

The DiagramEditorDemo app


So you wanted to add a forms editor to your application? A dialog editor? Something that allows drawing of HTML <div>s? Here is a feature rich skeleton (!) to get you started. CDiagramEditor is a package that gives you a basic visual editor intended for vector objects. Although perhaps not sufficient to create a CAD-application, you'll indeed be able to create a dialog editor. The editor itself is derived from CWnd, with a separate class handling the data, so you'll be able to either use it in a dialog or doc/view application.

Some of the built-in features:

  • Full mouse handling. Draw and drag multiple objects, drag draw, and resize single ones.
  • Paper size, margin, and grid easily configured.
  • Snap to grid, restrain moving and resizing to margin or paper. Or draw outside the paper, if you want.
  • Configurable keyboard interface.
  • Plug-in popup menu for the editor.
  • Unlimited zoom.
  • Unlimited undo.
  • Support for saving and loading to CStrings/CStringArrays.
  • For the programming aficionado, the different drawing functions of the editor are virtual, so if you're not satisfied with the look, derive a class and do it yourself.
  • Base objects for rectangles and lines, you derive the drawing objects you need from those.
  • Support for object-specific popup menus.
  • Support for object-specific property dialogs.

And more. Of course, this package is fiendishly difficult to use? No, add an instance of CDiagramEditor to your app, derive the drawing classes you need, and you have an editor.

I've added two demo applications. The smaller one, DiagramEditorDemo, shows the basics, adding an editor to a dialog application.

DialogEditorDemo is a SDI doc/view application showing how to use the separate data container class, how to plug into the document loading and saving, and using a factory to create the drawing objects, how to add print and print preview, custom background redraw, exporting, and much, much more.

The package consists of the following classes:

  • CDiagramEditor - The editor itself.
  • CDiagramEntityContainer - A container class for the editor data.
  • CDiagramEntity - Base class for the drawing objects.
  • CDiagramLine - A CDiagramEntity-derived class that can be used as a base class for line objects.
  • CDiagramMenu - Popup editor menu.
  • CDiagramPropertyDlg - Pure virtual base class for object property dialogs.

and a few small help classes.

As it is quite a lot of code, I've added HTML-documentation with an overview of the classes, and a page of How-tos and class details for the bigger classes. The code is commented as well.


The beginning of time

Original release.

1/5 2004

Working intensely with the CDiagramEditor, I've made a few enhancements to the package, mainly to:

  1. Facilitate deriving from CDiagramEntityContainer.
  2. Make it possible to use the same internal clipboard for several editors.

The second modification is to be able to use CDiagramEditor in a MDI-application, where you might want to copy and paste objects across editors. It is accomplished by separating out the copy/paste-functionality from CDiagramEntityContainer and putting it in a class of its own - CDiagramClipboardHandler.

Especially irritating, while doing these modifications using a MDI-app as the host, was that even though property dialogs were created with the editor as the parent, the parent returned calling GetParent in the OnOK-handlers. Thus, the editor was not updated correctly when changes where made to the objects. I had to work around this by adding an explicit redraw-parent to CDiagramPropertyDlg and adding a new member Redraw that should be used instead of GetParent()->RedrawWindow() in derived classes for MDI-applications.

Other than that, I must admit that refactoring is a major hassle in MSVC++ 6.0, something I thought only wimps complained about earlier (have I been lucky in the small amount of refactoring necessary in my life up to this point?).

The documentation is updated accordingly, and the changes are:

  • SendMessageToObjects sets the selected-flag to TRUE - sending the message only to selected objects.
  • Made some message mapping functions virtual to allow enhancements in derived classes.
  • Added accessors for states to allow access for derived classes.
  • Set interact mode to MODE_NONE after Ctrl+clicking item (to avoid undesired movement of lines).
  • Set scrollbar positions to zero in Clear. Earlier, when loading a document, the scrollbars were not reset to 0,0.
  • Sending this window as a parent to the property dialog. This is to redraw the editor properly after changes in the dialog in MDI-apps.
  • Changed C-style casts to static_cast.
  • Removed ShowProperties-const-ness.
  • Made RemoveAt virtual.
  • Made several undo- and copy/paste functions virtual. Added array accessors for derived classes. Moved the member function Find to the protected section. All this to simplify deriving from CDiagramEntityContainer.
  • Copy/paste-handling removed to a separate class (CDiagramClipboardHandler) to allow several containers to share the same clipboard.
  • Changed C-style casts to static_cast.
  • Changed accessors for m_type - SetType and GetType - to public.
  • Added colon as a replace-character for saving in FromString and GetString. Earlier, names or titles with embedded colons would have been invalid.
  • Added a redraw parent to the property dialog in ShowProperties.
  • Added a redraw parent, m_redrawWnd, to redraw the proper window in MDI-applications. Derived classes can now use Redraw if the editor needs to be updated.

If you are using CDiagramEditor in an existing project, the things affecting you will be Set interact mode..., Set scrollbar positions..., and Added colon as a replace-character... above. To use the new package, download the source code again and copy the files over the existing ones, and add CDiagramClipboardHandler.cpp and CDiagramClipboardHandler.h to your project.

15/5 2004

Bug fix in the dialog editor demo

The Export function of the CDiagramEntity-derived objects in the demo wasn't updated to const, and so was not called by the export-mechanism.

13/6 2004

This is definitely not an essential update. Mainly, I'm updating the framework because of an upcoming UML-editor, where a few more things have been made virtual or const to ease derived editors. Anyhow, on with the list:

Virtual size checks when scrolling

Graham suggested this (see below). Although the scroll position functionality ought to have reported correct values, it's better safe than sorry, so I've included page check in the VScrool and HScroll routines - not unnecessarily trying to scroll an editor window with no scroll bars.

Modifications for derived editors
  • CDiagramEditor
    • Added access to m_subMode in SetInteractMode.
    • Made OnObjectCommand virtual to allow interception in derived classes.
    • Made GetBackgroundColor const.
    • Made SelectAll virtual.
  • CDiagramEntityContainer
    • Made GetAt virtual.
    • RemoveAll, added check to see if there are any items in the object array.
    • Made RemoveAll access data container objects directly, to avoid chained deletes in derived classes. Applies if a delete should delete other items automatically.

Who should update the editor code? Anyone experiencing problems while trying to scroll outside the paper area?

8/7 2004

Time for another update! I've added some bug corrections, some enhancements to further assist derived editors, and added some new functionality. The corrections are:

  • Corrected a bug in SetZoom, where minimum size was not honored (pgrohs).
  • Zeroing m_internalData after a delete in SetDiagramEntityContainer to avoid crashes (pgrohs).
  • Corrected bug in alignment-handling in LeftAlignSelected et. al. - all, not only selected items where aligned.
  • Correction in VirtualToScreen, not deducting scrollbar positions any longer (Wolfgang Busch).
  • Added \\newline as a replace-character to allow newlines in titles and names when saving/loading (Unruled Boy).


  • Made AddObject virtual and added the virtual MoveObject function. This is to allow trapping of added or moved objects in the editor in derived classes (sunmoon9898).
  • Made clipboard-functions and DeleteAllSelected virtual.
  • Added a virtual GetCursor function to simplify the addition of customized cursors..
  • Coordinate conversion functions made public (Wolfgang Busch).
  • Made Add and Remove in the container virtual.
  • Added a GetSelectCount to the container.

New functionality:


Suggested by Unruled Boy

The selected objects can now be grouped by right-clicking the editor and selecting Group. Grouped objects can be moved, copied, and pasted as a single unit. By right-clicking and selecting Ungroup, all grouping will be removed for the selected items.

Programmatically, this can be accomplished by calling the public functions CDiagramEditor::Group and CDiagramEditor::Ungroup. CDiagramEditor::UpdateGroup( CCmdUI* pCmdUI ) and CDiagramEditor::UpdateUngroup( CCmdUI* pCmdUI ) can be called as command enablers from - for example - the view.

Grouping is implemented as a new attribute in CDiagramEntity.


Old data files for the demo applications based on CDiagramEditor are no longer compatible with the framework due to the new base attribute. I've considered this an acceptable tradeoff, and hope it is not an inconvenience. Derived works will have to be updated to load/save this attribute, and I've added functionality in CDiagramEntity to simplify this, LoadFromString, GetDefaultGetString, GetHeaderFromString, and GetDefaultFromString.

A typical FromString in a hypothetical CDiagramEntity-derived class, CSomeEntity, with an extra CString attribute. m_someattribute can now be written as:

BOOL CSomeEntity::FromString( const CString& str )

  BOOL result = FALSE;
  CString data( str );

  if( LoadFromString( data ) )
    CTokenizer tok( data );

    CString someattribute;
    tok.GetAt( 0, someattribute);

    SetSomeAttribute( someattribute );
    result = TRUE;

  return result;


where CDiagramEntity::LoadFromString is used to set the base class attributes, and the rest of the attributes are parsed from the modified input-string.

GetString can be written as:

CString CSomeEntity::GetString() const

  str.Format( _T( ",%s;" ), // Note the starting comma

  str = GetDefaultGetString() + str;
  return str;

Mouse-wheel support

Suggested by John A. Johnson.

By handling WM_MOUSEWHEEL in CDiagramEditor, the paper can now be scrolled with the mouse wheel. I've thought about making this a bit more flexible. Configurable scroll steps and zoom comes to mind, but this will have to wait. OnMouseWheel is made virtual to allow personal attempts in this direction :-)


Suggested by John A. Johnson.

Panning is implemented. By pressing the middle-button, a panning marker is displayed at the point of the cursor. If the mouse is moved, the editor is scrolled in the direction of the cursor. The scroll-amount is relative to the distance between the marker and the current cursor. The cursor changes to imply the current cursor direction. I've used built-in cursors for this, to avoid dependencies on resources.

I checked P J Arends' excellent class for this, CWindowScroller, and it was indeed possible to plug it in directly in the editor, but as I want to have a completely free license for the CDiagramEditor, I based the work on MSDN (The Visual Programmer article on panning by George Shepherd and Scot Wingo) instead.

Key functions for this are OnMButtonDown, SetPanning, and DrawPanning.

Zoom to fit

Suggested by John A. Johnson.

This function will set the zoom level so that all objects in the current diagram are visible. The function to call is the public function ZoomToFitScreen.

Finally, a very big thanks to all those giving feedback (especially those attributed above - but all feedback is welcome) on the framework.

4/8 2004

A handful of minor fixes and additions this time.

  • Added scroll wheel mode. By calling SetScrollWheelMode(WHEEL_SCROLL/WHEEL_ZOOM), the scroll wheel will either scroll or zoom.
  • Added virtual to more message handlers, among them the scrollbar ones.
  • Added virtual to SetZoom.
  • Added virtual functions to set the scrollbar positions to get one single point where this is made.
  • Bug: Checking if the cursor is outside of restraint when placing an item in OnLButtonDown.
  • Added ScrollIntoView commands. The function scrolls the currently selected object(s) into view.
  • Bug: Fixed bug with selection markers - virtualization of the mouse coordinates was in discord with the selection marker rectangles (Marc G).
  • Added SelectAll and UnselectAll to the container.

28/8 2004

Far too early, here comes, nevertheless, a bug correction round. Once again, a big, fat thanks to you all for the feedback!

  • CDiagramEditor: added check for non-normalized rect when hit-testing in OnLButtonDown, as lines have them.
  • CDiagramEntity: setting m_parent to NULL in the ctor (Marc G).
  • CTokenizer: changed a char to TCHAR to allow UNICODE builds (Enrico Detoma).

25/3 2005

A maintenance update, with a few additions:

  • Made UnselectAll virtual (Grisha Vinevich).
  • Added the minimum step size one pixel in OnKeyDown to avoid 0-pixel movement for arrow keys (Graham G Pearson).
  • Made UnselectAll virtual (Grisha Vinevich).
  • Added the PopUndo function to pop the latest undo item from the stack.
  • Made IsUndoPossible const.
  • Made SetParent/GetParent public.

as well as a correction to the line-selection mechanism (Graham G Pearson).

15/5 2005

Yet another maintenance update:

  • Routing all object selections through a virtual member function to allow customization of the selections (Janiv Ratson).
  • Added a Redo-command. This command will undo the last undo. Handlers and enablers as for Undo, but the message handled is, of course, ID_EDIT_REDO. Key-mappings to Ctrl+Y (Janiv Ratson).
  • Added message mapping for ID_EDIT_UNDO (Graham G Pearson).
  • Added message mapping for ID_EDIT_REDO.

Note: I've only updated the source code for the Download source files-link - not the demo projects. So, make sure you use this download when you incorporate the code into your own project!

23/6 2006

Long overdue, another update:

  • Added the PasteToPosition function (Janiv Ratson)
  • Bug: Corrected bug in ZoomToFit (DanMoshe)
  • Bug: Corrected bug when resizing several grouped objects with the mouse (obeea)
  • Bud: Added dirty-parameter to SendMessageToObjects for the dirty handling - not all commands should set the document as changed (Janiv Ratson)
  • Bug: Corrected CDiagramEntityContainer undo-stack handling to take stack size 0 into consideration (David Hoos)
  • Bug: Added the group to the data copied in CDiagramEntity::Copy (JeffBean)
  • Minor layout changes, and removal of redundant scrollbar handling (Alexey Shalnov)

Note: Once again, I've only updated the source code for the Download source files-link - not the demo projects. So, make sure you use this download when you incorporate the code into your own project!


This article, along with any associated source code and files, is licensed under A Public Domain dedication

Written By
Software Developer (Senior) Abstrakt Mekanik AB
Sweden Sweden
45 years old, married, three kids.

Started with computers more than 20 years ago on a CBM-64.

Read Theoretical Philosophy at the University of Lund.

Working as a C++ consultant developer.

Science-fiction freak. Enjoy vintage punkrock.

Comments and Discussions

QuestionHow to get a notify about any changes in editor? Pin
Eugene Pustovoyt15-Jan-20 17:59
Eugene Pustovoyt15-Jan-20 17:59 
QuestionCan we add free hand drawing in this project? Pin
gawadepd1-Jun-16 20:03
gawadepd1-Jun-16 20:03 
BugTwo problems Pin
Oscar Caulfield19-May-12 6:35
Oscar Caulfield19-May-12 6:35 
GeneralJust what I need. Pin
.dan.g.8-Jun-11 15:10
professional.dan.g.8-Jun-11 15:10 
GeneralThis is very useful article. Pin
Yasuhiko Yoshimura7-Jan-11 20:04
Yasuhiko Yoshimura7-Jan-11 20:04 
GeneralGreat Work!!!! Very Useful for SCADA IDE development Pin
gsheladia17-Aug-09 20:22
gsheladia17-Aug-09 20:22 
QuestionBezier curves handling? Pin
jasperlotus20-May-09 6:03
jasperlotus20-May-09 6:03 
QuestionGreat work! I am wondering how to keep the vitual page just the same size of the client window? Pin
tiger5491019-Mar-09 15:36
tiger5491019-Mar-09 15:36 
AnswerRe: Great work! I am wondering how to keep the vitual page just the same size of the client window? Pin
Johan Rosengren21-Mar-09 22:22
Johan Rosengren21-Mar-09 22:22 
GeneralThis is a great work !! Pin
arif.setiawan25-Nov-08 18:36
arif.setiawan25-Nov-08 18:36 
GeneralRe: This is a great work !! Pin
Johan Rosengren25-Nov-08 21:00
Johan Rosengren25-Nov-08 21:00 
QuestionDraw Text?? Pin
Member 449627030-May-08 1:46
Member 449627030-May-08 1:46 
AnswerRe: Draw Text?? Pin
Johan Rosengren30-May-08 20:20
Johan Rosengren30-May-08 20:20 
QuestionHow to draw an Activex object? Pin
kstone28-May-08 3:19
kstone28-May-08 3:19 
AnswerRe: How to draw an Activex object? Pin
Johan Rosengren28-May-08 9:00
Johan Rosengren28-May-08 9:00 
GeneralThanks ,I using your code in my SCADA project Pin
confideman200015-May-08 15:40
confideman200015-May-08 15:40 
GeneralRe: Thanks ,I using your code in my SCADA project Pin
Johan Rosengren16-May-08 20:10
Johan Rosengren16-May-08 20:10 
QuestionHI how to create that stand alone exe file ?? Pin
satishmanohar24-Jan-08 1:13
satishmanohar24-Jan-08 1:13 
AnswerRe: HI how to create that stand alone exe file ?? Pin
Johan Rosengren24-Jan-08 15:38
Johan Rosengren24-Jan-08 15:38 
GeneralRe: HI how to create that stand alone exe file ?? Pin
satishmanohar24-Jan-08 16:36
satishmanohar24-Jan-08 16:36 
GeneralRe: HI how to create that stand alone exe file ?? Pin
Johan Rosengren25-Jan-08 8:35
Johan Rosengren25-Jan-08 8:35 
GeneralRe: HI how to create that stand alone exe file ?? Pin
satishmanohar25-Jan-08 19:51
satishmanohar25-Jan-08 19:51 
JokeOnly to let you know Pin
andyj1153-Jan-08 10:29
andyj1153-Jan-08 10:29 
GeneralRe: Only to let you know Pin
Johan Rosengren3-Jan-08 18:08
Johan Rosengren3-Jan-08 18:08 
GeneralThe latest version Pin
transoft25-Nov-07 5:49
transoft25-Nov-07 5:49 

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