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16 August 2012

[ MFC ] - Creating Property Page Dialog using CPropertyPage, CPropertySheet


1. Introduction


Property Pages are widely used to accommodate multiple controls in different pages. Each Property Sheet defines a group of controls that together forms logically related information. In this article we will see how we can create a property page using MFC. With a little change you can deform the property pages as wizard pages.



2. About the Sample


The sample is a dialog application, which launches the property page dialog. Below is the screen shot of hosting dialog:



The below screen shot is the property page:



Note the sample has two pages and this will sufficient for the reader to add more on their property page dialog. When you click Settings… button in the main dialog, the property page dialog will be opened. Once you change any one of the default value from the displayed dialog, the apply button will be enabled. Clicking the apply button will make you change permanent not considering whether you cancel the dialog or click ok. You can also save the changes by clicking the OK button also. Then what is the use of apply button? In real world if you want to show the changes visually, the button is very useful and the user of the application will look at the visual changes and tune their settings further. Let us go ahead and start creating the sample.



3. How do we Create Property Page Dialog?


The below skeleton diagram explains how do we create the property page dialog.



First, we should create property pages. Then these property pages are attached to the property sheet, which provides the buttons required for property page dialog. OK and Cancel buttons are common for a dialog, and the Apply button is specially provided for property page dialogs. Creating the property pages is almost equal to creating the dialog boxes. In the resource, you can ask for property page and you will get a borderless dialog. In this dialog, you should drop the controls that you want for your property page.

In the above skeleton picture, first we will create property page1 and page2. Then the required controls are dropped into page1 and pagw2. Finally, through the source code we will add these pages to the property sheet created at runtime.



4. Create Property Pages


How do you create a dialog? Property page also created similar to that. The below given video shows creating first page of the property dialog.

Video 1: Watch it


Steps
1) From the Resource file add the Property Page
2) Then provide a meaningful ID Name for it
3) Open the Property page visual studio editor
4) From the Toolbox 3 radio buttons are added to it.

So that’s all we do for creating the pages of the property sheet that create a page template, drop the controls on it. Repeat the same process for all the pages. Once the pages are ready you should create associated class for it. The video provided below shows how do we create a class for the Property page added in the previous video:

Video 2: Watch It

Steps
1) The Property page template is opened in visual studio
2) Add class menu option is invoked from the context menu of the Property page template (By Right click)
3) In the class dialog a class name is chosen, and base class is set to CPropertyPage
4) Created class is shown in the class view

The Second page of sample is created property page 1 way as shown in video1 and video2. Now we have page1 and pag2 for the property dialog is ready. The design of second property page is shown below:





5. Add Control Variables


Now the Color and Font property page templates are ready. Now we will associate a variable to the controls in these property page templates. First a variable is associated to the radio buttons. For all the three radio buttons, only one variable is associated and we treat these radio buttons as single group. First we should make sure that the tab order (Format->tab Order or Ctrl+d when the dialog is opened in the editor) for all the radio buttons goes consecutively. Then for the first radio button in the tab order, set the group property to true.   The below specified video shows adding a control variable for the Radio buttons:

Video 3: Watch It


Steps
1) From the resource view, Property page for the font is opened
2) Make sure Group property is set to true. If not set it to true
3) Add variable dialog is opened for first radio button
4) Variable category is changed from control to variable
5) A variable of type BOOL is added (Later we will change this as int through the code)

Likewise we add three more value type variables for each text box control in the property page two. The below screen shot shows an int value variable m_edit_val_Red added for the first edit box. For blue and green also variables are added as shown in the below screen shot.





6. OnApply Message Map


To follow the code explanation with me, search for the comment //Sample in the solution and in the search result follow the Order 01,02,03 etc

ON_MESSAGE_VOID is a nice handler for dealing with custom messages that does not require passing any arguments. In out sample we are going to use this handler for dealing with WM_APPLY user define message. Below is the code change required for the dialog-based project.

1) First a required header is included in the dialog class header file

//Sample 01: Include the header required for OnMessageVoid
#include <afxpriv.h>

2) In the same header file declaration for the void message handler is given.

//Sample 02: Declare the Message Handler function
afx_msg void OnApply();

3) Next in the CPP file, ON_MESSAGE_VOID Macro is added in between Begin Message Map and End Message Map. The OnApply is not yet defined, so you will get a compiler error when you compile the program at present. To avoid this provide a dummy implementation for OnApply like void CPropPageSampleDlg::OnApply() {}

//Sample 03: Provide Message map entry for the Apply button click
ON_MESSAGE_VOID(WM_APPLY, OnApply)

4) WM_APPLY is not yet defined. So declare that user defined massage in the stdAfx.h. WM_USER macro is useful to define a user defines message in a safe way. That is the WM_APPLY does not clash with any existing user defined message as we use it safely like WM_USER+1

//Sample 04: Define the user defined message
#define WM_APPLY WM_USER + 1



7. Change Radio Button Variable


In video 3, we added a Boolean type variable for the radio buttons group. It will be very useful if we change this variable type from BOOL to integer type. When user makes a radio button selection, the data exchange mechanism will automatically set the variable to denote the currently selected radio button. You will get more clarity when we write the code for radio check state later. For now we will just change Boolean variable type to integer.

1) In the PropPageFont.h file, the variable type is changed from Boolean to Integer

//Sample 05: Change the variable type to Int
int m_ctrl_val_radio_font;

2) Next in the constructor of the CPropPageFont, variable is initialized to –1. This value denotes that none of the radio button is initilially checked.

//Sample 06: Set the Combo value variable to -1
CPropPageFont::CPropPageFont()
              : CPropertyPage(CPropPageFont::IDD)
              , m_ctrl_val_radio_font(-1)
{

}



8. CPropPageSampleDlg Dialog class


We know that the class CPropPageSampleDlg is created by the application wizard. Moreover, we are going to launch the Property page dialog from this dialog as a child dialog. The CPropPageSampleDlg will take the settings from the property page and caches it. When the property page is opened for next time, the settings cached by this parent dialog are supplied back to the property pages.

1) First the variables required to cache settings are declared in the class declaration, which is in the header file

//Sample 07: Add Member variables to keep track of settings
private:
int m_selected_font;
int m_blue_val;
int m_red_val;
int m_green_val;

2) Next in the OnInitDialog, these variables are initialized based on what the property page should show on very first display.

//Sample 08: Initialize the member variables
m_selected_font = -1;
m_red_val = 0;
m_green_val = 0;
m_blue_val = 0;



9. Create Property Dialog and Display it


From the dialog class the property page dialog is created and displayed as modal dialog. Once this property page dialog is closed by the user, the settings set by him/her is read back and cached inside the parent dialog.

1) In the button click handler, first we create a property sheet with a dialog title Settings. The second parameter passed is referred by the property sheet as its parent.

//Sample 09: Create Property Pages, Attach it to the sheet and Lauch it
void CPropPageSampleDlg::OnBnClickedButtonSettings()
{
              //Sample 9.1: Create Property Sheet
              CPropertySheet sheet(_T("Settings") , this);

2) Next we create the property pages in the heap. First we declare the variables in the header file of the dialog class, then we declare the required variables in the class with private scope

//Sample 9.2: Include Property pages
#include "PropPageFont.h"
#include "PropPageColor.h"

//Sample 07: Add Member variables to keep track of settings
private:
              int m_selected_font;
              int m_blue_val;
              int m_red_val;
              int m_green_val;
           CPropPageFont* m_page1_font;
           CPropPageColor* m_page2_color;

3) In the implementation file (Look at step 1), after creating the property sheet with title settings, we create both the property pages (i.e.) Font and Color pages.

//Sample 9.3: Create Property Pages
m_page1_font = new CPropPageFont();
m_page2_color = new CPropPageColor();

4) Once the pages are available, we set the dialog-cached values to the controls on the property pages

//Sample 9.4: Pass the previous settings to property pages
m_page1_font->m_ctrl_val_radio_font = m_selected_font ;
m_page2_color->m_edit_val_Red = m_red_val;
m_page2_color->m_edit_val_Green = m_green_val;
m_page2_color->m_edit_val_Blue = m_blue_val;

5) Then the property pages are attached to the property sheet. Once this step is complete, the property dialog is ready with two pages. The title of each tab is taken from its caption property that you set when you designed the Property Page.

//Sample 9.5: Add Property Pages to Property Sheet
sheet.AddPage(m_page1_font);
sheet.AddPage(m_page2_color);

6) When the property dialog is closed, we check the return value and cache (Copy) the settings provided in the pages to the calling dialog’s member variables. These variables are used to initialize the property page dialog when it is opened for next time. Note that during the button click, we create the pages on heap, copy the dialog members to the pages, add the pages to sheet and display it as modal dialog and when it closed before deleting the pages from heap we copy the settings into the local members.

//Sample 9.6: Display the property sheet and call on_apply when the sheet is closed
if (sheet.DoModal() == IDOK)
              OnApply();
delete m_page1_font;
delete m_page2_color;



10. Set Modified Flag to Enable Apply Button


The apply button in the property dialog is enables when the UI elements in the pages are changed. Say for example typing the new red value in the text box will enable the apply button. Once you click the apply button, the changes are informed to the parent. In our case we send the data entered or changed by the user so for, to the parent dialog that launched this property page. In real world, the apply button will immediately apply the settings to the application. So before clicking OK, user can observe the effect of the changed settings just by clicking the apply button.

So now, we need to track the changes done in the property dialog. For that we will handle the BN_CLICKED event for the Radio buttons in the Font property page and EN_CHANGE event for the text boxes in the Color property page. The event BN_CLICKED will appear when somebody clicked the radio button and the event EN_CHANGE will appear when the content of the text is changed.

The below video shows providing the handler for the Radio button click:

Video 4: Watch it


Steps
1) FONT property page is opened
2) First Radio button in the group is clicked
3) In the properties pane, navigation moved to control events
4) BN_CLICKED event is double clicked (You will enter the code editor)
5) The process is repeated for other two radio buttons.

The same way the EN_CHANGED event for all the three text boxes is provided. The screen shot below shows the request for the event handler for the control event EN_CHANGED:



1) In the handler provided by the Radio buttons, we set the flag to enable the apply button by calling the function SetModified.

// CPropPageFont message handlers
//Sample 10: Call Set Modified to Enable Apply Button.
void CPropPageFont::OnBnClickedRadio1()
{
              SetModified();
}

void CPropPageFont::OnBnClickedRadio2()
{
              SetModified();
}

void CPropPageFont::OnBnClickedRadio3()
{
              SetModified();
}

2) The same way we set the modified flag for the text boxes also. Below is the handler code:

//Sample 11: Call Set Modified to Enable Apply Button.
void CPropPageColor::OnEnChangeEdit1()
{
              SetModified();
}

void CPropPageColor::OnEnChangeEdit2()
{
              SetModified();
}

void CPropPageColor::OnEnChangeEdit3()
{
              SetModified();
}



11. Sending WM_APPLY through OnApply Override of PropertyPage

We had a dummy handler for the user-defined message WM_APPLY (Refer Section 6 of this article) and we will implement that now. The property page will send the notification to this dialog when the user clicks the apply button of the property page. Have a look at the implementation below:

//Sample 12: Provide handler for Applying the property sheet changes
void CPropPageSampleDlg::OnApply()
{
              m_selected_font = m_page1_font->m_ctrl_val_radio_font;
              m_red_val = m_page2_color->m_edit_val_Red;
              m_green_val = m_page2_color->m_edit_val_Green;
              m_blue_val = m_page2_color->m_edit_val_Blue;
}

The parent dialog will take the data from both the property pages and stores that internally. Also note that the property pages are wiped out from the memory after use and a new instances of property pages are created when we display it. Now refer the code at section 9.4, you will get an idea of how the data flow of the settings will happen.
1) When the Parent about to display the property page it copies the cached data to the property pages
2) When user clicks the OK button, this OnApply is called. Refer section 9.6
3) When user clicks the Apply button, WM_APPLY user message is sent to the CPropPageSampleDlg

The below code will send the WM_APPLY message to the parent dialog:

BOOL CPropPageFont::OnApply()
{
              //Sample 13: Set the Modified flag to false, and send message to dialog class
              CPropertySheet* pSheet = (CPropertySheet*) GetParent(); 
              pSheet->GetParent()->SendMessage(WM_APPLY);
              SetModified(FALSE);
              return CPropertyPage::OnApply();
}

Note that the OnApply is overridden in the property page class for Fonts. Moreover, the OnApply overridden function (For all the Property page that overrode OnApply) is called by the MFC Frame work when user clicks the apply button. As we are just going to send the message to the parent dialog of the property page when Apply button is clicked by the user, providing the overridden version of function in either Font or Color page is sufficient. The below video shows adding the OnApply override:

Video 5: Watch It

Steps
1) Property page for CPropPageFont is opened
2) In the Property Page Overrides toolbar icon is selected
3) Then, OnApply Override is added to the source code.



Video 6: Watch It

The above video shows the sample in Action.

 Source Code : DownLoad

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