Advanced MFC Programming

Chapter 16. Context Sensitive Help
ID Naming Rules
Button Used to
Enter Help Mode
Figure 16-9. Dialog box supporting context sensitive help
Adding context sensitive help for common controls is more complicated than that of menu commands.
First we must add footnotes for each common control contained in the dialog box, then we need to do the
ID mappings.
By default, MFC will generate help IDs for the commands or controls whose resource IDs start from
“ID_”, “IDM_”, “IDP_”, “IDR_”, “IDD_” and “IDW_” by prefixing a single character ‘H’ to them. Also,
the values of these help IDs are generated by adding a fixed number to the corresponding resource IDs.
This fixed number is different for different types of IDs. For example, for “ID_XXX” and “IDM_XXX”
types of IDs, 0x10000 will be added to the resource ID; for “IDP_XXX” type IDs, 0x30000 will be added;
for “IDR_XXX” and “IDD_XXX” types of IDs, 0x20000 will be added; for “IDW_XXX” type IDs,
0x50000 will be added.
By default, the IDs of the common controls in a dialog box all start with “IDC_” prefix, which is not
included in the default mapping. This means we must generate help IDs by ourselves. Actually, this can be
easily achieved. If we open file “Makehelp.bat” (in our case, this file should be located in “16.2\Help\”
directory), we will see that the help IDs are generated through “Makehm” utility, which can be executed
under DOS prompt.
“Makehm” has the following syntax:
Makehm argument 1, argument 2, argument 3, argument 4 >> “File name”
where
argument 1:
argument 2:
argument 3:
argument 4:
prefix of resource ID
prefix of help ID
base number
resource header file name
For example, if we want to generate symbolic help IDs for those IDs prefixed with “IDC_”, and add
0x10000 to the resource IDs to generate actual help IDs, we can execute this command as follows (Here,
the application resource header file name is “resource.h”, and the “.hm” file name is “Help.hm”, it is
located under the directory of “Hlp”):
Makehm IDC_, HIDC_, 0x10000, resource.h >> “hlp\Help.hm”
If we include the above statement in file “Makehelp.bat”, after executing it, we will see that all the
common controls will have corresponding help IDs in file “Help.hm”.
Enabling Context Sensitive Help for Common Controls
In sample 16.2-1\Help, a dialog box IDD_DIALOG is added to the project. The dialog box supports
context sensitive help implementation. There are four controls included in the dialog box: edit box
IDC_EDIT, radio button IDC_RADIO, combo box IDC_COMBO and a push button IDC_BUTTON. After adding the
“Makehm” command to “Makehelp.bat” file and executing it, we will see the following help IDs in file
“Help.hm”:
// Common Controls (IDC_*)
HIDC_EDIT
HIDC_BUTTON
0x103E8
0x103E9
487