Combo box / subclassing issues

This is a discussion on Combo box / subclassing issues within the Windows Programming forums, part of the Platform Specific Boards category; I've got 2 problems right now. 1. I'm trying to figure out how to catch the CBN_SELCHANGE or CB_SETCURSEL message, ...

  1. #1
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    Combo box / subclassing issues

    I've got 2 problems right now.

    1. I'm trying to figure out how to catch the CBN_SELCHANGE or CB_SETCURSEL message, but I'm not having any luck. What message goes to the combobox procedure when the selection is changed?

    2. Doesn't the combobox control have the ability to scroll vertically if it needs to? MSDN implies that it can in the description for CBS_DISABLENOSCROLL .

    Code:
    CONTROL "",CMB_CS_SEARCH_TYPE,"ComboBox",WS_CHILD|WS_VISIBLE|WS_TABSTOP|CBS_HASSTRINGS|CBS_DROPDOWNLIST,18,64,189,50
    Last edited by Viper187; 09-08-2008 at 03:01 PM.

  2. #2
    Registered User Codeplug's Avatar
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    >> What message goes to the combobox procedure when the selection is changed?
    WM_COMMAND's go to the parent, not the control itself. The parent will have to "reflect" the messages back to the control - if you want the control to handle them.

    gg

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    Ok. so why the hell won't it scroll vertically?

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    Banned master5001's Avatar
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    You will just get a typical WM_VSCROLL if I am not mistaken. Though it may be something else that is similar. Remember, the whole idea behind a WM_COMMAND message is to let a parent know that someone was accessing a child. Not the other way around. When subclassing you are basically going to control if and when you send a WM_COMMAND, not intercept it outright.

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    How am I supposed to handle a WM_VSCROLL for a combobox? Listboxes/Listviews scroll automatically, don't they?

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    if you specify WS_VSCROLL or WS_HSCROLL (i think it's those, might want to double check the exact name) it will have a scroll bar automatically be enabled when it needs to be. Here is a snippet i used when i wanted to get the selection change from a combobox, drop down list to be exact.

    Code:
    case WM_COMMAND:
            switch(LOWORD(wParam))
            {
               case CONSEL: //Con-Selection ID
                //gets the selection from the dropdown box
                int ConSel = SendDlgItemMessage(hwnd,CONSEL,CB_GETCURSEL,0,0);
    
                //desides where to send the message depending on selection
                if(ConSel == 0){
                   //do stuff
                }
    
                if(ConSel == 1){
    
                }
    
                if(ConSel == 2){
    
                }
    
                if(ConSel == 3){
    
                }
                break;
            }
            break;

  7. #7
    Banned master5001's Avatar
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    Quote Originally Posted by Viper187 View Post
    How am I supposed to handle a WM_VSCROLL for a combobox? Listboxes/Listviews scroll automatically, don't they?
    You are subclassing the control, you can intercept its WM_* messages with your subclass. I think there is a custom message for scrolling in a combo-box now that I really think about it. Since the scroll bar within a combobox is actually a child window within the control. Either way, the WIN32 API still lets you intercept these messages.

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    Quote Originally Posted by scwizzo View Post
    if you specify WS_VSCROLL or WS_HSCROLL (i think it's those, might want to double check the exact name) it will have a scroll bar automatically be enabled when it needs to be.
    AH! Thanks.

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