Winapi: combobox always returns previous text

Question

0.00/5 (No votes)

See more:

So i need to handle any change in a WinAPI combobox (its' type = Simple (you can modify the entry in edit box)). Everything is fine, except it always prints previous text, not the current.

C++

void onCommand(WPARAM wparam, LPARAM lparam)
{
    wchar_t str[100] = {0};
    ComboBox_GetText(GetDlgItem(mainWnd, IDC_COMBO1), str, 100);
    avPrint << str << av::endl;

    switch(LOWORD(wparam))
    {
        case IDCANCEL:     EndDialog(mainWnd, 0);   break;
    }
}

What am i doing wrong here?

What I have tried:

1) i've tried to print when ANY command occurs and i still get the previous edit values.
2) If i try to get text later (for example via mouse click) then the text is correct - window procedure code below:

C++

case WM_LBUTTONDOWN: onCommand(0, 0);            return true; // prints actual value
case WM_COMMAND:     onCommand(wparam, lparam);  return true; // prints previous value

Posted 7-Aug-21 4:37am

Avtem

Updated 7-Aug-21 22:24pm

v3

Add a Solution

Comments

Avtem 7-Aug-21 12:28pm

The only way i could get the current text was:
1) Get Edit handle of the combobox
2) Subclass the edit control
3) Get text on WM_PAINT (WM_SETTEXT gives previous results as well...)

Rick York 7-Aug-21 14:02pm

Have you tried catching the EN_CHANGE message and looking for the handle of the combobox's edit control?

I never use this kind of combobox so I am unfamiliar with it.

Avtem 8-Aug-21 14:12pm

Yep, it does seem to work, but i think i will stick with "intended" way to use it (if i understood it correctly).
Thank you!

Richard MacCutchan 8-Aug-21 4:21am

That is the wrong way to get data from a control. You should always use the control's notification messages which tell you when the data or selection changes.

Avtem 8-Aug-21 12:17pm

But that is my question - what is the right way to get data from the control?

Richard MacCutchan 8-Aug-21 12:19pm

Follow the link I provided below.

Avtem 8-Aug-21 12:28pm

Thank you!

1 solution

Add a Solution

Add your solution here

Treat my content as plain text, not as HTML

Preview 0

…

Existing Members

Sign in to your account

...or Join us

Download, Vote, Comment, Publish.

Your Email
Password
Forgot your password?

Your Email
This email is in use. Do you need your password?
Optional Password

I have read and agree to the Terms of Service and Privacy Policy
Please subscribe me to the CodeProject newsletters

When answering a question please:

Read the question carefully.
Understand that English isn't everyone's first language so be lenient of bad spelling and grammar.
If a question is poorly phrased then either ask for clarification, ignore it, or edit the question and fix the problem. Insults are not welcome.
Don't tell someone to read the manual. Chances are they have and don't get it. Provide an answer or move on to the next question.

Let's work to help developers, not make them feel stupid.

This content, along with any associated source code and files, is licensed under The Code Project Open License (CPOL)

Richard MacCutchan · Accepted Answer · 2021-08-07T22:24:00

Solution 1

You should study Combo Box (Windows Controls) - Win32 apps | Microsoft Docs[^] which explains how to use the control.

Posted 7-Aug-21 22:24pm

Richard MacCutchan

Comments

Avtem 8-Aug-21 14:09pm

Wow. i found how to do this by accident... Turns out if you want to handle combobox changes you have to handle CBN_EDITCHANGE which is not sent when user selects an item in the listbox and handle CBN_SELCHANGE, but not use WM_GETTEXT this time. They decided that programmer must retrieve Edit text by getting item in the listbox by index sent with CBN_SELCHANGE notification.

This is so confusing to me. Why just don't send CBN_EDITCHANGE for any change in the edit?

Richard MacCutchan 9-Aug-21 3:47am

If you think this is a bad design then you should tell Microsoft, it's their product.

Avtem 9-Aug-21 4:00am

Oh, there are more important things that i told them about, but they do not anything about it (Crashes in Visual Studio).

Anyway - did i understand how to use it properly?

Richard MacCutchan 9-Aug-21 4:13am

"did i understand how to use it properly?"
I don't know, you need to test your code to find out.

Avtem 9-Aug-21 4:27am

Well, it works perfectly.
Maybe i could not find the answer using Google because others understood it right away