By default, every Pocket PC edit control has text completion enabled. In that mode, when Pocket PC OS sees that there is a potential completion for a text in the edit control, it shows a window with the suggestions. It can be selected either by tapping on it or using 5-way navigation up and center press.

This behaviour is not always desirable since it prevents from handling 5-way up event inside edit control.

Also, sometimes edit control is in suggestion mode but suggestion window is not displayed. I haven't figured out why, but this can cause a lot of head-scratching if suddently edit control swallows up events with no apparent reason.

It's possible to control auto-completion by changing sip (soft input panel) flags using SHSipInfo. Unfortunately this is a global setting.

In order to turn completion off only for a given edit control, we need to subclass edit control, write our own windows proc and enable/disable completion on WM_KILLFOCUS/WM_SETFOCUS messages, as the snippet below shows.

A better implementation would remember what was the completion state was on WM_SETFOCUS and restore it on WM_KILLFOCUS.

This jumping through hoop should not be necessary - Pocket PC should provide a flag to disable auto completion that could be set on edit control during its creation.

#include <aygshell.h>

// see http://pocketpcdn.com/articles/wordcompletion.html for details
// edit boxes on pocket pc by default have spelling suggestion/completion.
// Sometimes we want/need to disable that and those functions do it.
void sip_completion_disable(void)
{
    SIPINFO     info;

    SHSipInfo(SPI_GETSIPINFO, 0, &info, 0);
    info.fdwFlags |= SIPF_DISABLECOMPLETION;
    SHSipInfo(SPI_SETSIPINFO, 0, &info, 0);
}

void sip_completion_enable(void)
{
    SIPINFO     info;

    SHSipInfo(SPI_GETSIPINFO, 0, &info, 0);
    info.fdwFlags &= ~SIPF_DISABLECOMPLETION;
    SHSipInfo(SPI_SETSIPINFO, 0, &info, 0);
}

LRESULT EditWinProc(HWND hwnd, UINT msg, UINT wparam, LONG lparam)
{
    switch (msg) {
        case WM_KILLFOCUS:
            sip_completion_enable();
            break;
        case WM_SETFOCUS:
            sip_completion_disable();
            break;    
    }
}