OS/2 codes: How to support DBCS #4 Process WM_QUERYCONVERTPOS

WM_QUERYCONVERTPOS is sent in order to query a position of a conversion window and a candiate window. However, an application is not aware of IME and not needed to control IME at all.

Let's see a syntax of WM_QUERYCONVERTPOS.

This message is sent by an application to determine whether it is appropriate to begin conversion of DBCS characters.

param1
     PRECTL  pCursorPos  /*  Cursor position. */

param2
     ULONG   ulReserved  /*  Reserved value, should be 0. */

This message may return QCP_CONVERT or QCP_NOCONVERT. If you return QCP_NOCONVERT, then an window does not receive DBCS characters. That is, this has an effect to disable IME. If you return QCP_CONVERT, then an window receives DBCS characters. In this case, [pCursorPos] should be updated. [pCursorPos->xLeft] and [pCursorPos->yBottom] is a bottom-left corner of a conversion window and a upper-left corner of a candidate window. [pCursorPos->xRight] and [pCursorPos-yTop] is a upper-right corner of a conversion window. However, [pCursorPos->xRight] and [pCursorPos->yTop] seems to be ignored. And remember that each positions should be in screen coordinates. For example, if you set [pCursorPos->xLeft] and [pCursorPos->yBottom] to 0, then a conversion window will show at bottom-left corner of screen. If you apply WinMapWindowPoints() to this [pCursorPos], then a conversion window will show at bottom-left corner of screen a window (2016/01/04).

WinMapWindowPoints( hwnd, HWND_DESKTOP, pCursorPos, 1 );

Here is a simple code snippet.

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case WM_QUERYCONVERTPOS: {         PRECTL pcp = ( PRECTL )mp1;         /* Set a position of a bottom-left corner of a conversion window            and a candiate window. */         pcp->xLeft = cursor.x;         pcp->yBottom = cursor.y;         /* Set a position of a upper-right corner of a conversion window. */         pcp->xRight = pcp->xLeft + cursor.width;         pcp->yTop = pcp->yBottom + cursor.height;         /* Convert a position relative to a window to a position relative to            screen. */         WinMapWindowPoints( hwnd, HWND_DESKTOP, pcp, 2 );         return (MRESULT)QCP_CONVERT;     }

[mp1] is param1, [cursor] contains a current position of a cursor relative to a window. [hwnd] is a window handle.

Glossary

Conversion window is a window to show characters that users is inputting.

Candidate window is a window to show candidate characters which inputted characters by users will be converted to.