Input Mechanism in DBCS PM

DBCS PM provides an input handling mechanism to handle the DBCS keyboard and input method functions. The Structure of the DBCS Keyboard and Input Method in DBCS PM shows its process flow.

              Keyboard data (from kbd D/D)
              Mouse data (from Mou D/D)
                   │   │ (*1)
                      
              ┌────────────┐
              │            │
              │System Queue│
              │            │
              └────────────┘
                     │             Input Playback Hook (*7)
                     │─────────────────────┐
                VKey │   WinSetGlyphXlatTbl │
                Char │   WinSetCharXlatTbl  │
                     │                      │
                     │─────────────┐(*3)   │
                     │              │       │
       PreAccel Hook │ WM_CHAR  ┌───────────────┐
       (*2)          │          │               │
                     │─────────│ DBCS Keyboard │  (*4)  ┌───────┐
                     │          │               │───────│       │
                     │          │ Input Method  │        │ I M E │
                     │          │               │───────│       │
                     │          │ Mechanism     │  (*5)  └───────┘
                     │          │               │        Provided by system
             WM_CHAR │          └───────────────┘           or ISV
                     │              │ Provided by system
                                   │ (*2)
              ┌──────────────┐      │
              │              │      │
              │ Application  │ ────┘ (*6)
              │              │
              └──────────────┘

Structure of the DBCS Keyboard and Input Method in DBCS PM

The function is implemented as follows:

• The keyboard and mouse input data from the PDDs (Physical Device Drivers), are sent to the PM System Queue, and are reformatted to the PM messages. (Same as in SBCS PM)

• The keyboard message WM_CHAR then is sent to the application that is waiting for the event (Same as in SBCS PM). However, the DBCS PM provides a input method mechanism. This mechanism sets a pre─accel hook to intercept the WM_CHAR message from the keyboard PDD.

  Note: Pre─accel hook is a mechanism which the PM input module uses to handle the accelerator keys that are defined by the application program.

• If the DBCS keyboard mode is changed and some keys are pressed, the input method mechanism will request the system queue to set the new keyboard data translation table for the v─key data and character data.

• IME(Input Method Editor) is a plugged in a module. The IME provided by the system is installed as a default and an end user can add or install some other IME that provided by IBM or other ISV. The input method mechanism sends the WM_CHAR to the active IME asks for conversion services.

• IME will return the result of each key data transaction to the input method mechanism.

• Depending on the returned result from IME, the input handling mechanism will display the YOMI string or update the keyboard status line of the focus window of the application program.

• If the IME returns the final result string, for example a user presses the enter key to fix the target string, this string will be formatted as several WM_CHAR messages and sent back to the system queue from the input playback hook.