Add preedit text callback API

Fixes #41.
Closes #658.

.gitignore

@@ -81,4 +81,3 @@ tests/timeout
 tests/title
 tests/vulkan
 tests/windows
-

CMakeLists.txt

@@ -226,6 +226,7 @@ endif()
 if (_GLFW_WIN32)
 
     list(APPEND glfw_PKG_LIBS "-lgdi32")
+    list(APPEND glfw_LIBRARIES "imm32")
 
     if (GLFW_USE_HYBRID_HPG)
         set(_GLFW_USE_HYBRID_HPG 1)

docs/input.dox

@@ -206,6 +206,96 @@ void charmods_callback(GLFWwindow* window, unsigned int codepoint, int mods)
 }
 @endcode
 
+@subsection preedit IME Support
+
+All desktop operating systems support IME (Input Method Editor) to input characters
+that are not mapped with physical keys. IME have been popular among Eeastern Asian people.
+And some operating systems start supporting voice input via IME mechanism.
+
+GLFW provides IME support functions to help
+you implement better text input features. You should add suitable visualization code for
+preedit text.
+
+IME works in front of actual character input events (@ref input_char).
+If your application uses text input and you want to support IME,
+you should register preedit callback to receive preedit text before committed.
+
+@code
+glfwSetPreeditCallback(window, preedit_callback);
+@endcode
+
+The callback function receives chunk of text and focused block information.
+
+@code
+static void preedit_callback(GLFWwindow* window, int strLength, unsigned int* string, int blockLength, int* blocks, int focusedBlock) {
+}
+@endcode
+
+strLength and string parameter reprsent whole preedit text. Each character of the preedit string is a codepoint like @ref input_char.
+
+If you want to type the text "寿司(sushi)", Usually the callback is called several times like the following sequence:
+
+-# key event: s
+-# preedit: [string: "ｓ", block: [1], focusedBlock: 0]
+-# key event: u
+-# preedit: [string: "す", block: [1], focusedBlock: 0]
+-# key event: s
+-# preedit: [string: "すｓ", block: [2], focusedBlock: 0]
+-# key event: h
+-# preedit: [string: "すｓｈ", block: [2], focusedBlock: 0]
+-# key event: i
+-# preedit: [string: "すし", block: [2], focusedBlock: 0]
+-# key event: ' '
+-# preedit: [string: "寿司", block: [2], focusedBlock: 0]
+-# char: '寿'
+-# char: '司'
+-# preedit: [string: "", block: [], focusedBlock: 0]
+
+If preedit text includes several semantic blocks, preedit callbacks returns several blocks after a space key pressed:
+
+-# preedit: [string: "わたしはすしをたべます", block: [11], focusedBlock: 0]
+-# preedit: [string: "私は寿司を食べます", block: [2, 7], focusedBlock: 1]
+
+"blocks" is a list of block length. The above case, it contains the following blocks and second block is focused.
+
+- 私は
+- [寿司を食べます]
+
+commited text(passed via regular @ref input_char event), unfocused block, focused block should have different text style.
+
+
+GLFW provides helper function to teach suitable position of the candidate window to window system.
+Window system decides the best position from text cursor geometry (x, y coords and height). You should call this function
+in the above preedit text callback function.
+
+@code
+glfwSetPreeditCursorPos(window, x, y, h);
+glfwGetPreeditCursorPos(window, &x, &y, &h);
+@endcode
+
+Sometimes IME task is interrupted by user or application. There are several functions to support these situation.
+You can receive notification about IME status change(on/off) by using the following function:
+
+@code
+glfwSetIMEStatusCallback(window, imestatus_callback);
+@endcode
+
+imestatus_callback has simple sigunature like this:
+
+@code
+static void imestatus_callback(GLFWwindow* window) {
+}
+@endcode
+
+You can implement the code that resets or commits preedit text when IME status is changed and preedit text is not empty.
+
+When the focus is gone from text box, you can use the following functions to reset IME status:
+
+@code
+void glfwResetPreeditText(GLFWwindow* window);
+void glfwSetIMEStatus(GLFWwindow* window, int active)
+int glfwGetIMEStatus(GLFWwindow* window)
+@endcode
 
 @subsection input_key_name Key names
 

include/GLFW/glfw3.h

@@ -686,6 +686,7 @@ extern "C" {
 #define GLFW_CURSOR                 0x00033001
 #define GLFW_STICKY_KEYS            0x00033002
 #define GLFW_STICKY_MOUSE_BUTTONS   0x00033003
+#define GLFW_IME                    0x00033004
 
 #define GLFW_CURSOR_NORMAL          0x00034001
 #define GLFW_CURSOR_HIDDEN          0x00034002
@@ -1100,6 +1101,37 @@ typedef void (* GLFWcharfun)(GLFWwindow*,unsigned int);
  */
 typedef void (* GLFWcharmodsfun)(GLFWwindow*,unsigned int,int);
 
+/*! @brief The function signature for preedit callbacks.
+ *
+ *  This is the function signature for preedit callback functions.
+ *
+ *  @param[in] window The window that received the event.
+ *  @param[in] length Preedit string length.
+ *  @param[in] string Preedit string.
+ *  @param[in] count Attributed block count.
+ *  @param[in] blocksizes List of attributed block size.
+ *  @param[in] focusedblock Focused block index.
+ *
+ *  @sa @ref preedit
+ *  @sa glfwSetPreeditCallback
+ *
+ *  @ingroup input
+ */
+typedef void (* GLFWpreeditfun)(GLFWwindow*,int,unsigned int*,int,int*,int);
+
+/*! @brief The function signature for IME status change callbacks.
+ *
+ *  This is the function signature for IME status change callback functions.
+ *
+ *  @param[in] window The window that received the event.
+ *
+ *  @sa @ref preedit
+ *  @sa glfwSetIMEStatusCallback
+ *
+ *  @ingroup monitor
+ */
+typedef void (* GLFWimestatusfun)(GLFWwindow*);
+
 /*! @brief The function signature for file drop callbacks.
  *
  *  This is the function signature for file drop callbacks.
@@ -3009,12 +3041,12 @@ GLFWAPI void glfwPostEmptyEvent(void);
 /*! @brief Returns the value of an input option for the specified window.
  *
  *  This function returns the value of an input option for the specified window.
- *  The mode must be one of `GLFW_CURSOR`, `GLFW_STICKY_KEYS` or
+ *  The mode must be one of `GLFW_CURSOR`, `GLFW_STICKY_KEYS`,
- *  `GLFW_STICKY_MOUSE_BUTTONS`.
+ *  `GLFW_STICKY_MOUSE_BUTTONS` or `GLFW_IME`.
  *
  *  @param[in] window The window to query.
- *  @param[in] mode One of `GLFW_CURSOR`, `GLFW_STICKY_KEYS` or
+ *  @param[in] mode One of `GLFW_CURSOR`, `GLFW_STICKY_KEYS`,
- *  `GLFW_STICKY_MOUSE_BUTTONS`.
+ *  `GLFW_STICKY_MOUSE_BUTTONS` or `GLFW_IME`.
  *
  *  @errors Possible errors include @ref GLFW_NOT_INITIALIZED and @ref
  *  GLFW_INVALID_ENUM.
@@ -3032,8 +3064,8 @@ GLFWAPI int glfwGetInputMode(GLFWwindow* window, int mode);
 /*! @brief Sets an input option for the specified window.
  *
  *  This function sets an input mode option for the specified window.  The mode
- *  must be one of `GLFW_CURSOR`, `GLFW_STICKY_KEYS` or
+ *  must be one of `GLFW_CURSOR`, `GLFW_STICKY_KEYS`,
- *  `GLFW_STICKY_MOUSE_BUTTONS`.
+ *  `GLFW_STICKY_MOUSE_BUTTONS` or `GLFW_IME`.
  *
  *  If the mode is `GLFW_CURSOR`, the value must be one of the following cursor
  *  modes:
@@ -3059,9 +3091,12 @@ GLFWAPI int glfwGetInputMode(GLFWwindow* window, int mode);
  *  you are only interested in whether mouse buttons have been pressed but not
  *  when or in which order.
  *
+ *  If the mode is `GLFW_IME`, the value must be either `GLFW_TRUE` to turn on IME,
+ *  or `GLFW_FALSE` to turn off it.
+ *
  *  @param[in] window The window whose input mode to set.
- *  @param[in] mode One of `GLFW_CURSOR`, `GLFW_STICKY_KEYS` or
+ *  @param[in] mode One of `GLFW_CURSOR`, `GLFW_STICKY_KEYS`,
- *  `GLFW_STICKY_MOUSE_BUTTONS`.
+ *  `GLFW_STICKY_MOUSE_BUTTONS` or `GLFW_IME`
  *  @param[in] value The new value of the specified input mode.
  *
  *  @errors Possible errors include @ref GLFW_NOT_INITIALIZED, @ref
@@ -3422,6 +3457,67 @@ GLFWAPI void glfwDestroyCursor(GLFWcursor* cursor);
  */
 GLFWAPI void glfwSetCursor(GLFWwindow* window, GLFWcursor* cursor);
 
+/*! @brief Retrieves the position of the text cursor relative to the client area of window.
+ *
+ *  This function returns position hint to decide the candidate window.
+ *
+ *  @param[in] window The window to set the text cursor for.
+ *  @param[out] x The text cursor x position (relative position from window coordinates).
+ *  @param[out] y The text cursor y position (relative position from window coordinates).
+ *  @param[out] h The text cursor height.
+ *
+ *  @par Thread Safety
+ *  This function may only be called from the main thread.
+ *
+ *  @sa @ref input_char
+ *
+ *  @since Added in GLFW 3.X.
+ *
+ *  @ingroup input
+ */
+GLFWAPI void glfwGetPreeditCursorPos(GLFWwindow* window, int *x, int *y, int *h);
+
+/*! @brief Notify the text cursor position to window system to decide the candidate window position.
+ *
+ *  This function teach position hint to decide the candidate window. The candidate window
+ *  is a part of IME(Input Method Editor) and show several candidate strings.
+ *
+ *  Windows sytems decide proper pisition from text cursor geometry.
+ *  You should call this function in preedit callback.
+ *
+ *  @param[in] window The window to set the text cursor for.
+ *  @param[in] x The text cursor x position (relative position from window coordinates).
+ *  @param[in] y The text cursor y position (relative position from window coordinates).
+ *  @param[in] h The text cursor height.
+ *
+ *  @par Thread Safety
+ *  This function may only be called from the main thread.
+ *
+ *  @sa @ref input_char
+ *
+ *  @since Added in GLFW 3.X.
+ *
+ *  @ingroup input
+ */
+GLFWAPI void glfwSetPreeditCursorPos(GLFWwindow* window, int x, int y, int h);
+
+/*! @brief Reset IME input status.
+ *
+ *  This function resets IME's preedit text.
+ *
+ *  @param[in] window The window.
+ *
+ *  @par Thread Safety
+ *  This function may only be called from the main thread.
+ *
+ *  @sa @ref preedit
+ *
+ *  @since Added in GLFW 3.X.
+ *
+ *  @ingroup input
+ */
+GLFWAPI void glfwResetPreeditText(GLFWwindow* window);
+
 /*! @brief Sets the key callback.
  *
  *  This function sets the key callback of the specified window, which is called
@@ -3536,6 +3632,58 @@ GLFWAPI GLFWcharfun glfwSetCharCallback(GLFWwindow* window, GLFWcharfun cbfun);
  */
 GLFWAPI GLFWcharmodsfun glfwSetCharModsCallback(GLFWwindow* window, GLFWcharmodsfun cbfun);
 
+/*! @brief Sets the preedit callback.
+ *
+ *  This function sets the  preedit callback of the specified
+ *  window, which is called when an IME is processing text before commited.
+ *
+ *  Callback receives relative position of input cursor inside preedit text and
+ *  attributed text blocks. This callback is used for on-the-spot text editing
+ *  with IME.
+ *
+ *  @param[in] window The window whose callback to set.
+ *  @param[in] cbfun The new callback, or `NULL` to remove the currently set
+ *  callback.
+ *  @return The previously set callback, or `NULL` if no callback was set or an
+ *  error occurred.
+ *
+ *  @par Thread Safety
+ *  This function may only be called from the main thread.
+ *
+ *  @sa @ref input_char
+ *
+ *  @since Added in GLFW 3.X
+ *
+ *  @ingroup input
+ */
+GLFWAPI GLFWpreeditfun glfwSetPreeditCallback(GLFWwindow* window, GLFWpreeditfun cbfun);
+
+/*! @brief Sets the IME status change callback.
+ *
+ *  This function sets the  preedit callback of the specified
+ *  window, which is called when an IME is processing text before commited.
+ *
+ *  Callback receives relative position of input cursor inside preedit text and
+ *  attributed text blocks. This callback is used for on-the-spot text editing
+ *  with IME.
+ *
+ *  @param[in] window The window whose callback to set.
+ *  @param[in] cbfun The new callback, or `NULL` to remove the currently set
+ *  callback.
+ *  @return The previously set callback, or `NULL` if no callback was set or an
+ *  error occurred.
+ *
+ *  @par Thread Safety
+ *  This function may only be called from the main thread.
+ *
+ *  @sa @ref input_char
+ *
+ *  @since Added in GLFW 3.X
+ *
+ *  @ingroup input
+ */
+GLFWAPI GLFWimestatusfun glfwSetIMEStatusCallback(GLFWwindow* window, GLFWimestatusfun cbfun);
+
 /*! @brief Sets the mouse button callback.
  *
  *  This function sets the mouse button callback of the specified window, which

src/cocoa_window.m

@@ -316,8 +316,11 @@ static const NSRange kEmptyRange = { NSNotFound, 0 };
     _glfwInputWindowFocus(window, GLFW_FALSE);
 }
 
-@end
+- (void)imeStatusChangeNotified:(NSNotification *)notification {
+    _glfwInputIMEStatus(window);
+}
 
+@end
 
 //------------------------------------------------------------------------
 // Delegate for application related notifications
@@ -714,6 +717,56 @@ static const NSRange kEmptyRange = { NSNotFound, 0 };
         [markedText initWithAttributedString:string];
     else
         [markedText initWithString:string];
+    NSString* markedTextString = markedText.string;
+
+    NSUInteger i, length = [markedTextString length];
+    int ctext = window->ctext;
+    while (ctext < length+1) {
+        ctext = (ctext == 0) ? 1 : ctext*2;
+    }
+    if (ctext != window->ctext) {
+        unsigned int* preeditText = realloc(window->preeditText, sizeof(unsigned int)*ctext);
+        if (preeditText == NULL) {
+            return;
+        }
+        window->preeditText = preeditText;
+        window->ctext = ctext;
+    }
+    window->ntext = length;
+    window->preeditText[length] = 0;
+    for (i = 0;  i < length;  i++)
+    {
+        const unichar codepoint = [markedTextString characterAtIndex:i];
+        window->preeditText[i] = codepoint;
+    }
+    int focusedBlock = 0;
+    NSInteger offset = 0;
+    window->nblocks = 0;
+    while (offset < length) {
+        NSRange effectiveRange;
+        NSDictionary *attributes = [markedText attributesAtIndex:offset effectiveRange:&effectiveRange];
+        
+        if (window->nblocks == window->cblocks) {
+            int cblocks = window->cblocks * 2;
+            int* blocks = realloc(window->preeditAttributeBlocks, sizeof(int)*cblocks);
+            if (blocks == NULL) {
+                return;
+            }
+            window->preeditAttributeBlocks = blocks;
+            window->cblocks = cblocks;
+        }
+        window->preeditAttributeBlocks[window->nblocks] = effectiveRange.length;
+        offset += effectiveRange.length;
+        if (effectiveRange.length == 0) {
+            break;
+        }
+        NSNumber* underline = (NSNumber*) [attributes objectForKey:@"NSUnderline"];
+        if ([underline intValue] != 1) {
+            focusedBlock = window->nblocks;
+        }
+        window->nblocks++;
+    }
+    _glfwInputPreedit(window, focusedBlock);
 }
 
 - (void)unmarkText
@@ -742,8 +795,7 @@ static const NSRange kEmptyRange = { NSNotFound, 0 };
 {
     int xpos, ypos;
     _glfwPlatformGetWindowPos(window, &xpos, &ypos);
-    const NSRect contentRect = [window->ns.view frame];
+    return NSMakeRect(xpos + window->preeditCursorPosX, transformY(ypos + window->preeditCursorPosY), 0.0, window->preeditCursorHeight);
-    return NSMakeRect(xpos, transformY(ypos + contentRect.size.height), 0.0, 0.0);
 }
 
 - (void)insertText:(id)string replacementRange:(NSRange)replacementRange
@@ -1049,6 +1101,11 @@ static GLFWbool createNativeWindow(_GLFWwindow* window,
     [window->ns.object setAcceptsMouseMovedEvents:YES];
     [window->ns.object setRestorable:NO];
 
+    [[NSNotificationCenter defaultCenter]
+        addObserver: window->ns.delegate
+        selector:@selector(imeStatusChangeNotified:)
+        name:NSTextInputContextKeyboardSelectionDidChangeNotification
+        object: nil];
     return GLFW_TRUE;
 }
 
@@ -1102,6 +1159,8 @@ void _glfwPlatformDestroyWindow(_GLFWwindow* window)
     if (_glfw.ns.disabledCursorWindow == window)
         _glfw.ns.disabledCursorWindow = NULL;
 
+    [[NSNotificationCenter defaultCenter] removeObserver: window->ns.delegate];
+
     [window->ns.object orderOut:nil];
 
     if (window->monitor)
@@ -1735,6 +1794,49 @@ VkResult _glfwPlatformCreateWindowSurface(VkInstance instance,
 #endif
 }
 
+void _glfwPlatformResetPreeditText(_GLFWwindow* window)
+{
+    NSTextInputContext *context = [NSTextInputContext currentInputContext];
+    [context discardMarkedText];
+    [window->ns.view unmarkText];
+}
+
+void _glfwPlatformSetIMEStatus(_GLFWwindow* window, int active)
+{
+    // Mac OS has several input sources.
+    // this code assumes input methods not in ascii capable inputs using IME.
+    NSArray* asciiInputSources = CFBridgingRelease(TISCreateASCIICapableInputSourceList());
+    TISInputSourceRef asciiSource = (__bridge TISInputSourceRef)([asciiInputSources firstObject]);
+    if (active) {
+        NSArray* allInputSources = CFBridgingRelease(TISCreateInputSourceList(NULL, false));
+        NSString* asciiSourceID = (__bridge NSString *)(TISGetInputSourceProperty(asciiSource, kTISPropertyInputSourceID));
+        int i;
+        int count = [allInputSources count];
+        for (i = 0; i < count; i++) {
+            TISInputSourceRef source = (__bridge TISInputSourceRef)([allInputSources objectAtIndex: i]);
+            NSString* sourceID = (__bridge NSString *)(TISGetInputSourceProperty(source, kTISPropertyInputSourceID));
+            if ([asciiSourceID compare: sourceID] != NSOrderedSame) {
+                TISSelectInputSource(source);
+                break;
+            }
+        }
+    } else if (asciiSource) {
+        TISSelectInputSource(asciiSource);
+    }
+}
+
+int _glfwPlatformGetIMEStatus(_GLFWwindow* window)
+{
+    TISInputSourceRef currentSource = TISCopyCurrentKeyboardInputSource();
+    NSString* currentSourceID = (__bridge NSString *)(TISGetInputSourceProperty(currentSource, kTISPropertyInputSourceID));
+    NSArray* asciiInputSources = CFBridgingRelease(TISCreateASCIICapableInputSourceList());
+    TISInputSourceRef asciiSource = (__bridge TISInputSourceRef)([asciiInputSources firstObject]);
+    if (asciiSource) {
+        NSString* asciiSourceID = (__bridge NSString *)(TISGetInputSourceProperty(asciiSource, kTISPropertyInputSourceID));
+        return ([asciiSourceID compare: currentSourceID] == NSOrderedSame) ? GLFW_FALSE : GLFW_TRUE;
+    }
+    return GLFW_FALSE;
+}
 
 //////////////////////////////////////////////////////////////////////////
 //////                        GLFW native API                       //////

src/input.c

@@ -79,6 +79,20 @@ void _glfwInputChar(_GLFWwindow* window, unsigned int codepoint, int mods, GLFWb
     }
 }
 
+void _glfwInputPreedit(_GLFWwindow* window, int focusedBlock)
+{
+    if (window->callbacks.preedit) {
+        window->callbacks.preedit((GLFWwindow*) window, window->ntext, window->preeditText, window->nblocks, window->preeditAttributeBlocks, focusedBlock);
+    }
+}
+
+void _glfwInputIMEStatus(_GLFWwindow* window)
+{
+    if (window->callbacks.imestatus) {
+        window->callbacks.imestatus((GLFWwindow*) window);
+    }
+}
+
 void _glfwInputScroll(_GLFWwindow* window, double xoffset, double yoffset)
 {
     if (window->callbacks.scroll)
@@ -162,6 +176,8 @@ GLFWAPI int glfwGetInputMode(GLFWwindow* handle, int mode)
             return window->stickyKeys;
         case GLFW_STICKY_MOUSE_BUTTONS:
             return window->stickyMouseButtons;
+        case GLFW_IME:
+            return _glfwPlatformGetIMEStatus(window);
         default:
             _glfwInputError(GLFW_INVALID_ENUM, "Invalid input mode %i", mode);
             return 0;
@@ -245,6 +261,13 @@ GLFWAPI void glfwSetInputMode(GLFWwindow* handle, int mode, int value)
             window->stickyMouseButtons = value ? GLFW_TRUE : GLFW_FALSE;
             return;
         }
+
+        case GLFW_IME:
+            _glfwPlatformSetIMEStatus(window, value ? GLFW_TRUE : GLFW_FALSE);
+            break;    
+        default:
+            _glfwInputError(GLFW_INVALID_ENUM, "Invalid input mode %i", mode);
+            break;
     }
 
     _glfwInputError(GLFW_INVALID_ENUM, "Invalid input mode %i", mode);
@@ -469,6 +492,30 @@ GLFWAPI void glfwSetCursor(GLFWwindow* windowHandle, GLFWcursor* cursorHandle)
     _glfwPlatformSetCursor(window, cursor);
 }
 
+GLFWAPI void glfwGetPreeditCursorPos(GLFWwindow* handle, int *x, int *y, int *h)
+{
+    _GLFWwindow* window = (_GLFWwindow*) handle;
+    if (x)
+        *x = window->preeditCursorPosX;
+    if (y)
+        *y = window->preeditCursorPosY;
+    if (h)
+        *h = window->preeditCursorHeight;
+}
+
+GLFWAPI void glfwSetPreeditCursorPos(GLFWwindow* handle, int x, int y, int h)
+{
+    _GLFWwindow* window = (_GLFWwindow*) handle;
+    window->preeditCursorPosX = x;
+    window->preeditCursorPosY = y;
+    window->preeditCursorHeight = h;
+}
+
+GLFWAPI void glfwResetPreeditText(GLFWwindow* handle) {
+    _GLFWwindow* window = (_GLFWwindow*) handle;
+    _glfwPlatformResetPreeditText(window);
+}
+
 GLFWAPI GLFWkeyfun glfwSetKeyCallback(GLFWwindow* handle, GLFWkeyfun cbfun)
 {
     _GLFWwindow* window = (_GLFWwindow*) handle;
@@ -499,6 +546,22 @@ GLFWAPI GLFWcharmodsfun glfwSetCharModsCallback(GLFWwindow* handle, GLFWcharmods
     return cbfun;
 }
 
+GLFWAPI GLFWpreeditfun glfwSetPreeditCallback(GLFWwindow* handle, GLFWpreeditfun cbfun)
+{
+    _GLFWwindow* window = (_GLFWwindow*) handle;
+    _GLFW_REQUIRE_INIT_OR_RETURN(NULL);
+    _GLFW_SWAP_POINTERS(window->callbacks.preedit, cbfun);
+    return cbfun;
+}
+
+GLFWAPI GLFWimestatusfun glfwSetIMEStatusCallback(GLFWwindow* handle, GLFWimestatusfun cbfun)
+{
+    _GLFWwindow* window = (_GLFWwindow*) handle;
+    _GLFW_REQUIRE_INIT_OR_RETURN(NULL);
+    _GLFW_SWAP_POINTERS(window->callbacks.imestatus, cbfun);
+    return cbfun;
+}
+
 GLFWAPI GLFWmousebuttonfun glfwSetMouseButtonCallback(GLFWwindow* handle,
                                                       GLFWmousebuttonfun cbfun)
 {

src/internal.h

@@ -370,9 +370,19 @@ struct _GLFWwindow
     int                 cursorMode;
     char                mouseButtons[GLFW_MOUSE_BUTTON_LAST + 1];
     char                keys[GLFW_KEY_LAST + 1];
+
     // Virtual cursor position when cursor is disabled
     double              virtualCursorPosX, virtualCursorPosY;
 
+    // Preedit texts
+    unsigned int*       preeditText;
+    int                 ntext;
+    int                 ctext;
+    int*                preeditAttributeBlocks;
+    int                 nblocks;
+    int                 cblocks;
+    int                 preeditCursorPosX, preeditCursorPosY, preeditCursorHeight;
+
     _GLFWcontext        context;
 
     struct {
@@ -391,6 +401,8 @@ struct _GLFWwindow
         GLFWkeyfun              key;
         GLFWcharfun             character;
         GLFWcharmodsfun         charmods;
+        GLFWpreeditfun          preedit;
+        GLFWimestatusfun        imestatus;
         GLFWdropfun             drop;
     } callbacks;
 
@@ -818,6 +830,46 @@ int _glfwPlatformGetPhysicalDevicePresentationSupport(VkInstance instance, VkPhy
  */
 VkResult _glfwPlatformCreateWindowSurface(VkInstance instance, _GLFWwindow* window, const VkAllocationCallbacks* allocator, VkSurfaceKHR* surface);
 
+/*! @copydoc glfwResetPreeditText
+ *  @ingroup platform
+ */
+void _glfwPlatformResetPreeditText(_GLFWwindow* window);
+
+/*! @brief Set IME status.
+ *
+ *  This function set IME status.
+ *
+ *  @param[in] window The window.
+ *  @param[in] active Turns on IME if `GFLW_TRUE` is given. Otherwise (`GLFW_FALSE`) turns off.
+ *
+ *  @par Thread Safety
+ *  This function may only be called from the main thread.
+ *
+ *  @sa @ref preedit
+ *
+ *  @since Added in GLFW 3.X.
+ *
+ *  @ingroup platform
+ */
+void _glfwPlatformSetIMEStatus(_GLFWwindow* window, int active);
+
+/*! @brief Get IME status.
+ *
+ *  This function get IME status.
+ *
+ *  @param[in] window The window.
+ *  @return When IME is active, this function returns `GFLW_TRUE`. Otherwise `GLFW_FALSE`.
+ *
+ *  @par Thread Safety
+ *  This function may only be called from the main thread.
+ *
+ *  @sa @ref preedit
+ *
+ *  @since Added in GLFW 3.X.
+ *
+ *  @ingroup platform
+ */
+int  _glfwPlatformGetIMEStatus(_GLFWwindow* window);
 
 //========================================================================
 // Event API functions
@@ -904,6 +956,19 @@ void _glfwInputKey(_GLFWwindow* window, int key, int scancode, int action, int m
  */
 void _glfwInputChar(_GLFWwindow* window, unsigned int codepoint, int mods, GLFWbool plain);
 
+/*! @brief Notifies shared code of a IME preedit text update event.
+ *  @param[in] window The window that received the event.
+ *  @param[in] focusedBlock Focused preedit text block index.
+ *  @ingroup event
+ */
+void _glfwInputPreedit(_GLFWwindow* window, int focusedBlock);
+
+/*! @brief Notifies shared code of a IME status change.
+ *  @param[in] window The window that received the event.
+ *  @ingroup event
+ */
+void _glfwInputIMEStatus(_GLFWwindow* window);
+
 /*! @brief Notifies shared code of a scroll event.
  *  @param[in] window The window that received the event.
  *  @param[in] xoffset The scroll offset along the x-axis.

src/mir_window.c

@@ -890,6 +890,25 @@ VkResult _glfwPlatformCreateWindowSurface(VkInstance instance,
     return err;
 }
 
+void _glfwPlatformResetPreeditText(_GLFWwindow* window)
+{
+    _glfwInputError(GLFW_PLATFORM_ERROR,
+                    "Mir: Unsupported function %s", __PRETTY_FUNCTION__);
+}
+
+void _glfwPlatformSetIMEStatus(_GLFWwindow* window, int active)
+{
+    _glfwInputError(GLFW_PLATFORM_ERROR,
+                    "Mir: Unsupported function %s", __PRETTY_FUNCTION__);
+}
+
+int _glfwPlatformGetIMEStatus(_GLFWwindow* window)
+{
+    _glfwInputError(GLFW_PLATFORM_ERROR,
+                    "Mir: Unsupported function %s", __PRETTY_FUNCTION__);
+    return GLFW_FALSE;
+}
+
 
 //////////////////////////////////////////////////////////////////////////
 //////                        GLFW native API                       //////

src/osmesa_window.c

@@ -301,3 +301,16 @@ VkResult _glfwPlatformCreateWindowSurface(VkInstance instance,
     return VK_ERROR_INITIALIZATION_FAILED;
 }
 
+void _glfwPlatformResetPreeditText(_GLFWwindow* window)
+{
+}
+
+void _glfwPlatformSetIMEStatus(_GLFWwindow* window, int active)
+{
+}
+
+int _glfwPlatformGetIMEStatus(_GLFWwindow* window)
+{
+    return GLFW_FALSE;
+}
+

src/win32_window.c

@@ -33,6 +33,7 @@
 #include <string.h>
 #include <windowsx.h>
 #include <shellapi.h>
+#include <imm.h>
 
 #define _GLFW_KEY_INVALID -2
 
@@ -422,6 +423,15 @@ static void releaseMonitor(_GLFWwindow* window)
     _glfwRestoreVideoModeWin32(window->monitor);
 }
 
+// Set cursor position to decide candidate window
+static void _win32ChangeCursorPosition(HIMC hIMC, _GLFWwindow* window) {
+    int x = window->preeditCursorPosX;
+    int y = window->preeditCursorPosY;
+    int h = window->preeditCursorHeight;
+    CANDIDATEFORM excludeRect = {0, CFS_EXCLUDE, {x, y}, {x, y, x, y+h}};
+    ImmSetCandidateWindow(hIMC, &excludeRect);
+}
+
 // Window callback function (handles window messages)
 //
 static LRESULT CALLBACK windowProc(HWND hWnd, UINT uMsg,
@@ -536,7 +546,7 @@ static LRESULT CALLBACK windowProc(HWND hWnd, UINT uMsg,
             }
 
             _glfwInputChar(window, (unsigned int) wParam, getKeyMods(), plain);
-            return 0;
+            return TRUE;
         }
 
         case WM_KEYDOWN:
@@ -570,7 +580,93 @@ static LRESULT CALLBACK windowProc(HWND hWnd, UINT uMsg,
 
             break;
         }
-
+        case WM_IME_COMPOSITION:
+        {
+            if (lParam & GCS_RESULTSTR) {
+                window->nblocks = 0;
+                window->ntext = 0;
+                _glfwInputPreedit(window, 0);
+                return TRUE;
+            }
+            if (lParam & GCS_COMPSTR) {
+                HIMC hIMC = ImmGetContext(hWnd);
+                // get preedit data sizes
+                LONG preeditTextLength = ImmGetCompositionStringW(hIMC, GCS_COMPSTR, NULL, 0);
+                LONG attrLength = ImmGetCompositionString(hIMC, GCS_COMPATTR, NULL, 0);
+                LONG clauseLength = ImmGetCompositionString(hIMC, GCS_COMPCLAUSE, NULL, 0);
+                if (preeditTextLength > 0) {
+                    // get preedit data
+                    int length = preeditTextLength/sizeof(WCHAR);
+                    LPWSTR buffer = (LPWSTR)malloc(sizeof(WCHAR)+preeditTextLength);
+                    LPSTR attributes = (LPSTR)malloc(attrLength);
+                    DWORD *clauses = (DWORD*)malloc(clauseLength);
+                    ImmGetCompositionStringW(hIMC, GCS_COMPSTR, buffer, preeditTextLength);
+                    ImmGetCompositionString(hIMC, GCS_COMPATTR, attributes, attrLength);
+                    ImmGetCompositionString(hIMC, GCS_COMPCLAUSE, clauses, clauseLength);
+                    // store preedit text
+                    int ctext = window->ctext;
+                    while (ctext < length+1) {
+                        ctext = (ctext == 0) ? 1 : ctext*2;
+                    }
+                    if (ctext != window->ctext) {
+                        unsigned int* preeditText = realloc(window->preeditText, sizeof(unsigned int)*ctext);
+                        if (preeditText == NULL) {
+                            return 0;
+                            free(buffer);
+                            free(attributes);
+                            free(clauses);
+                        }
+                        window->preeditText = preeditText;
+                        window->ctext = ctext;
+                    }
+                    window->ntext = length;
+                    window->preeditText[length] = 0;
+                    int i;
+                    for (i=0; i < length; i++) {
+                        window->preeditText[i] = buffer[i];
+                    }
+                    // store blocks
+                    window->nblocks = clauseLength/sizeof(DWORD)-1;
+                    // last element of clauses is a block count, but
+                    // text length is convenient.
+                    clauses[window->nblocks] = length;
+                    int cblocks = window->cblocks;
+                    while (cblocks < window->nblocks) {
+                        cblocks = (cblocks == 0) ? 1 : cblocks*2;
+                    }
+                    if (cblocks != window->cblocks) {
+                        int* blocks = realloc(window->preeditAttributeBlocks, sizeof(int)*cblocks);
+                        if (blocks == NULL) {
+                            return 0;
+                            free(buffer);
+                            free(attributes);
+                            free(clauses);
+                        }
+                        window->preeditAttributeBlocks = blocks;
+                        window->cblocks = cblocks;
+                    }
+                    int focusedBlock = 0;
+                    for (i=0; i < window->nblocks; i++) {
+                        window->preeditAttributeBlocks[i] = clauses[i+1]-clauses[i];
+                        if (attributes[clauses[i]] != ATTR_CONVERTED) {
+                            focusedBlock = i;
+                        }
+                    }
+                    free(buffer);
+                    free(attributes);
+                    free(clauses);
+                    _glfwInputPreedit(window, focusedBlock);
+                    _win32ChangeCursorPosition(hIMC, window);
+                }
+                ImmReleaseContext(hWnd, hIMC);
+                return TRUE;
+            }
+            break;
+        }
+        case WM_IME_NOTIFY:
+            if (wParam == IMN_SETOPENSTATUS)
+                _glfwInputIMEStatus(window);
+            break;
         case WM_LBUTTONDOWN:
         case WM_RBUTTONDOWN:
         case WM_MBUTTONDOWN:
@@ -1705,6 +1801,30 @@ VkResult _glfwPlatformCreateWindowSurface(VkInstance instance,
     return err;
 }
 
+void _glfwPlatformResetPreeditText(_GLFWwindow* window)
+{
+    HWND hWnd = window->win32.handle;
+    HIMC hIMC = ImmGetContext(hWnd);
+    ImmNotifyIME(hIMC, NI_COMPOSITIONSTR, CPS_CANCEL, 0);
+    ImmReleaseContext(hWnd, hIMC);
+}
+
+void _glfwPlatformSetIMEStatus(_GLFWwindow* window, int active)
+{
+    HWND hWnd = window->win32.handle;
+    HIMC hIMC = ImmGetContext(hWnd);
+    ImmSetOpenStatus(hIMC, active ? TRUE : FALSE);
+    ImmReleaseContext(hWnd, hIMC);
+}
+
+int _glfwPlatformGetIMEStatus(_GLFWwindow* window)
+{
+    HWND hWnd = window->win32.handle;
+    HIMC hIMC = ImmGetContext(hWnd);
+    BOOL result = ImmGetOpenStatus(hIMC);
+    ImmReleaseContext(hWnd, hIMC);
+    return result ? GLFW_TRUE : GLFW_FALSE;
+}
 
 //////////////////////////////////////////////////////////////////////////
 //////                        GLFW native API                       //////

src/window.c

@@ -230,6 +230,10 @@ GLFWAPI GLFWwindow* glfwCreateWindow(int width, int height,
             if (wndconfig.focused)
                 _glfwPlatformFocusWindow(window);
         }
+
+        window->preeditCursorPosX = 0;
+        window->preeditCursorPosY = height;
+        window->preeditCursorHeight = 0;
     }
 
     return (GLFWwindow*) window;
@@ -408,7 +412,11 @@ GLFWAPI void glfwDestroyWindow(GLFWwindow* handle)
 
         *prev = window->next;
     }
-
+    // Clear memory for preedit text
+    if (window->preeditText)
+        free(window->preeditText);
+    if (window->preeditAttributeBlocks)
+        free(window->preeditAttributeBlocks);
     free(window);
 }
 

src/wl_window.c

@@ -1027,6 +1027,28 @@ VkResult _glfwPlatformCreateWindowSurface(VkInstance instance,
     return err;
 }
 
+void _glfwPlatformResetPreeditText(_GLFWwindow* window)
+{
+    // TODO
+    _glfwInputError(GLFW_PLATFORM_ERROR,
+                    "Wayland: IME not implemented yet");
+}
+
+void _glfwPlatformSetIMEStatus(_GLFWwindow* window, int active)
+{
+    // TODO
+    _glfwInputError(GLFW_PLATFORM_ERROR,
+                    "Wayland: IME not implemented yet");
+}
+
+int _glfwPlatformGetIMEStatus(_GLFWwindow* window)
+{
+    // TODO
+    _glfwInputError(GLFW_PLATFORM_ERROR,
+                    "Wayland: IME not implemented yet");
+    return GLFW_FALSE;
+}
+
 
 //////////////////////////////////////////////////////////////////////////
 //////                        GLFW native API                       //////

src/x11_platform.h

@@ -128,6 +128,16 @@ typedef struct _GLFWwindowX11
     unsigned int    lastKeyCode;
     Time            lastKeyTime;
 
+    // Preedit callbacks
+    XIMCallback preeditStartCallback;
+    XIMCallback preeditDoneCallback;
+    XIMCallback preeditDrawCallback;
+    XIMCallback preeditCaretCallback;
+    XIMCallback statusStartCallback;
+    XIMCallback statusDoneCallback;
+    XIMCallback statusDrawCallback;
+
+    int imeFocus;
 } _GLFWwindowX11;
 
 // X11-specific global data

src/x11_window.c

@@ -48,6 +48,9 @@
 #define Button6            6
 #define Button7            7
 
+#if defined(X_HAVE_UTF8_STRING)
+static unsigned int decodeUTF8(const char** s);
+#endif
 
 // Wait for data to arrive using select
 // This avoids blocking other threads via the per-display Xlib lock that also
@@ -437,6 +440,196 @@ static char** parseUriList(char* text, int* count)
     return paths;
 }
 
+// Update cursor position to decide candidate window
+static void _ximChangeCursorPosition(XIC xic, _GLFWwindow* window)
+{
+    XVaNestedList preedit_attr;
+    XPoint        spot;
+
+    spot.x = window->preeditCursorPosX;
+    spot.y = window->preeditCursorPosY + window->preeditCursorHeight;
+    preedit_attr = XVaCreateNestedList(0, XNSpotLocation, &spot, NULL);
+    XSetICValues(xic, XNPreeditAttributes, preedit_attr, NULL);
+    XFree(preedit_attr);
+}
+
+// IME Start callback (do nothing)
+static void _ximPreeditStartCallback(XIC xic, XPointer clientData, XPointer callData)
+{
+}
+
+// IME Done callback (do nothing)
+static void _ximPreeditDoneCallback(XIC xic, XPointer clientData, XPointer callData)
+{
+}
+
+// IME Draw callback
+static void _ximPreeditDrawCallback(XIC xic, XPointer clientData, XIMPreeditDrawCallbackStruct *callData)
+{
+    int i, j, length, ctext, rstart, rend;
+    XIMText* text;
+    const char* src;
+    unsigned int codePoint;
+    unsigned int* preeditText;
+    XIMFeedback f;
+    _GLFWwindow* window = (_GLFWwindow*)clientData;
+
+    // keep cursor position to reduce API call
+    int cursorX = window->preeditCursorPosX;
+    int cursorY = window->preeditCursorPosY;
+    int cursorHeight = window->preeditCursorHeight;
+
+    if (!callData->text) {
+        // preedit text is empty
+        window->ntext = 0;
+        window->nblocks = 0;
+        _glfwInputPreedit(window, 0);
+        return;
+    } else {
+        text = callData->text;
+        length = callData->chg_length;
+        if (text->encoding_is_wchar) {
+            // wchar is not supported
+            return;
+        }
+        ctext = window->ctext;
+        while (ctext < length+1) {
+            ctext = (ctext == 0) ? 1 : ctext * 2;
+        }
+        if (ctext != window->ctext) {
+            preeditText = realloc(window->preeditText, sizeof(unsigned int)*ctext);
+            if (preeditText == NULL) {
+                return;
+            }
+            window->preeditText = preeditText;
+            window->ctext = ctext;
+        }
+        window->ntext = length;
+        window->preeditText[length] = 0;
+        if (window->cblocks == 0) {
+            window->preeditAttributeBlocks = malloc(sizeof(int)*4);
+            window->cblocks = 4;
+        }
+        src = text->string.multi_byte;
+        rend = 0;
+        rstart = length;
+        for (i = 0, j = 0; i < text->length; i++) {
+            #if defined(X_HAVE_UTF8_STRING)
+            codePoint = decodeUTF8(&src);
+            #else
+            codePoint = *src;
+            src++;
+            #endif
+            if (i < callData->chg_first || callData->chg_first+length < i) {
+                continue;
+            }
+            window->preeditText[j++] = codePoint;
+            f = text->feedback[i];
+            if ((f & XIMReverse) || (f & XIMHighlight)) {
+                rend = i;
+                if (i < rstart) {
+                    rstart = i;
+                }
+            }
+        }
+        if (rstart == length) {
+            window->nblocks = 1;
+            window->preeditAttributeBlocks[0] = length;
+            window->preeditAttributeBlocks[1] = 0;
+            _glfwInputPreedit(window, 0);
+        } else if (rstart == 0) {
+            if (rend == length -1) {
+                window->nblocks = 1;
+                window->preeditAttributeBlocks[0] = length;
+                window->preeditAttributeBlocks[1] = 0;
+                _glfwInputPreedit(window, 0);
+            } else {
+                window->nblocks = 2;
+                window->preeditAttributeBlocks[0] = rend + 1;
+                window->preeditAttributeBlocks[1] = length - rend - 1;
+                window->preeditAttributeBlocks[2] = 0;
+                _glfwInputPreedit(window, 0);
+            }
+        } else if (rend == length -1) {
+            window->nblocks = 2;
+            window->preeditAttributeBlocks[0] = rstart;
+            window->preeditAttributeBlocks[1] = length - rstart;
+            window->preeditAttributeBlocks[2] = 0;
+            _glfwInputPreedit(window, 1);
+        } else {
+            window->nblocks = 3;
+            window->preeditAttributeBlocks[0] = rstart;
+            window->preeditAttributeBlocks[1] = rend - rstart + 1;
+            window->preeditAttributeBlocks[2] = length - rend - 1;
+            window->preeditAttributeBlocks[3] = 0;
+            _glfwInputPreedit(window, 1);
+        }
+        if ((cursorX != window->preeditCursorPosX)
+                || (cursorY != window->preeditCursorPosY)
+                || (cursorHeight != window->preeditCursorHeight)) {
+            _ximChangeCursorPosition(xic, window);
+        }
+    }
+}
+
+// IME Caret callback (do nothing)
+static void _ximPreeditCaretCallback(XIC xic, XPointer clientData, XPointer callData)
+{
+}
+
+static void _ximStatusStartCallback(XIC xic, XPointer clientData, XPointer callData)
+{
+    _GLFWwindow* window = (_GLFWwindow*)clientData;
+    window->x11.imeFocus = GLFW_TRUE;
+}
+
+static void _ximStatusDoneCallback(XIC xic, XPointer clientData, XPointer callData)
+{
+    _GLFWwindow* window = (_GLFWwindow*)clientData;
+    window->x11.imeFocus = GLFW_FALSE;
+}
+
+static void _ximStatusDrawCallback(XIC xic, XPointer clientData, XIMStatusDrawCallbackStruct* callData)
+{
+    _GLFWwindow* window = (_GLFWwindow*)clientData;
+    _glfwInputIMEStatus(window);
+}
+
+// Create XIM Preedit callback
+static XVaNestedList _createXIMPreeditCallbacks(_GLFWwindow* window)
+{
+    window->x11.preeditStartCallback.client_data = (XPointer)window;
+    window->x11.preeditStartCallback.callback = (XIMProc)_ximPreeditStartCallback;
+    window->x11.preeditDoneCallback.client_data = (XPointer)window;
+    window->x11.preeditDoneCallback.callback = (XIMProc)_ximPreeditDoneCallback;
+    window->x11.preeditDrawCallback.client_data = (XPointer)window;
+    window->x11.preeditDrawCallback.callback = (XIMProc)_ximPreeditDrawCallback;
+    window->x11.preeditCaretCallback.client_data = (XPointer)window;
+    window->x11.preeditCaretCallback.callback = (XIMProc)_ximPreeditCaretCallback;
+    return XVaCreateNestedList (0,
+        XNPreeditStartCallback, &window->x11.preeditStartCallback.client_data,
+        XNPreeditDoneCallback, &window->x11.preeditDoneCallback.client_data,
+        XNPreeditDrawCallback, &window->x11.preeditDrawCallback.client_data,
+        XNPreeditCaretCallback, &window->x11.preeditCaretCallback.client_data,
+        NULL);
+}
+
+// Create XIM status callback
+static XVaNestedList _createXIMStatusCallbacks(_GLFWwindow* window)
+{
+    window->x11.statusStartCallback.client_data = (XPointer)window;
+    window->x11.statusStartCallback.callback = (XIMProc)_ximStatusStartCallback;
+    window->x11.statusDoneCallback.client_data = (XPointer)window;
+    window->x11.statusDoneCallback.callback = (XIMProc)_ximStatusDoneCallback;
+    window->x11.statusDrawCallback.client_data = (XPointer)window;
+    window->x11.statusDrawCallback.callback = (XIMProc)_ximStatusDrawCallback;
+    return XVaCreateNestedList (0,
+        XNStatusStartCallback, &window->x11.statusStartCallback.client_data,
+        XNStatusDoneCallback, &window->x11.statusDoneCallback.client_data,
+        XNStatusDrawCallback, &window->x11.statusDrawCallback.client_data,
+        NULL);
+}
+
 // Centers the cursor over the window client area
 //
 static void centerCursor(_GLFWwindow* window)
@@ -646,14 +839,23 @@ static GLFWbool createNativeWindow(_GLFWwindow* window,
 
     if (_glfw.x11.im)
     {
+        XVaNestedList preeditList = _createXIMPreeditCallbacks(window);
+        XVaNestedList statusList = _createXIMStatusCallbacks(window);
         window->x11.ic = XCreateIC(_glfw.x11.im,
                                    XNInputStyle,
-                                   XIMPreeditNothing | XIMStatusNothing,
+                                   XIMPreeditCallbacks | XIMStatusCallbacks,
                                    XNClientWindow,
                                    window->x11.handle,
                                    XNFocusWindow,
                                    window->x11.handle,
+                                   XNPreeditAttributes,
+                                   preeditList,
+                                   XNStatusAttributes,
+                                   statusList,
                                    NULL);
+        XFree(preeditList);
+        XFree(statusList);
+        window->x11.imeFocus = GLFW_FALSE;
     }
 
     _glfwPlatformGetWindowPos(window, &window->x11.xpos, &window->x11.ypos);
@@ -2480,6 +2682,46 @@ VkResult _glfwPlatformCreateWindowSurface(VkInstance instance,
     }
 }
 
+void _glfwPlatformResetPreeditText(_GLFWwindow* window) {
+    XIC ic = window->x11.ic;
+
+    /* restore conversion state after resetting ic later */
+    XIMPreeditState preedit_state = XIMPreeditUnKnown;
+    XVaNestedList preedit_attr;
+    char* result;
+
+    if (window->ntext == 0)
+        return;
+
+    preedit_attr = XVaCreateNestedList(0, XNPreeditState, &preedit_state, NULL);
+    XGetICValues(ic, XNPreeditAttributes, preedit_attr, NULL);
+    XFree(preedit_attr);
+
+    result = XmbResetIC(ic);
+
+    preedit_attr = XVaCreateNestedList(0, XNPreeditState, preedit_state, NULL);
+    XSetICValues(ic, XNPreeditAttributes, preedit_attr, NULL);
+    XFree(preedit_attr);
+
+    window->ntext = 0;
+    window->nblocks = 0;
+    _glfwInputPreedit(window, 0);
+
+    XFree (result);
+}
+
+void _glfwPlatformSetIMEStatus(_GLFWwindow* window, int active) {
+    XIC ic = window->x11.ic;
+    if (active) {
+        XSetICFocus(ic);
+    } else {
+        XUnsetICFocus(ic);
+    }
+}
+
+int  _glfwPlatformGetIMEStatus(_GLFWwindow* window) {
+    return window->x11.imeFocus;
+}
 
 //////////////////////////////////////////////////////////////////////////
 //////                        GLFW native API                       //////

tests/events.c

@@ -420,6 +420,45 @@ static void char_mods_callback(GLFWwindow* window, unsigned int codepoint, int m
             get_mods_name(mods));
 }
 
+static void preedit_callback(GLFWwindow* window, int strLength, unsigned int* string, int blockLength, int* blocks, int focusedBlock) {
+    Slot* slot = glfwGetWindowUserPointer(window);
+    int i, blockIndex = -1, blockCount = 0;
+    int width, height;
+    printf("%08x to %i at %0.3f: Preedit text ",
+           counter++, slot->number, glfwGetTime());
+    if (strLength == 0 || blockLength == 0) {
+        printf("(empty)\n");
+    } else {
+        for (i = 0; i < strLength; i++) {
+            if (blockCount == 0) {
+                if (blockIndex == focusedBlock) {
+                    printf("]");
+                }
+                blockIndex++;
+                blockCount = blocks[blockIndex];
+                printf("\n   block %d: ", blockIndex);
+                if (blockIndex == focusedBlock) {
+                    printf("[");
+                }
+            }
+            printf("%s", get_character_string(string[i]));
+            blockCount--;
+        }
+        if (blockIndex == focusedBlock) {
+            printf("]");
+        }
+        printf("\n");
+        glfwGetWindowSize(window, &width, &height);
+        glfwSetPreeditCursorPos(window, width/2, height/2, 20);
+    }
+}
+
+static void ime_callback(GLFWwindow* window) {
+    Slot* slot = glfwGetWindowUserPointer(window);
+    printf("%08x to %i at %0.3f: IME switched\n",
+           counter++, slot->number, glfwGetTime());
+}
+
 static void drop_callback(GLFWwindow* window, int count, const char** paths)
 {
     int i;
@@ -596,6 +635,8 @@ int main(int argc, char** argv)
         glfwSetKeyCallback(slots[i].window, key_callback);
         glfwSetCharCallback(slots[i].window, char_callback);
         glfwSetCharModsCallback(slots[i].window, char_mods_callback);
+        glfwSetPreeditCallback(slots[i].window, preedit_callback);
+        glfwSetIMEStatusCallback(slots[i].window, ime_callback);
         glfwSetDropCallback(slots[i].window, drop_callback);
 
         glfwMakeContextCurrent(slots[i].window);