Support preedit candidate

Support the GLFW preedit candidate feature.
This feature supports only Win32 currently.
We can use this feature by enabling `FLAG_MANAGE_PREEDIT_CANDIDATE` flag
on Win32.

Author: daipom

src/platforms/rcore_android.c

@@ -638,6 +638,12 @@ void ResetPreedit(void)
     TRACELOG(LOG_WARNING, "ResetPreedit() not implemented on target platform");
 }
 
+// Get the text of the preedie candidate
+int *GetPreeditCandidate(int index, int *textCount)
+{
+    TRACELOG(LOG_WARNING, "GetPreeditCandidate() not implemented on target platform");
+}
+
 // Set internal gamepad mappings
 int SetGamepadMappings(const char *mappings)
 {

src/platforms/rcore_desktop_glfw.c

@@ -119,6 +119,7 @@ static void WindowContentScaleCallback(GLFWwindow *window, float scalex, float s
 static void KeyCallback(GLFWwindow *window, int key, int scancode, int action, int mods);  // GLFW3 Keyboard Callback, runs on key pressed
 static void CharCallback(GLFWwindow *window, unsigned int codepoint);                      // GLFW3 Char Callback, runs on key pressed (get codepoint value)
 static void PreeditCallbackInner(GLFWwindow *window, int preeditLength, unsigned int *preeditString, int blockCount, int *blockSizes, int focusedBlock, int caret); // GLFW3 Preedit Callback
+static void PreeditCandidateCallbackInner(GLFWwindow *window, int candidatesCount, int selectedIndex, int pageStart, int pageSize); // GLFW3 Preedit Candidate Callback
 static void MouseButtonCallback(GLFWwindow *window, int button, int action, int mods);     // GLFW3 Mouse Button Callback, runs on mouse button pressed
 static void MouseCursorPosCallback(GLFWwindow *window, double x, double y);                // GLFW3 Cursor Position Callback, runs on mouse move
 static void MouseScrollCallback(GLFWwindow *window, double xoffset, double yoffset);       // GLFW3 Scrolling Callback, runs on mouse wheel
@@ -1075,6 +1076,12 @@ void ResetPreedit(void)
     glfwResetPreeditText(platform.handle);
 }
 
+// Get the text of the preedie candidate
+int *GetPreeditCandidate(int index, int *textCount)
+{
+    return (int *)glfwGetPreeditCandidate(platform.handle, index, textCount);
+}
+
 // Set internal gamepad mappings
 int SetGamepadMappings(const char *mappings)
 {
@@ -1293,6 +1300,10 @@ int InitPlatform(void)
 #if defined(__APPLE__)
     glfwInitHint(GLFW_COCOA_CHDIR_RESOURCES, GLFW_FALSE);
 #endif
+
+    if ((CORE.Window.flags & FLAG_MANAGE_PREEDIT_CANDIDATE) > 0) glfwInitHint(GLFW_MANAGE_PREEDIT_CANDIDATE, GLFW_TRUE); // Manage the drawing of preedit candidates.
+    else glfwInitHint(GLFW_MANAGE_PREEDIT_CANDIDATE, GLFW_FALSE); // Leave the drawing of preedit candidates to the IME 
+
     // Initialize GLFW internal global state
     int result = glfwInit();
     if (result == GLFW_FALSE) { TRACELOG(LOG_WARNING, "GLFW: Failed to initialize GLFW"); return -1; }
@@ -1633,6 +1644,7 @@ int InitPlatform(void)
     glfwSetKeyCallback(platform.handle, KeyCallback);
     glfwSetCharCallback(platform.handle, CharCallback);
     glfwSetPreeditCallback(platform.handle, PreeditCallbackInner);
+    glfwSetPreeditCandidateCallback(platform.handle, PreeditCandidateCallbackInner);
     glfwSetMouseButtonCallback(platform.handle, MouseButtonCallback);
     glfwSetCursorPosCallback(platform.handle, MouseCursorPosCallback);   // Track mouse position changes
     glfwSetScrollCallback(platform.handle, MouseScrollCallback);
@@ -1824,6 +1836,13 @@ static void PreeditCallbackInner(GLFWwindow *window, int preeditLength, unsigned
     CORE.Input.Keyboard.preeditCallback(preeditLength, (int *)preeditString, blockCount, blockSizes, focusedBlock, caret);
 }
 
+// GLFW3 Preedit Candidate Callback
+static void PreeditCandidateCallbackInner(GLFWwindow *window, int candidatesCount, int selectedIndex, int pageStart, int pageSize)
+{
+    if (!CORE.Input.Keyboard.preeditCandidateCallback) return;
+    CORE.Input.Keyboard.preeditCandidateCallback(candidatesCount, selectedIndex, pageStart, pageSize);
+}
+
 // GLFW3 Mouse Button Callback, runs on mouse button pressed
 static void MouseButtonCallback(GLFWwindow *window, int button, int action, int mods)
 {

src/platforms/rcore_desktop_sdl.c

@@ -959,6 +959,12 @@ void ResetPreedit(void)
     TRACELOG(LOG_WARNING, "ResetPreedit() not implemented on target platform");
 }
 
+// Get the text of the preedie candidate
+int *GetPreeditCandidate(int index, int *textCount)
+{
+    TRACELOG(LOG_WARNING, "GetPreeditCandidate() not implemented on target platform");
+}
+
 // Set internal gamepad mappings
 int SetGamepadMappings(const char *mappings)
 {

src/platforms/rcore_drm.c

@@ -634,6 +634,12 @@ void ResetPreedit(void)
     TRACELOG(LOG_WARNING, "ResetPreedit() not implemented on target platform");
 }
 
+// Get the text of the preedie candidate
+int *GetPreeditCandidate(int index, int *textCount)
+{
+    TRACELOG(LOG_WARNING, "GetPreeditCandidate() not implemented on target platform");
+}
+
 // Set internal gamepad mappings
 int SetGamepadMappings(const char *mappings)
 {

src/platforms/rcore_template.c

@@ -396,6 +396,12 @@ void ResetPreedit(void)
     TRACELOG(LOG_WARNING, "ResetPreedit() not implemented on target platform");
 }
 
+// Get the text of the preedie candidate
+int *GetPreeditCandidate(int index, int *textCount)
+{
+    TRACELOG(LOG_WARNING, "GetPreeditCandidate() not implemented on target platform");
+}
+
 // Set internal gamepad mappings
 int SetGamepadMappings(const char *mappings)
 {

src/platforms/rcore_web.c

@@ -123,6 +123,7 @@ static void WindowContentScaleCallback(GLFWwindow *window, float scalex, float s
 static void KeyCallback(GLFWwindow *window, int key, int scancode, int action, int mods); // GLFW3 Keyboard Callback, runs on key pressed
 static void CharCallback(GLFWwindow *window, unsigned int key);                           // GLFW3 Char Key Callback, runs on key pressed (get char value)
 static void PreeditCallbackInner(GLFWwindow *window, int preeditLength, unsigned int *preeditString, int blockCount, int *blockSizes, int focusedBlock, int caret); // GLFW3 Preedit Callback
+static void PreeditCandidateCallbackInner(GLFWwindow *window, int candidatesCount, int selectedIndex, int pageStart, int pageSize); // GLFW3 Preedit Candidate Callback
 static void MouseButtonCallback(GLFWwindow *window, int button, int action, int mods);    // GLFW3 Mouse Button Callback, runs on mouse button pressed
 static void MouseCursorPosCallback(GLFWwindow *window, double x, double y);               // GLFW3 Cursor Position Callback, runs on mouse move
 static void MouseScrollCallback(GLFWwindow *window, double xoffset, double yoffset);      // GLFW3 Srolling Callback, runs on mouse wheel
@@ -881,6 +882,12 @@ void ResetPreedit(void)
     glfwResetPreeditText(platform.handle);
 }
 
+// Get the text of the preedie candidate
+int *GetPreeditCandidate(int index, int *textCount)
+{
+    return (int *)glfwGetPreeditCandidate(platform.handle, index, textCount);
+}
+
 // Set internal gamepad mappings
 int SetGamepadMappings(const char *mappings)
 {
@@ -1054,6 +1061,9 @@ int InitPlatform(void)
 {
     glfwSetErrorCallback(ErrorCallback);
 
+    if ((CORE.Window.flags & FLAG_MANAGE_PREEDIT_CANDIDATE) > 0) glfwInitHint(GLFW_MANAGE_PREEDIT_CANDIDATE, GLFW_TRUE); // Manage the drawing of preedit candidates.
+    else glfwInitHint(GLFW_MANAGE_PREEDIT_CANDIDATE, GLFW_FALSE); // Leave the drawing of preedit candidates to the IME 
+
     // Initialize GLFW internal global state
     int result = glfwInit();
     if (result == GLFW_FALSE) { TRACELOG(LOG_WARNING, "GLFW: Failed to initialize GLFW"); return -1; }
@@ -1254,6 +1264,7 @@ int InitPlatform(void)
     glfwSetKeyCallback(platform.handle, KeyCallback);
     glfwSetCharCallback(platform.handle, CharCallback);
     glfwSetPreeditCallback(platform.handle, PreeditCallbackInner);
+    glfwSetPreeditCandidateCallback(platform.handle, PreeditCandidateCallbackInner);
     glfwSetMouseButtonCallback(platform.handle, MouseButtonCallback);
     glfwSetCursorPosCallback(platform.handle, MouseCursorPosCallback); // Track mouse position changes
     glfwSetScrollCallback(platform.handle, MouseScrollCallback);
@@ -1495,6 +1506,13 @@ static void PreeditCallbackInner(GLFWwindow *window, int preeditLength, unsigned
     CORE.Input.Keyboard.preeditCallback(preeditLength, (int *)preeditString, blockCount, blockSizes, focusedBlock, caret);
 }
 
+// GLFW3 Preedit Callback
+static void PreeditCallbackInner(GLFWwindow *window, int preeditLength, unsigned int *preeditString, int blockCount, int *blockSizes, int focusedBlock, int caret)
+{
+    if (!CORE.Input.Keyboard.preeditCallback) return;
+    CORE.Input.Keyboard.preeditCallback(preeditLength, (int *)preeditString, blockCount, blockSizes, focusedBlock, caret);
+}
+
 // GLFW3 Mouse Button Callback, runs on mouse button pressed
 static void MouseButtonCallback(GLFWwindow *window, int button, int action, int mods)
 {

src/raylib.h

@@ -533,6 +533,7 @@ typedef struct AutomationEventList {
 typedef enum {
     FLAG_VSYNC_HINT         = 0x00000040,   // Set to try enabling V-Sync on GPU
     FLAG_FULLSCREEN_MODE    = 0x00000002,   // Set to run program in fullscreen
+    FLAG_MANAGE_PREEDIT_CANDIDATE = 0x00020000, // Set to manage the drawing of preedit candidates by the application side
     FLAG_WINDOW_RESIZABLE   = 0x00000004,   // Set to allow resizable window
     FLAG_WINDOW_UNDECORATED = 0x00000008,   // Set to disable window decoration (frame and buttons)
     FLAG_WINDOW_HIDDEN      = 0x00000080,   // Set to hide window
@@ -1152,6 +1153,7 @@ RLAPI void PlayAutomationEvent(AutomationEvent event);
 //------------------------------------------------------------------------------------
 // Input Handling Functions (Module: core)
 //------------------------------------------------------------------------------------
+
 // Callback for preedit text.
 // preeditLength: The length of preedit text
 // preeditString: The preedit text (unicode)
@@ -1161,6 +1163,13 @@ RLAPI void PlayAutomationEvent(AutomationEvent event);
 // caret: The index of the caret in preeditString
 typedef void (*PreeditCallback)(int preeditLength, int *preeditString, int blockCount, int *blockSizes, int focusedBlock, int caret);
 
+// Callback for preedit candidate, which is called only when `FLAG_MANAGE_PREEDIT_CANDIDATE` ConfigFlag is enabled on Win32
+// candidatesCount: The number of all preedit candidates
+// selectedIndex: The index of the currently selected candidate in the all candidates
+// pageStart: The index of the first candidate on the current displaying page
+// pageSize: The number of the candidates on the current displaying page
+typedef void (*PreeditCandidateCallback)(int candidatesCount, int selectedIndex, int pageStart, int pageSize);
+
 // Input-related functions: keyboard
 RLAPI bool IsKeyPressed(int key);                             // Check if a key has been pressed once
 RLAPI bool IsKeyPressedRepeat(int key);                       // Check if a key has been pressed again (Only PLATFORM_DESKTOP)
@@ -1176,6 +1185,8 @@ RLAPI void GetPreeditCursorRectangle(int *x, int *y, int *w, int *h); // Get the
 RLAPI bool IsImeOn(void);                                     // Check if IME is ON
 RLAPI void SetImeStatus(bool on);                             // Set IME status
 RLAPI void ResetPreedit(void);                                // Reset preedit text
+RLAPI void SetPreeditCandidateCallback(PreeditCandidateCallback callback); // Set a callback for preedit candidates
+RLAPI int *GetPreeditCandidate(int index, int *textCount);    // Get the text of the preedie candidate. This can be used only when `FLAG_MANAGE_PREEDIT_CANDIDATE` ConfigFlag is enabled on Win32
 
 // Input-related functions: gamepads
 RLAPI bool IsGamepadAvailable(int gamepad);                                        // Check if a gamepad is available

src/rcore.c

@@ -307,6 +307,7 @@ typedef struct CoreData {
             int charPressedQueueCount;      // Input characters queue count
 
             PreeditCallback preeditCallback; // Preedit callback
+            PreeditCandidateCallback preeditCandidateCallback; // Preedit candidate callback
 
         } Keyboard;
         struct {
@@ -2871,6 +2872,12 @@ void SetPreeditCallback(PreeditCallback callback)
     CORE.Input.Keyboard.preeditCallback = callback;
 }
 
+// Set a callback for preedit candidate
+void SetPreeditCandidateCallback(PreeditCandidateCallback callback)
+{
+    CORE.Input.Keyboard.preeditCandidateCallback = callback;
+}
+
 // Set a custom key to exit program
 // NOTE: default exitKey is set to ESCAPE
 void SetExitKey(int key)