Platform IME: reworked internals to simplify adding new features.

imgui.cpp

@@ -4146,7 +4146,9 @@ void ImGui::NewFrame()
 
     g.MouseCursor = ImGuiMouseCursor_Arrow;
     g.WantCaptureMouseNextFrame = g.WantCaptureKeyboardNextFrame = g.WantTextInputNextFrame = -1;
-    g.PlatformImePos = ImVec2(1.0f, 1.0f); // OS Input Method Editor showing on top-left of our window by default
+
+    // Platform IME data: reset for the frame
+    g.PlatformImeDataPrev = g.PlatformImeData;
 
     // Mouse wheel scrolling, scale
     UpdateMouseWheel();
@@ -4552,14 +4554,9 @@ void ImGui::EndFrame()
 
     ErrorCheckEndFrameSanityChecks();
 
-    // Notify OS when our Input Method Editor cursor has moved (e.g. CJK inputs using Microsoft IME)
-    if (g.IO.SetPlatformImeDataFn && (g.PlatformImeLastPos.x == FLT_MAX || ImLengthSqr(g.PlatformImeLastPos - g.PlatformImePos) > 0.0001f))
-    {
-        ImGuiPlatformImeData data;
-        data.InputPos = g.PlatformImePos;
-        g.IO.SetPlatformImeDataFn(GetMainViewport(), &data);
-        g.PlatformImeLastPos = g.PlatformImePos;
-    }
+    // Notify Platform/OS when our Input Method Editor cursor has moved (e.g. CJK inputs using Microsoft IME)
+    if (g.IO.SetPlatformImeDataFn && memcmp(&g.PlatformImeData, &g.PlatformImeDataPrev, sizeof(ImGuiPlatformImeData)) != 0)
+        g.IO.SetPlatformImeDataFn(GetMainViewport(), &g.PlatformImeData);
 
     // Hide implicit/fallback "Debug" window if it hasn't been used
     g.WithinFrameScopeWithImplicitWindow = false;

imgui_internal.h

@@ -1705,8 +1705,8 @@ struct ImGuiContext
     ImVector<ImGuiID>       MenusIdSubmittedThisFrame;          // A list of menu IDs that were rendered at least once
 
     // Platform support
-    ImVec2                  PlatformImePos;                     // Cursor position request & last passed to the OS Input Method Editor
-    ImVec2                  PlatformImeLastPos;
+    ImGuiPlatformImeData    PlatformImeData;                    // Data updated by current frame
+    ImGuiPlatformImeData    PlatformImeDataPrev;                // Previous frame data (when changing we will call io.SetPlatformImeDataFn
     char                    PlatformLocaleDecimalPoint;         // '.' or *localeconv()->decimal_point
 
     // Settings
@@ -1870,7 +1870,8 @@ struct ImGuiContext
         TooltipOverrideCount = 0;
         TooltipSlowDelay = 0.50f;
 
-        PlatformImePos = PlatformImeLastPos = ImVec2(FLT_MAX, FLT_MAX);
+        PlatformImeData.InputPos = ImVec2(0.0f, 0.0f);
+        PlatformImeDataPrev.InputPos = ImVec2(-1.0f, -1.0f); // Different to ensure initial submission
         PlatformLocaleDecimalPoint = '.';
 
         SettingsLoaded = false;

imgui_widgets.cpp

@@ -4760,7 +4760,7 @@ bool ImGui::InputTextEx(const char* label, const char* hint, char* buf, int buf_
 
             // Notify OS of text input position for advanced IME (-1 x offset so that Windows IME can cover our cursor. Bit of an extra nicety.)
             if (!is_readonly)
-                g.PlatformImePos = ImVec2(cursor_screen_pos.x - 1.0f, cursor_screen_pos.y - g.FontSize);
+                g.PlatformImeData.InputPos = ImVec2(cursor_screen_pos.x - 1.0f, cursor_screen_pos.y - g.FontSize);
         }
     }
     else