Platform IME: added ImGuiPlatformImeData::WantTextInput, ViewportId. Backends: SDL3: honor WantTextInput. (#8584, #7492, #6341)

backends/imgui_impl_sdl3.cpp

@@ -20,6 +20,7 @@
 
 // CHANGELOG
 // (minor and older changes stripped away, please see git history for details)
+//  2025-04-22: IME: honor ImGuiPlatformImeData->WantTextInput as an alternative way to call SDL_StartTextInput(), without IME being necessarily visible.
 //  2025-04-09: Don't attempt to call SDL_CaptureMouse() on drivers where we don't call SDL_GetGlobalMouseState(). (#8561)
 //  2025-03-30: Update for SDL3 api changes: Revert SDL_GetClipboardText() memory ownership change. (#8530, #7801)
 //  2025-03-21: Fill gamepad inputs and set ImGuiBackendFlags_HasGamepad regardless of ImGuiConfigFlags_NavEnableGamepad being set.
@@ -150,7 +151,7 @@ static void ImGui_ImplSDL3_PlatformSetImeData(ImGuiContext*, ImGuiViewport* view
     ImGui_ImplSDL3_Data* bd = ImGui_ImplSDL3_GetBackendData();
     SDL_WindowID window_id = (SDL_WindowID)(intptr_t)viewport->PlatformHandle;
     SDL_Window* window = SDL_GetWindowFromID(window_id);
-    if ((data->WantVisible == false || bd->ImeWindow != window) && bd->ImeWindow != nullptr)
+    if ((!(data->WantVisible || data->WantTextInput) || bd->ImeWindow != window) && bd->ImeWindow != nullptr)
     {
         SDL_StopTextInput(bd->ImeWindow);
         bd->ImeWindow = nullptr;
@@ -163,9 +164,10 @@ static void ImGui_ImplSDL3_PlatformSetImeData(ImGuiContext*, ImGuiViewport* view
         r.w = 1;
         r.h = (int)data->InputLineHeight;
         SDL_SetTextInputArea(window, &r, 0);
-        SDL_StartTextInput(window);
         bd->ImeWindow = window;
     }
+    if (data->WantVisible || data->WantTextInput)
+        SDL_StartTextInput(window);
 }
 
 // Not static to allow third-party code to use that if they want to (but undocumented)

docs/CHANGELOG.txt

@@ -91,6 +91,10 @@ Other changes:
   would use a +1 offset instead of advancing to the next UTF-8 codepoint. (#8540)
 - Style, InputText: added ImGuiCol_InputTextCursor to configure color of
   the InputText cursor/caret. (#7031)
+- Platform IME: added ImGuiPlatformImeData::ViewportId info (backported from Docking branch).
+- Platform IME: added ImGuiPlatformImeData::WantTextInput which might set independently
+  of WantVisible. This is set in the same structure because activating text input generally
+  requires providing a window to the backend. (#8584, #6341)
 - Misc: added extra operators to ImVec4 in IMGUI_DEFINE_MATH_OPERATORS block. (#8510) [@gan74]
 - Backends: SDL2, SDL3, OSX: Fill gamepad inputs and set ImGuiBackendFlags_HasGamepad
   regardless of ImGuiConfigFlags_NavEnableGamepad being set. (#8508)
@@ -99,6 +103,8 @@ Other changes:
   the same white-list as SDL_GetGlobalMouseState(). (#8561) [@vs49688]
 - Backends: SDL3: Update for SDL3 api changes: revert SDL_GetClipboardText()
   memory ownership change. (#8530, #7801) [@Green-Sky]
+- Backends: SDL3: honor ImGuiPlatformImeData->WantTextInput as an alternative
+  way to call SDL_StartTextInput(), without IME being necessarily visible. (#8584)
 - Backends: SDLGPU3: Made ImGui_ImplSDLGPU3_PrepareDrawData() reuse GPU Transfer Buffers which
   were unusually slow to recreate every frame. Much faster now. (#8534) [@ocornut, @TheMode]
 - Backends: Vulkan: Deep-copy ImGui_ImplVulkan_InitInfo::PipelineRenderingCreateInfo's

imgui.cpp

@@ -5362,7 +5362,7 @@ void ImGui::NewFrame()
 
     // Platform IME data: reset for the frame
     g.PlatformImeDataPrev = g.PlatformImeData;
-    g.PlatformImeData.WantVisible = false;
+    g.PlatformImeData.WantVisible = g.PlatformImeData.WantTextInput = false;
 
     // Mouse wheel scrolling, scale
     UpdateMouseWheel();
@@ -5654,9 +5654,11 @@ void ImGui::EndFrame()
     if (g.PlatformIO.Platform_SetImeDataFn != NULL && memcmp(ime_data, &g.PlatformImeDataPrev, sizeof(ImGuiPlatformImeData)) != 0)
     {
         IMGUI_DEBUG_LOG_IO("[io] Calling Platform_SetImeDataFn(): WantVisible: %d, InputPos (%.2f,%.2f)\n", ime_data->WantVisible, ime_data->InputPos.x, ime_data->InputPos.y);
+        IM_ASSERT(ime_data->ViewportId == IMGUI_VIEWPORT_DEFAULT_ID); // master branch
         ImGuiViewport* viewport = GetMainViewport();
         g.PlatformIO.Platform_SetImeDataFn(&g, viewport, ime_data);
     }
+    g.WantTextInputNextFrame = ime_data->WantTextInput ? 1 : 0;
 
     // Hide implicit/fallback "Debug" window if it hasn't been used
     g.WithinFrameScopeWithImplicitWindow = false;

imgui.h

@@ -3626,14 +3626,16 @@ struct ImGuiPlatformIO
     void*       Renderer_RenderState;
 };
 
-// (Optional) Support for IME (Input Method Editor) via the platform_io.Platform_SetImeDataFn() function.
+// (Optional) Support for IME (Input Method Editor) via the platform_io.Platform_SetImeDataFn() function. Handler is called during EndFrame().
 struct ImGuiPlatformImeData
 {
-    bool    WantVisible;        // A widget wants the IME to be visible
-    ImVec2  InputPos;           // Position of the input cursor
-    float   InputLineHeight;    // Line height
+    bool    WantVisible;            // A widget wants the IME to be visible.
+    bool    WantTextInput;          // A widget wants text input, not necessarily IME to be visible. This is automatically set to the upcoming value of io.WantTextInput.
+    ImVec2  InputPos;               // Position of input cursor (for IME).
+    float   InputLineHeight;        // Line height (for IME).
+    ImGuiID ViewportId;             // ID of platform window/viewport.
 
-    ImGuiPlatformImeData() { memset(this, 0, sizeof(*this)); }
+    ImGuiPlatformImeData()          { memset(this, 0, sizeof(*this)); }
 };
 
 //-----------------------------------------------------------------------------

imgui_internal.h

@@ -2360,7 +2360,7 @@ struct ImGuiContext
     ImGuiTypingSelectState  TypingSelectState;                  // State for GetTypingSelectRequest()
 
     // Platform support
-    ImGuiPlatformImeData    PlatformImeData;                    // Data updated by current frame
+    ImGuiPlatformImeData    PlatformImeData;                    // Data updated by current frame. Will be applied at end of the frame. For some backends, this is required to have WantVisible=true in order to receive text message.
     ImGuiPlatformImeData    PlatformImeDataPrev;                // Previous frame data. When changed we call the platform_io.Platform_SetImeDataFn() handler.
 
     // Settings
@@ -2428,7 +2428,7 @@ struct ImGuiContext
     float                   FramerateSecPerFrameAccum;
     int                     WantCaptureMouseNextFrame;          // Explicit capture override via SetNextFrameWantCaptureMouse()/SetNextFrameWantCaptureKeyboard(). Default to -1.
     int                     WantCaptureKeyboardNextFrame;       // "
-    int                     WantTextInputNextFrame;
+    int                     WantTextInputNextFrame;             // Copied in EndFrame() from g.PlatformImeData.WanttextInput. Needs to be set for some backends (SDL3) to emit character inputs.
     ImVector<char>          TempBuffer;                         // Temporary text buffer
     char                    TempKeychordName[64];
 

imgui_widgets.cpp

@@ -5161,8 +5161,6 @@ bool ImGui::InputTextEx(const char* label, const char* hint, char* buf, int buf_
     // Otherwise request text input ahead for next frame.
     if (g.ActiveId == id && clear_active_id)
         ClearActiveID();
-    else if (g.ActiveId == id)
-        g.WantTextInputNextFrame = 1;
 
     // Render frame
     if (!is_multiline)
@@ -5343,11 +5341,15 @@ bool ImGui::InputTextEx(const char* label, const char* hint, char* buf, int buf_
                 draw_window->DrawList->AddLine(cursor_screen_rect.Min, cursor_screen_rect.GetBL(), GetColorU32(ImGuiCol_InputTextCursor), 1.0f); // FIXME-DPI: Cursor thickness (#7031)
 
             // 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)
+            // This is required for some backends (SDL3) to start emitting character/text inputs.
+            // As per #6341, make sure we don't set that on the deactivating frame.
+            if (!is_readonly && g.ActiveId == id)
             {
                 g.PlatformImeData.WantVisible = true;
+                g.PlatformImeData.WantTextInput = true;
                 g.PlatformImeData.InputPos = ImVec2(cursor_screen_pos.x - 1.0f, cursor_screen_pos.y - g.FontSize);
                 g.PlatformImeData.InputLineHeight = g.FontSize;
+                g.PlatformImeData.ViewportId = window->Viewport->ID;
             }
         }
     }