InputText: calling ReloadUserBuf doesn't clear undo stack. (#2890)

imgui_internal.h

@@ -1133,7 +1133,7 @@ struct IMGUI_API ImGuiInputTextState
     bool                    CursorFollow;           // set when we want scrolling to follow the current cursor position (not always!)
     bool                    SelectedAllMouseLock;   // after a double-click to select all, we ignore further mouse drags to update selection
     bool                    Edited;                 // edited this frame
-    bool                    ReloadUserBuf;          // force a reload of user buf so it may be modified externally. may be automatic in future version.
+    bool                    WantReloadUserBuf;      // force a reload of user buf so it may be modified externally. may be automatic in future version.
     int                     ReloadSelectionStart;
     int                     ReloadSelectionEnd;
 
@@ -1159,7 +1159,6 @@ struct IMGUI_API ImGuiInputTextState
     //   strcpy(my_buf, "hello");
     //   if (ImGuiInputTextState* state = ImGui::GetInputTextState(id)) // id may be ImGui::GetItemID() is last item
     //       state->ReloadUserBufAndSelectAll();
-    // THIS CURRENTLY RESETS THE UNDO STACK.
     void        ReloadUserBufAndSelectAll();
     void        ReloadUserBufAndKeepSelection();
     void        ReloadUserBufAndMoveToEnd();

imgui_widgets.cpp

@@ -4169,9 +4169,9 @@ int  ImGuiInputTextState::GetCursorPos() const              { return Stb->cursor
 int  ImGuiInputTextState::GetSelectionStart() const         { return Stb->select_start; }
 int  ImGuiInputTextState::GetSelectionEnd() const           { return Stb->select_end; }
 void ImGuiInputTextState::SelectAll()                       { Stb->select_start = 0; Stb->cursor = Stb->select_end = TextLen; Stb->has_preferred_x = 0; }
-void ImGuiInputTextState::ReloadUserBufAndSelectAll()       { ReloadUserBuf = true; ReloadSelectionStart = 0; ReloadSelectionEnd = INT_MAX; }
-void ImGuiInputTextState::ReloadUserBufAndKeepSelection()   { ReloadUserBuf = true; ReloadSelectionStart = Stb->select_start; ReloadSelectionEnd = Stb->select_end; }
-void ImGuiInputTextState::ReloadUserBufAndMoveToEnd()       { ReloadUserBuf = true; ReloadSelectionStart = ReloadSelectionEnd = INT_MAX; }
+void ImGuiInputTextState::ReloadUserBufAndSelectAll()       { WantReloadUserBuf = true; ReloadSelectionStart = 0; ReloadSelectionEnd = INT_MAX; }
+void ImGuiInputTextState::ReloadUserBufAndKeepSelection()   { WantReloadUserBuf = true; ReloadSelectionStart = Stb->select_start; ReloadSelectionEnd = Stb->select_end; }
+void ImGuiInputTextState::ReloadUserBufAndMoveToEnd()       { WantReloadUserBuf = true; ReloadSelectionStart = ReloadSelectionEnd = INT_MAX; }
 
 ImGuiInputTextCallbackData::ImGuiInputTextCallbackData()
 {
@@ -4503,32 +4503,40 @@ bool ImGui::InputTextEx(const char* label, const char* hint, char* buf, int buf_
 
     float scroll_y = is_multiline ? draw_window->Scroll.y : FLT_MAX;
 
-    const bool init_reload_from_user_buf = (state != NULL && state->ReloadUserBuf);
+    const bool init_reload_from_user_buf = (state != NULL && state->WantReloadUserBuf);
     const bool init_changed_specs = (state != NULL && state->Stb->single_line != !is_multiline); // state != NULL means its our state.
     const bool init_make_active = (user_clicked || user_scroll_finish || input_requested_by_nav);
     const bool init_state = (init_make_active || user_scroll_active);
-    if ((init_state && g.ActiveId != id) || init_changed_specs || init_reload_from_user_buf)
+    if (init_reload_from_user_buf)
+    {
+        int new_len = (int)strlen(buf);
+        state->WantReloadUserBuf = false;
+        InputTextReconcileUndoState(state, state->TextA.Data, state->TextLen, buf, new_len);
+        state->TextA.resize(buf_size + 1);          // we use +1 to make sure that .Data is always pointing to at least an empty string.
+        state->TextLen = new_len;
+        memcpy(state->TextA.Data, buf, state->TextLen + 1);
+        state->Stb->select_start = state->ReloadSelectionStart;
+        state->Stb->cursor = state->Stb->select_end = state->ReloadSelectionEnd;
+        state->CursorClamp();
+    }
+    else if ((init_state && g.ActiveId != id) || init_changed_specs)
     {
         // Access state even if we don't own it yet.
         state = &g.InputTextState;
         state->CursorAnimReset();
-        state->ReloadUserBuf = false;
 
         // Backup state of deactivating item so they'll have a chance to do a write to output buffer on the same frame they report IsItemDeactivatedAfterEdit (#4714)
         InputTextDeactivateHook(state->ID);
 
+        // Take a copy of the initial buffer value.
         // From the moment we focused we are normally ignoring the content of 'buf' (unless we are in read-only mode)
         const int buf_len = (int)strlen(buf);
-        if (!init_reload_from_user_buf)
-        {
-            // Take a copy of the initial buffer value.
-            state->TextToRevertTo.resize(buf_len + 1);    // UTF-8. we use +1 to make sure that .Data is always pointing to at least an empty string.
-            memcpy(state->TextToRevertTo.Data, buf, buf_len + 1);
-        }
+        state->TextToRevertTo.resize(buf_len + 1);    // UTF-8. we use +1 to make sure that .Data is always pointing to at least an empty string.
+        memcpy(state->TextToRevertTo.Data, buf, buf_len + 1);
 
         // Preserve cursor position and undo/redo stack if we come back to same widget
         // FIXME: Since we reworked this on 2022/06, may want to differentiate recycle_cursor vs recycle_undostate?
-        bool recycle_state = (state->ID == id && !init_changed_specs && !init_reload_from_user_buf);
+        bool recycle_state = (state->ID == id && !init_changed_specs);
         if (recycle_state && (state->TextLen != buf_len || (strncmp(state->TextA.Data, buf, buf_len) != 0)))
             recycle_state = false;
 
@@ -4550,13 +4558,7 @@ bool ImGui::InputTextEx(const char* label, const char* hint, char* buf, int buf_
         else
             stb_textedit_initialize_state(state->Stb, !is_multiline);
 
-        if (init_reload_from_user_buf)
-        {
-            state->Stb->select_start = state->ReloadSelectionStart;
-            state->Stb->cursor = state->Stb->select_end = state->ReloadSelectionEnd;
-            state->CursorClamp();
-        }
-        else if (!is_multiline)
+        if (!is_multiline)
         {
             if (flags & ImGuiInputTextFlags_AutoSelectAll)
                 select_all = true;