FIX: keyup event maybe not processed

jira: STUDIO-10958

Change-Id: I6d56f92f7cb2823b0d0a036d1da515270ebdba59

src/slic3r/GUI/ImGuiWrapper.cpp

@@ -510,6 +510,39 @@ void ImGuiWrapper::new_frame()
         init_font(true);
     }
 
+    ImGuiIO& io = ImGui::GetIO();
+
+    // BBL: copy & paste form prusa github repo (https://github.com/prusa3d/PrusaSlicer/blob/master/src/slic3r/GUI/ImGuiWrapper.cpp#L375C5-L402C6)
+    // synchronize key states
+    // when the application loses the focus it may happen that the key up event is not processed
+
+    // synchronize modifier keys
+    constexpr std::array<std::pair<ImGuiKeyModFlags_, wxKeyCode>, 3> imgui_mod_keys{
+        std::make_pair(ImGuiKeyModFlags_Ctrl, WXK_CONTROL),
+        std::make_pair(ImGuiKeyModFlags_Shift, WXK_SHIFT),
+        std::make_pair(ImGuiKeyModFlags_Alt, WXK_ALT) };
+    for (const std::pair<ImGuiKeyModFlags_, wxKeyCode>& key : imgui_mod_keys) {
+        if ((io.KeyMods & key.first) != 0 && !wxGetKeyState(key.second))
+            io.KeyMods &= ~key.first;
+    }
+
+    // Not sure if it is neccessary
+    // values from 33 to 126 are reserved for the standard ASCII characters
+    for (size_t i = 33; i <= 126; ++i) {
+        wxKeyCode keycode = static_cast<wxKeyCode>(i);
+        if (io.KeysDown[i] && keycode != WXK_NONE && !wxGetKeyState(keycode))
+            io.KeysDown[i] = false;
+    }
+
+    // special keys: delete, backspace, ...
+    for (int key : io.KeyMap) {
+        wxKeyCode keycode = static_cast<wxKeyCode>(key);
+        if (io.KeysDown[key] && keycode != WXK_NONE && !wxGetKeyState(keycode))
+            io.KeysDown[key] = false;
+    }
+
+    // BBL: end copy & paste
+
     ImGui::NewFrame();
     m_new_frame_open = true;
 }