Win32 FileChooser: Fix truncated initial file text

modules/juce_gui_basics/native/juce_win32_FileChooser.cpp

@@ -245,10 +245,42 @@ private:
             JUCE_COMRESULT OnFolderChanging (IFileDialog* d, IShellItem*) override                                { return updateHwnd (d); }
             JUCE_COMRESULT OnFileOk (IFileDialog* d) override                                                     { return updateHwnd (d); }
             JUCE_COMRESULT OnFolderChange (IFileDialog* d) override                                               { return updateHwnd (d); }
-            JUCE_COMRESULT OnSelectionChange (IFileDialog* d) override                                            { return updateHwnd (d); }
+            JUCE_COMRESULT OnSelectionChange (IFileDialog* d) override                                            { focusWorkaround(); return updateHwnd (d); }
             JUCE_COMRESULT OnShareViolation (IFileDialog* d, IShellItem*, FDE_SHAREVIOLATION_RESPONSE*) override  { return updateHwnd (d); }
             JUCE_COMRESULT OnOverwrite (IFileDialog* d, IShellItem*, FDE_OVERWRITE_RESPONSE*) override            { return updateHwnd (d); }
 
+            /** Workaround for a bug in Vista+, OpenFileDialog will truncate the initialFile text.
+                Moving the caret along the full length of the text and back will reveal the full string.
+            */
+            void focusWorkaround()
+            {
+                if (! defaultFileNameTextCaretMoved)
+                {
+                    auto makeKeyInput = [] (WORD vk, bool pressed)
+                    {
+                        INPUT i;
+
+                        ZeroMemory (&i, sizeof (INPUT));
+
+                        i.type = INPUT_KEYBOARD;
+                        i.ki.wVk = vk;
+                        i.ki.dwFlags = pressed ? 0 : KEYEVENTF_KEYUP;
+
+                        return i;
+                    };
+
+                    INPUT inputs[] = {
+                        makeKeyInput (VK_HOME, true),
+                        makeKeyInput (VK_HOME, false),
+                        makeKeyInput (VK_END,  true),
+                        makeKeyInput (VK_END,  false),
+                    };
+
+                    SendInput ((UINT) std::size (inputs), inputs, sizeof (INPUT));
+                    defaultFileNameTextCaretMoved = true;
+                }
+            }
+
             JUCE_COMRESULT updateHwnd (IFileDialog* d)
             {
                 HWND hwnd = nullptr;
@@ -266,6 +298,7 @@ private:
                 return S_OK;
             }
 
+            bool defaultFileNameTextCaretMoved = false;
             Win32NativeFileChooser& owner;
         };