1 files changed, 138 insertions, 11 deletions

diff --git a/src/envshell.cpp b/src/envshell.cpp
index f7033fba..ca392a9c 100644
--- a/src/envshell.cpp
+++ b/src/envshell.cpp
@@ -2,6 +2,7 @@
 #include "env.h"
 #include <log.h>
 #include <utility.h>
+#include <windowsx.h>
 
 namespace env
 {
@@ -26,8 +27,8 @@ public:
 class WndProcFilter : public QAbstractNativeEventFilter
 {
 public:
-  WndProcFilter(IContextMenu* cm)
-    : m_cm2(nullptr), m_cm3(nullptr)
+  WndProcFilter(QMainWindow* mw, IContextMenu* cm)
+    : m_mw(mw), m_cm(cm), m_cm2(nullptr), m_cm3(nullptr)
   {
     IContextMenu2* cm2 = nullptr;
     if (SUCCEEDED(cm->QueryInterface(IID_IContextMenu2, (void**)&cm2))) {
@@ -40,10 +41,23 @@ public:
     }
   }
 
+  ~WndProcFilter()
+  {
+    if (auto* sb=m_mw->statusBar()) {
+      sb->clearMessage();
+    }
+  }
+
   bool nativeEventFilter(const QByteArray& type, void* m, long* lresultOut) override
   {
+    MSG* msg = (MSG*)m;
+
+    if (msg->message == WM_MENUSELECT) {
+      HANDLE_WM_MENUSELECT(msg->hwnd, msg->wParam, msg->lParam, onMenuSelect);
+      return true;
+    }
+
     if (m_cm3) {
-      MSG* msg = (MSG*)m;
       LRESULT lresult = 0;
 
       const auto r = m_cm3->HandleMenuMsg2(
@@ -59,8 +73,6 @@ public:
     }
 
     if (m_cm2) {
-      MSG* msg = (MSG*)m;
-
       const auto r = m_cm2->HandleMenuMsg(
         msg->message, msg->wParam, msg->lParam);
 
@@ -77,8 +89,104 @@ public:
   }
 
 private:
+  QMainWindow* m_mw;
+  IContextMenu* m_cm;
   COMPtr<IContextMenu2> m_cm2;
   COMPtr<IContextMenu3> m_cm3;
+
+  // adapted from
+  // https://devblogs.microsoft.com/oldnewthing/20040928-00/?p=37723
+  //
+  void onMenuSelect(
+    HWND hwnd, HMENU hmenu, int item, HMENU hmenuPopup, UINT flags)
+  {
+    if (m_cm && item >= QCM_FIRST && item <= QCM_LAST) {
+      WCHAR szBuf[MAX_PATH];
+
+      const auto r = IContextMenu_GetCommandString(
+        m_cm, item - QCM_FIRST, GCS_HELPTEXTW, NULL, szBuf, MAX_PATH);
+
+      if (FAILED(r)) {
+        lstrcpynW(szBuf, L"No help available.", MAX_PATH);
+      }
+
+      if (m_mw) {
+        if (auto* sb=m_mw->statusBar()) {
+          sb->showMessage(QString::fromWCharArray(szBuf));
+        }
+      }
+    }
+  }
+
+  // adapted from
+  // https://devblogs.microsoft.com/oldnewthing/20040928-00/?p=37723
+  //
+  HRESULT IContextMenu_GetCommandString(
+    IContextMenu *pcm, UINT_PTR idCmd, UINT uFlags,
+    UINT *pwReserved, LPWSTR pszName, UINT cchMax)
+  {
+    // Callers are expected to be using Unicode.
+    if (!(uFlags & GCS_UNICODE)) {
+      return E_INVALIDARG;
+    }
+
+    // Some context menu handlers have off-by-one bugs and will
+    // overflow the output buffer. Let’s artificially reduce the
+    // buffer size so a one-character overflow won’t corrupt memory.
+    if (cchMax <= 1) {
+      return E_FAIL;
+    }
+
+    cchMax--;
+
+    // First try the Unicode message.  Preset the output buffer
+    // with a known value because some handlers return S_OK without
+    // doing anything.
+    pszName[0] = L'\0';
+
+    HRESULT hr = pcm->GetCommandString(
+      idCmd, uFlags, pwReserved, (LPSTR)pszName, cchMax);
+
+    if (SUCCEEDED(hr) && pszName[0] == L'\0') {
+      // Rats, a buggy IContextMenu handler that returned success
+      // even though it failed.
+      hr = E_NOTIMPL;
+    }
+
+    if (FAILED(hr)) {
+      // try again with ANSI – pad the buffer with one extra character
+      // to compensate for context menu handlers that overflow by
+      // one character.
+      LPSTR pszAnsi = (LPSTR)LocalAlloc(
+        LMEM_FIXED, (cchMax + 1) * sizeof(CHAR));
+
+      if (pszAnsi) {
+        pszAnsi[0] = '\0';
+
+        hr = pcm->GetCommandString(
+          idCmd, uFlags & ~GCS_UNICODE, pwReserved, pszAnsi, cchMax);
+
+        if (SUCCEEDED(hr) && pszAnsi[0] == '\0') {
+          // Rats, a buggy IContextMenu handler that returned success
+          // even though it failed.
+          hr = E_NOTIMPL;
+        }
+
+        if (SUCCEEDED(hr)) {
+          if (MultiByteToWideChar(CP_ACP, 0, pszAnsi, -1, pszName, cchMax) == 0) {
+            hr = E_FAIL;
+          }
+        }
+
+        LocalFree(pszAnsi);
+
+      } else {
+        hr = E_OUTOFMEMORY;
+      }
+    }
+
+    return hr;
+  }
 };
 
 
@@ -145,16 +253,20 @@ HMenuPtr createMenu(IContextMenu* cm)
   return HMenuPtr(hmenu);
 }
 
-int runMenu(IContextMenu* cm, HWND hwnd, HMENU menu, const QPoint& p)
+int runMenu(QMainWindow* mw, IContextMenu* cm, HMENU menu, const QPoint& p)
 {
-  auto filter = std::make_unique<WndProcFilter>(cm);
+  const auto hwnd = (HWND)mw->winId();
+
+  auto filter = std::make_unique<WndProcFilter>(mw, cm);
   QCoreApplication::instance()->installNativeEventFilter(filter.get());
 
   return TrackPopupMenuEx(menu, TPM_RETURNCMD, p.x(), p.y(), hwnd, nullptr);
 }
 
-void invoke(HWND hwnd, const QPoint& p, int cmd, IContextMenu* cm)
+void invoke(QMainWindow* mw, const QPoint& p, int cmd, IContextMenu* cm)
 {
+  const auto hwnd = (HWND)mw->winId();
+
   CMINVOKECOMMANDINFOEX info = {};
 
   info.cbSize = sizeof(info);
@@ -184,24 +296,39 @@ void invoke(HWND hwnd, const QPoint& p, int cmd, IContextMenu* cm)
   }
 }
 
+QMainWindow* getMainWindow(QWidget* w)
+{
+  QWidget* p = w;
+
+  while (p) {
+    if (auto* mw=dynamic_cast<QMainWindow*>(p)) {
+      return mw;
+    }
+
+    p = p->parentWidget();
+  }
+
+  return nullptr;
+}
+
 void showShellMenu(QWidget* parent, const QFileInfo& file, const QPoint& pos)
 {
   const auto path = QDir::toNativeSeparators(file.absoluteFilePath());
 
   try
   {
+    auto* mw = getMainWindow(parent);
     auto idl = getIDL(path.toStdWString().c_str());
     auto [sf, childIdl] = getShellFolder(idl.get());
     auto cm = getContextMenu(sf.get(), childIdl);
     auto hmenu = createMenu(cm.get());
-    auto hwnd = (HWND)parent->window()->winId();
 
-    const int cmd = runMenu(cm.get(), hwnd, hmenu.get(), pos);
+    const int cmd = runMenu(mw, cm.get(), hmenu.get(), pos);
     if (cmd <= 0) {
       return;
     }
 
-    invoke(hwnd, pos, cmd - QCM_FIRST, cm.get());
+    invoke(mw, pos, cmd - QCM_FIRST, cm.get());
   }
   catch(MenuFailed& e)
   {