Implement the Windows Task Dialog

Documentation/src/System/Windows/Forms/TaskDialog/Issue_AccessViolation_NavigationInButtonClicked.md

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+# Windows Task Dialog Issue
+
+## Access Violation when receiving [`TDN_NAVIGATED`](https://docs.microsoft.com/en-us/windows/desktop/Controls/tdn-navigated) within [`TDN_BUTTON_CLICKED`](https://docs.microsoft.com/en-us/windows/desktop/Controls/tdn-button-clicked)
+
+An Access violation can occur when receiving a navigation notification ([`TDN_NAVIGATED`](https://docs.microsoft.com/en-us/windows/desktop/Controls/tdn-navigated))
+within a [`TDN_BUTTON_CLICKED`](https://docs.microsoft.com/en-us/windows/desktop/Controls/tdn-button-clicked)
+notification (e.g. due to running the message loop) and then returning `S_OK`.
+
+* Run the code.
+* Click on the "My Custom Button" button.
+* Notice that the dialog navigates and an inner dialog shows.
+* Close the inner dialog by clicking the OK button.
+* **Issue:** In most cases, an access violation occurs now (if not, try again a
+  few times).
+* Notice the problem also occurs when you (after the navigation) first close
+  the original dialog, and then close the inner dialog.
+* The problem can be avoided by returning `S_FALSE` from the `TDN_BUTTON_CLICKED`
+  notification.
+
+```cpp
+#include "stdafx.h"
+#include "CommCtrl.h"
+
+HRESULT WINAPI TaskDialogCallbackProc(_In_ HWND hwnd, _In_ UINT msg, _In_ WPARAM wParam, _In_ LPARAM lParam, _In_ LONG_PTR lpRefData)
+{
+    switch (msg) {
+    case TDN_BUTTON_CLICKED:
+        if (wParam == 100) {
+            TASKDIALOGCONFIG* navigationConfig = new TASKDIALOGCONFIG;
+            *navigationConfig = { 0 };
+            navigationConfig->cbSize = sizeof(TASKDIALOGCONFIG);
+
+            navigationConfig->pszMainInstruction = L"After navigation !!!";
+            navigationConfig->pszContent = L"Text";
+            navigationConfig->pszMainIcon = MAKEINTRESOURCEW(0xFFF7);
+
+            // Navigate the dialog.
+            SendMessageW(hwnd, TDM_NAVIGATE_PAGE, 0, (LPARAM)navigationConfig);
+            delete navigationConfig;
+
+            // After that, run the event loop by show an inner dialog.
+            TaskDialog(nullptr, nullptr, L"Inner Dialog", L"Inner Dialog", nullptr, 0, 0, nullptr);
+        }
+
+        break;
+    }
+
+    return S_OK;
+}
+
+void ShowTaskDialogNavigationInButtonClickedNotification()
+{
+    TASKDIALOGCONFIG* tConfig = new TASKDIALOGCONFIG;
+    *tConfig = { 0 };
+    tConfig->cbSize = sizeof(TASKDIALOGCONFIG);
+
+    tConfig->nDefaultRadioButton = 100;
+    tConfig->pszMainInstruction = L"Before navigation";
+    tConfig->pfCallback = TaskDialogCallbackProc;
+
+    // Create 50 radio buttons.
+    int radioButtonCount = 50;
+    TASKDIALOG_BUTTON* radioButtons = new TASKDIALOG_BUTTON[radioButtonCount];
+    for (int i = 0; i < radioButtonCount; i++) {
+        radioButtons[i].nButtonID = 100 + i;
+        radioButtons[i].pszButtonText = L"My Radio Button";
+    }
+    tConfig->pRadioButtons = radioButtons;
+    tConfig->cRadioButtons = radioButtonCount;
+
+    // Create a custom button.
+    TASKDIALOG_BUTTON* customButton = new TASKDIALOG_BUTTON;
+    customButton->nButtonID = 100;
+    customButton->pszButtonText = L"My Custom Button";
+    tConfig->pButtons = customButton;
+    tConfig->cButtons = 1;
+
+    int nButton, nRadioButton;
+    BOOL checkboxSelected;
+    TaskDialogIndirect(tConfig, &nButton, &nRadioButton, &checkboxSelected);
+
+    delete customButton;
+    delete radioButtons;
+    delete tConfig;
+}
+
+int APIENTRY wWinMain(_In_ HINSTANCE hInstance,
+    _In_opt_ HINSTANCE hPrevInstance,
+    _In_ LPWSTR    lpCmdLine,
+    _In_ int       nCmdShow)
+{
+    UNREFERENCED_PARAMETER(hPrevInstance);
+    UNREFERENCED_PARAMETER(lpCmdLine);
+
+    ShowTaskDialogNavigationInButtonClickedNotification();
+
+    return 0;
+}
+```

Documentation/src/System/Windows/Forms/TaskDialog/Issue_AccessViolation_NavigationInRadioButtonClicked.md

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+# Windows Task Dialog Issue
+
+## Access Violation when receiving [`TDN_NAVIGATED`](https://docs.microsoft.com/en-us/windows/desktop/Controls/tdn-navigated) within [`TDN_RADIO_BUTTON_CLICKED`](https://docs.microsoft.com/en-us/windows/desktop/Controls/tdn-radio-button-clicked)
+
+An Access Violation occurs when receiving a navigation notification
+([`TDN_NAVIGATED`](https://docs.microsoft.com/en-us/windows/desktop/Controls/tdn-navigated))
+within a [`TDN_RADIO_BUTTON_CLICKED`](https://docs.microsoft.com/en-us/windows/desktop/Controls/tdn-radio-button-clicked)
+notification (e.g. due to running the message loop).
+
+* Run the code and select one of the radio buttons.
+* Notice the dialog has navigated and an inner dialog is opened.
+* Close the inner dialog.
+* **Issue:** Notice the application crashes with an access violation.
+
+```cpp
+#include "stdafx.h"
+#include "CommCtrl.h"
+
+HRESULT WINAPI TaskDialogCallbackProc(_In_ HWND hwnd, _In_ UINT msg, _In_ WPARAM wParam, _In_ LPARAM lParam, _In_ LONG_PTR lpRefData)
+{
+    switch (msg) {
+    case TDN_RADIO_BUTTON_CLICKED:
+        // When the user clicked the second radio button, navigate the dialog, then show an inner dialog.
+
+        // Navigate
+        TASKDIALOGCONFIG* navigationConfig = new TASKDIALOGCONFIG;
+        *navigationConfig = { 0 };
+        navigationConfig->cbSize = sizeof(TASKDIALOGCONFIG);
+
+        navigationConfig->pszMainInstruction = L"After navigation !!";
+
+        SendMessageW(hwnd, TDM_NAVIGATE_PAGE, 0, (LPARAM)navigationConfig);
+        delete navigationConfig;
+
+        // After navigating, run the event loop by showing an inner dialog.
+        TaskDialog(nullptr, nullptr, L"Inner Dialog", L"Inner Dialog", nullptr, 0, 0, nullptr);
+
+        break;
+    }
+
+    return S_OK;
+}
+
+void ShowTaskDialogRadioButtonsBehavior()
+{
+    TASKDIALOGCONFIG* tConfig = new TASKDIALOGCONFIG;
+    *tConfig = { 0 };
+    tConfig->cbSize = sizeof(TASKDIALOGCONFIG);
+
+    tConfig->dwFlags = TDF_NO_DEFAULT_RADIO_BUTTON;
+    tConfig->pszMainInstruction = L"Before Navigation";
+    tConfig->pfCallback = TaskDialogCallbackProc;
+
+    // Create 2 radio buttons.
+    int radioButtonCount = 2;
+
+    TASKDIALOG_BUTTON* radioButtons = new TASKDIALOG_BUTTON[radioButtonCount];
+    for (int i = 0; i < radioButtonCount; i++) {
+        radioButtons[i].nButtonID = 100 + i;
+        radioButtons[i].pszButtonText = i == 0 ? L"Radio Button 1" : L"Radio Button 2";
+    }
+    tConfig->pRadioButtons = radioButtons;
+    tConfig->cRadioButtons = radioButtonCount;
+
+    int nButton, nRadioButton;
+    BOOL checkboxSelected;
+    TaskDialogIndirect(tConfig, &nButton, &nRadioButton, &checkboxSelected);
+
+    delete radioButtons;
+    delete tConfig;
+}
+
+int APIENTRY wWinMain(_In_ HINSTANCE hInstance,
+    _In_opt_ HINSTANCE hPrevInstance,
+    _In_ LPWSTR    lpCmdLine,
+    _In_ int       nCmdShow)
+{
+    UNREFERENCED_PARAMETER(hPrevInstance);
+    UNREFERENCED_PARAMETER(lpCmdLine);
+
+    ShowTaskDialogRadioButtonsBehavior();
+
+    return 0;
+}
+```

Documentation/src/System/Windows/Forms/TaskDialog/Issue_ButtonClickHandlerCalledTwice.md

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+# Windows Task Dialog Issue
+
+## [`TDN_BUTTON_CLICKED`](https://docs.microsoft.com/en-us/windows/desktop/Controls/tdn-button-clicked) notification sent twice when pressing a button with its access key
+
+When you "click" a button by pressing its access key (mnemonic) and the dialog
+is still open when the message loop continues, the [`TDN_BUTTON_CLICKED`](https://docs.microsoft.com/en-us/windows/desktop/Controls/tdn-button-clicked)
+notification is sent twice instead of once.
+
+* Run the code.
+* Click one of the buttons with the mouse, or press space or enter, and notice
+  that the counter increments by 1.
+* **Issue:** Press <kbd>Alt</kbd>+<kbd>M</kbd> or <kbd>Alt</kbd>+<kbd>N</kbd> and 
+  notice the counter increments by 2.
+
+```cpp
+#include "stdafx.h"
+#include "CommCtrl.h"
+
+int counter = 0;
+wchar_t* counterTextBuffer;
+HRESULT WINAPI ShowTaskDialogButtonClickHandlerCalledTwice_Callback(_In_ HWND hwnd, _In_ UINT msg, _In_ WPARAM wParam, _In_ LPARAM lParam, _In_ LONG_PTR lpRefData) {
+    switch (msg) {
+    case TDN_BUTTON_CLICKED:
+        // Increment the counter.
+        counter++;
+        swprintf_s(counterTextBuffer, 100, L"Counter: %d", counter);
+        SendMessageW(hwnd, TDM_SET_ELEMENT_TEXT, TDE_MAIN_INSTRUCTION, (LPARAM)counterTextBuffer);
+
+        // When the user clicks the custom button, return false so that the dialog
+        // stays open.
+        if (wParam == 100) {
+            return S_FALSE;
+        }
+        else if (wParam == IDNO) {
+            // Otherwise, when the user clicks the common button, run the message loop.
+            MSG msg;
+            int bRet;
+            while ((bRet = GetMessageW(&msg, nullptr, 0, 0)) != 0) {
+                if (bRet == -1) {
+                    // Error
+                }
+                else {
+                    TranslateMessage(&msg);
+                    DispatchMessageW(&msg);
+                }
+            }
+        }
+
+        break;
+    }
+
+    return S_OK;
+}
+
+void ShowTaskDialogButtonClickHandlerCalledTwice() {
+    counterTextBuffer = new wchar_t[100];
+
+    TASKDIALOGCONFIG* tConfig = new TASKDIALOGCONFIG;
+    *tConfig = { 0 };
+    tConfig->cbSize = sizeof(TASKDIALOGCONFIG);
+
+    tConfig->dwFlags = TDF_USE_COMMAND_LINKS;
+    tConfig->pszMainInstruction = L"Text...";
+    tConfig->pfCallback = ShowTaskDialogButtonClickHandlerCalledTwice_Callback;
+
+    // Create a custom button and a common ("No") button.
+    tConfig->dwCommonButtons = TDCBF_NO_BUTTON;    
+
+    TASKDIALOG_BUTTON customButton = { 0 };
+    customButton.nButtonID = 100;
+    customButton.pszButtonText = L"&My Button";
+    tConfig->pButtons = &customButton;
+    tConfig->cButtons = 1;
+
+    int nButton, nRadioButton;
+    BOOL checkboxSelected;
+    TaskDialogIndirect(tConfig, &nButton, &nRadioButton, &checkboxSelected);
+
+    delete tConfig;
+    delete[] counterTextBuffer;
+}
+
+int APIENTRY wWinMain(_In_ HINSTANCE hInstance,
+    _In_opt_ HINSTANCE hPrevInstance,
+    _In_ LPWSTR    lpCmdLine,
+    _In_ int       nCmdShow)
+{
+    UNREFERENCED_PARAMETER(hPrevInstance);
+    UNREFERENCED_PARAMETER(lpCmdLine);
+
+    ShowTaskDialogButtonClickHandlerCalledTwice();
+
+    return 0;
+}
+```

Documentation/src/System/Windows/Forms/TaskDialog/Issue_RadioButton_InfiniteLoop.md

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+# Windows Task Dialog Issue
+
+## Infinite loop with radio buttons
+
+An infinite loop occurs when sending a
+[`TDM_CLICK_RADIO_BUTTON`](https://docs.microsoft.com/en-us/windows/desktop/Controls/tdm-click-radio-button) message within a
+[`TDN_RADIO_BUTTON_CLICKED`](https://docs.microsoft.com/en-us/windows/desktop/Controls/tdn-radio-button-clicked) notification.
+
+* Run the code and select the second radio button.
+* **Issue:** Notice that the GUI doesn't respond any more. When debugging, you can see that
+  the callback is flooded with `TDN_RADIO_BUTTON_CLICKED` notifications even though we
+  don't send any more messages to the dialog.
+
+```cpp
+#include "stdafx.h"
+#include "CommCtrl.h"
+
+bool done = false;
+HRESULT WINAPI TaskDialogCallbackProc(_In_ HWND hwnd, _In_ UINT msg, _In_ WPARAM wParam, _In_ LPARAM lParam, _In_ LONG_PTR lpRefData)
+{
+    switch (msg) {
+    case TDN_RADIO_BUTTON_CLICKED:
+        // When the user clicked the second radio button, select the first one.
+        // However, do this only once.
+        if (wParam == 101 && !done) {
+            done = true;
+            SendMessageW(hwnd, TDM_CLICK_RADIO_BUTTON, 100, 0);
+        }
+        break;
+    }
+
+    return S_OK;
+}
+
+void ShowTaskDialogRadioButtonsBehavior()
+{
+    TASKDIALOGCONFIG* tConfig = new TASKDIALOGCONFIG;
+    *tConfig = { 0 };
+    tConfig->cbSize = sizeof(TASKDIALOGCONFIG);
+
+    tConfig->dwFlags = TDF_NO_DEFAULT_RADIO_BUTTON;
+    tConfig->pszMainInstruction = L"Radio Button Example";
+    tConfig->pfCallback = TaskDialogCallbackProc;
+
+    // Create 2 radio buttons.
+    int radioButtonCount = 2;
+
+    TASKDIALOG_BUTTON* radioButtons = new TASKDIALOG_BUTTON[radioButtonCount];
+    for (int i = 0; i < radioButtonCount; i++) {
+        radioButtons[i].nButtonID = 100 + i;
+        radioButtons[i].pszButtonText = i == 0 ? L"Radio Button 1" : L"Radio Button 2";
+    }
+    tConfig->pRadioButtons = radioButtons;
+    tConfig->cRadioButtons = radioButtonCount;
+
+    int nButton, nRadioButton;
+    BOOL checkboxSelected;
+    TaskDialogIndirect(tConfig, &nButton, &nRadioButton, &checkboxSelected);
+
+    delete radioButtons;
+    delete tConfig;
+}
+
+int APIENTRY wWinMain(_In_ HINSTANCE hInstance,
+    _In_opt_ HINSTANCE hPrevInstance,
+    _In_ LPWSTR    lpCmdLine,
+    _In_ int       nCmdShow)
+{
+    UNREFERENCED_PARAMETER(hPrevInstance);
+    UNREFERENCED_PARAMETER(lpCmdLine);
+
+    ShowTaskDialogRadioButtonsBehavior();
+
+    return 0;
+}
+```