Why am I not getting WM_UPDATEUISTATE? - c

Question

I have a main window with an edit control and a custom button. When the edit control has focus and I press the Tab key, the button control gets the focus but it never receives WM_UPDATEUISTATE? I'm using IsDialogMessage() in the message loop of main window. Any ideas on why this is happening?
Edit: Why isn't the custom button control receiving WM_UPDATEUISTATE?
Edit: IsDialogMessage() is not sending WM_UPDATEUISTATE or WM_CHANGUISTATE in this example
#include <windows.h>
#include <tchar.h>
HINSTANCE g_hInst;
LRESULT CALLBACK WndProc(HWND hwnd, UINT msg, WPARAM wParam, LPARAM lParam)
{
static HWND hBtn1, hBtn2;
switch(msg)
{
case WM_CREATE:
hBtn1 = CreateWindowEx(0, TEXT("Button"), TEXT("Button 1"), WS_VISIBLE | WS_CHILD | BS_PUSHBUTTON,
4, 4, 100, 40, hwnd, 0, g_hInst, 0);
if(!hBtn1) return -1;
hBtn2 = CreateWindowEx(0, TEXT("Button"), TEXT("Button 2"), WS_VISIBLE | WS_CHILD | BS_PUSHBUTTON,
114, 4, 100, 40, hwnd, 0, g_hInst, 0);
if(!hBtn1) return -1;
break;
case WM_DESTROY:
PostQuitMessage(0);
break;
default:
return DefWindowProc(hwnd, msg, wParam, lParam);
}
return 0;
}
int WINAPI _tWinMain(HINSTANCE hInstance, HINSTANCE hPrevInstance, LPTSTR lpCmdLine, int nCmdShow)
{
const TCHAR szClassName[] = TEXT("Main////");
WNDCLASSEX wc;
HWND hwnd;
MSG msg;
SecureZeroMemory(&wc, sizeof(WNDCLASSEX));
wc.cbSize = sizeof(WNDCLASSEX);
wc.hbrBackground = (HBRUSH)(COLOR_WINDOW + 1);
wc.hCursor = LoadCursor(0, IDC_ARROW);
wc.hIcon = LoadIcon(0, IDI_APPLICATION);;
wc.hInstance = hInstance;
wc.lpfnWndProc = WndProc;
wc.lpszClassName = szClassName;
if(!RegisterClassEx(&wc)) return 0;
g_hInst = hInstance;
hwnd = CreateWindowEx(0, szClassName, TEXT("Main"), WS_OVERLAPPEDWINDOW, 140, 140, 440, 240, 0, 0, hInstance, 0);
if(!hwnd) return 0;
ShowWindow(hwnd, nCmdShow);
while(GetMessage(&msg, 0, 0, 0) > 0)
{
if(!IsDialogMessage(hwnd, &msg))
{
TranslateMessage(&msg);
DispatchMessage(&msg);
}
}
return (int)msg.wParam;
}
I've used spy++ for the main window and the 2 buttons when pressing the Tab key and I don't see neither WM_UPDATEUISTATE nor WM_CHANGEUISTATE anywhere, but the standard button control draws the focus rect. How does the standard button know when to draw the focus rect?

Answer 1

A window should show its focus indicator when it has focus. For that, a control should watch for WM_SETFOCUS and WM_KILLFOCUS. When it has the focus, a well-behaved control will check the UI state by sending WM_QUERYUISTATE to itself, and, if the UI state has the UISF_HIDEFOCUS flag set, the control would not draw the focus indicator.
The WM_CHANGEUISTATE and WM_UPDATEUISTATE are responsible for controlling whether a tree of windows (including controls) should display keyboard "cues" and focus indicators in general. For example, if the cues aren't showing and you tap the ALT key, these messages will update the UI state of the windows in the tree so that they start showing the cues. These messages are not used for hiding the focus indicator from one control and showing it on the next as the user TABs through the controls. That effect happens because the controls pay attention to the focus change messages.
Generally speaking, a custom control should watch for the focus change messages and let DefWindowProc handle the UI state messages.
Raymond Chen has a series of blog posts about the UI state and how these messages propagate.
Untangling the confusingly-named WM_UPDATEUISTATE and WM_CHANGEUISTATE messages
Who sends the initial WM_UPDATEUISTATE message?
Why does tapping the Alt key cause my owner-draw static control to repaint?
What is the documentation for SetParent trying to tell me about synchronizing the UI state?
Demonstrating what happens when a parent and child window have different UI states
Getting a parent and child window to have the same UI states
I found these helpful when I recently tried to work all this out again. The current state of the official documentation on this topic is a bit vague and ambiguous in places.
Note: The terms "mnemonics," "accelerators," and "hot keys" have blurred together, even in the official Microsoft documentation and some of the API names. When I say "keyboard cues," I'm mostly referring to mnemonics (sometimes called "shortcuts" or "access keys"). Those are the underlined characters in control labels and menu items that let the user know that ALT+<character> will select the labeled item.