From 17709f1fc7979b9b37f03963770b175b7c32a62c Mon Sep 17 00:00:00 2001
From: Jonas Kümmerlin <jonas@kuemmerlin.eu>
Date: Tue, 26 May 2020 23:27:31 +0200
Subject: focus and default button handling: fixes and some documenting
 comments

---
 alf/alf.cpp       |  4 ++--
 alf/alf.h         | 19 ++++++++++++++++++-
 alf/alfwindow.cpp | 16 +++++-----------
 widgetfactory.cpp |  1 +
 4 files changed, 26 insertions(+), 14 deletions(-)

diff --git a/alf/alf.cpp b/alf/alf.cpp
index 717bd18..8929a5b 100644
--- a/alf/alf.cpp
+++ b/alf/alf.cpp
@@ -523,7 +523,7 @@ void
 ALF_SetFocus(HWND target)
 {
     if (GetWindowStyle(target) & WS_CHILD)
-        PostMessage(GetParent(target), WM_NEXTDLGCTL, (WPARAM)target, TRUE);
+        SendMessage(GetParent(target), WM_NEXTDLGCTL, (WPARAM)target, TRUE);
     else
-        PostMessage(target, WM_NEXTDLGCTL, (WPARAM)target, TRUE);
+        SendMessage(target, WM_NEXTDLGCTL, (WPARAM)target, TRUE);
 }
diff --git a/alf/alf.h b/alf/alf.h
index 2e07736..e1ad26e 100644
--- a/alf/alf.h
+++ b/alf/alf.h
@@ -8,7 +8,7 @@ extern "C" {
 #endif
 
 typedef struct {
-    void (*create)(void * /*closure*/, HWND /*window*/);
+    BOOL (*initialize)(void * /*closure*/, HWND /*window*/); // return FALSE if you set the focus, TRUE if you want default initial focus
     void (*destroy)(void * /*closure*/, HWND /*window*/);
     BOOL (*close)(void * /*closure*/, HWND /*window*/);
     void (*postdestroy)(void * /*closure*/);
@@ -189,6 +189,23 @@ ALF_AddEdit(HWND win, WORD id, int x, int y, const TCHAR *text);
 HWND
 ALF_AddButton(HWND win, WORD id, int x, int y, const TCHAR *text);
 
+// NOTE about default buttons:
+//
+// - If no default button is specified, the default button will be the button
+//   with the id IDOK. A WM_COMMAND message on pressing the return key will be
+//   sent even if no widget with the default id can be found.
+// - In NT 3.51, the default button must be a direct child of the window. Otherwise
+//   the default button effect will not work.
+// - In Win32s on Win3.1, the default button should be a direct child of the window.
+//   Otherwise the default button effect will be buggy when setting the focus
+//   via WM_NEXTDLGCTL or ALF_SetFocus(), but it will work correctly when using
+//   the TAB key.
+// - Changing the default button will only fully take effect after a focus change.
+//   It might temporarily lead to artifacts such as having two or no default buttons.
+//
+// Recommendation: Set the default button during window initialization, and then
+// immediately set the focus via ALF_SetFocus(). If you want to support NT 3.51
+// or Win32s, ensure that the default button is a direct child of the toplevel window.
 void
 ALF_SetDefaultButton(HWND win, WORD id);
 
diff --git a/alf/alfwindow.cpp b/alf/alfwindow.cpp
index 8e765ea..15b635b 100644
--- a/alf/alfwindow.cpp
+++ b/alf/alfwindow.cpp
@@ -117,18 +117,12 @@ ALF_WindowProc(HWND hwnd, UINT msg, WPARAM wparam, LPARAM lparam)
         int dpi = (int)ALF_Compat_GetDpiForWindow(hwnd);
         SendMessage(hwnd, ALF_WM_DPICHANGE, 0, (LPARAM)dpi); // will also update fonts
 
-        if (priv->vtbl && priv->vtbl->create) {
-            priv->vtbl->create(priv->closure, hwnd);
+        // TODO: after initializing, update window size and layout
+        if (priv->vtbl && priv->vtbl->initialize) {
+            return priv->vtbl->initialize(priv->closure, hwnd);
+        } else {
+            return TRUE;
         }
-
-        // FIXME! still necessary?
-        /*BOOL alwaysUnderline = FALSE;
-        SystemParametersInfo(SPI_GETKEYBOARDCUES, 0, &alwaysUnderline, 0);
-        if (!alwaysUnderline) {
-            SendMessage(hwnd, WM_UPDATEUISTATE, MAKEWPARAM(UIS_INITIALIZE, 0), 0);
-        }*/
-
-        ALF_Layout_Apply(&priv->layout, hwnd);
     }
 
     ALFWindowPriv *priv = (ALFWindowPriv*)(void*)GetWindowLongPtr(hwnd, DLGWINDOWEXTRA);
diff --git a/widgetfactory.cpp b/widgetfactory.cpp
index 315a95c..db720ac 100644
--- a/widgetfactory.cpp
+++ b/widgetfactory.cpp
@@ -865,6 +865,7 @@ WinMain
     ALF_LayoutSetColumnExpandNumerator(win, 4, 1);
 
     ALF_SetDefaultButton(win, ID_HELLO);
+    ALF_SetFocus(GetNextDlgTabItem(win, win, FALSE));
 
     ALF_ResizeWindow(win, 1, 1);
 
-- 
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