Added the sharedWndProc() spiel to Tab now that it stores Controls directly. Will need to add the same to Group.

newctrl/tab_windows.c

@@ -0,0 +1,111 @@
+// 25 july 2014
+
+#include "winapi_windows.h"
+#include "_cgo_export.h"
+
+// provided for cgo's benefit
+LPWSTR xWC_TABCONTROL = WC_TABCONTROL;
+
+static LRESULT CALLBACK tabSubProc(HWND hwnd, UINT uMsg, WPARAM wParam, LPARAM lParam, UINT_PTR id, DWORD_PTR data)
+{
+	NMHDR *nmhdr = (NMHDR *) lParam;
+	LRESULT r;
+	LRESULT lResult;
+
+	if (sharedWndProc(hwnd, uMsg, wParam, lParam, &lResult))
+		return lResult;
+	switch (uMsg) {
+	case msgNOTIFY:
+		switch (nmhdr->code) {
+		case TCN_SELCHANGING:
+			r = SendMessageW(hwnd, TCM_GETCURSEL, 0, 0);
+			if (r == (LRESULT) -1)	// no tab currently selected
+				return FALSE;
+			tabChanging((void *) data, r);
+			return FALSE;			// allow change
+		case TCN_SELCHANGE:
+			tabChanged((void *) data, SendMessageW(hwnd, TCM_GETCURSEL, 0, 0));
+			return 0;
+		}
+		return (*fv_DefSubclassProc)(hwnd, uMsg, wParam, lParam);
+	case msgTabCurrentTabHasChildren:
+		return (LRESULT) tabTabHasChildren((void *) data, SendMessageW(hwnd, TCM_GETCURSEL, 0, 0));
+	case WM_NCDESTROY:
+		if ((*fv_RemoveWindowSubclass)(hwnd, tabSubProc, id) == FALSE)
+			xpanic("error removing Tab subclass (which was for its own event handler)", GetLastError());
+		return (*fv_DefSubclassProc)(hwnd, uMsg, wParam, lParam);
+	default:
+		return (*fv_DefSubclassProc)(hwnd, uMsg, wParam, lParam);
+	}
+	xmissedmsg("Tab", "tabSubProc()", uMsg);
+	return 0;		// unreached
+}
+
+void setTabSubclass(HWND hwnd, void *data)
+{
+	if ((*fv_SetWindowSubclass)(hwnd, tabSubProc, 0, (DWORD_PTR) data) == FALSE)
+		xpanic("error subclassing Tab to give it its own event handler", GetLastError());
+}
+
+void tabAppend(HWND hwnd, LPWSTR name)
+{
+	TCITEM item;
+	LRESULT n;
+
+	ZeroMemory(&item, sizeof (TCITEM));
+	item.mask = TCIF_TEXT;
+	item.pszText = name;
+	// MSDN's example code uses the first invalid index directly for this
+	n = SendMessageW(hwnd, TCM_GETITEMCOUNT, 0, 0);
+	if (SendMessageW(hwnd, TCM_INSERTITEM, (WPARAM) n, (LPARAM) (&item)) == (LRESULT) -1)
+		xpanic("error adding tab to Tab", GetLastError());
+}
+
+void tabGetContentRect(HWND hwnd, RECT *r)
+{
+	// not &r; already a pointer (thanks MindChild in irc.efnet.net/#winprog for spotting my failure)
+	SendMessageW(hwnd, TCM_ADJUSTRECT, FALSE, (LPARAM) r);
+}
+
+// theoretically we don't need to iterate over every tab for this, but let's do it just to be safe
+LONG tabGetTabHeight(HWND hwnd)
+{
+	RECT r;
+	LRESULT i, n;
+	LONG tallest;
+
+	n = SendMessageW(hwnd, TCM_GETITEMCOUNT, 0, 0);
+	// if there are no tabs, then the control just draws a box over the full window rect, reserving no space for tabs; this is handled with the next line
+	tallest = 0;
+	for (i = 0; i < n; i++) {
+		if (SendMessageW(hwnd, TCM_GETITEMRECT, (WPARAM) i, (LPARAM) (&r)) == FALSE)
+			xpanic("error getting tab height for Tab.preferredSize()", GetLastError());
+		if (tallest < (r.bottom - r.top))
+			tallest = r.bottom - r.top;
+	}
+	return tallest;
+}
+
+void tabEnterChildren(HWND hwnd)
+{
+	DWORD style, xstyle;
+
+	style = (DWORD) GetWindowLongPtrW(hwnd, GWL_STYLE);
+	xstyle = (DWORD) GetWindowLongPtrW(hwnd, GWL_EXSTYLE);
+	style &= ~((DWORD) WS_TABSTOP);
+	xstyle |= WS_EX_CONTROLPARENT;
+	SetWindowLongPtrW(hwnd, GWL_STYLE, (LONG_PTR) style);
+	SetWindowLongPtrW(hwnd, GWL_EXSTYLE, (LONG_PTR) xstyle);
+}
+
+void tabLeaveChildren(HWND hwnd)
+{
+	DWORD style, xstyle;
+
+	style = (DWORD) GetWindowLongPtrW(hwnd, GWL_STYLE);
+	xstyle = (DWORD) GetWindowLongPtrW(hwnd, GWL_EXSTYLE);
+	style |= WS_TABSTOP;
+	xstyle &= ~((DWORD) WS_EX_CONTROLPARENT);
+	SetWindowLongPtrW(hwnd, GWL_STYLE, (LONG_PTR) style);
+	SetWindowLongPtrW(hwnd, GWL_EXSTYLE, (LONG_PTR) xstyle);
+}