Decided to revert the transparency changes; I'll try flicker-free first.

redo/container_windows.c

@@ -37,69 +37,6 @@ static LRESULT CALLBACK containerWndProc(HWND hwnd, UINT uMsg, WPARAM wParam, LP
 		return forwardCommand(hwnd, uMsg, wParam, lParam);
 	case WM_NOTIFY:
 		return forwardNotify(hwnd, uMsg, wParam, lParam);
-	case WM_PAINT:
-#ifndef BROKEN
-		/* paint the parent's background in a flicker-free way */
-		dc = BeginPaint(hwnd, &ps);
-		if (dc == NULL)
-			abort();//TODO
-		parent = GetParent(hwnd);
-		if (parent == NULL)
-			abort();//TODO
-		if (GetWindowRect(hwnd, &r) == 0)
-			abort();//TODO
-		/* GetWindowRect() returns in screen coordinates; we want parent client */
-		client.x = r.left;
-		client.y = r.top;
-		if (ScreenToClient(parent, &client) == 0)
-			abort();//TODO
-		if (SetWindowOrgEx(dc, client.x, client.y, NULL) == 0)
-			abort();//TODO
-		SendMessageW(parent, WM_PRINTCLIENT, (WPARAM) dc, PRF_CLIENT);
-		EndPaint(hwnd, &ps);
-		return 0;
-#else
-		/* paint the parent's background in a flicker-free way */
-		dc = BeginPaint(hwnd, &ps);
-		if (dc == NULL)
-			abort();//TODO
-		parent = GetParent(hwnd);
-		if (parent == NULL)
-			abort();//TODO
-		if (GetWindowRect(hwnd, &r) == 0)
-			abort();//TODO
-		/* GetWindowRect() returns in screen coordinates; we want parent client */
-		client.x = r.left;
-		client.y = r.top;
-		if (ScreenToClient(parent, &client) == 0)
-			abort();//TODO
-		rdc = CreateCompatibleDC(dc);
-		if (rdc == NULL)
-			abort();//TODO
-		rbitmap = CreateCompatibleBitmap(dc, r.right - r.left, r.bottom - r.top);
-		if (rbitmap == NULL)
-			abort();//TODO
-		prevrbitmap = SelectObject(rdc, rbitmap);
-		if (prevrbitmap == NULL)
-			abort();//TODO
-		if (SetWindowOrgEx(rdc, client.x, client.y, NULL) == 0)
-			abort();//TODO
-		SendMessageW(parent, WM_PRINTCLIENT, (WPARAM) rdc, PRF_CLIENT);
-		if (BitBlt(dc, 0, 0, (int) (r.right - r.left), (int) (r.bottom - r.top),
-			rdc, 0, 0, SRCCOPY) == 0)
-			abort();//TODO
-		if (SelectObject(rdc, prevrbitmap) != rbitmap)
-			abort();//TODO
-		if (DeleteObject(rbitmap) == 0)
-			abort();//TODO
-		if (DeleteDC(rdc) == 0)
-			abort();//TODO
-		EndPaint(hwnd, &ps);
-		return 0;
-#endif
-	case WM_ERASEBKGND:
-		/* we paint our own background above */
-		return 1;
 	case WM_SIZE:
 		if (GetClientRect(hwnd, &r) == 0)
 			xpanic("error getting client rect for Window in WM_SIZE", GetLastError());
@@ -121,7 +58,7 @@ DWORD makeContainerWindowClass(char **errmsg)
 	wc.hInstance = hInstance;
 	wc.hIcon = hDefaultIcon;
 	wc.hCursor = hArrowCursor;
-	wc.hbrBackground = NULL;		/* we paint our own background */
+	wc.hbrBackground = (HBRUSH) (COLOR_BTNFACE + 1);
 	wc.lpszClassName = containerclass;
 	if (RegisterClassW(&wc) == 0) {
 		*errmsg = "error registering container window class";
@@ -135,7 +72,7 @@ HWND newContainer(void *data)
 	HWND hwnd;
 
 	hwnd = CreateWindowExW(
-		WS_EX_TRANSPARENT,
+		0,
 		containerclass, L"",
 		WS_CHILD | WS_VISIBLE,
 		CW_USEDEFAULT, CW_USEDEFAULT,

redo/mergeback/container_windows_transparent.c

@@ -0,0 +1,147 @@
+/* 17 july 2014 */
+
+#include "winapi_windows.h"
+#include "_cgo_export.h"
+
+/*
+This could all just be part of Window, but doing so just makes things complex.
+In this case, I chose to waste a window handle rather than keep things super complex.
+If this is seriously an issue in the future, I can roll it back.
+*/
+
+#define containerclass L"gouicontainer"
+
+static LRESULT CALLBACK containerWndProc(HWND hwnd, UINT uMsg, WPARAM wParam, LPARAM lParam)
+{
+	void *data;
+	RECT r;
+	HDC dc;
+	PAINTSTRUCT ps;
+	HWND parent;
+	POINT client;
+
+	data = (void *) GetWindowLongPtrW(hwnd, GWLP_USERDATA);
+	if (data == NULL) {
+		/* the lpParam is available during WM_NCCREATE and WM_CREATE */
+		if (uMsg == WM_NCCREATE) {
+			storelpParam(hwnd, lParam);
+			data = (void *) GetWindowLongPtrW(hwnd, GWLP_USERDATA);
+			storeContainerHWND(data, hwnd);
+		}
+		/* act as if we're not ready yet, even during WM_NCCREATE (nothing important to the switch statement below happens here anyway) */
+		return DefWindowProcW(hwnd, uMsg, wParam, lParam);
+	}
+
+	switch (uMsg) {
+	case WM_COMMAND:
+		return forwardCommand(hwnd, uMsg, wParam, lParam);
+	case WM_NOTIFY:
+		return forwardNotify(hwnd, uMsg, wParam, lParam);
+	case WM_PAINT:
+#ifndef BROKEN
+		/* paint the parent's background in a flicker-free way */
+		dc = BeginPaint(hwnd, &ps);
+		if (dc == NULL)
+			abort();//TODO
+		parent = GetParent(hwnd);
+		if (parent == NULL)
+			abort();//TODO
+		if (GetWindowRect(hwnd, &r) == 0)
+			abort();//TODO
+		/* GetWindowRect() returns in screen coordinates; we want parent client */
+		client.x = r.left;
+		client.y = r.top;
+		if (ScreenToClient(parent, &client) == 0)
+			abort();//TODO
+		if (SetWindowOrgEx(dc, client.x, client.y, NULL) == 0)
+			abort();//TODO
+		SendMessageW(parent, WM_PRINTCLIENT, (WPARAM) dc, PRF_CLIENT);
+		EndPaint(hwnd, &ps);
+		return 0;
+#else
+		/* paint the parent's background in a flicker-free way */
+		dc = BeginPaint(hwnd, &ps);
+		if (dc == NULL)
+			abort();//TODO
+		parent = GetParent(hwnd);
+		if (parent == NULL)
+			abort();//TODO
+		if (GetWindowRect(hwnd, &r) == 0)
+			abort();//TODO
+		/* GetWindowRect() returns in screen coordinates; we want parent client */
+		client.x = r.left;
+		client.y = r.top;
+		if (ScreenToClient(parent, &client) == 0)
+			abort();//TODO
+		rdc = CreateCompatibleDC(dc);
+		if (rdc == NULL)
+			abort();//TODO
+		rbitmap = CreateCompatibleBitmap(dc, r.right - r.left, r.bottom - r.top);
+		if (rbitmap == NULL)
+			abort();//TODO
+		prevrbitmap = SelectObject(rdc, rbitmap);
+		if (prevrbitmap == NULL)
+			abort();//TODO
+		if (SetWindowOrgEx(rdc, client.x, client.y, NULL) == 0)
+			abort();//TODO
+		SendMessageW(parent, WM_PRINTCLIENT, (WPARAM) rdc, PRF_CLIENT);
+		if (BitBlt(dc, 0, 0, (int) (r.right - r.left), (int) (r.bottom - r.top),
+			rdc, 0, 0, SRCCOPY) == 0)
+			abort();//TODO
+		if (SelectObject(rdc, prevrbitmap) != rbitmap)
+			abort();//TODO
+		if (DeleteObject(rbitmap) == 0)
+			abort();//TODO
+		if (DeleteDC(rdc) == 0)
+			abort();//TODO
+		EndPaint(hwnd, &ps);
+		return 0;
+#endif
+	case WM_ERASEBKGND:
+		/* we paint our own background above */
+		return 1;
+	case WM_SIZE:
+		if (GetClientRect(hwnd, &r) == 0)
+			xpanic("error getting client rect for Window in WM_SIZE", GetLastError());
+		containerResize(data, &r);
+		return 0;
+	default:
+		return DefWindowProcW(hwnd, uMsg, wParam, lParam);
+	}
+	xmissedmsg("container", "containerWndProc()", uMsg);
+	return 0;		/* unreached */
+}
+
+DWORD makeContainerWindowClass(char **errmsg)
+{
+	WNDCLASSW wc;
+
+	ZeroMemory(&wc, sizeof (WNDCLASSW));
+	wc.lpfnWndProc = containerWndProc;
+	wc.hInstance = hInstance;
+	wc.hIcon = hDefaultIcon;
+	wc.hCursor = hArrowCursor;
+	wc.hbrBackground = NULL;		/* we paint our own background */
+	wc.lpszClassName = containerclass;
+	if (RegisterClassW(&wc) == 0) {
+		*errmsg = "error registering container window class";
+		return GetLastError();
+	}
+	return 0;
+}
+
+HWND newContainer(void *data)
+{
+	HWND hwnd;
+
+	hwnd = CreateWindowExW(
+		WS_EX_TRANSPARENT,
+		containerclass, L"",
+		WS_CHILD | WS_VISIBLE,
+		CW_USEDEFAULT, CW_USEDEFAULT,
+		100, 100,
+		msgwin, NULL, hInstance, data);
+	if (hwnd == NULL)
+		xpanic("container creation failed", GetLastError());
+	return hwnd;
+}