andlabs-ui/redo/mergeback/container_windows_transparent.c

/* 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;
}