[英]BeginPaint fails when called from injected dll, even after EndPaint is called in target application
基本上我的标题说的是。 我正在尝试在目标应用程序中注入dll,以便在每次目标应用程序收到WM_PAINT消息时显示内容。 我的目标是WNDPROC:
#include <windows.h>
#include <stdio.h>
LRESULT CALLBACK WndProc(HWND hwnd, UINT msg, WPARAM wParam, LPARAM lParam)
{
PAINTSTRUCT ps;
switch(msg)
{
case WM_PAINT:
BeginPaint(hwnd, &ps);
TextOut(ps.hdc, 0, 0, "Hello, Windows!", 15);
EndPaint(hwnd, &ps);
break;
case WM_CLOSE:
DestroyWindow(hwnd);
break;
case WM_DESTROY:
PostQuitMessage(0);
break;
default:
return DefWindowProc(hwnd, msg, wParam, lParam);
}
return 0;
}
这是我注入的dll:
#include <Windows.h>
#include <stdio.h>
WNDPROC wpOrigProc;
HWND target_hwnd = (HWND)0x909E6; // HWND of the window I'm detouring
LRESULT APIENTRY MyWndProc(HWND hwnd, UINT msg, WPARAM wParam, LPARAM lParam)
{
PAINTSTRUCT ps;
LRESULT result = CallWindowProc(wpOrigProc, hwnd, msg, wParam, lParam);
switch(msg)
{
case WM_PAINT:
BeginPaint(hwnd, &ps);
TextOut(ps.hdc, 0, 50, "That was injected!", 18);
EndPaint(hwnd, &ps);
break;
}
return result;
}
int APIENTRY DllMain(HMODULE module, DWORD reason, LPVOID reserved)
{
HHOOK msgHook;
FILE* stream;
switch (reason)
{
case DLL_PROCESS_ATTACH:
wpOrigProc = (WNDPROC)SetWindowLongPtr(target_hwnd, GWLP_WNDPROC, (LONG)MyWndProc);
break;
case DLL_PROCESS_DETACH:
SetWindowLong(target_hwnd, GWL_WNDPROC, (LONG)wpOrigProc);
break;
}
return 1;
}
现在,我知道问题出在BeginPaint,因为如果我改用GetDC和ReleaseDC,它将起作用。 如果我在BeginPaint之前不调用CallWindowProc,它也可以工作。
对我来说这没有意义,因为原始WNDPROC在其WM_PAINT的末尾调用EndPaint,这意味着它不应干扰我注入的WM_PAINT ...任何想法吗?
EndPaint()
验证窗口,因此下一个BeginPaint()
获得一个没有可绘制(无效)区域的DC。 这是关于GetDC()/ ReleaseDC()与BeginPaint()/ EndPaint()的讨论 。
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