[英]Window created with WINAPI is not drawing objects. What's the problem?
我有我的窗口文件( Window.h
):
LRESULT CALLBACK MessageHandler(HWND, UINT, WPARAM, LPARAM);
class Window
{
private:
HWND hWnd;
HINSTANCE hInstance;
bool running = true;
const char* ID = "WINAPI_JVM64";
public:
Window()
{
init();
}
virtual void draw(Gdiplus::Graphics*) = 0;
void init()
{
hInstance = (HINSTANCE)GetModuleHandle(NULL);
WNDCLASS wc;
wc = {};
wc.style = CS_HREDRAW | CS_VREDRAW;
wc.lpfnWndProc = MessageHandler;
wc.hInstance = hInstance;
wc.hIcon = LoadIcon(NULL, IDI_WINLOGO);
wc.hCursor = LoadCursor(NULL, IDC_HAND);
wc.hbrBackground = (HBRUSH)COLOR_WINDOW;
wc.lpszClassName = ID;
assert(RegisterClass(&wc));
hWnd = CreateWindow(ID, "Title", WS_OVERLAPPEDWINDOW | WS_VISIBLE,
200, 200, 400, 400, NULL, NULL, hInstance, NULL);
ShowCursor(true);
SetForegroundWindow(hWnd);
SetFocus(hWnd);
}
void run()
{
MSG msg;
PeekMessage(&msg, hWnd, 0, 0, PM_REMOVE);
while(running)
{
if(PeekMessage(&msg, hWnd, 0, 0, PM_REMOVE))
{
if(msg.message == WM_QUIT)
running = false;
TranslateMessage(&msg);
DispatchMessage(&msg);
}
else
{
// Here, the draw function is called.
PAINTSTRUCT ps;
HDC hdc = BeginPaint(hWnd, &ps);
Gdiplus::Graphics* g = Gdiplus::Graphics::FromHDC(hdc);
draw(g);
EndPaint(hWnd, &ps);
}
}
UnregisterClass(ID, hInstance);
}
};
和主文件( main.cpp
):
#include "Window.h"
LRESULT CALLBACK MessageHandler(HWND hWnd, UINT uMsg, WPARAM wParam, LPARAM lParam)
{
switch(uMsg)
{
case WM_CLOSE:
PostQuitMessage(0);
break;
default:
return DefWindowProc(hWnd, uMsg, wParam, lParam);
}
return 0;
}
class AppWindow : public Window
{
public:
void draw(Gdiplus::Graphics* g) override
{
Gdiplus::SolidBrush brown_brush(Gdiplus::Color(255, 128, 57, 0));
g->FillRectangle(&brown_brush, 0, 0, 200, 200);
}
};
int main()
{
Gdiplus::GdiplusStartupInput gdiplusStartupInput;
ULONG_PTR gdiplusToken;
Gdiplus::GdiplusStartup(&gdiplusToken, &gdiplusStartupInput, nullptr);
AppWindow w;
w.run();
Gdiplus::GdiplusShutdown(gdiplusToken);
return 0;
}
我的問題是它不會畫!
它處理每條消息,一切都很好,但它不繪制。 甚至發送了WM_PAINT
類型的消息,但沒有任何反應。
你能發現問題嗎?
我只想要一個窗口類,它有一個可覆蓋的draw()
函數和一個處理所有事件的run()
函數,例如WM_LBUTTONDOWN
。 所有這些工作正常,屏幕只是保持空白。
另外,我無法關閉窗口,當按下右上角的X
按鈕時,窗口只是停留; 只有在調整大小並快速按下X
,它才會關閉。
正如你所看到的,我有一些非常奇怪的行為,我不知道問題是什么。
你的繪圖邏輯在錯誤的地方。 處理WM_PAINT
消息時,它需要在MessageHandler
內部。 如果需要繪制窗口並且沒有其他消息待處理, PeekMessage()
將生成WM_PAINT
消息。 您不能從WM_PAINT
處理程序的外部在窗口上繪圖。
此外,您在init()
為wc.hbrBackground
分配了錯誤的值。 如果您使用像COLOR_WINDOW
這樣的顏色常量,則需要向其添加1
。 WNDCLASS
文檔中對此進行了詳細說明。
此外,在run()
,您創建消息隊列的第一個PeekMessage()
會丟棄初始消息(如果有待處理的消息),則您的調度循環不會處理該消息。 第一次調用應該使用PM_NOREMOVE
標志。
另外,請注意在消息循環中過濾窗口消息的危險。
話雖如此,請試試這個:
LRESULT CALLBACK MessageHandler(HWND, UINT, WPARAM, LPARAM);
class Window
{
private:
HWND hWnd;
HINSTANCE hInstance;
const char* ID = "WINAPI_JVM64";
public:
Window()
{
init();
}
~Window()
{
cleanup();
}
virtual void draw(Gdiplus::Graphics*) = 0;
void init()
{
hInstance = (HINSTANCE)GetModuleHandle(NULL);
WNDCLASS wc{};
wc.style = CS_HREDRAW | CS_VREDRAW;
wc.lpfnWndProc = &MessageHandler;
wc.hInstance = hInstance;
wc.hIcon = LoadIcon(NULL, IDI_WINLOGO);
wc.hCursor = LoadCursor(NULL, IDC_HAND);
wc.hbrBackground = (HBRUSH)COLOR_WINDOW;
wc.lpszClassName = ID;
assert(RegisterClass(&wc));
hWnd = CreateWindow(ID, "Title", WS_OVERLAPPEDWINDOW | WS_VISIBLE,
200, 200, 400, 400, NULL, NULL, hInstance, this);
assert(hWnd != NULL);
ShowCursor(true);
SetForegroundWindow(hWnd);
SetFocus(hWnd);
}
void cleanup()
{
UnregisterClass(ID, hInstance);
}
void run()
{
MSG msg;
PeekMessage(&msg, NULL, 0, 0, PM_NOREMOVE);
while (GetMessage(&msg, NULL, 0, 0))
{
TranslateMessage(&msg);
DispatchMessage(&msg);
}
}
};
#include "Window.h"
LRESULT CALLBACK MessageHandler(HWND hWnd, UINT uMsg, WPARAM wParam, LPARAM lParam)
{
switch (uMsg)
{
case WM_NCCREATE:
{
Window *pThis = static_cast<Window*>(reinterpret_cast<CREATESTRUCT*>(lParam)->lpCreateParams);
SetWindowLongPtr(hWnd, GWLP_USERDATA, reinterpret_cast<LONG_PTR>(pThis));
break;
}
// DefWindowProc(WM_CLOSE) calls DestroyWindow(),
// WM_CLOSE is not the right place to call PostQuitMessage()...
//case WM_CLOSE:
case WM_DESTROY:
PostQuitMessage(0);
break;
case WM_PAINT:
{
Window *pThis = reinterpret_cast<Window*>(GetWindowLongPtr(hWnd, GWLP_USERDATA));
PAINTSTRUCT ps;
HDC hdc = BeginPaint(hWnd, &ps);
if (pThis)
{
Gdiplus::Graphics* g = Gdiplus::Graphics::FromHDC(hdc);
pThis->draw(g);
delete g;
}
EndPaint(hWnd, &ps);
return 0;
}
}
return DefWindowProc(hWnd, uMsg, wParam, lParam);
}
class AppWindow : public Window
{
public:
void draw(Gdiplus::Graphics* g) override
{
Gdiplus::SolidBrush brown_brush(Gdiplus::Color(255, 128, 57, 0));
g->FillRectangle(&brown_brush, 0, 0, 200, 200);
}
};
int main()
{
Gdiplus::GdiplusStartupInput gdiplusStartupInput;
ULONG_PTR gdiplusToken;
Gdiplus::GdiplusStartup(&gdiplusToken, &gdiplusStartupInput, nullptr);
AppWindow w;
w.run();
Gdiplus::GdiplusShutdown(gdiplusToken);
return 0;
}
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