void GameMain(HDC hdc, HWND hwnd)
{
if(KEYDOWN(VK_ESCAPE))
SendMessage(hwnd,WM_CLOSE,0,0);
// create random pen
HPEN rand_pen = CreatePen(PS_SOLID,1,RGB(rand()%255, rand()%255, rand()%255));
// select the pen into context
HPEN old_pen = SelectObject(hdc,rand_pen); // LINE 175 *********
// draw the line
MoveToEx(hdc,rand()%400,rand()%400,NULL);
LineTo(hdc,rand()%400,rand()%400);
// restore old pen
SelectObject(hdc,old_pen);
// delete pen
DeleteObject(rand_pen);
}
Problem with drawing lines: Win GDI
Author
I get this error from the code below, copied directly from my book.
------ Build started: Project: Example 2, Configuration: Debug Win32 ------
Compiling...
main.cpp
.\main.cpp(175) : error C2440: 'initializing' : cannot convert from 'HGDIOBJ' to 'HPEN'
Conversion from 'void*' to pointer to non-'void' requires an explicit cast
Build log was saved at "file://c:\Documents and Settings\Owner\Desktop\Programming\Windows Game Programming Book\Chapter 4\Example 2\Example 2\Debug\BuildLog.htm"
Example 2 - 1 error(s), 0 warning(s)
========== Build: 0 succeeded, 1 failed, 0 up-to-date, 0 skipped ==========
SelectObject returns an HGDIOBJ, not an HPEN. You need to cast it. Change the line to:
HPEN old_pen = (HPEN)SelectObject(hdc,rand_pen);
EDIT: A little offtopic, but you should avoid creating and destroying objects every frame like that. You should create it at startup and delete it at shutdown.
EDIT 2: Also, those colour values for the pen should ideally be rand()%256, otherwise you'll never get a completely white (255, 255, 255) pen.
HPEN old_pen = (HPEN)SelectObject(hdc,rand_pen);
EDIT: A little offtopic, but you should avoid creating and destroying objects every frame like that. You should create it at startup and delete it at shutdown.
EDIT 2: Also, those colour values for the pen should ideally be rand()%256, otherwise you'll never get a completely white (255, 255, 255) pen.
when you get these types of errors:
you need to do a cast, such as the one below.
HPEN old_pen = (HPEN)SelectObject(hdc,rand_pen);
edit: i've been beaten... arggggggh
.\main.cpp(175) : error C2440: 'initializing' : cannot convert from 'HGDIOBJ' to 'HPEN'Conversion from 'void*' to pointer to non-'void' requires an explicit castyou need to do a cast, such as the one below.
HPEN old_pen = (HPEN)SelectObject(hdc,rand_pen);
edit: i've been beaten... arggggggh
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