HFONT&上的SelectObject GDI资源泄漏. [英] SelectObject on HFONT & GDI resource leaks.

问题描述

(添加了更多内容)
你好''

关于SelectObject的一个小问题(包括Win32，而不是CDC).

我正在审查一大段绘制文本的代码，我们在调用SelectObject(fontHandle)之后查询文本metrix，但我们从不保留旧对象，也从未恢复过旧句柄:
(1)

(added more stuff )
Howdy''

Small question regarding SelectObject (mosly the Win32 one, not the CDC one).

I''m reviewing a large piece of code that draws text and we query the text metrix after calling SelectObject( fontHandle) but we never keep the old object and never restore the old handle:
(1)

{
 /// ... some code...
 ::SelectObject( validHDC, validHFONT );
 /// ... do something ...
}

通常我习惯看到像
这样的seomthing (2)

normally I''m used to seeing seomthing like
(2)

void f{)
{
 /// ... some code...
 HFONT oldFont = ::SelectObject( validHDC, validHFONT );
 /// ... do something ...

 ::SelectObject( validHDC, oldFont);
}

如果我在代码中有成千上万个SelectObject时执行(1)而不是(2)，是否会引起很多问题(资源泄漏和/或性能)?

最后，当我在同一函数中有多个SelectObject时，首选的方法是什么?我是否只需要保留第一个SelectObject的旧句柄并在最后将其重置?

Will that cause a lot of issues (resource leaks and/or performance) if I do (1) instead of (2) when there are gazillion SelectObject in the code ?

and finally, what is the preferred way to do it when I have multiple SelectObject in the same function? do I only need to keep the old handle for the first SelectObject and reset it at the end ?

void f{)
{
 /// ... some code...
 HFONT oldFont = ::SelectObject( validHDC, validHFONT );
 /// ... do something ...
 ::SelectObject( validHDC, anotherHFONT );
 /// ... do something ...

 ::SelectObject( validHDC, thirdHFONT );
 /// ... do something ...

 ::SelectObject( validHDC, fourthHFONT );
 /// ... do something ...

 ::SelectObject( validHDC, oldFont);
}

谢谢.
最多

Thanks.
Max.

推荐答案

简短答案:是.
更长的答案:请参见"此处"的备注部分 [

Short answer: Yes.
Longer answer: See the remarks section here[^]. GDI objects consume system resources so not returning them after use could result in your system being unable to satisfy a request, and your program could then produce the wrong results, or fail completely.

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