GdiplusStartup function
Applies to: desktop apps only
The GdiplusStartup function initializes Windows GDI+. Call GdiplusStartup before making any other GDI+ calls, and call GdiplusShutdown when you have finished using GDI+.
函數用來初始化windows gdi+。在調用任何gdi+的函數之前，要先調用GdiplusStartup
在用完之後，需要調用GdiplusShutdown 。
Syntax
Status GdiplusStartup( __out ULONG_PTR token *token, __in const GdiplusStartupInput *input, __out GdiplusStartupOutput *output );
Parameters
- token [out]
-
Type: ULONG_PTR token*
Pointer to a ULONG_PTR that receives a token. Pass the token to GdiplusShutdown when you have finished using GDI+.
- input [in]
-
Type: const GdiplusStartupInput*
Pointer to a GdiplusStartupInput structure that contains the GDI+ version, a pointer to a debug callback function, a Boolean value that specifies whether to suppress the background thread, and a Boolean value that specifies whether to suppress external image codecs.
- output [out]
-
Type: GdiplusStartupOutput*
Pointer to a GdiplusStartupOutput structure that receives a pointer to a notification hook function and a pointer to a notification unhook function. If the SuppressBackgroundThread data member of the inputparameter is FALSE, then this parameter can be NULL.
Return value
Type:
Type: Status
If the function succeeds, it returns Ok, which is an element of the Status enumeration.
If the function fails, it returns one of the other elements of the Status enumeration.
Remarks
You must call GdiplusStartup before you create any GDI+ objects, and you must delete all of your GDI+ objects (or have them go out of scope) before you call GdiplusShutdown.
在調用gdiplusshutdown之前，一定要銷燬gdi+的對象。這裏的先後順序很重要!! 這點是比較容易犯錯誤的。
很多時候我們在析構函數裏銷燬對象，對於全局的對象，析構函數的調用時間是在程序退出點，如果你在這之前就調用了gdiplusshutdown，那麼你的程序
很容易在析構函數退出的時候報內存錯誤。
原因是應爲gdi+的對象的內存是由他自己的堆來管理的。gdi對象的new和delete操作符都被重載過。
解決方法：
You can call GdiplusStartup on one thread and call GdiplusShutdown on another thread as long as you delete all of your GDI+ objects (or have them go out of scope) before you call GdiplusShutdown.
Do not call GdiplusStartup or GdiplusShutdown in DllMain or in any function that is called by DllMain. If you want to create a DLL that uses GDI+, you should use one of the following techniques to initialize GDI+:
- Require your clients to call GdiplusStartup before they call the functions in your DLL and to callGdiplusShutdown when they have finished using your DLL.
- Export your own startup function that calls GdiplusStartup and your own shutdown function that callsGdiplusShutdown. Require your clients to call your startup function before they call other functions in your DLL and to call your shutdown function when they have finished using your DLL.
- Call GdiplusStartup and GdiplusShutdown in each of your functions that make GDI+ calls.
Warning For info about how to use dynamic data exchange (DDE) with GDI+, see Special CWinApp Services.
Examples
For an example of calling GdiplusStartup and GdiplusShutdown in a Windows application, see Getting Started.
The following console application uses a GDI+Image object to retrieve the width and height of a JPEG image. The code calls GdiplusStartup before creating the Image object and calls GdiplusShutdown before terminating. Note that the Image object is deleted before the call to GdiplusShutdown.
In the following code, the variable gdiplusStartupInput is initialized by the default constructor of theGdiplusStartupInput structure. The default constructor sets the data members of the structure to the following values:
- GdiplusVersion = 1
- DebugEventCallback = NULL
- SuppressBackgroundThread = FALSE
- SuppressExternalCodecs = FALSE
#include <windows.h>
#include <gdiplus.h>
#include <stdio.h>
using namespace Gdiplus;
INT main()
{
GdiplusStartupInput gdiplusStartupInput;
ULONG_PTR gdiplusToken;
GdiplusStartup(&gdiplusToken, &gdiplusStartupInput, NULL);
Image* image = new Image(L"FakePhoto.jpg");
printf("The width of the image is %u.\n", image->GetWidth());
printf("The height of the image is %u.\n", image->GetHeight());
delete image;
GdiplusShutdown(gdiplusToken);
return 0;
}