从.NET打印API检索设备上下文 [英] Retrieving Device Context from .NET print API

问题描述

我正在使用.NET应用程序来控制DataCard桌面证卡打印机，但我偶然发现了一个问题.为了执行磁条和芯片编码，我必须在本机打印机API dll中调用一个函数以启用打印机的交互模式.

I am working on a .NET application to control DataCard Desktop Card printers, and I have stumbled upon a problem. In order to execute Magnetic Stripe and Chip encoding, I have to call a function in a native printer API dll to enable the printers Interactive mode.

我设法创建了P/Invoke代码来调用此本机函数.但是问题在于，该方法将打印机的设备上下文句柄作为参数，并且必须在调用Gdi32 StartDoc函数之前被调用.

I have managed to create the P/Invoke code to call this native function. But the problem is that this method takes the printer Device Context handle as a parameter, and have to be called BEFORE the Gdi32 StartDoc function is called.

在.NET打印API中，我确实可以从Graphics对象访问hDC.但据我所知，只有在调用StartDoc函数之后，才可以使用Graphics对象.

In the .NET printing API I do have access to the hDC from the Graphics object. But as far as I can see the Graphics object is only availible AFTER the StartDoc function is invoked.

所以我的问题是在调用StartDoc之前是否有人知道一种检索上下文的方法?

So my question is if anyone knows a way to retrieve the context before StartDoc is called?

推荐答案

您可以执行OpenPrinter来检索打印机句柄(HANDLE)，然后通过传入该句柄以获取打印机DC来调用CreateDC.随时(在StartDoc之前).

You can do a OpenPrinter to retrieve a printer handle (HANDLE) and then call CreateDC by passing in this handle to get a printer DC anytime (before StartDoc).

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