The primary advantage of a micro presentation space over a cached-micro presentation space is that it can be used for printing as well as painting in a window. An application that uses a micro presentation space must explicitly associate it with a device context. This makes the micro presentation space useful for painting to a printer, a plotter, or an off-screen memory bit map.
A micro presentation space does not support the full set of OS/2 graphics functions. Unlike a normal presentation space, a micro presentation space does not support retained graphics.
An application that must display graphics or text in a window and print to a printer or plotter typically maintains two presentation spaces: one for the window and one for the printing device. The following figure shows how an application's graphics output can be routed through separate presentation spaces to produce a screen display and printed copy. An application creates a micro presentation space by calling the GpiCreatePS function. A device context must be supplied at the time the micro presentation space is created. An application typically creates a device context and then a presentation space. The following code fragment demonstrates this by obtaining a device context for a window and associating it with a new micro presentation space:
hdc = WinOpenWindowDC(...);
hps = GpiCreatePS(..., hdc, ..., GPIA_ASSOC);
To create a micro presentation space for a device other than the screen, replace the call to the WinOpenWindowDC function with a call to the DevOpenDC function, which obtains a device context for a device other than the screen. Then the device context that is obtained by this call can be used as an argument to GpiCreatePS.
An application typically creates a micro presentation space during initialization and uses it until termination. Each time the application receives a WM_PAINT message, it should pass the handle of the micro presentation space as an argument to the WinBeginPaint function; this prevents the system from returning a cached-micro presentation space. The system modifies the visible region of the supplied micro presentation space and returns the presentation space to the application. This method enables the application to use the same presentation space for all drawing in a specified window.
Micro presentation spaces created by using GpiCreatePS should be destroyed by calling GpiDestroyPS before the application terminates. Do not call the WinReleasePS function to release a presentation space obtained by using GpiCreatePS. Before terminating, applications must use the DevCloseDC function to close any device contexts opened using the DevOpenDC function. No action is necessary for device contexts obtained using WinOpenWindowDC, because the system automatically closes these device contexts when destroying the associated windows.