The Extension Load ('load') Resource(IM:XP)

The Extension Load ('load') Resource
The extension load resource, of type gxExtensionLoadType, tells QuickDraw GX where to load an extension into the printing message chain. You must include a load resource in your extension file. The value that you define in your extension load resource specifies the default loading order for your extension when it is first added to the system. The user can modify the loading order of extensions by using the Extension Setup dialog box for each desktop printer.
Figure 6-7 shows the structure of an extension load resource.
Figure 6-7 The extension load resource

The extension load resource consists of a single value.

Load priority type. The default location in the message chain where your extension is to be loaded. Constants for the three load priority types are shown inTable 6-10.
Table 6-10 Extension load priority constants
Constant Value Explanation
gxExtensionLoadFirst 0x00000100 Load this extension as the first handler in the print message handling chain so that it has the first opportunity to respond to messages that it overrides
gxExtensionLoadAnywhere 0x7FFFFFFF Load this extension anywhere in the print message handling chain
gxExtensionLoadLast 0xFFFFFF00 Load this extension last in the print message handling chain so that it receives its message after any other handlers have performed their operations

The extension load resource ID needs to be the constant gxExtensionLoadID.
Listing 6-6 shows an example of an extension load resource.
Listing 6-6 An example of an extension load resource
resource gxExtensionLoadType (gxExtensionLoadID, sysHeap,
                                                 purgeable)
{
   gxExtensionLoadLast
};
This resource tells QuickDraw GX to load the extension last in the message chain, which allows the extension to modify the contents of a page after any other message handlers have performed their modifications. However, the user can change this by using the Extension Setup dialog box for each desktop printer.

**Table 6-10 Extension load priority constants**
Constant	Value	Explanation
gxExtensionLoadFirst	0x00000100	Load this extension as the first handler in the print message handling chain so that it has the first opportunity to respond to messages that it overrides
gxExtensionLoadAnywhere	0x7FFFFFFF	Load this extension anywhere in the print message handling chain
gxExtensionLoadLast	0xFFFFFF00	Load this extension last in the print message handling chain so that it receives its message after any other handlers have performed their operations