Programming Tools:prgtools

Using constants with ARC.EXE Foundation

Instead of numeric IDs, #define constants can be used in an ARC file just as in a PRG file. This has the obvious advantage that resources can be identified in both ARC and PRG files using the same constants. To accomplish this, the constants are defined in a CH file. The resource compiler understands the directives #inlude, #define, #ifdef, #ifndef, #elseand #endif, and treats them in the same way as the Xbase++ compiler. Therefore, it is possible to declare resources in the following way:

** CH file: BITMAPID.CH               // Include file defines 
                                      // constants for 
#define ID_BMP_LOGO          10       // XPP.EXE and ARC.EXE 
#define ID_BMP_BACKGROUND    11 
#define ID_BMP_NEXT          12 
#define ID_BMP_PREVIOUS      13 

** EOF 


** ARC file: TEST.ARC                 // Declaration of resources 

#include ""                // Include CH file 

BITMAP                                // Keyword introduces 
   ID_BMP_LOGO       = "Logo.bmp"     // a block of resources 
   ID_BMP_BACKGROUND = "Backgrd.bmp"  // of the same type 
   ID_BMP_NEXT       = "Next.bmp" 
   ID_BMP_PREVIOUS   = "Prev.bmp" 

   #ifdef __OS2__                     // Conditional 
      100 = "\bitmaps\os2\test.bmp"   // compiling due to 
   #else                              // implicit constant 
      100 = "\bitmaps\w32\test.bmp" 

** EOF 

This example shows the code for a CH file which defines constants for the numeric resource IDs. The constants are used in the ARC file since ARC.EXE can resolve the #include directive.

Only bitmap resources are declared in the example. The keyword BITMAP is written in a separate line and is followed by a block of resource declarations of the same type. ARC supports this syntactical form for declaring resources which results in better readability of the ARC file. If a keyword is written on a line by itself, all following lines declare the same resource type without repeating the keyword.

The last lines in the example demonstrate how operating system-specific resources can be declared in one and the same ARC file. The directives #ifdef, #else and #endif are used, thus allowing for a conditional compilation. ARC.EXE uses the same implicit #define constants as the Xbase++ compiler: __OS2__ and __WIN32__.

Additionally, the resource compiler predefines a constant to identify the compiler. The #define is:

Predefined #define constant
#define Meaning
__ARC__ Xbase++ resource compiler in use

For example, if the same CH file is to be included from a PRG source file and from an ARC resource file then resource compiler specific directives can be hidden from the Xbase++ compiler as follows:

Header file "":

// ARC and XPP common code 
#define ICON_APPLICATION  100 
#define ICON_MAN          100 
// ARC specific code 
#ifdef __ARC__ 
      ICON_MAN          =  "MAN.ICO" 

In this way resource IDs and their associated source files can be maintained in the very same header file even so they are compiled by the Xbase++ compiler and the resource compiler.


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