Cogs and Levers A blog full of technical stuff

Using resource files in your masm projects

17 Sep 2015

In a previous post we built a boilerplate program that we can start to work with. For today’s post, we’re going to go through the development of a resource file that you can incorporate into your own projects.

What are resource files?

You can use resource files to organise your external resources (images, audio, text, etc.) into a compilable (and ultimately linkable) resource. The items that you add to your resource file are then statically added to your resulting executable, ready for you to reference.

From the Microsoft site:

You should place every element of the user interface that needs to be localized in a Windows resource file, including pictures, strings, messages, menus, dialog boxes, and version information. The table below lists the individual resource elements defined by Windows.

Resource Type Element File Format Comment/ Description
RT_CURSOR Cursor .CUR #include in .RC file
RT_BITMAP Bitmap or toolbar .BMP #include in .RC file
RT_ICON Icon .ICO #include in .RC file
RT_MENU Menu or pop up menu .RC #include in .RC file
RT_DIALOG Dialog .DLG or .RC #include .DLG file in .RC file
RT_STRING String .RC  
RT_FONTDIR Font .FNT  
RT_FONT Font .FNT  
RT_ACCELERATORS Accelerator .RC  
RT_RCDATA User-defined resource .RC Can use for constants or application specific structures
RT_MESSAGETABLE Messages .MC #include compiled message table in .RC file
RT_GROUP_CURSOR Cursor N/A Generated internally by resource compiler to provide Windows with information about cursor’s resolution and type
RT_GROUP_ICON Icon N/A Generated internally by resource compiler to provide Windows with information about icon’s resolution and type
RT_VERSION Version information .RC  
RT_DLGINCLUDE Header file that contains menu and dialog box #define statements .RC Used by resource editing tools; Visual C++ uses its own mechanism tools;

What does a resource file look like?

The .RC file itself is just text. There are IDs that are defined throughout that you can create symbolic constants for in your code, just so you’re not doing so much “magic number” work. Here’s a simple menu:

600 MENUEX MOVEABLE IMPURE LOADONCALL DISCARDABLE
BEGIN
    POPUP "&File", , , 0
    BEGIN
        MENUITEM "&Exit", 1000
    END
    POPUP "&Help", , , 0
    BEGIN
        MENUITEM "&About", 1900
    END
END

600 in this example is the ID of the menu. Referencing this menu in your code is as simple as passing 600 to the menu name parameter of a LoadMenu call:

invoke LoadMenu, hInstance, 600
invoke SetMenu, hWnd, eax

How do I compile one?

rc.exe is the resource compiler that comes along with masm32. You give it your resource script and it’ll give you back a compiled .RES file.

rc /v rsrc.rc

You then take the .RES file that was output; in this case it was rsrc.res and feed it into another utility cvtres.exe.

cvtres /machine:ix86 rsrc.res

This utility converts your compiled .RES file into object code. It produces you an .OBJ file that you can then link into your exe.

Related Posts