QNX Photon: Displaying an Icon using a Button Command

1. Create a base window.
2. Add a PtLabel widget to the window, and give it a suitable name.
3. Set its Label Type resource (Pt_ARG_LABEL_TYPE) to Pt_Image (see Pt_Image_t).
4. Add a PtButton widget to the window, and give it a suitable name.
5. Select the button widget, and go to the Callbacks control panel.
6. Click the Activate event, and the Callback editor appears.
7. Ensure the code button is depressed, and click on the Function name text box.
8. Enter a suitable name for the function (e.g. ShowImage). The function needn't exist yet, appbuilder will create the file and the function stub for you.
9. Go the the Application menu, and select Build + Run.
10. Ensure the correct platform is selected, and click Generate.
11. In the list of module files, select the module named after the function you named earlier.
12. Click Edit.
13. In the following code sample, the changes you need to make to the generated function stub are stongly emphasised like this.

    /* Standard headers */
    #include <stdio.h>
    #include <stdlib.h>
    #include <unistd.h>
    #include <string.h>
    
    /* Local headers */
    #include "ablibs.h"
    #include "abimport.h"
    #include "proto.h"
    
    #include <photon/PxImage.h>
    
    int
    ShowImage( PtWidget_t *widget, ApInfo_t *apinfo, PtCallbackInfo_t *cbinfo )
    
       {
       
       PhImage_t   *myImg;
       char        myImgFlnm[20] = "PICTURE.BMP";
    
       /* eliminate 'unreferenced' warnings */
       widget = widget, apinfo = apinfo, cbinfo = cbinfo;
        
       if ((myImg = PxLoadImage( myImgFlnm, NULL)) == NULL) {
          fprintf( stderr, "Error loading image file %s\n", myImgFlnm);
          PtExit( EXIT_FAILURE );
       }
       PtSetResource(ABW_lblMyImg, Pt_ARG_LABEL_IMAGE, myImg, 0);
        
       return( Pt_CONTINUE );
       }
    

Explanation

• An area of memory (with a pointer to it) is set aside for the image by the PhImage_t definition.
• The image is loaded from file and stored at a pointer location by the PxLoadImage function. The second parameter is a pointer variable that allows the behaviour of the function to be customised, but for the default behaviour just use the NULL pointer.
• The stored image is applied to the label widget by the function PtSetResource. The widget to be modified is given by the first parameter of PtSetResource and is identified by its ABW_ manifest. The particular resource to be modified (set) is given by the second parameter, which is specified using the Pt_ARG_ identifier. The use of the last parameter depends on the resource being set.

Content last updated: 2003-09-23