QNX Photon: Getting Window Resources and Setting Label Resources

1. Create a base window.
2. Add a PtButton widget to the window, and give it a suitable name.
3. Set its Text resource (Pt_ARG_TEXT_STRING) to Move Label.
4. Add a PtLabel 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. MoveLabel). 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 containing the function you named earlier (the file probably has the same name as the function).
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 <Ph.h>
    
    int
    MoveLabel( PtWidget_t *widget, ApInfo_t *apinfo, PtCallbackInfo_t *cbinfo )
    
       {
    
       PhPoint_t lbl_pos;
       unsigned short *wnd_width;
       unsigned short *wnd_height;
       PtWidget_t *parent_wnd;
       
       /* eliminate 'unreferenced' warnings */
       widget = widget, apinfo = apinfo, cbinfo = cbinfo;
    
       /* Specifying a position outside the window's area does not generate an error.
       But the widget will not be visible. */
    
       parent_wnd = PtGetParent(widget, PtWindow);
       PtGetResource( parent_wnd, Pt_ARG_WIDTH, &wnd_width, 0); 
       PtGetResource( parent_wnd, Pt_ARG_HEIGHT, &wnd_height, 0); 
       
       lbl_pos.x = (int) *wnd_width / 2;
       lbl_pos.y = (int) *wnd_height / 2;
       
       PtSetResource( ABW_lbl1, Pt_ARG_POS, &lbl_pos, 0); 
    
       return( Pt_CONTINUE );
       }
    
    

Explanation:

• First, we need a pointer to the window that contains the label and button. This is achieved with the function PtGetParent. The second parameter to this function (PtWindow) is the type of widget that we are looking for; Photon will keep searching higher in the ancestry until it finds the widget that matches the given type.
• Next, we obtain the width (Pt_ARG_WIDTH) and height (Pt_ARG_HEIGHT) of the window with the PtGetResource function. Note that this function takes the address of the variable where we will store this value, so we need the address operator (&)
• Once we have the window's height and width, we find the middle point, which is where we will place the label.
• The position of a widget is held in the Pt_ARG_POS resource, which is a struct. The PtSetResource function requires a pointer to the structure containing the new value, so it is a call-by-reference, using the address operator.

Content last updated: 2003-09-23