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Volume Number: | 1 | |
Issue Number: | 2 | |
Column Tag: | C Workshop |
“Template” Application
By Robert B. Denny
This month’s C Workshop presents a “template” application. Most Macintosh programs share a common overall structure, dictated by the operating system environment. The purpose of the template program is to give you a framework for developing your own applications. It will also be used as the basis for topics discussed in future C Workshops. The functions that do the actual work of the program have been “stubbed”.
Since “a program is worth a thousand words”, most of this month’s column is the program itself, sprinkled liberally with comments. Please take the time to study the program. But first, a few introductory words.
Some C Basics for the Macintosh
Many data structures that you’ll be working with are stored in the “heap”, dynamic memory. Most of these struc- tures are accessed by a “handle” rather than a pointer. A handle is a pointer to a pointer. Why this extra level of indirection?
The heap is used for almost everything. Code goes there. Resources go there (code is really a resource). Data structures allocated at run time go there. Nothing is preallocated. The memory manager is rather dumb about allocating and deallocating blocks of space in the heap.
As a result, the heap can (and does) get chopped up into small pieces. When someone makes a request for a block of space that exceeds the size of the largest free block, the memory manager compacts the heap. It moves blocks of data around in an effort to collect enough contiguous space to satisfy the request. Blocks that are eligible to be moved are called relocatable. Most Mac data structures fall into this class. You can control whether or not your own data structures are relocatable. The tradeoff should be obvious.
Relocatable data structures are accessed via handles so that your references remain valid if the structure is moved. The handle points to a master pointer which in turn points to the relocatable structure. If the structure is moved, the memory manager updates the master pointer and your handle reference remains valid. Obviously, the area containing the master pointers is not relocatable.
Accessing data structures defined by struct statements via handles isn’t too difficult. The example is shown in figure 1 below:
The expression assigns the value contained in the relocatable structure via its handle to “intval”. The only safe way to access relocatable structures is to use the double-indirect access shown above at all times. Do not attempt to cache the pointer (*foo_handle) at any time. To do so is to defeat the purpose of handle access.
Template Application
Now to the template application. It is written for the Consulair Mac C system and Toolkit. Changes to the details of the program will probably be necessary for other languages since there is little consistency in the toolbox interface.
/* * ************* * * TEMPL.H * * ************* * * Common stuff for template program * (C) 1984, MacTech by Robert B. Denny * * NOTE:Dependent on the menu * structure defined in the resources. */ // Toolbox traps must start with ‘#’ now. #Options -N // // Include Macintosh data structure // definitions. These files are included // with the Mac C Toolkit, or from the // Stanford University Macintosh C // Programming system (SuMacC). // #include <MacDefs.H> #include<QuickDraw.H> #include<Control.H> #include<Events.H> #include<Menu.H> #include<TextEdit.H> #define MAX_WINDOWS8 #define MAX_MENUS8 #define TRUE1 #define FALSE 0 #define NULL0 /* * Each window requires a window * control block to define it’s structure. * Note which things are handles and * which are pointers. * * wcb = Window Control Block */ struct wcb { WindowPtrwp; // Pointer to window rec in heap Rect drag_rect; // Dragging limits Rect grow_rect; // Window size limits TEHandle te_handle; // Handle to textEdit rec in heap Point te_origin; // Text origin ControlHandle vs_handle; // Vert scroller’s handle ControlHandle hs_handle; // Horiz scroller’s handle }; // // Supress extern declarations in module // containing the real declarations. // #ifndef GLOB_DATA extern struct wcb dw[MAX_WINDOWS]; extern struct wcb *dwp; // --> Current doc-window extern unsigned n_windows;// No. of open windows extern EventRecord Event; // Our event record (duh) extern short EvType; // Event result type extern WindowPtr EvWindow;// Event window /* * Array of menu handles */ extern MenuHandle menus[];// Our menu contexts #define APPLE 1 #define FILE2 #define EDIT3 #define OPTIONS 4 #endif /* * Resource ID’s of menus in rsrc file. */ #define APPLE_ID 1 #define FILE_ID 256 #define EDIT_ID 257 #define OPTIONS_ID 258 //Add more menu resource ID’s here /* * File menu item numbers */ #define FM_EXIT // This should reflect file menu rsrc /* * Edit menu item numbers * * Note that SystemEdit expects the Edit * menu items as follows: * * 0: undo (** YES, zero-based **) * 1: -------- * 2: cut * 3: copy * 4: paste * * The rest of the items may be chosen * at will by the application. */ #define EM_UNDO 1 #define EM_CUT 3 #define EM_COPY 4 #define EM_PASTE 5 #define EM_CLEAR 6 /* * Options menu assignments */ #define MM_EDIT_WINDOW 1 #define MM_SCRAWL_WINDOW 2 #define MM_MUSIC 4 /* * Other resource ID’s */ #define ABOUT_ID 256 #define WINDOW_ID256 /* * Macro to hack the Point struct, * composed of 2 short (16-bit) ints * into a long, which can be passed by * value to toolbox routines. * Takes address of a Point and turns it * into a scalar long. NOTE * this generates NO runtime code. */ #define PtLong(ptr) *((long *)ptr)
MAIN PROGRAM
A Template Application in C
Template program for the C Workshop. Has hooks for multiple dynamically allocated windows (to be added in future columns), supports desk accessories, has a menu bar with 4 menus and an “about” dialog in the Apple menu. The program will eventually support multiple dynamically allocated text edit and drawing windows. The text edit windows will have scroll bar controls and resizing (“grow”) capability. Also, an interface to the sound system will be added. The components of this program are:
TMAIN.C This module, the main program & global data.
TMENU.C Menu handling functions, fig. 6.
TEMPL.H Common “include” file of definitions, fig. 4.
TEMPL.R RMAKER source for program resources, fig. 5.
TEMPL.LINK Linker command file, fig. 3.
TEMPL.JOB Exec command procedure to build template, fig. 2.
Additional modules will be added in future C Workshop columns. This program was written for the MAC C system by Consulair Corp. Changes will be needed for other C systems. Also, prerelease versions of MAC C and RMAKER may not work with this program. [Note: one or two obscure Mac C statements may have been changed in the current Mac C so that a change may be needed to fully compile this program using present Mac C systems. This program was written with an early version of Mac C. Any offending lines should be obvious at compile time. -Ed.]
/* * TMAIN.C - Template application * (c) 1984 MacTech by Robert B. Denny */ * GLOBALS DEFINITIONS #define GLOB_DATA #include <Templ.H> /* Define window control block for window management. See Templ.H file. */ struct wcb dw[MAX_WINDOWS]; // our windows struct wcb *dwp = NULL; // --> Current window unsigned n_windows = 0; // Number of open windows EventRecord Event; // Our event record short EvType; // Event result type WindowPtr EvWindow;// Event window MenuHandle menus[MAX_MENUS]; // Our menus /* * MAIN PROGRAM * * Link with MacCLib, which does * Quickdraw and Window initialization. * */ main() { register WindowPtr wp; // Try to save space/time int i; #InitFonts(); // Not done in MacCLib ... #InitDialogs(0);// No restart function #OpenResFile(“\011TemplRsrc”);// Open resfile (Pstring) setup_menu(); // Set up our menus #TEInit(); // Initialize TextEdit #FlushEvents(-1,0); // Flush all events #InitCursor(); // Make arrow cursor for(i=0; i<MAX_WINDOWS; i++) // Mark all WCB’s free dw[i].wp = NULL; dwp = NULL;// No windows n_windows = 0; // -- EVENT LOOP -- // This is the “outer loop” of a typical // application. All event types // are dequeued, most are processed. // Those not processed are ignored. // while(TRUE)// Loop here forever { #SystemTask(); // Handle desk accessories // dwp always points to the WCB //for the active (front) window. // If dwp = NULL, than it’s not //”our” window. // (Is this possible??) dwp = (struct wcb *)find_wcb(#FrontWindow()); if(dwp != NULL && dwp->te_handle != 0) // If active wind & text #TEIdle(dwp->te_handle); // Flash the insertion mark if(!#GetNextEvent(-1, &Event)) // Process only our events continue; switch(Event.what)// Dispatch on event type { case mouseDown: // Mouse click do_mouse();// Dispatch on mouse location break; case keyDown: // Keypress case autoKey: // Repeat-key generator do_key(); break; case updateEvt: // window needs refresh EvWindow = (WindowPtr)Event.message; // Which window? upd_wind(EvWindow); // Do the update break; case activateEvt: // Activate/deactivate EvWindow = (WindowPtr)Event.message; // Which window? if(Event.modifiers & 1) // If Activate act_wind(EvWindow); // Activate window else // If Deactivate deact_wind(EvWindow); // Deactivate window // Additional cases for other event types default: // Do nothing for other events } } // // -- END OF EVENT LOOP -- // } /* * * LOCAL FUNCTIONS * * Handle mouse-down events */ do_mouse() { short window_part;// FindWindow result code // // Following fills in EvWindow with //--> window in which the click // occurred (or NULL if none). // window_part = #FindWindow(PtLong(&Event.where), &EvWindow); switch(window_part) // Dispatch on where clicked { case inMenuBar: do_menu(#MenuSelect(PtLong(&Event.where))); break; case inSysWindow: #SystemClick(&Event, EvWindow); break; case inContent: // Click in content of a window #SelectWindow(EvWindow); // Activate window #SetPort(EvWindow); // Hook QuickDraw up break; case inDrag: #SelectWindow(EvWindow); // Activate #SetPort(EvWindow); // Hook QuickDraw up break; case inGoAway: // Go-away handling break; case inGrow: // Grow handling break; // Add dispatches for other area types default: } } /* * - Handle keypress and command keys * Handles edit command keys */ do_key() { unsigned short ch; ch = (unsigned short)Event.message; // Isolate key codes if(Event.modifiers & cmdKey) // If command character do_menu(#MenuKey(ch)); // Try menu shortcut cmd } // Stub functions upd_wind(wp) WindowPtr wp; { return(0); } act_wind(wp) WindowPtr wp; { return(0); } deact_wind(wp) WindowPtr wp; { return(0); } find_wcb(wp)// Never one of our windows WindowPtr wp; { return(0); }
MENU SUB-PROGRAM IN C /* * TMenu.C - Handle menu selections for * template program * * (c) 1984, MacTutor by Bob Denny */ #include<Templ.H> /* * SETUP_MENU() - Initialize menu system * * Fills in an array of menu handles. Not * used in this version of the program. */ setup_menu() { #InitMenus(); #InsertMenu(menus[APPLE] = (MenuHandle)#GetMenu(APPLE_ID), 0); #AddResMenu(menus[APPLE], ‘DRVR’); #InsertMenu(menus[FILE] = (MenuHandle)#GetMenu(FILE_ID), 0); #InsertMenu(menus[EDIT] = (MenuHandle)#GetMenu(EDIT_ID), 0); #InsertMenu(menus[OPTIONS] = (MenuHandle)#GetMenu(OPTIONS_ID), 0); #DrawMenuBar(); } /* * DO_MENU() - Handle menu selection * * Input: * Result longword from MenuSelect * or MenuKey */ do_menu(result) unsigned result; { unsigned short menu_id; // Resource ID of selected menu unsigned short item_no; // Item number selected char item_name[64]; // Item name (for desk acc.) Ptr dp;// Dialog pointer for “about ...” unsigned short item_hit; // Dialog item that was hit if(result == 0) // Just for safety with MenuKey return;// Ignore zero results menu_id = (short)#HiWord(result); // Use toolbox item_no = (short)#LoWord(result); switch(menu_id) { case APPLE_ID: // “Apple” menu if(item_no > 1) // If desk accessory { #GetItem(menus[APPLE], item_no, item_name); #OpenDeskAcc(item_name); } else // Our About ... dialog { dp = #GetNewDialog(ABOUT_ID, 0, -1); // Bring in dialog to front #SetPort(dp); // Hook QuickDraw up to dialog #ModalDialog(0, &item_hit); // dialog item hit #DisposeDialog(dp); // Close & free heap } break; case FILE_ID: // File menu if(item_no == FM_EXIT) #ExitToShell(); // Ugly exit break; case EDIT_ID: // // First we must hand off any // desk-accessory edit commands. // Note the comments in Demo.H // regarding implicit assumptions // in numbering items in Edit menu. // if(#SystemEdit(item_no - 1)) // Relies on item no.!! break; // // Do the requested edit function only // if this is an editing window and there // is a window open. For now, we have // no windows, so we just return. // break; case OPTIONS_ID: // Options menu. switch(item_no) { case MM_MUSIC: play_tune(); break; case MM_EDIT_WINDOW: edit_window(); break; case MM_SCRAWL_WINDOW: scrawl_window(); break; default: } break; default: } #HiliteMenu(0); // Turn off highlighted title } // Stub functions play_tune() // Make crude music -- demo driver { return(0); } edit_window() // Create a new editing window { return(0); } scrawl_window() // Create a new “scrawling” window { return(0); }
Resource File
This is the RMAKER source for the Mac C template application. The dialog box will not come out right with the version of the RMAKER that I have. The \0D entries in the staticText item are supposed to be “hard” carriage returns in the text. Instead, they come out as “D”. To fix this, use the AlertDialog Editor on the file after building it to put the 2 carriage returns in and remove the “D”s. Perhaps RMAKER (or it’s successor) will work some day ...
The menu items for things that aren’t in the template (yet) have been dimmed. As things are filled in, you’ll have to edit this file to un-dim & thus activate the corresponding menu items. Note that the Edit menu is enabled to support SystemEdit editing in desk accessories.
* Templ.R -- Resources for the * template program * * (C) 1984, MacTech by R. B. Denny TemplRsrc RSRCXXXX TYPE WIND ,256 Please Wait ... 50 50 250 250 Visible GoAway 0 0 TYPE MENU ,1 \14 About Template ... (- ,256 File Quit ,257 Edit (Can’t Undo (- Cut/X Copy/C Paste/V Clear/D ,258 Options (New Edit Window (New Scrawl Window (- (Play a tune TYPE DLOG ,256 54 145 203 376 Visible NoGoAway 1 0 256 TYPE DITL ,256 2 button 116 58 142 174 RESUME DEMO staticText Disabled 9 9 105 228 This program was written as an example of native Macintosh ++ application programming in the C language, using Mac C. \0D \0D ++ Bob Denny October, 1984
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