Related Info: Quickdraw

Getting A Handle On Objects

By Jörg Langowski, MacTutor Editorial Board

“C++/MacApp - resizing objects”

As promised last month, this time we’ll start adding some code to our MacApp drawing program to change the basic shapes once they’ve been drawn. I have chosen to implement a resize operation; other functions, like changing colors and patterns, manipulating the order of objects, etc., will follow later.

We are going to use an interface similar to MacDraw, where a selected object has a number of small black squares connected with itself that can be used to change its shape. We’ll call them ‘tags’ in the following. Objects that can be circumscribed by a rectangle have eight tags: four on the corners and four on the centers of the edges. Dragging a corner tag will move the two sides of the rectangle adjacent to the corner, while dragging the edge tag will only move the side of the rectangle that contains the tag.

We’ll need code to display the tags, determine whether the mouse was clicked in one of them, and take action (track the mouse) depending on what tag it was clicked in. Of course, all operations should be undoable, but that’s almost implicit in MacApp.

Detecting the mouse click will proceed in two stages: first, we’ll check whether the mouse has been clicked in any one of the eight tags. If so, we’ll create a new command object of class TSizer, which then does the mouse tracking and track feedback. The command object determines where the mouse was clicked exactly, and the tracking and action will depend on the tag.

For the first phase - determining whether the mouse was clicked in one of the tags at all - it is convenient to create a region that consists of all the eight tags. This region is stored in a new instance variable of TBox, fTagRgn, and created when an object is selected and redrawn (see changes to the TBox::DrawShape method in listing 3). Also, the eight tags are stored individually as Rect instance variables.

The changes to the mouse down command handler are shown in listing 2. We shall now create a TSketcher, a TDragger, or a TSizer command object, depending on where the mouse was clicked - outside any object, inside a selected object, or inside one of the tags of a selected object.

In the TSizer::TrackMouse method we determine which of the eight tags was clicked in, and allow for changes in the top, bottom, left and right coordinates of the object (flags pT, pB, pL, pR). While those coordinates are continuously changed in the TrackMove phase of the TrackMouse method, the TrackFeedback method simply redraws the object rectangle in XOR mode. Undoing can be implemented very simply by remembering the old coordinates of the object.

Sounds simple? It is, and again the modifications are only to a very limited part of the total code - one of MacApp’s great advantages. We still have to add one more ‘Buzzword’ to the list of commands that appear after the Undo/Redo menu item (Listing 4), and extend the Make file a little. By now our code has grown too big to fit into one segment (compiling in Debug mode). Thus, you’ll also see how to segment a MacApp program.

I have put the code that is supposed to go into the new segment into the file TBox.cp, containing TSizer and all the Box/Shape classes. We then have to tell the MacApp builder that this file should be linked in under a different segment name. The necessary changes are shown in listing 5. We add the name of the new source file (TBox.cp) to the list of OtherInterfaces, and the corresponding object file (TBox.cp.o) to the list of OtherLinkFiles. Last, we add the dependency rule for generating the object file (also containing a comment line showing the build progress).

The drawing example will certainly still be extended over the next few months, but we’ll also take up some Forth again soon. Until then.

Listing 1: Changes to TEDrag.h

class TBox : public TObject {
public:
 Rect fLocation;
 BooleanfSelected;
 RgnHandlefTagRgn;
 Rect fTL,fTR,fBL,fBR,
 fT,fB,fL,fR;
 virtual pascal void IBox(Rect *itsLocation);
 virtual pascal void DrawShape();
 virtual pascal void NeedDiskSpace(long *data);
 virtual pascal void Read(short aRefNum);
 virtual pascal void Write(short aRefNum);
#ifdef qDebug
 virtual pascal void Fields(pascal void (*DoToField) 
 (StringPtr fieldName, Ptr fieldAddr, 
 short fieldType, void *link), void *link);
#endif
};

class TSizer : public TCommand {
public:
 TTEDocument   *fTEDocument;
 TTextView*fTextView;
 TBox   *fBox;   RectoldLocation;  RectnewLocation;      Point 
 fStart;  // mouse pressed here
 Point  fDelta;  // offset moved
 BooleanpT,pB,pL,pR; 
 // flags to indicate which coordinates to change
 pascal void ISizer(TBox *itsBox, 
 TTEDocument *itsDocument, TTextView *itsView);
 pascal struct TCommand *TrackMouse
 (TrackPhase aTrackPhase, VPoint *anchorPoint, 
 VPoint *previousPoint, VPoint *nextPoint, 
 Boolean mouseDidMove);
 pascal void TrackFeedback
 (VPoint *anchorPoint, VPoint *nextPoint,
 Boolean turnItOn, Boolean mouseDidMove);
 pascal void DoIt();
 pascal void RedoIt();
 pascal void UndoIt();
#ifdef qDebug
 virtual pascal void Fields(pascal void (*DoToField) 
 (StringPtr fieldName, Ptr fieldAddr, 
 short fieldType, void *link), void *link);
#endif
};

Listing 2: Change to TTextView::DoMouseCommand (file TEDrag.cp)
   
 if (aFindBoxStruct.myBox->fSelected)
 { if (info->theShiftKey) 
 { aFindBoxStruct.myBox->fSelected = false;
 InvalidRect (&aFindBoxStruct.myBox->fLocation);
 return inherited::DoMouseCommand
 (theMouse,info,hysteresis);   
 }
 else
 { if (PtInRgn(*theMouse,
 aFindBoxStruct.myBox->fTagRgn))
 { aSizer = new TSizer;
 FailNIL(aSizer);
 aSizer->ISizer (aFindBoxStruct.myBox,
  fTEDocument, this);
 return aSizer;   }
 else
 { aDragger = new TDragger;
 FailNIL(aDragger);
 aDragger->IDragger
 (aFindBoxStruct.myBox, fTEDocument, this);
 return aDragger;   }
 }
 }
 else
 {
 if (!info->theShiftKey) 
 { fTEDocument->ForEachShapeDo
 ((DoToObject)Deselect, &aSelectStruct); }
 aFindBoxStruct.myBox->fSelected = true;
 InvalidRect(&aFindBoxStruct.myBox-> fLocation);
 return inherited::DoMouseCommand
 (theMouse,info,hysteresis);
 }
   

Listing 3: TBox.cp
#include <UMacApp.h>
#include <UTEView.h>
#include <ToolUtils.h>
#include “TEDrag.h”

const int kBoxColor= redColor;
const int cSizer = 4001;
// Resizing support, JL 2/91
pascal void TSizer::ISizer(TBox *itsBox, 
 TTEDocument *itsDocument, TTextView *itsView)
{
 TScroller *aScroller;

 aScroller = itsView->GetScroller(true);
 ICommand(cSizer, itsDocument, itsView, aScroller);
 fTEDocument = itsDocument;
 fTextView = itsView;
 fBox = itsBox;  
 pT = false; pB = false; pL = false; pR = false;
 oldLocation = fBox->fLocation;
 newLocation = oldLocation;
}

pascal struct TCommand *TSizer::TrackMouse
 (TrackPhase aTrackPhase, VPoint *anchorPoint, 
 VPoint *previousPoint,  VPoint *nextPoint, 
 Boolean mouseDidMove)
{
 fStart = fTextView->ViewToQDPt(anchorPoint);
 
 if (aTrackPhase == trackPress) {
 if (PtInRect(fStart,&fBox->fTR)) { pT = true; pR = true; }
 else if (PtInRect(fStart,&fBox->fTL))
 { pT = true; pL = true; }
 else if (PtInRect(fStart,&fBox->fBR))
 { pB = true; pR = true; }
 else if (PtInRect(fStart,&fBox->fBL))
 { pB = true; pL = true; }
 else if (PtInRect(fStart,&fBox->fT)) { pT = true; }
 else if (PtInRect(fStart,&fBox->fB)) { pB = true; }
 else if (PtInRect(fStart,&fBox->fL)) { pL = true; }
 else if (PtInRect(fStart,&fBox->fR)) { pR = true; }
 }

 if ((aTrackPhase == trackMove) && mouseDidMove) {
 fDelta = fTextView->ViewToQDPt(nextPoint);
 SubPt(fTextView->ViewToQDPt(anchorPoint), &fDelta);
 
 if ( !((fDelta.h == 0) && (fDelta.v == 0)) ) {                
 if (pT){ newLocation.top = 
 oldLocation.top + fDelta.v;  }
 if (pB){ newLocation.bottom = 
 oldLocation.bottom + fDelta.v; }
 if (pL){ newLocation.left = 
 oldLocation.left + fDelta.h; }
 if (pR){ newLocation.right = 
 oldLocation.right + fDelta.h; }
 }
 }

 if ((aTrackPhase == trackRelease) && mouseDidMove) {
 fDelta = fTextView->ViewToQDPt(nextPoint);
 SubPt(fTextView->ViewToQDPt(anchorPoint), &fDelta);
 if ((fDelta.h == 0) && (fDelta.v == 0))
 { return gNoChanges; }
 fBox->fLocation = newLocation;
 }
 return this;
}

pascal void TSizer::TrackFeedback
 (VPoint *anchorPoint, VPoint *nextPoint,
 Boolean turnItOn, Boolean mouseDidMove)
{
 PenState oldState;
 
 if (mouseDidMove) {
 GetPenState(&oldState);
 PenNormal();
 PenMode(patXor);
 FrameRect(&newLocation);
 SetPenState(&oldState);
 }
}

pascal void TSizer::DoIt()
{fTextView->InvalidRect(&newLocation);
 fTextView->InvalidRect(&oldLocation);   }

pascal void TSizer::RedoIt()  
{  fBox->fLocation = newLocation; DoIt();    }

pascal void TSizer::UndoIt()
{fBox->fLocation = oldLocation; DoIt();      }

#ifdef qDebug
pascal void TSizer::Fields(pascal void (*DoToField) 
 (StringPtr fieldName, Ptr fieldAddr, 
 short fieldType, void *link), void *link)
{
 DoToField(“\pTSizer”, nil, bClass, link);
 DoToField(“\pfTEDocument”, 
 (Ptr) &fTEDocument, bObject, link);
 DoToField(“\pfTextView”, (Ptr) &fTextView, bObject, link);
 DoToField(“\pfBox”, (Ptr) &fBox, bObject, link);
 DoToField(“\poldLocation”, (Ptr) &oldLocation, bRect, link);
 DoToField(“\pnewLocation”, (Ptr) &newLocation, bRect, link);
 DoToField(“\pfStart”, (Ptr) &fStart, bPoint, link);
 DoToField(“\pfDelta”, (Ptr) &fDelta, bPoint, link);
 DoToField(“\ppT”, (Ptr) &pT, bBoolean, link);
 DoToField(“\ppB”, (Ptr) &pB, bBoolean, link);
 DoToField(“\ppL”, (Ptr) &pL, bBoolean, link);
 DoToField(“\ppR”, (Ptr) &pR, bBoolean, link);
 inherited::Fields(DoToField, link);
}
#endif

pascal void TBox::IBox(Rect *itsLocation)
 {    fLocation = *itsLocation; fSelected = false; }

pascal void TBox::DrawShape()
{
 if (fSelected) {
 short halfH, halfV;
 
 halfH = (fLocation.right-fLocation.left)/2;
 halfV = (fLocation.bottom-fLocation.top)/2;
 
 PenSize (1,1);
 ForeColor(blackColor);
 FrameRect(&fLocation);
 
 fTagRgn = MakeNewRgn();
 OpenRgn();
 
 fTL.top = fLocation.top;
 fTL.left = fLocation.left;
 fTL.bottom = fTL.top + 4;
 fTL.right = fTL.left + 4;
 FrameRect(&fTL);
 
 fT.top = fLocation.top;
 fT.bottom = fT.top + 4;
 fT.left = fLocation.left + halfH - 2;
 fT.right = fT.left + 4;
 FrameRect(&fT);
 
 fTR.top = fLocation.top;
 fTR.bottom = fTR.top + 4;
 fTR.right = fLocation.right;
 fTR.left = fTR.right - 4;
 FrameRect(&fTR);
 
 fBL.bottom = fLocation.bottom;
 fBL.top = fBL.bottom - 4;
 fBL.left = fLocation.left;
 fBL.right = fBL.left + 4;
 FrameRect(&fBL);
 
 fB.bottom = fLocation.bottom;
 fB.top = fB.bottom - 4;
 fB.left = fLocation.left + halfH - 2;
 fB.right = fB.left + 4;
 FrameRect(&fB);
 
 fBR.bottom = fLocation.bottom;
 fBR.top = fBR.bottom - 4;
 fBR.right = fLocation.right;
 fBR.left = fBR.right - 4;
 FrameRect(&fBR);
 
 fL.top = fLocation.top + halfV - 2;
 fL.bottom = fL.top + 4;
 fL.left = fLocation.left;
 fL.right = fL.left + 4;
 FrameRect(&fL);
 
 fR.top = fLocation.top + halfV - 2;
 fR.bottom = fR.top + 4;
 fR.right = fLocation.right;
 fR.left = fR.right - 4;
 FrameRect(&fR);
 
 CloseRgn(fTagRgn);
 FillRgn(fTagRgn,qd.black);
 ForeColor(kBoxColor);  }
}
   the rest of the file (TShape and following definitions) stays unchanged 
  

Listing 4: Change to TEDrag.r

#define cSizer   4001
resource ‘cmnu’ (128) {
 128, textMenuProc, allEnabled, enabled, “Buzzwords”,          /* these 
words appear after Undo in the Edit menu */
  {
 “Page Setup Change”, noIcon, noKey, 
 noMark, plain, cChangePrinterStyle;
 “Typing”, noIcon, noKey, noMark, plain, cTyping;
 “Drawing”,  noIcon, noKey, 
 noMark, plain, cDrawBox;
 “Dragging”,  noIcon, noKey, 
 noMark, plain, cDragBox;
 “Resize”,  noIcon, noKey, noMark, plain, cSizer
 }
};

Listing 5: TEDrag.MAMake
AppName = TEDrag
OtherInterfaces =  
 “{SrcApp}TBox.cp”
OtherLinkFiles = 
 “{ObjApp}TBox.cp.o”
“{ObjApp}TBox.cp.o”ƒ 
 “{SrcApp}TBox.cp” 
 “{SrcApp}TEDrag.MAMake” 
  {MacAppIntf} 
  {BuildingBlocksIntf}
 {MAEcho} {EchoOptions} “Compiling:     TBox.cp”
 {MACPlus} 
 {CPlusOptions} 
 -s TBox 
 -i “{SrcApp}” 
 -i “{MACIncludes}” 
 -o “{ObjApp}TBox.cp.o” 
 “{SrcApp}TBox.cp”
OtherRsrcFiles = 
 “{MAObj}Printing.rsrc” 
 “TEOther.rsrc”