// ShowInitIcon - version 1.0.1, May 30th, 1995
// This code is intended to let INIT writers easily display an icon at startup time.
// View in Geneva 9pt, 4-space tabs

// Written by: Peter N Lewis <peter@mail.peter.com.au>, Jim Walker <JWWalker@aol.com>
// and Fran¨ois Pottier <pottier@dmi.ens.fr>, with thanks to previous ShowINIT authors.
// Send comments and bug reports to Fran¨ois Pottier.

// Hacked a bit by Valtteri Koskivuori on 08.09.2023:
// * Removed Sys7/Color QD code
// * Added missing QDGlobals struct
// * Now compiles in Think C 5.0.1 under System 6


// This version features:
// - Short and readable code.
// - Correctly wraps around when more than one row of icons has been displayed.
// - works with System 6
// - Built with Universal Headers & CodeWarrior. Should work with other headers/compilers.

#include <Memory.h>
#include <Resources.h>
#include <Icons.h>
#include <OSUtils.h>
#include <Quickdraw.h>
#include "ShowInitIcon.h"

// You should set SystemSixOrLater in your headers to avoid including glue for SysEnvirons.

// ---------------------------------------------------------------------------------------------------------------------
// Set this flag to 1 if you want to compile this file into a stand-alone resource (see note below).
// Set it to 0 if you want to include this source file into your INIT project.

#if 0
#define ShowInitIcon main
#endif

// ---------------------------------------------------------------------------------------------------------------------
// The ShowINIT mechanism works by having each INIT read/write data from these globals.
// The MPW C compiler doesn't accept variables declared at an absolute address, so I use these macros instead.
// Only one macro is defined per variable; there is no need to define a Set and a Get accessor like in <LowMem.h>.

#define	LMVCoord			(* (short*) 0x92A)
#define	LMVCheckSum		(* (short*) 0x928)
#define	LMHCoord			(* (short*) 0x92C)
#define	LMHCheckSum		(* (short*) 0x92E)

// ---------------------------------------------------------------------------------------------------------------------
// Prototypes for the subroutines. The main routine comes first; this is necessary to make THINK C's "Custom Header" option work.

static unsigned short CheckSum (unsigned short x);
static void ComputeIconRect (Rect* iconRect, Rect* screenBounds);
static void AdvanceIconPosition (Rect* iconRect);
static void DrawBWIcon (short iconID, Rect *iconRect);

// ---------------------------------------------------------------------------------------------------------------------
// Main routine.

// vkoskiv 08.09.2023:
// This file is probably too new for our Sys6 environment, since Think C 5
// doesn't know about QDGlobals. Luckily they document it, so I'll just patch
// in a suitable struct.

// The offsets from A5 are negative, so we flip the order they appear in the doc
typedef struct {
	char privates[76]; // No idea what this is, spotted it elsewhere
	long randSeed;
	BitMap screenBits;
	Cursor arrow;
	Pattern dkGray;
	Pattern ltGray;
	Pattern gray;
	Pattern black;
	Pattern white;
	GrafPtr thePort;
} QDGlobals;

typedef struct {
	QDGlobals qd;      // Storage for the QuickDraw globals
	long qdGlobalsPtr; // A5 points to this place; it will contain a pointer to qd
} QDStorage;

pascal void ShowInitIcon (short iconFamilyID, Boolean advance)
{
	long oldA5; // Original value of register A5
	QDStorage qds; // Fake QD globals
	CGrafPort colorPort;
	GrafPort bwPort;
	Rect destRect;
	
	oldA5 = SetA5((long) &qds.qdGlobalsPtr); // Tell A5 to point to the end of the fake QD Globals
	InitGraf(&qds.qd.thePort); // Initialize the fake QD Globals

	ComputeIconRect(&destRect, &qds.qd.screenBits.bounds); // Compute where the icon should be drawn

	OpenPort(&bwPort);
	DrawBWIcon(iconFamilyID, &destRect);
	ClosePort(&bwPort);
	
	if (advance) AdvanceIconPosition (&destRect);
		
	SetA5(oldA5); // Restore A5 to its previous value
}

// ---------------------------------------------------------------------------------------------------------------------
// A checksum is used to make sure that the data in there was left by another ShowINIT-aware INIT.

static unsigned short CheckSum (unsigned short x)
{
	return ((x << 1) | (x >> 15)) ^ 0x1021;
}

// ---------------------------------------------------------------------------------------------------------------------
// ComputeIconRect computes where the icon should be displayed.

static void ComputeIconRect (Rect* iconRect, Rect* screenBounds)
{
	if (CheckSum(LMHCoord) != LMHCheckSum) // If we are first, we need to initialize the shared data.
		LMHCoord = 8;
	if (CheckSum(LMVCoord) != LMVCheckSum)
		LMVCoord = screenBounds->bottom - 40;
	
	if (LMHCoord + 34 > screenBounds->right) { // Check whether we must wrap
		iconRect->left = 8;
		iconRect->top = LMVCoord - 40;
	}
	else {
		iconRect->left = LMHCoord;
		iconRect->top = LMVCoord;
	}
	iconRect->right = iconRect->left + 32;
	iconRect->bottom = iconRect->top + 32;
}

// AdvanceIconPosition updates the shared global variables so that the next extension will draw its icon beside ours.

static void AdvanceIconPosition (Rect* iconRect)
{
	LMHCoord = iconRect->left + 40; // Update the shared data
	LMVCoord = iconRect->top;
	LMHCheckSum = CheckSum(LMHCoord);
	LMVCheckSum = CheckSum(LMVCoord);
}

// DrawBWIcon draws the 'ICN#' member of the icon family. It works under System 6.

static void DrawBWIcon (short iconID, Rect *iconRect)
{
	Handle		icon;
	BitMap		source, destination;
	GrafPtr		port;
	
	icon = Get1Resource('ICN#', iconID);
	if (icon != NULL) {
		HLock(icon);
		// Prepare the source and destination bitmaps.
		source.baseAddr = *icon + 128; // Mask address.
		source.rowBytes = 4;
		SetRect(&source.bounds, 0, 0, 32, 32);
		GetPort(&port);
		destination = port->portBits;
		// Transfer the mask.
		CopyBits(&source, &destination, &source.bounds, iconRect, srcBic, nil);
		// Then the icon.
		source.baseAddr = *icon;
		CopyBits(&source, &destination, &source.bounds, iconRect, srcOr, nil);
		//HUnlock(icon);
	}
}