package org.eclipse.swt.widgets;

/*
 * (c) Copyright IBM Corp. 2000, 2001.
 * All Rights Reserved
 */

import org.eclipse.swt.internal.win32.*;
import org.eclipse.swt.*;
import org.eclipse.swt.graphics.*;
import org.eclipse.swt.internal.Compatibility;
import org.eclipse.swt.widgets.*;

/**
 * Instances of this class allow the user to select a font
 * from all available fonts in the system.
 * <p>
 * IMPORTANT: This class is intended to be subclassed <em>only</em>
 * within the SWT implementation.
 * </p>
 */
public class FontDialog extends Dialog {
	FontData fontData;
	
/**
 * Constructs a new instance of this class given only its
 * parent.
 * <p>
 * Note: Currently, null can be passed in for the parent.
 * This has the effect of creating the dialog on the currently active
 * display if there is one. If there is no current display, the 
 * dialog is created on a "default" display. <b>Passing in null as
 * the parent is not considered to be good coding style,
 * and may not be supported in a future release of SWT.</b>
 * </p>
 *
 * @param parent a shell which will be the parent of the new instance
 *
 * @exception IllegalArgumentException <ul>
 *    <li>ERROR_NULL_ARGUMENT - if the parent is null</li>
 * </ul>
 * @exception SWTException <ul>
 *    <li>ERROR_THREAD_INVALID_ACCESS - if not called from the thread that created the parent</li>
 *    <li>ERROR_INVALID_SUBCLASS - if this class is not an allowed subclass</li>
 * </ul>
 */
public FontDialog (Shell parent) {
	this (parent, SWT.PRIMARY_MODAL);
}

/**
 * Constructs a new instance of this class given its parent
 * and a style value describing its behavior and appearance.
 * <p>
 * The style value is either one of the style constants defined in
 * class <code>SWT</code> which is applicable to instances of this
 * class, or must be built by <em>bitwise OR</em>'ing together 
 * (that is, using the <code>int</code> "|" operator) two or more
 * of those <code>SWT</code> style constants. The class description
 * for all SWT dialog classes should include a comment which
 * describes the style constants which are applicable to the class.
 * </p>
 * Note: Currently, null can be passed in for the parent.
 * This has the effect of creating the dialog on the currently active
 * display if there is one. If there is no current display, the 
 * dialog is created on a "default" display. <b>Passing in null as
 * the parent is not considered to be good coding style,
 * and may not be supported in a future release of SWT.</b>
 * </p>
 *
 * @param parent a shell which will be the parent of the new instance
 *
 * @exception IllegalArgumentException <ul>
 *    <li>ERROR_NULL_ARGUMENT - if the parent is null</li>
 * </ul>
 * @exception SWTException <ul>
 *    <li>ERROR_THREAD_INVALID_ACCESS - if not called from the thread that created the parent</li>
 *    <li>ERROR_INVALID_SUBCLASS - if this class is not an allowed subclass</li>
 * </ul>
 */
public FontDialog (Shell parent, int style) {
	super (parent, style);
	checkSubclass ();
}

/**
 * Returns a FontData object describing the font that was
 * selected in the dialog, or null if none is available.
 * 
 * @return the FontData for the selected font, or null
 */
public FontData getFontData() {
	return fontData;
}

/**
 * Makes the dialog visible and brings it to the front
 * of the display.
 *
 * @return a FontData object describing the font that was selected,
 *         or null if the dialog was cancelled or an error occurred
 *
 * @exception SWTException <ul>
 *    <li>ERROR_WIDGET_DISPOSED - if the dialog has been disposed</li>
 *    <li>ERROR_THREAD_INVALID_ACCESS - if not called from the thread that created the dialog</li>
 * </ul>
 */
public FontData open () {
	if (OS.IsWinCE) SWT.error (SWT.ERROR_NOT_IMPLEMENTED);
	
	/* Get the owner HWND for the dialog */
	int hwndOwner = 0;
	if (parent != null) hwndOwner = parent.handle;

	/* Open the dialog */
	int hHeap = OS.GetProcessHeap ();
	CHOOSEFONT lpcf = new CHOOSEFONT ();
	lpcf.lStructSize = CHOOSEFONT.sizeof;
	lpcf.hwndOwner = hwndOwner;
	lpcf.Flags = OS.CF_SCREENFONTS | OS.CF_EFFECTS;
	int lpLogFont = OS.HeapAlloc (hHeap, OS.HEAP_ZERO_MEMORY, LOGFONT.sizeof);
	if (fontData != null && fontData.data != null) {
		lpcf.Flags |= OS.CF_INITTOLOGFONTSTRUCT;
		OS.MoveMemory (lpLogFont, fontData.data, LOGFONT.sizeof);
	}
	lpcf.lpLogFont = lpLogFont;
	fontData = null;
	if (OS.ChooseFont (lpcf)) {
		LOGFONT logFont = new LOGFONT ();
		OS.MoveMemory (logFont, lpLogFont, LOGFONT.sizeof);

		/*
		 * This will not work on multiple screens or
		 * for printing. Should use DC for the proper device.
		 */
		int hDC = OS.GetDC(0);
		int logPixelsY = OS.GetDeviceCaps(hDC, OS.LOGPIXELSY);
		int pixels = 0; 
		if (logFont.lfHeight > 0) {
			/*
			 * Feature in Windows. If the lfHeight of the LOGFONT structure
			 * is positive, the lfHeight measures the height of the entire
			 * cell, including internal leading, in logical units. Since the
			 * height of a font in points does not include the internal leading,
			 * we must subtract the internal leading, which requires a TEXTMETRIC,
			 * which in turn requires font creation.
			 */
			int hFont = OS.CreateFontIndirect(logFont);
			int oldFont = OS.SelectObject(hDC, hFont);
			TEXTMETRIC lptm = new TEXTMETRIC();
			OS.GetTextMetrics(hDC, lptm);
			OS.SelectObject(hDC, oldFont);
			OS.DeleteObject(hFont);
			pixels = logFont.lfHeight - lptm.tmInternalLeading;
		} else {
			pixels = -logFont.lfHeight;
		}
		OS.ReleaseDC(0, hDC);

		int points = Compatibility.round(pixels * 72, logPixelsY);
		fontData = FontData.win32_new (logFont, points);
	}
		
	/* Free the OS memory */
	if (lpLogFont != 0) OS.HeapFree (hHeap, 0, lpLogFont);

	/*
	* This code is intentionally commented.  On some
	* platforms, the owner window is repainted right
	* away when a dialog window exits.  This behavior
	* is currently unspecified.
	*/
//	if (hwndOwner != 0) OS.UpdateWindow (hwndOwner);
	
	return fontData;
}

/**
 * Sets a FontData object describing the font to be
 * selected by default in the dialog, or null to let
 * the platform choose one.
 * 
 * @param fontData the FontData to use initially, or null
 */
public void setFontData (FontData fontData) {
	this.fontData = fontData;
}

}