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/*******************************************************************************
 * Copyright (c) 2000, 2016 IBM Corporation and others.
 *
 * This program and the accompanying materials
 * are made available under the terms of the Eclipse Public License 2.0
 * which accompanies this distribution, and is available at
 * https://www.eclipse.org/legal/epl-2.0/
 *
 * SPDX-License-Identifier: EPL-2.0
 *
 * Contributors:
 *     IBM Corporation - initial API and implementation
 *******************************************************************************/
package org.eclipse.swt.widgets;


import org.eclipse.swt.*;
import org.eclipse.swt.events.*;
import org.eclipse.swt.graphics.*;
import org.eclipse.swt.internal.gtk.*;
import org.eclipse.swt.internal.gtk3.*;
import org.eclipse.swt.internal.gtk4.*;

/**
 * Instances of this class are selectable user interface
 * objects that represent a range of positive, numeric values.
 * 
 * At any given moment, a given slider will have a
 * single 'selection' that is considered to be its
 * value, which is constrained to be within the range of
 * values the slider represents (that is, between its
 * minimum and maximum values).
 * 

 * Typically, sliders will be made up of five areas:
 * 
 * 
 * an arrow button for decrementing the value
 * a page decrement area for decrementing the value by a larger amount
 * a thumb for modifying the value by mouse dragging
 * a page increment area for incrementing the value by a larger amount
 * an arrow button for incrementing the value
 * 
 * 
 * Based on their style, sliders are either HORIZONTAL
 * (which have a left facing button for decrementing the value and a
 * right facing button for incrementing it) or VERTICAL
 * (which have an upward facing button for decrementing the value
 * and a downward facing buttons for incrementing it).
 * 

 * On some platforms, the size of the slider's thumb can be
 * varied relative to the magnitude of the range of values it
 * represents (that is, relative to the difference between its
 * maximum and minimum values). Typically, this is used to
 * indicate some proportional value such as the ratio of the
 * visible area of a document to the total amount of space that
 * it would take to display it. SWT supports setting the thumb
 * size even if the underlying platform does not, but in this
 * case the appearance of the slider will not change.
 * 
 * 
 * Styles:
 * HORIZONTAL, VERTICAL
 * Events:
 * Selection
 * 
 * 
 * Note: Only one of the styles HORIZONTAL and VERTICAL may be specified.
 * 

 * IMPORTANT: This class is not intended to be subclassed.
 * 
 *
 * @see ScrollBar
 * @see Slider snippets
 * @see SWT Example: ControlExample
 * @see Sample code and further information
 * @noextend This class is not intended to be subclassed by clients.
 */
public class Slider extends Control {

	/**
	 * Stores the GtkRange handle of the GtkScrollbar.
	 * Used to hook events and access the GtkAdjustment.
	 */
	long rangeHandle;
	int scrollType;
	boolean dragSent;
/**
 * Constructs a new instance of this class given its parent
 * and a style value describing its behavior and appearance.
 * 
 * The style value is either one of the style constants defined in
 * class SWT which is applicable to instances of this
 * class, or must be built by bitwise OR'ing together
 * (that is, using the int "|" operator) two or more
 * of those SWT style constants. The class description
 * lists the style constants that are applicable to the class.
 * Style bits are also inherited from superclasses.
 * 
 *
 * @param parent a composite control which will be the parent of the new instance (cannot be null)
 * @param style the style of control to construct
 *
 * @exception IllegalArgumentException 
 *    ERROR_NULL_ARGUMENT - if the parent is null
 * 
 * @exception SWTException 
 *    ERROR_THREAD_INVALID_ACCESS - if not called from the thread that created the parent
 *    ERROR_INVALID_SUBCLASS - if this class is not an allowed subclass
 * 
 *
 * @see SWT#HORIZONTAL
 * @see SWT#VERTICAL
 * @see Widget#checkSubclass
 * @see Widget#getStyle
 */
public Slider (Composite parent, int style) {
	super (parent, checkStyle (style));
}

/**
 * Adds the listener to the collection of listeners who will
 * be notified when the user changes the receiver's value, by sending
 * it one of the messages defined in the SelectionListener
 * interface.
 * 
 * When widgetSelected is called, the event object detail field contains one of the following values:
 * SWT.NONE - for the end of a drag.
 * SWT.DRAG.
 * SWT.HOME.
 * SWT.END.
 * SWT.ARROW_DOWN.
 * SWT.ARROW_UP.
 * SWT.PAGE_DOWN.
 * SWT.PAGE_UP.
 * widgetDefaultSelected is not called.
 * 
 *
 * @param listener the listener which should be notified when the user changes the receiver's value
 *
 * @exception IllegalArgumentException 
 *    ERROR_NULL_ARGUMENT - if the listener is null
 * 
 * @exception SWTException 
 *    ERROR_WIDGET_DISPOSED - if the receiver has been disposed
 *    ERROR_THREAD_INVALID_ACCESS - if not called from the thread that created the receiver
 * 
 *
 * @see SelectionListener
 * @see #removeSelectionListener
 * @see SelectionEvent
 */
public void addSelectionListener (SelectionListener listener) {
	addTypedListener(listener, SWT.Selection, SWT.DefaultSelection);
}

static int checkStyle (int style) {
	return checkBits (style, SWT.HORIZONTAL, SWT.VERTICAL, 0, 0, 0, 0);
}

@Override
void createHandle (int index) {
	state |= HANDLE;
	fixedHandle = OS.g_object_new(display.gtk_fixed_get_type(), 0);
	if (fixedHandle == 0) error(SWT.ERROR_NO_HANDLES);

	// Initialize GtkScrollbar with default GtkAdjustment values
	long adjustmentHandle = GTK.gtk_adjustment_new(0, 0, 100, 1, 10, 10);
	if (adjustmentHandle == 0) error(SWT.ERROR_NO_HANDLES);
	if ((style & SWT.HORIZONTAL) != 0) {
		handle = GTK.gtk_scrollbar_new(GTK.GTK_ORIENTATION_HORIZONTAL, adjustmentHandle);
	} else {
		handle = GTK.gtk_scrollbar_new(GTK.GTK_ORIENTATION_VERTICAL, adjustmentHandle);
	}
	if (handle == 0) error(SWT.ERROR_NO_HANDLES);

	/*
	 * On GTK4, the GtkRange widget is a child of the GtkScrollbar
	 * On GTK3, GtkRange is the base class for GtkScrollbar
	 */
	rangeHandle = GTK.GTK4 ? GTK4.gtk_widget_get_first_child(handle) : handle;

	if (GTK.GTK4) {
		OS.swt_fixed_add(fixedHandle, handle);
	} else {
		GTK3.gtk_widget_set_has_window(fixedHandle, true);
		GTK3.gtk_container_add(fixedHandle, handle);
	}
}

@Override
long gtk_button_press_event(long widget, long eventPtr) {
	long result = super.gtk_button_press_event (widget, eventPtr);
	if (result != 0) return result;
	scrollType = GTK.GTK_SCROLL_NONE;
	dragSent = false;
	return result;
}

@Override
boolean gtk_change_value(long widget, int scroll, double value, long user_data) {
	scrollType = scroll;
	return false;
}

@Override
long gtk_value_changed(long range) {
	Event event = new Event ();
	dragSent = scrollType == GTK.GTK_SCROLL_JUMP;
	switch (scrollType) {
		case GTK.GTK_SCROLL_NONE:			event.detail = SWT.NONE; break;
		case GTK.GTK_SCROLL_JUMP:			event.detail = SWT.DRAG; break;
		case GTK.GTK_SCROLL_START:			event.detail = SWT.HOME; break;
		case GTK.GTK_SCROLL_END:				event.detail = SWT.END; break;
		case GTK.GTK_SCROLL_PAGE_DOWN:
		case GTK.GTK_SCROLL_PAGE_RIGHT:
		case GTK.GTK_SCROLL_PAGE_FORWARD:	event.detail = SWT.PAGE_DOWN; break;
		case GTK.GTK_SCROLL_PAGE_UP:
		case GTK.GTK_SCROLL_PAGE_LEFT:
		case GTK.GTK_SCROLL_PAGE_BACKWARD:	event.detail = SWT.PAGE_UP; break;
		case GTK.GTK_SCROLL_STEP_DOWN:
		case GTK.GTK_SCROLL_STEP_RIGHT:
		case GTK.GTK_SCROLL_STEP_FORWARD:	event.detail = SWT.ARROW_DOWN; break;
		case GTK.GTK_SCROLL_STEP_UP:
		case GTK.GTK_SCROLL_STEP_LEFT:
		case GTK.GTK_SCROLL_STEP_BACKWARD:	event.detail = SWT.ARROW_UP; break;
	}
	if (!dragSent) scrollType = GTK.GTK_SCROLL_NONE;
	sendSelectionEvent (SWT.Selection, event, false);
	return 0;
}

@Override
long gtk_event_after (long widget, long gdkEvent) {
	int eventType = GDK.gdk_event_get_event_type(gdkEvent);
	eventType = Control.fixGdkEventTypeValues(eventType);
	switch (eventType) {
		case GDK.GDK_BUTTON_RELEASE: {
			int [] eventButton = new int [1];
			if (GTK.GTK4) {
				eventButton[0] = GDK.gdk_button_event_get_button(gdkEvent);
			} else {
				GDK.gdk_event_get_button(gdkEvent, eventButton);
			}

			if (eventButton[0] == 1 && scrollType == SWT.DRAG) {
				if (!dragSent) {
					Event event = new Event ();
					event.detail = SWT.DRAG;
					sendSelectionEvent (SWT.Selection, event, false);
				}
				sendSelectionEvent (SWT.Selection);
			}
			scrollType = GTK.GTK_SCROLL_NONE;
			dragSent = false;
			break;
		}
	}
	return super.gtk_event_after (widget, gdkEvent);
}

@Override
void hookEvents() {
	super.hookEvents();

	OS.g_signal_connect_closure(rangeHandle, OS.change_value, display.getClosure(CHANGE_VALUE), false);
	OS.g_signal_connect_closure(rangeHandle, OS.value_changed, display.getClosure(VALUE_CHANGED), false);
}

@Override
void register() {
	super.register();

	if (GTK.GTK4) {
		display.addWidget(rangeHandle, this);
	} else {
		long hAdjustment = GTK.gtk_range_get_adjustment(handle);
		display.addWidget(hAdjustment, this);
	}
}

@Override
void deregister() {
	super.deregister();

	if (GTK.GTK4) {
		display.removeWidget(rangeHandle);
	} else {
		long hAdjustment = GTK.gtk_range_get_adjustment(handle);
		display.removeWidget(hAdjustment);
	}
}

@Override
Point computeSizeInPixels (int wHint, int hHint, boolean changed) {
	checkWidget();
	GTK.gtk_widget_realize(handle);
	if (wHint != SWT.DEFAULT && wHint < 0) wHint = 0;
	if (hHint != SWT.DEFAULT && hHint < 0) hHint = 0;
	Point size = computeNativeSize(handle, wHint, hHint, changed);
	if ((style & SWT.HORIZONTAL) != 0) {
		if (wHint == SWT.DEFAULT) size.x = 2 * size.x;
	} else {
		if (hHint == SWT.DEFAULT) size.y = 2 * size.y;
	}
	return size;
}

/**
 * Returns the amount that the receiver's value will be
 * modified by when the up/down (or right/left) arrows
 * are pressed.
 *
 * @return the increment
 *
 * @exception SWTException 
 *    ERROR_WIDGET_DISPOSED - if the receiver has been disposed
 *    ERROR_THREAD_INVALID_ACCESS - if not called from the thread that created the receiver
 * 
 */
public int getIncrement() {
	checkWidget();
	long adjustmentHandle = GTK.gtk_range_get_adjustment(rangeHandle);
	return (int) GTK.gtk_adjustment_get_step_increment(adjustmentHandle);
}

/**
 * Returns the maximum value which the receiver will allow.
 *
 * @return the maximum
 *
 * @exception SWTException 
 *    ERROR_WIDGET_DISPOSED - if the receiver has been disposed
 *    ERROR_THREAD_INVALID_ACCESS - if not called from the thread that created the receiver
 * 
 */
public int getMaximum() {
	checkWidget();
	long adjustmentHandle = GTK.gtk_range_get_adjustment(rangeHandle);
	return (int) GTK.gtk_adjustment_get_upper(adjustmentHandle);
}

/**
 * Returns the minimum value which the receiver will allow.
 *
 * @return the minimum
 *
 * @exception SWTException 
 *    ERROR_WIDGET_DISPOSED - if the receiver has been disposed
 *    ERROR_THREAD_INVALID_ACCESS - if not called from the thread that created the receiver
 * 
 */
public int getMinimum() {
	checkWidget();
	long adjustmentHandle = GTK.gtk_range_get_adjustment(rangeHandle);
	return (int) GTK.gtk_adjustment_get_lower(adjustmentHandle);
}

/**
 * Returns the amount that the receiver's value will be
 * modified by when the page increment/decrement areas
 * are selected.
 *
 * @return the page increment
 *
 * @exception SWTException 
 *    ERROR_WIDGET_DISPOSED - if the receiver has been disposed
 *    ERROR_THREAD_INVALID_ACCESS - if not called from the thread that created the receiver
 * 
 */
public int getPageIncrement() {
	checkWidget();
	long adjustmentHandle = GTK.gtk_range_get_adjustment(rangeHandle);
	return (int) GTK.gtk_adjustment_get_page_increment(adjustmentHandle);
}

/**
 * Returns the 'selection', which is the receiver's value.
 *
 * @return the selection
 *
 * @exception SWTException 
 *    ERROR_WIDGET_DISPOSED - if the receiver has been disposed
 *    ERROR_THREAD_INVALID_ACCESS - if not called from the thread that created the receiver
 * 
 */
public int getSelection() {
	checkWidget();
	return (int) GTK.gtk_range_get_value(rangeHandle);
}

/**
 * Returns the receiver's thumb value.
 *
 * @return the thumb value
 *
 * @exception SWTException 
 *    ERROR_WIDGET_DISPOSED - if the receiver has been disposed
 *    ERROR_THREAD_INVALID_ACCESS - if not called from the thread that created the receiver
 * 
 */
public int getThumb() {
	checkWidget();
	long adjustmentHandle = GTK.gtk_range_get_adjustment(rangeHandle);
	return (int) GTK.gtk_adjustment_get_page_size(adjustmentHandle);
}

/**
 * Removes the listener from the collection of listeners who will
 * be notified when the user changes the receiver's value.
 *
 * @param listener the listener which should no longer be notified
 *
 * @exception IllegalArgumentException 
 *    ERROR_NULL_ARGUMENT - if the listener is null
 * 
 * @exception SWTException 
 *    ERROR_WIDGET_DISPOSED - if the receiver has been disposed
 *    ERROR_THREAD_INVALID_ACCESS - if not called from the thread that created the receiver
 * 
 *
 * @see SelectionListener
 * @see #addSelectionListener
 */
public void removeSelectionListener (SelectionListener listener) {
	checkWidget();
	if (listener == null) error (SWT.ERROR_NULL_ARGUMENT);
	if (eventTable == null) return;
	eventTable.unhook (SWT.Selection, listener);
	eventTable.unhook (SWT.DefaultSelection,listener);
}

/**
 * Sets the amount that the receiver's value will be
 * modified by when the up/down (or right/left) arrows
 * are pressed to the argument, which must be at least
 * one.
 *
 * @param value the new increment (must be greater than zero)
 *
 * @exception SWTException 
 *    ERROR_WIDGET_DISPOSED - if the receiver has been disposed
 *    ERROR_THREAD_INVALID_ACCESS - if not called from the thread that created the receiver
 * 
 */
public void setIncrement(int value) {
	checkWidget();
	if (value < 1) return;

	OS.g_signal_handlers_block_matched(handle, OS.G_SIGNAL_MATCH_DATA, 0, 0, 0, 0, VALUE_CHANGED);
	GTK.gtk_range_set_increments(rangeHandle, value, getPageIncrement());
	OS.g_signal_handlers_unblock_matched(handle, OS.G_SIGNAL_MATCH_DATA, 0, 0, 0, 0, VALUE_CHANGED);
}

/**
 * Sets the maximum. If this value is negative or less than or
 * equal to the minimum, the value is ignored. If necessary, first
 * the thumb and then the selection are adjusted to fit within the
 * new range.
 *
 * @param value the new maximum, which must be greater than the current minimum
 *
 * @exception SWTException 
 *    ERROR_WIDGET_DISPOSED - if the receiver has been disposed
 *    ERROR_THREAD_INVALID_ACCESS - if not called from the thread that created the receiver
 * 
 */
public void setMaximum(int value) {
	checkWidget();
	long adjustmentHandle = GTK.gtk_range_get_adjustment(rangeHandle);
	GtkAdjustment adjustment = new GtkAdjustment();
	gtk_adjustment_get(adjustmentHandle, adjustment);

	int minimum = (int) adjustment.lower;
	if (value <= minimum) return;
	adjustment.upper = value;
	adjustment.page_size = Math.min((int)adjustment.page_size, value - minimum);
	adjustment.value = Math.min((int)adjustment.value, (int)(value - adjustment.page_size));

	OS.g_signal_handlers_block_matched(handle, OS.G_SIGNAL_MATCH_DATA, 0, 0, 0, 0, VALUE_CHANGED);
	GTK.gtk_adjustment_configure(adjustmentHandle, adjustment.value, adjustment.lower, adjustment.upper,
		adjustment.step_increment, adjustment.page_increment, adjustment.page_size);
	OS.g_signal_handlers_unblock_matched(handle, OS.G_SIGNAL_MATCH_DATA, 0, 0, 0, 0, VALUE_CHANGED);
}

/**
 * Sets the minimum value. If this value is negative or greater
 * than or equal to the maximum, the value is ignored. If necessary,
 * first the thumb and then the selection are adjusted to fit within
 * the new range.
 *
 * @param value the new minimum
 *
 * @exception SWTException 
 *    ERROR_WIDGET_DISPOSED - if the receiver has been disposed
 *    ERROR_THREAD_INVALID_ACCESS - if not called from the thread that created the receiver
 * 
 */
public void setMinimum(int value) {
	checkWidget();
	if (value < 0) return;
	long adjustmentHandle = GTK.gtk_range_get_adjustment(rangeHandle);
	GtkAdjustment adjustment = new GtkAdjustment();
	gtk_adjustment_get(adjustmentHandle, adjustment);

	int maximum = (int) adjustment.upper;
	if (value >= maximum) return;
	adjustment.lower = value;
	adjustment.page_size = Math.min ((int)adjustment.page_size, maximum - value);
	adjustment.value = Math.max ((int)adjustment.value, value);

	OS.g_signal_handlers_block_matched (handle, OS.G_SIGNAL_MATCH_DATA, 0, 0, 0, 0, VALUE_CHANGED);
	GTK.gtk_adjustment_configure(adjustmentHandle, adjustment.value, adjustment.lower, adjustment.upper,
		adjustment.step_increment, adjustment.page_increment, adjustment.page_size);
	OS.g_signal_handlers_unblock_matched (handle, OS.G_SIGNAL_MATCH_DATA, 0, 0, 0, 0, VALUE_CHANGED);
}

@Override
void setOrientation(boolean create) {
	super.setOrientation(create);

	if ((style & SWT.RIGHT_TO_LEFT) != 0 || !create) {
		if ((style & SWT.HORIZONTAL) != 0) {
			GTK.gtk_range_set_inverted(rangeHandle, (style & SWT.RIGHT_TO_LEFT) != 0);
		}
	}
}

/**
 * Sets the amount that the receiver's value will be
 * modified by when the page increment/decrement areas
 * are selected to the argument, which must be at least
 * one.
 *
 * @param value the page increment (must be greater than zero)
 *
 * @exception SWTException 
 *    ERROR_WIDGET_DISPOSED - if the receiver has been disposed
 *    ERROR_THREAD_INVALID_ACCESS - if not called from the thread that created the receiver
 * 
 */
public void setPageIncrement(int value) {
	checkWidget();
	if (value < 1) return;

	OS.g_signal_handlers_block_matched (handle, OS.G_SIGNAL_MATCH_DATA, 0, 0, 0, 0, VALUE_CHANGED);
	GTK.gtk_range_set_increments(rangeHandle, getIncrement(), value);
	OS.g_signal_handlers_unblock_matched (handle, OS.G_SIGNAL_MATCH_DATA, 0, 0, 0, 0, VALUE_CHANGED);
}

/**
 * Sets the 'selection', which is the receiver's
 * value, to the argument which must be greater than or equal
 * to zero.
 *
 * @param value the new selection (must be zero or greater)
 *
 * @exception SWTException 
 *    ERROR_WIDGET_DISPOSED - if the receiver has been disposed
 *    ERROR_THREAD_INVALID_ACCESS - if not called from the thread that created the receiver
 * 
 */
public void setSelection(int value) {
	checkWidget();

	OS.g_signal_handlers_block_matched (handle, OS.G_SIGNAL_MATCH_DATA, 0, 0, 0, 0, VALUE_CHANGED);
	GTK.gtk_range_set_value(rangeHandle, value);
	OS.g_signal_handlers_unblock_matched (handle, OS.G_SIGNAL_MATCH_DATA, 0, 0, 0, 0, VALUE_CHANGED);
}

/**
 * Sets the thumb value. The thumb value should be used to represent
 * the size of the visual portion of the current range. This value is
 * usually the same as the page increment value.
 * 
 * This new value will be ignored if it is less than one, and will be
 * clamped if it exceeds the receiver's current range.
 * 
 *
 * @param value the new thumb value, which must be at least one and not
 * larger than the size of the current range
 *
 * @exception SWTException 
 *    ERROR_WIDGET_DISPOSED - if the receiver has been disposed
 *    ERROR_THREAD_INVALID_ACCESS - if not called from the thread that created the receiver
 * 
 */
public void setThumb(int value) {
	checkWidget();
	if (value < 1) return;

	long adjustmentHandle = GTK.gtk_range_get_adjustment(rangeHandle);
	GtkAdjustment adjustment = new GtkAdjustment();
	gtk_adjustment_get(adjustmentHandle, adjustment);

	value = (int) Math.min(value, (int) (adjustment.upper - adjustment.lower));
	adjustment.page_size = (double) value;
	adjustment.value = Math.min ((int)adjustment.value, (int)(adjustment.upper - value));
	OS.g_signal_handlers_block_matched(handle, OS.G_SIGNAL_MATCH_DATA, 0, 0, 0, 0, VALUE_CHANGED);
	GTK.gtk_adjustment_configure(adjustmentHandle, adjustment.value, adjustment.lower, adjustment.upper,
		adjustment.step_increment, adjustment.page_increment, adjustment.page_size);
	OS.g_signal_handlers_unblock_matched(handle, OS.G_SIGNAL_MATCH_DATA, 0, 0, 0, 0, VALUE_CHANGED);
}

/**
 * Sets the receiver's selection, minimum value, maximum
 * value, thumb, increment and page increment all at once.
 * 
 * Note: This is similar to setting the values individually
 * using the appropriate methods, but may be implemented in a
 * more efficient fashion on some platforms.
 * 
 *
 * @param selection the new selection value
 * @param minimum the new minimum value
 * @param maximum the new maximum value
 * @param thumb the new thumb value
 * @param increment the new increment value
 * @param pageIncrement the new pageIncrement value
 *
 * @exception SWTException 
 *    ERROR_WIDGET_DISPOSED - if the receiver has been disposed
 *    ERROR_THREAD_INVALID_ACCESS - if not called from the thread that created the receiver
 * 
 */
public void setValues (int selection, int minimum, int maximum, int thumb, int increment, int pageIncrement) {
	checkWidget();
	if (minimum < 0 || maximum < 0 || thumb < 1 || increment < 1 || pageIncrement < 1) return;
	thumb = Math.min(thumb, maximum - minimum);

	long adjustmentHandle = GTK.gtk_range_get_adjustment(rangeHandle);
	GtkAdjustment adjustment = new GtkAdjustment();
	adjustment.value = Math.min(Math.max(selection, minimum), maximum - thumb);
	adjustment.lower = (double) minimum;
	adjustment.upper = (double) maximum;
	adjustment.page_size = (double) thumb;
	adjustment.step_increment = (double) increment;
	adjustment.page_increment = (double) pageIncrement;

	OS.g_signal_handlers_block_matched (handle, OS.G_SIGNAL_MATCH_DATA, 0, 0, 0, 0, VALUE_CHANGED);
	GTK.gtk_adjustment_configure(adjustmentHandle, adjustment.value, adjustment.lower, adjustment.upper,
		adjustment.step_increment, adjustment.page_increment, adjustment.page_size);
	OS.g_signal_handlers_unblock_matched (handle, OS.G_SIGNAL_MATCH_DATA, 0, 0, 0, 0, VALUE_CHANGED);
}

}