src/jexer/TVScroller.java

   1 /*
   2  * Jexer - Java Text User Interface
   3  *
   4  * License: LGPLv3 or later
   5  *
   6  * This module is licensed under the GNU Lesser General Public License
   7  * Version 3.  Please see the file "COPYING" in this directory for more
   8  * information about the GNU Lesser General Public License Version 3.
   9  *
  10  *     Copyright (C) 2015  Kevin Lamonte
  11  *
  12  * This program is free software; you can redistribute it and/or
  13  * modify it under the terms of the GNU Lesser General Public License
  14  * as published by the Free Software Foundation; either version 3 of
  15  * the License, or (at your option) any later version.
  16  *
  17  * This program is distributed in the hope that it will be useful, but
  18  * WITHOUT ANY WARRANTY; without even the implied warranty of
  19  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  20  * General Public License for more details.
  21  *
  22  * You should have received a copy of the GNU Lesser General Public
  23  * License along with this program; if not, see
  24  * http://www.gnu.org/licenses/, or write to the Free Software
  25  * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA
  26  * 02110-1301 USA
  27  *
  28  * @author Kevin Lamonte [kevin.lamonte@gmail.com]
  29  * @version 1
  30  */
  31 package jexer;
  32
  33 import jexer.bits.CellAttributes;
  34 import jexer.bits.GraphicsChars;
  35 import jexer.event.TMouseEvent;
  36
  37 /**
  38  * TVScroller implements a simple vertical scroll bar.
  39  */
  40 public final class TVScroller extends TWidget {
  41
  42     /**
  43      * Value that corresponds to being on the top edge of the scroll bar.
  44      */
  45     private int topValue = 0;
  46
  47     /**
  48      * Get the value that corresponds to being on the top edge of the scroll
  49      * bar.
  50      *
  51      * @return the scroll value
  52      */
  53     public int getTopValue() {
  54         return topValue;
  55     }
  56
  57     /**
  58      * Set the value that corresponds to being on the top edge of the scroll
  59      * bar.
  60      *
  61      * @param topValue the new scroll value
  62      */
  63     public void setTopValue(final int topValue) {
  64         this.topValue = topValue;
  65     }
  66
  67     /**
  68      * Value that corresponds to being on the bottom edge of the scroll bar.
  69      */
  70     private int bottomValue = 100;
  71
  72     /**
  73      * Get the value that corresponds to being on the bottom edge of the
  74      * scroll bar.
  75      *
  76      * @return the scroll value
  77      */
  78     public int getBottomValue() {
  79         return bottomValue;
  80     }
  81
  82     /**
  83      * Set the value that corresponds to being on the bottom edge of the
  84      * scroll bar.
  85      *
  86      * @param bottomValue the new scroll value
  87      */
  88     public void setBottomValue(final int bottomValue) {
  89         this.bottomValue = bottomValue;
  90     }
  91
  92     /**
  93      * Current value of the scroll.
  94      */
  95     private int value = 0;
  96
  97     /**
  98      * Get current value of the scroll.
  99      *
 100      * @return the scroll value
 101      */
 102     public int getValue() {
 103         return value;
 104     }
 105
 106     /**
 107      * Set current value of the scroll.
 108      *
 109      * @param value the new scroll value
 110      */
 111     public void setValue(final int value) {
 112         this.value = value;
 113     }
 114
 115     /**
 116      * The increment for clicking on an arrow.
 117      */
 118     private int smallChange = 1;
 119
 120     /**
 121      * Set the increment for clicking on an arrow.
 122      *
 123      * @param smallChange the new increment value
 124      */
 125     public void setSmallChange(final int smallChange) {
 126         this.smallChange = smallChange;
 127     }
 128
 129     /**
 130      * The increment for clicking in the bar between the box and an arrow.
 131      */
 132     private int bigChange = 20;
 133
 134     /**
 135      * Set the increment for clicking in the bar between the box and an
 136      * arrow.
 137      *
 138      * @param bigChange the new increment value
 139      */
 140     public void setBigChange(final int bigChange) {
 141         this.bigChange = bigChange;
 142     }
 143
 144     /**
 145      * When true, the user is dragging the scroll box.
 146      */
 147     private boolean inScroll = false;
 148
 149     /**
 150      * Public constructor.
 151      *
 152      * @param parent parent widget
 153      * @param x column relative to parent
 154      * @param y row relative to parent
 155      * @param height height of scroll bar
 156      */
 157     public TVScroller(final TWidget parent, final int x, final int y,
 158         final int height) {
 159
 160         // Set parent and window
 161         super(parent, x, y, 1, height);
 162     }
 163
 164     /**
 165      * Compute the position of the scroll box (a.k.a. grip, thumb).
 166      *
 167      * @return Y position of the box, between 1 and height - 2
 168      */
 169     private int boxPosition() {
 170         return (getHeight() - 3) * (value - topValue) / (bottomValue - topValue) + 1;
 171     }
 172
 173     /**
 174      * Draw a vertical scroll bar.
 175      */
 176     @Override
 177     public void draw() {
 178         CellAttributes arrowColor = getTheme().getColor("tscroller.arrows");
 179         CellAttributes barColor = getTheme().getColor("tscroller.bar");
 180         getScreen().putCharXY(0, 0, GraphicsChars.CP437[0x1E], arrowColor);
 181         getScreen().putCharXY(0, getHeight() - 1, GraphicsChars.CP437[0x1F],
 182             arrowColor);
 183
 184         // Place the box
 185         if (bottomValue > topValue) {
 186             getScreen().vLineXY(0, 1, getHeight() - 2,
 187                 GraphicsChars.CP437[0xB1], barColor);
 188             getScreen().putCharXY(0, boxPosition(), GraphicsChars.BOX,
 189                 arrowColor);
 190         } else {
 191             getScreen().vLineXY(0, 1, getHeight() - 2, GraphicsChars.HATCH,
 192                 barColor);
 193         }
 194
 195     }
 196
 197     /**
 198      * Perform a small step change up.
 199      */
 200     public void decrement() {
 201         if (bottomValue == topValue) {
 202             return;
 203         }
 204         value -= smallChange;
 205         if (value < topValue) {
 206             value = topValue;
 207         }
 208     }
 209
 210     /**
 211      * Perform a small step change down.
 212      */
 213     public void increment() {
 214         if (bottomValue == topValue) {
 215             return;
 216         }
 217         value += smallChange;
 218         if (value > bottomValue) {
 219             value = bottomValue;
 220         }
 221     }
 222
 223     /**
 224      * Perform a big step change up.
 225      */
 226     public void bigDecrement() {
 227         if (bottomValue == topValue) {
 228             return;
 229         }
 230         value -= bigChange;
 231         if (value < topValue) {
 232             value = topValue;
 233         }
 234     }
 235
 236     /**
 237      * Perform a big step change down.
 238      */
 239     public void bigIncrement() {
 240         if (bottomValue == topValue) {
 241             return;
 242         }
 243         value += bigChange;
 244         if (value > bottomValue) {
 245             value = bottomValue;
 246         }
 247     }
 248
 249     /**
 250      * Go to the top edge of the scroller.
 251      */
 252     public void toTop() {
 253         value = topValue;
 254     }
 255
 256     /**
 257      * Go to the bottom edge of the scroller.
 258      */
 259     public void toBottom() {
 260         value = bottomValue;
 261     }
 262
 263     /**
 264      * Handle mouse button releases.
 265      *
 266      * @param mouse mouse button release event
 267      */
 268     @Override
 269     public void onMouseUp(final TMouseEvent mouse) {
 270         if (bottomValue == topValue) {
 271             return;
 272         }
 273
 274         if (inScroll) {
 275             inScroll = false;
 276             return;
 277         }
 278
 279         if ((mouse.getX() == 0)
 280             && (mouse.getY() == 0)
 281         ) {
 282             // Clicked on the top arrow
 283             decrement();
 284             return;
 285         }
 286
 287         if ((mouse.getX() == 0)
 288             && (mouse.getY() == getHeight() - 1)
 289         ) {
 290             // Clicked on the bottom arrow
 291             increment();
 292             return;
 293         }
 294
 295         if ((mouse.getX() == 0)
 296             && (mouse.getY() > 0)
 297             && (mouse.getY() < boxPosition())
 298         ) {
 299             // Clicked between the top arrow and the box
 300             value -= bigChange;
 301             if (value < topValue) {
 302                 value = topValue;
 303             }
 304             return;
 305         }
 306
 307         if ((mouse.getX() == 0)
 308             && (mouse.getY() > boxPosition())
 309             && (mouse.getY() < getHeight() - 1)
 310         ) {
 311             // Clicked between the box and the bottom arrow
 312             value += bigChange;
 313             if (value > bottomValue) {
 314                 value = bottomValue;
 315             }
 316             return;
 317         }
 318     }
 319
 320     /**
 321      * Handle mouse movement events.
 322      *
 323      * @param mouse mouse motion event
 324      */
 325     @Override
 326     public void onMouseMotion(final TMouseEvent mouse) {
 327         if (bottomValue == topValue) {
 328             return;
 329         }
 330
 331         if ((mouse.isMouse1())
 332             && (inScroll)
 333             && (mouse.getY() > 0)
 334             && (mouse.getY() < getHeight() - 1)
 335         ) {
 336             // Recompute value based on new box position
 337             value = (bottomValue - topValue)
 338                 * (mouse.getY()) / (getHeight() - 3) + topValue;
 339             return;
 340         }
 341
 342         inScroll = false;
 343     }
 344
 345     /**
 346      * Handle mouse press events.
 347      *
 348      * @param mouse mouse button press event
 349      */
 350     @Override
 351     public void onMouseDown(final TMouseEvent mouse) {
 352         if (bottomValue == topValue) {
 353             return;
 354         }
 355
 356         if ((mouse.getX() == 0)
 357             && (mouse.getY() == boxPosition())
 358         ) {
 359             inScroll = true;
 360             return;
 361         }
 362     }
 363
 364 }