Implemented saving/loading from checkpoints.

- A checkpoint (track position) can be set in the options screen, and also while playing by pressing "CTRL+S".
- A checkpoint can be loaded by pressing "CTRL+L" while playing.  This will reset all game data and begin from the checkpoint time; the ranking screen will be skipped upon song completion.

Other changes:
- Don't draw grade if no objects have been processed (previously defaulted to GRADE_D).
- Calculate slider start/end angles based on a step difference (previously an arbitrary 0.01 difference).
- Always end a slider curve base on the last control point.

Signed-off-by: Jeffrey Han <itdelatrisu@gmail.com>

src/itdelatrisu/opsu/GameScore.java

@@ -550,11 +550,14 @@ public class GameScore {
 				drawSymbolString(String.format("%dx", combo), 10, height - 10 - symbolHeight, 1.0f, false);
 		} else {
 			// grade
-			Image grade = gradesSmall[getGrade()];
+			int grade = getGrade();
-			float gradeScale = symbolHeight * 0.75f / grade.getHeight();
+			if (grade != -1) {
-			gradesSmall[getGrade()].getScaledCopy(gradeScale).draw(
+				Image gradeImage = gradesSmall[grade];
-					circleX - grade.getWidth(), symbolHeight
+				float gradeScale = symbolHeight * 0.75f / gradeImage.getHeight();
-			);
+				gradeImage.getScaledCopy(gradeScale).draw(
+						circleX - gradeImage.getWidth(), symbolHeight
+				);
+			}
 		}
 	}
 
@@ -566,10 +569,13 @@ public class GameScore {
 	 */
 	public void drawRankingElements(Graphics g, int width, int height) {
 		// grade
-		Image grade = gradesLarge[getGrade()];
+		int grade = getGrade();
-		float gradeScale = (height * 0.5f) / grade.getHeight();
+		if (grade != -1) {
-		grade = grade.getScaledCopy(gradeScale);
+			Image gradeImage = gradesLarge[grade];
-		grade.draw(width - grade.getWidth(), height * 0.09f);
+			float gradeScale = (height * 0.5f) / gradeImage.getHeight();
+			gradeImage = gradeImage.getScaledCopy(gradeScale);
+			gradeImage.draw(width - gradeImage.getWidth(), height * 0.09f);
+		}
 
 		// header & "Ranking" text
 		Image rankingTitle = GameImage.RANKING_TITLE.getImage();
@@ -719,10 +725,11 @@ public class GameScore {
 
 	/**
 	 * Returns (current) letter grade.
+	 * If no objects have been processed, -1 will be returned.
 	 */
 	private int getGrade() {
 		if (objectCount < 1)  // avoid division by zero
-			return GRADE_D;
+			return -1;
 
 		// TODO: silvers
 		float percent = getScorePercent();

src/itdelatrisu/opsu/MusicController.java

@@ -227,8 +227,8 @@ public class MusicController {
 	}
 
 	/**
-	 * Returns the position in the current track.
+	 * Returns the position in the current track, in ms.
-	 * If no track is playing, 0f will be returned.
+	 * If no track is playing, 0 will be returned.
 	 */
 	public static int getPosition() {
 		if (isPlaying())

src/itdelatrisu/opsu/objects/Slider.java

@@ -160,22 +160,24 @@ public class Slider {
 
 			// calculate curve points for drawing
 			int N = (int) (1 / step);
-			this.curveX = new float[N];
+			this.curveX = new float[N + 1];
-			this.curveY = new float[N];
+			this.curveY = new float[N + 1];
 			float t = 0f;
 			for (int i = 0; i < N; i++, t += step) {
 				float[] c = pointAt(t);
 				curveX[i] = c[0];
 				curveY[i] = c[1];
 			}
+			curveX[N] = getX(order - 1);
+			curveY[N] = getY(order - 1);
 
 			// calculate angles (if needed)
 			if (hitObject.repeat > 1) {
 				float[] c1 = pointAt(0f);
-				float[] c2 = pointAt(0.01f);
+				float[] c2 = pointAt(step);
 				startAngle = (float) (Math.atan2(c2[1] - c1[1], c2[0] - c1[0]) * 180 / Math.PI);
 				c1 = pointAt(1f);
-				c2 = pointAt(0.99f);
+				c2 = pointAt(1f - step);
 				endAngle = (float) (Math.atan2(c2[1] - c1[1], c2[0] - c1[0]) * 180 / Math.PI);
 			}
 		}

src/itdelatrisu/opsu/states/Game.java

@@ -181,6 +181,11 @@ public class Game extends BasicGameState {
 	 */
 	private Image playfield;
 
+	/**
+	 * Whether a checkpoint has been loaded during this game.
+	 */
+	private boolean checkpointLoaded = false;
+
 	// game-related variables
 	private GameContainer container;
 	private StateBasedGame game;
@@ -233,6 +238,16 @@ public class Game extends BasicGameState {
 		if (pauseTime > -1)  // returning from pause screen
 			trackPosition = pauseTime;
 
+		// checkpoint
+		if (checkpointLoaded) {
+			String checkpointText = "~ Playing from checkpoint. ~";
+			Utils.FONT_MEDIUM.drawString(
+					(container.getWidth() - Utils.FONT_MEDIUM.getWidth(checkpointText)) / 2,
+					container.getHeight() - 15 - Utils.FONT_MEDIUM.getLineHeight(),
+					checkpointText, Color.white
+			);
+		}
+
 		// break periods
 		if (osu.breaks != null && breakIndex < osu.breaks.size()) {
 			if (breakTime > 0) {
@@ -430,7 +445,9 @@ public class Game extends BasicGameState {
 
 		// map complete!
 		if (objectIndex >= osu.objects.length) {
-			game.enterState(Opsu.STATE_GAMERANKING, new FadeOutTransition(Color.black), new FadeInTransition(Color.black));
+			// if checkpoint used, don't show the ranking screen
+			int state = (checkpointLoaded) ? Opsu.STATE_SONGMENU : Opsu.STATE_GAMERANKING;
+			game.enterState(state, new FadeOutTransition(Color.black), new FadeInTransition(Color.black));
 			return;
 		}
 
@@ -544,10 +561,11 @@ public class Game extends BasicGameState {
 			game.enterState(Opsu.STATE_GAMEPAUSEMENU, new EmptyTransition(), new FadeInTransition(Color.black));
 			break;
 		case Input.KEY_SPACE:
-			// skip
+			// skip intro
 			skipIntro();
 			break;
 		case Input.KEY_R:
+			// restart
 			if (input.isKeyDown(Input.KEY_RCONTROL) || input.isKeyDown(Input.KEY_LCONTROL)) {
 				try {
 					restart = RESTART_MANUAL;
@@ -558,6 +576,44 @@ public class Game extends BasicGameState {
 				}
 			}
 			break;
+		case Input.KEY_S:
+			// save checkpoint
+			if (input.isKeyDown(Input.KEY_RCONTROL) || input.isKeyDown(Input.KEY_LCONTROL)) {
+				if (isLeadIn())
+					break;
+
+				int position = (pauseTime > -1) ? pauseTime : MusicController.getPosition();
+				if (Options.setCheckpoint(position / 1000))
+					SoundController.playSound(SoundController.SOUND_MENUCLICK);
+			}
+			break;
+		case Input.KEY_L:
+			// load checkpoint
+			if (input.isKeyDown(Input.KEY_RCONTROL) || input.isKeyDown(Input.KEY_LCONTROL)) {
+				int checkpoint = Options.getCheckpoint();
+				if (checkpoint == 0 || checkpoint > MusicController.getTrackLength())
+					break;  // invalid checkpoint
+				try {
+					restart = RESTART_MANUAL;
+					enter(container, game);
+					checkpointLoaded = true;
+					if (isLeadIn()) {
+						leadInTime = 0;
+						MusicController.resume();
+					}
+					SoundController.playSound(SoundController.SOUND_MENUHIT);
+
+					// skip to checkpoint
+					MusicController.setPosition(checkpoint);
+					while (objectIndex < osu.objects.length &&
+							osu.objects[objectIndex++].time <= MusicController.getPosition())
+						;
+					objectIndex--;
+				} catch (SlickException e) {
+					Log.error("Failed to load checkpoint.", e);
+				}
+			}
+			break;
 		case Input.KEY_Z:
 			// left-click
 			if (!Keyboard.isRepeatEvent())
@@ -690,6 +746,7 @@ public class Game extends BasicGameState {
 			countdown1Sound = false;
 			countdown2Sound = false;
 			countdownGoSound = false;
+			checkpointLoaded = false;
 
 			// load the first timingPoint
 			if (!osu.timingPoints.isEmpty()) {

src/itdelatrisu/opsu/states/Options.java

@@ -32,6 +32,7 @@ import java.io.IOException;
 import java.io.OutputStreamWriter;
 import java.text.SimpleDateFormat;
 import java.util.Date;
+import java.util.concurrent.TimeUnit;
 
 import org.newdawn.slick.Color;
 import org.newdawn.slick.GameContainer;
@@ -140,7 +141,8 @@ public class Options extends BasicGameState {
 		FIXED_HP,
 		FIXED_AR,
 		FIXED_OD,
-		LOAD_VERBOSE;
+		LOAD_VERBOSE,
+		CHECKPOINT;
 	};
 
 	/**
@@ -216,7 +218,8 @@ public class Options extends BasicGameState {
 		GameOption.FIXED_CS,
 		GameOption.FIXED_HP,
 		GameOption.FIXED_AR,
-		GameOption.FIXED_OD
+		GameOption.FIXED_OD,
+		GameOption.CHECKPOINT
 	};
 
 	/**
@@ -353,6 +356,11 @@ public class Options extends BasicGameState {
 	 */
 	private static boolean loadVerbose = true;
 
+	/**
+	 * Track checkpoint time, in seconds.
+	 */
+	private static int checkpoint = 0;
+
 	/**
 	 * Game option coordinate modifiers (for drawing).
 	 */
@@ -651,6 +659,9 @@ public class Options extends BasicGameState {
 		case FIXED_OD:
 			fixedOD = getBoundedValue(fixedOD, diff / 10f, 0f, 10f);
 			break;
+		case CHECKPOINT:
+			checkpoint = getBoundedValue(checkpoint, diff * multiplier, 0, 3599);
+			break;
 		default:
 			break;
 		}
@@ -855,6 +866,14 @@ public class Options extends BasicGameState {
 					"Determines the time window for hit results."
 			);
 			break;
+		case CHECKPOINT:
+			drawOption(pos, "Track Checkpoint",
+					(checkpoint == 0) ? "Disabled" : String.format("%02d:%02d",
+							TimeUnit.SECONDS.toMinutes(checkpoint),
+						    checkpoint - TimeUnit.MINUTES.toSeconds(TimeUnit.SECONDS.toMinutes(checkpoint))),
+					"Press CTRL+L while playing to load a checkpoint, and CTRL+S to set one."
+			);
+			break;
 		default:
 			break;
 		}
@@ -1075,6 +1094,25 @@ public class Options extends BasicGameState {
 	 */
 	public static boolean isLoadVerbose() { return loadVerbose; }
 
+	/**
+	 * Returns the track checkpoint time.
+	 * @return the checkpoint time (in ms)
+	 */
+	public static int getCheckpoint() { return checkpoint * 1000; }
+
+	/**
+	 * Sets the track checkpoint time, if within bounds.
+	 * @param time the track position (in ms)
+	 * @return true if within bounds
+	 */
+	public static boolean setCheckpoint(int time) {
+		if (time >= 0 && time < 3600) {
+			checkpoint = time;
+			return true;
+		}
+		return false;
+	}
+
 	/**
 	 * Returns the beatmap directory.
 	 * If invalid, this will attempt to search for the directory,
@@ -1242,6 +1280,9 @@ public class Options extends BasicGameState {
 				case "FixedOD":
 					fixedOD = Float.parseFloat(value);
 					break;
+				case "Checkpoint":
+					setCheckpoint(Integer.parseInt(value));
+					break;
 				}
 			}
 		} catch (IOException e) {
@@ -1321,6 +1362,8 @@ public class Options extends BasicGameState {
 			writer.newLine();
 			writer.write(String.format("FixedOD = %.1f", fixedOD));
 			writer.newLine();
+			writer.write(String.format("Checkpoint = %d", checkpoint));
+			writer.newLine();
 			writer.close();
 		} catch (IOException e) {
 			Log.error(String.format("Failed to write to file '%s'.", OPTIONS_FILE.getAbsolutePath()), e);