Add focus cycling to panels

Closes #37. Closes #54.

6 files changed, 151 insertions, 8 deletions

diff --git a/src/main/java/io/github/cottonmc/cotton/gui/GuiDescription.java b/src/main/java/io/github/cottonmc/cotton/gui/GuiDescription.java
index fec799b..815b179 100644
--- a/src/main/java/io/github/cottonmc/cotton/gui/GuiDescription.java
+++ b/src/main/java/io/github/cottonmc/cotton/gui/GuiDescription.java
@@ -2,6 +2,7 @@ package io.github.cottonmc.cotton.gui;
 
 import javax.annotation.Nullable;
 
+import io.github.cottonmc.cotton.gui.impl.FocusHandler;
 import io.github.cottonmc.cotton.gui.widget.WPanel;
 import io.github.cottonmc.cotton.gui.widget.WWidget;
 import net.fabricmc.api.EnvType;
@@ -50,5 +51,14 @@ public interface GuiDescription {
 	
 	/** Notifies this gui that the widget wants to give up its hold over focus. */
 	public void releaseFocus(WWidget widget);
-	
+
+	/**
+	 * Cycles the focused widget in the GUI.
+	 *
+	 * @param lookForwards whether this should cycle forwards (true) or backwards (false)
+	 * @since 2.0.0
+	 */
+	default void cycleFocus(boolean lookForwards) {
+		FocusHandler.cycleFocus(this, lookForwards);
+	}
 }
diff --git a/src/main/java/io/github/cottonmc/cotton/gui/client/CottonClientScreen.java b/src/main/java/io/github/cottonmc/cotton/gui/client/CottonClientScreen.java
index b5ac34e..96546fa 100644
--- a/src/main/java/io/github/cottonmc/cotton/gui/client/CottonClientScreen.java
+++ b/src/main/java/io/github/cottonmc/cotton/gui/client/CottonClientScreen.java
@@ -224,4 +224,13 @@ public class CottonClientScreen extends Screen implements TextHoverRendererScree
 	public void renderTextHover(MatrixStack matrices, Text text, int x, int y) {
 		renderTextHoverEffect(matrices, text, x, y);
 	}
+
+	@Override
+	public boolean changeFocus(boolean lookForwards) {
+		if (description != null) {
+			description.cycleFocus(lookForwards);
+		}
+
+		return true;
+	}
 }
diff --git a/src/main/java/io/github/cottonmc/cotton/gui/client/CottonInventoryScreen.java b/src/main/java/io/github/cottonmc/cotton/gui/client/CottonInventoryScreen.java
index ea24abf..fb73dd2 100644
--- a/src/main/java/io/github/cottonmc/cotton/gui/client/CottonInventoryScreen.java
+++ b/src/main/java/io/github/cottonmc/cotton/gui/client/CottonInventoryScreen.java
@@ -87,6 +87,9 @@ public class CottonInventoryScreen<T extends CottonInventoryController> extends
 		if (ch==GLFW.GLFW_KEY_ESCAPE) {
 			this.client.player.closeHandledScreen();
 			return true;
+		} else if (ch==GLFW.GLFW_KEY_TAB) {
+			changeFocus(!hasShiftDown());
+			return true;
 		} else {
 			//if (super.keyPressed(ch, keyCode, modifiers)) return true;
 			if (description.getFocus()==null) {
@@ -236,4 +239,13 @@ public class CottonInventoryScreen<T extends CottonInventoryController> extends
 	public void renderTextHover(MatrixStack matrices, Text text, int x, int y) {
 		renderTextHoverEffect(matrices, text, x, y);
 	}
+
+	@Override
+	public boolean changeFocus(boolean lookForwards) {
+		if (description != null) {
+			description.cycleFocus(lookForwards);
+		}
+
+		return true;
+	}
 }
diff --git a/src/main/java/io/github/cottonmc/cotton/gui/impl/FocusHandler.java b/src/main/java/io/github/cottonmc/cotton/gui/impl/FocusHandler.java
new file mode 100644
index 0000000..df0ef32
--- /dev/null
+++ b/src/main/java/io/github/cottonmc/cotton/gui/impl/FocusHandler.java
@@ -0,0 +1,41 @@
+package io.github.cottonmc.cotton.gui.impl;
+
+import io.github.cottonmc.cotton.gui.GuiDescription;
+import io.github.cottonmc.cotton.gui.widget.WPanel;
+import io.github.cottonmc.cotton.gui.widget.WWidget;
+
+/**
+ * The implementation for focus cycling.
+ */
+public final class FocusHandler {
+	public static void cycleFocus(GuiDescription host, boolean lookForwards) {
+		boolean result;
+		WWidget focus = host.getFocus();
+		if (focus == null) {
+			result = cycleFocus(host, lookForwards, host.getRootPanel(), null);
+		} else {
+			WPanel parent = focus.getParent();
+			result = cycleFocus(host, lookForwards, parent != null ? parent : host.getRootPanel(), focus);
+		}
+
+		if (!result) {
+			// Try again from the beginning
+			cycleFocus(host, lookForwards, host.getRootPanel(), null);
+		}
+	}
+
+	private static boolean cycleFocus(GuiDescription host, boolean lookForwards, WPanel panel, WWidget pivot) {
+		WWidget next = panel.cycleFocus(lookForwards, pivot);
+		if (next != null) {
+			host.requestFocus(next);
+			return true;
+		} else {
+			WPanel parent = panel.getParent();
+			if (parent != null) {
+				return cycleFocus(host, lookForwards, parent, panel);
+			}
+		}
+
+		return false;
+	}
+}
diff --git a/src/main/java/io/github/cottonmc/cotton/gui/impl/package-info.java b/src/main/java/io/github/cottonmc/cotton/gui/impl/package-info.java
new file mode 100644
index 0000000..678ba6f
--- /dev/null
+++ b/src/main/java/io/github/cottonmc/cotton/gui/impl/package-info.java
@@ -0,0 +1,6 @@
+/**
+ * Internal implementation classes.
+ *
+ * @since 2.0.0
+ */
+package io.github.cottonmc.cotton.gui.impl;
diff --git a/src/main/java/io/github/cottonmc/cotton/gui/widget/WPanel.java b/src/main/java/io/github/cottonmc/cotton/gui/widget/WPanel.java
index d1f0f4a..987248f 100644
--- a/src/main/java/io/github/cottonmc/cotton/gui/widget/WPanel.java
+++ b/src/main/java/io/github/cottonmc/cotton/gui/widget/WPanel.java
@@ -9,6 +9,8 @@ import net.fabricmc.api.EnvType;
 import net.fabricmc.api.Environment;
 import net.minecraft.client.util.math.MatrixStack;
 
+import javax.annotation.Nullable;
+
 /**
  * Panels are widgets that contain other widgets.
  */
@@ -21,7 +23,7 @@ public abstract class WPanel extends WWidget {
 	protected final List<WWidget> children = new ArrayList<>();
 	@Environment(EnvType.CLIENT)
 	private BackgroundPainter backgroundPainter = null;
-	
+
 	@Override
 	public void createPeers(GuiDescription c) {
 		super.createPeers(c);
@@ -38,7 +40,7 @@ public abstract class WPanel extends WWidget {
 	public void remove(WWidget w) {
 		children.remove(w);
 	}
-	
+
 	@Override
 	public boolean canResize() {
 		return true;
@@ -65,7 +67,7 @@ public abstract class WPanel extends WWidget {
 	public BackgroundPainter getBackgroundPainter() {
 		return this.backgroundPainter;
 	}
-	
+
 	/**
 	 * Uses this Panel's layout rules to reposition and resize components to fit nicely in the panel.
 	 */
@@ -150,7 +152,7 @@ public abstract class WPanel extends WWidget {
 			}
 		}
 	}*/
-	
+
 	/**
 	 * Finds the most specific child node at this location.
 	 */
@@ -168,7 +170,7 @@ public abstract class WPanel extends WWidget {
 		}
 		return this;
 	}
-	
+
 	@Override
 	public void validate(GuiDescription c) {
 		layout();
@@ -177,12 +179,12 @@ public abstract class WPanel extends WWidget {
 		}
 		if (c!=null) createPeers(c);
 	}
-	
+
 	@Environment(EnvType.CLIENT)
 	@Override
 	public void paint(MatrixStack matrices, int x, int y, int mouseX, int mouseY) {
 		if (backgroundPainter!=null) backgroundPainter.paintBackground(x, y, this);
-		
+
 		for(WWidget child : children) {
 			child.paint(matrices, x + child.getX(), y + child.getY(), mouseX-child.getX(), mouseY-child.getY());
 		}
@@ -196,4 +198,67 @@ public abstract class WPanel extends WWidget {
 	public void tick() {
 		for(WWidget child : children) child.tick();
 	}
+
+	/**
+	 * Cycles the focus inside this panel.
+	 *
+	 * @param lookForwards whether this should cycle forwards (true) or backwards (false)
+	 * @param pivot        the widget that should be cycled around (can be null for beginning / end)
+	 * @return the next focused widget, or null if should exit to the parent panel
+	 * @since 2.0.0
+	 */
+	@Nullable
+	public WWidget cycleFocus(boolean lookForwards, @Nullable WWidget pivot) {
+		if (pivot == null) {
+			if (lookForwards) {
+				for (WWidget child : children) {
+					WWidget result = checkFocusCycling(lookForwards, child);
+					if (result != null) return result;
+				}
+			} else if (!children.isEmpty()) {
+				for (int i = children.size() - 1; i >= 0; i--) {
+					WWidget child = children.get(i);
+					WWidget result = checkFocusCycling(lookForwards, child);
+					if (result != null) return result;
+				}
+			}
+		} else {
+			int currentIndex = children.indexOf(pivot);
+
+			if (currentIndex == -1) { // outside widget
+				currentIndex = lookForwards ? 0 : children.size() - 1;
+			}
+
+			if (lookForwards) {
+				if (currentIndex < children.size() - 1) {
+					for (int i = currentIndex + 1; i < children.size(); i++) {
+						WWidget child = children.get(i);
+						WWidget result = checkFocusCycling(lookForwards, child);
+						if (result != null) return result;
+					}
+				}
+			} else { // look forwards = false
+				if (currentIndex > 0) {
+					for (int i = currentIndex - 1; i >= 0; i--) {
+						WWidget child = children.get(i);
+						WWidget result = checkFocusCycling(lookForwards, child);
+						if (result != null) return result;
+					}
+				}
+			}
+		}
+
+		return null;
+	}
+
+	@Nullable
+	private WWidget checkFocusCycling(boolean lookForwards, WWidget child) {
+		if (child.canFocus()) {
+			return child;
+		} else if (child instanceof WPanel) {
+			return ((WPanel) child).cycleFocus(lookForwards, null);
+		}
+
+		return null;
+	}
 }