minecraft-src/net/minecraft/client/gui/components/AbstractScrollWidget.java

package net.minecraft.client.gui.components;

import net.fabricmc.api.EnvType;
import net.fabricmc.api.Environment;
import net.minecraft.client.gui.GuiGraphics;
import net.minecraft.client.renderer.RenderType;
import net.minecraft.network.chat.Component;
import net.minecraft.resources.ResourceLocation;
import net.minecraft.util.Mth;

@Environment(EnvType.CLIENT)
public abstract class AbstractScrollWidget extends AbstractWidget {
	private static final WidgetSprites BACKGROUND_SPRITES = new WidgetSprites(
		ResourceLocation.withDefaultNamespace("widget/text_field"), ResourceLocation.withDefaultNamespace("widget/text_field_highlighted")
	);
	private static final ResourceLocation SCROLLER_SPRITE = ResourceLocation.withDefaultNamespace("widget/scroller");
	private static final int INNER_PADDING = 4;
	private static final int SCROLL_BAR_WIDTH = 8;
	private double scrollAmount;
	private boolean scrolling;

	public AbstractScrollWidget(int x, int y, int width, int height, Component message) {
		super(x, y, width, height, message);
	}

	@Override
	public boolean mouseClicked(double mouseX, double mouseY, int button) {
		if (!this.visible) {
			return false;
		} else {
			boolean bl = this.withinContentAreaPoint(mouseX, mouseY);
			boolean bl2 = this.scrollbarVisible()
				&& mouseX >= this.getX() + this.width
				&& mouseX <= this.getX() + this.width + 8
				&& mouseY >= this.getY()
				&& mouseY < this.getY() + this.height;
			if (bl2 && button == 0) {
				this.scrolling = true;
				return true;
			} else {
				return bl || bl2;
			}
		}
	}

	@Override
	public boolean mouseReleased(double mouseX, double mouseY, int button) {
		if (button == 0) {
			this.scrolling = false;
		}

		return super.mouseReleased(mouseX, mouseY, button);
	}

	@Override
	public boolean mouseDragged(double mouseX, double mouseY, int button, double dragX, double dragY) {
		if (this.visible && this.isFocused() && this.scrolling) {
			if (mouseY < this.getY()) {
				this.setScrollAmount(0.0);
			} else if (mouseY > this.getY() + this.height) {
				this.setScrollAmount(this.getMaxScrollAmount());
			} else {
				int i = this.getScrollBarHeight();
				double d = Math.max(1, this.getMaxScrollAmount() / (this.height - i));
				this.setScrollAmount(this.scrollAmount + dragY * d);
			}

			return true;
		} else {
			return false;
		}
	}

	@Override
	public boolean mouseScrolled(double mouseX, double mouseY, double scrollX, double scrollY) {
		if (!this.visible) {
			return false;
		} else {
			this.setScrollAmount(this.scrollAmount - scrollY * this.scrollRate());
			return true;
		}
	}

	@Override
	public boolean keyPressed(int keyCode, int scanCode, int modifiers) {
		boolean bl = keyCode == 265;
		boolean bl2 = keyCode == 264;
		if (bl || bl2) {
			double d = this.scrollAmount;
			this.setScrollAmount(this.scrollAmount + (bl ? -1 : 1) * this.scrollRate());
			if (d != this.scrollAmount) {
				return true;
			}
		}

		return super.keyPressed(keyCode, scanCode, modifiers);
	}

	@Override
	public void renderWidget(GuiGraphics guiGraphics, int mouseX, int mouseY, float partialTick) {
		if (this.visible) {
			this.renderBackground(guiGraphics);
			guiGraphics.enableScissor(this.getX() + 1, this.getY() + 1, this.getX() + this.width - 1, this.getY() + this.height - 1);
			guiGraphics.pose().pushPose();
			guiGraphics.pose().translate(0.0, -this.scrollAmount, 0.0);
			this.renderContents(guiGraphics, mouseX, mouseY, partialTick);
			guiGraphics.pose().popPose();
			guiGraphics.disableScissor();
			this.renderDecorations(guiGraphics);
		}
	}

	private int getScrollBarHeight() {
		return Mth.clamp((int)((float)(this.height * this.height) / this.getContentHeight()), 32, this.height);
	}

	protected void renderDecorations(GuiGraphics guiGraphics) {
		if (this.scrollbarVisible()) {
			this.renderScrollBar(guiGraphics);
		}
	}

	protected int innerPadding() {
		return 4;
	}

	protected int totalInnerPadding() {
		return this.innerPadding() * 2;
	}

	protected double scrollAmount() {
		return this.scrollAmount;
	}

	protected void setScrollAmount(double scrollAmount) {
		this.scrollAmount = Mth.clamp(scrollAmount, 0.0, (double)this.getMaxScrollAmount());
	}

	protected int getMaxScrollAmount() {
		return Math.max(0, this.getContentHeight() - (this.height - 4));
	}

	private int getContentHeight() {
		return this.getInnerHeight() + 4;
	}

	protected void renderBackground(GuiGraphics guiGraphics) {
		this.renderBorder(guiGraphics, this.getX(), this.getY(), this.getWidth(), this.getHeight());
	}

	protected void renderBorder(GuiGraphics guiGraphics, int x, int y, int width, int height) {
		ResourceLocation resourceLocation = BACKGROUND_SPRITES.get(this.isActive(), this.isFocused());
		guiGraphics.blitSprite(RenderType::guiTextured, resourceLocation, x, y, width, height);
	}

	private void renderScrollBar(GuiGraphics guiGraphics) {
		int i = this.getScrollBarHeight();
		int j = this.getX() + this.width;
		int k = Math.max(this.getY(), (int)this.scrollAmount * (this.height - i) / this.getMaxScrollAmount() + this.getY());
		guiGraphics.blitSprite(RenderType::guiTextured, SCROLLER_SPRITE, j, k, 8, i);
	}

	protected boolean withinContentAreaTopBottom(int top, int bottom) {
		return bottom - this.scrollAmount >= this.getY() && top - this.scrollAmount <= this.getY() + this.height;
	}

	protected boolean withinContentAreaPoint(double x, double y) {
		return x >= this.getX() && x < this.getX() + this.width && y >= this.getY() && y < this.getY() + this.height;
	}

	protected boolean scrollbarVisible() {
		return this.getInnerHeight() > this.getHeight();
	}

	public int scrollbarWidth() {
		return 8;
	}

	protected abstract int getInnerHeight();

	protected abstract double scrollRate();

	protected abstract void renderContents(GuiGraphics guiGraphics, int mouseX, int mouseY, float partialTick);
}