common/src/main/java/org/saturnclient/ui/Popup.java

package org.saturnclient.ui;

import java.util.List;

/**
 * A single element drawn above the rest of the screen, such as a dropdown's
 * options or a color picker. It gets mouse events before anything else, and a
 * click or scroll outside it closes it.
 *
 * Only one screen is open at a time, so the popup is kept here rather than on
 * the screen; {@link SaturnScreen} forwards to it and clears it when it's
 * rebuilt.
 */
public final class Popup {
    private static final int SCREEN_MARGIN = 8;
    private static final int OWNER_GAP = 4;

    private static Element popup;
    private static Element owner;
    private static int screenWidth, screenHeight;

    private Popup() {
    }

    /**
     * Opens {@code popup} with its top-left corner at ({@code x}, {@code y}) on
     * the screen, moved as needed to stay on it.
     *
     * @param owner the element that opened it, for {@link #isOpenFor}
     */
    public static void open(Element owner, Element popup, int x, int y) {
        Popup.owner = owner;
        Popup.popup = popup;

        popup.x = clamp(x, popup.width, screenWidth);
        popup.y = clamp(y, popup.height, screenHeight);
    }

    /**
     * Opens {@code popup} just below its owner if it fits in the part of the
     * screen where the owner can be seen, such as a scroll's box; otherwise
     * above it if it fits there, or else on the side with more room.
     *
     * @param ownerContext the owner's context from its last render
     */
    public static void openBelow(Element owner, Element popup, ElementContext ownerContext) {
        openBelow(owner, popup, ownerContext, 0);
    }

    /**
     * Like {@link #openBelow(Element, Element, ElementContext)}, with the popup
     * moved {@code offsetX} from the owner's left edge.
     */
    public static void openBelow(Element owner, Element popup, ElementContext ownerContext, int offsetX) {
        int top = Math.max(ownerContext.visibleTop, SCREEN_MARGIN);
        int bottom = Math.min(ownerContext.visibleBottom, screenHeight - SCREEN_MARGIN);

        int below = ownerContext.originY + owner.height + OWNER_GAP;
        int above = ownerContext.originY - OWNER_GAP - popup.height;

        boolean fitsBelow = below + popup.height <= bottom;
        boolean fitsAbove = above >= top;
        boolean moreRoomBelow = bottom - below >= ownerContext.originY - OWNER_GAP - top;

        int y = fitsBelow || (!fitsAbove && moreRoomBelow) ? below : above;
        open(owner, popup, ownerContext.originX + offsetX, y);
    }

    public static void close() {
        popup = null;
        owner = null;
    }

    public static boolean isOpenFor(Element element) {
        return popup != null && owner == element;
    }

    // ---------------------------------------------------------------
    // Called by SaturnScreen
    // ---------------------------------------------------------------

    static void reset(int width, int height) {
        close();
        screenWidth = width;
        screenHeight = height;
    }

    static void render(RenderScope renderScope, long elapsed, int mouseX, int mouseY) {
        if (popup != null) {
            ElementRenderer.render(List.of(popup), elapsed, renderScope, mouseX, mouseY);
        }
    }

    /**
     * @return whether the popup took the click; a click outside it closes it
     *         and is taken too, so it doesn't reach what's underneath
     */
    static boolean mouseClicked(double mouseX, double mouseY, int button) {
        if (popup == null) {
            return false;
        }

        if (isInside(mouseX, mouseY)) {
            ElementRenderer.mouseClicked(List.of(popup), mouseX, mouseY, button);
        } else {
            close();
        }

        return true;
    }

    static boolean mouseDragged(double mouseX, double mouseY, int button, double deltaX, double deltaY) {
        if (popup == null) {
            return false;
        }

        ElementRenderer.mouseDragged(List.of(popup), mouseX, mouseY, button, deltaX, deltaY);
        return true;
    }

    static void mouseReleased(double mouseX, double mouseY, int button) {
        if (popup != null) {
            ElementRenderer.mouseReleased(List.of(popup), mouseX, mouseY, button);
        }
    }

    /**
     * @return whether the popup took the scroll; scrolling outside it closes it,
     *         since it wouldn't move with what's underneath
     */
    static boolean mouseScrolled(double mouseX, double mouseY, double horizontalAmount, double verticalAmount) {
        if (popup == null) {
            return false;
        }

        if (isInside(mouseX, mouseY)) {
            ElementRenderer.mouseScrolled(List.of(popup), mouseX, mouseY, horizontalAmount, verticalAmount);
        } else {
            close();
        }

        return true;
    }

    private static boolean isInside(double mouseX, double mouseY) {
        return mouseX >= popup.x && mouseX <= popup.x + popup.width
                && mouseY >= popup.y && mouseY <= popup.y + popup.height;
    }

    private static int clamp(int position, int size, int screenSize) {
        return Math.max(SCREEN_MARGIN, Math.min(position, screenSize - SCREEN_MARGIN - size));
    }
}