(*
    Copyright 2021 Anton Krotov

    This file is part of CEdit.

    CEdit is free software: you can redistribute it and/or modify
    it under the terms of the GNU General Public License as published by
    the Free Software Foundation, either version 3 of the License, or
    (at your option) any later version.

    CEdit is distributed in the hope that it will be useful,
    but WITHOUT ANY WARRANTY; without even the implied warranty of
    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
    GNU General Public License for more details.

    You should have received a copy of the GNU General Public License
    along with CEdit. If not, see <http://www.gnu.org/licenses/>.
*)

MODULE Scroll;

IMPORT G := Graph;

TYPE

    tScroll* = POINTER TO RECORD
        vertical, mouse: BOOLEAN;
        canvas: G.tCanvas;
        xSize*, ySize*, pos, mousePos: INTEGER;
        color, bkColor: INTEGER;
        value*, maxVal*: INTEGER
    END;


PROCEDURE draw* (scroll: tScroll; x, y: INTEGER);
VAR
    pos, a, b: INTEGER;
    canvas: G.tCanvas;
BEGIN
    IF scroll.vertical THEN
        a := scroll.ySize;
        b := scroll.xSize
    ELSE
        a := scroll.xSize;
        b := scroll.ySize
    END;
    IF scroll.maxVal > 0 THEN
        pos := (a - b)*scroll.value DIV scroll.maxVal
    ELSE
        pos := 0
    END;
    canvas := scroll.canvas;
    G.SetColor(canvas, scroll.bkColor);
    G.clear(canvas);
    G.SetColor(canvas, 0808080H);
    G.Rect(canvas, 0, 0, scroll.xSize - 1, scroll.ySize - 1);
    G.SetColor(canvas, scroll.color);
    DEC(b, 2);
    IF scroll.vertical THEN
        G.FillRect(canvas, 1, pos + 1, b, pos + b);
        G.SetColor(canvas, 0404040H);
        G.HLine(canvas, pos + 1 + b DIV 2, 4, b - 4);
        G.HLine(canvas, pos + 1 + b DIV 2 - 3, 6, b - 6);
        G.HLine(canvas, pos + 1 + b DIV 2 + 3, 6, b - 6);
    ELSE
        G.FillRect(canvas, pos + 1, 1, pos + b, b);
        G.SetColor(canvas, 0404040H);
        G.VLine(canvas, pos + b DIV 2, 4, b - 4);
        G.VLine(canvas, pos + b DIV 2 - 3, 6, b - 6);
        G.VLine(canvas, pos + b DIV 2 + 3, 6, b - 6);
    END;
    scroll.pos := pos;
    G.DrawCanvas(canvas, x, y);
END draw;


PROCEDURE create* (xSize, ySize: INTEGER; color, bkColor: INTEGER): tScroll;
VAR
    scroll: tScroll;
BEGIN
    NEW(scroll);
    scroll.xSize := xSize;
    scroll.ySize := ySize;
    scroll.vertical := xSize < ySize;
    scroll.maxVal := 30;
    scroll.value := 0;
    scroll.mouse := FALSE;
    scroll.bkColor := bkColor;
    scroll.color := color;
    scroll.canvas := G.CreateCanvas(xSize, ySize)
    RETURN scroll
END create;


PROCEDURE resize* (scroll: tScroll; xSize, ySize: INTEGER);
BEGIN
    scroll.xSize := xSize;
    scroll.ySize := ySize;
    scroll.vertical := xSize < ySize;
    G.destroy(scroll.canvas);
    scroll.canvas := G.CreateCanvas(xSize, ySize);
END resize;


PROCEDURE mouse* (scroll: tScroll; x, y: INTEGER);
VAR
    pos, b: INTEGER;
BEGIN
    IF scroll.vertical THEN
        pos := y - 1;
        b := scroll.xSize - 2
    ELSE
        pos := x - 1;
        b := scroll.ySize - 2
    END;
    IF ~scroll.mouse THEN
        scroll.mouse := TRUE;
        IF (scroll.pos <= pos) & (pos <= scroll.pos + b - 1) THEN
            scroll.mousePos := pos - scroll.pos
        ELSE
            scroll.mousePos := b DIV 2;
            scroll.value := (pos - scroll.mousePos)*scroll.maxVal DIV ABS(scroll.xSize - scroll.ySize)
        END
    ELSE
        scroll.value := (pos - scroll.mousePos)*scroll.maxVal DIV ABS(scroll.xSize - scroll.ySize)
    END;
    IF scroll.value < 0 THEN
        scroll.value := 0
    ELSIF scroll.value > scroll.maxVal THEN
        scroll.value := scroll.maxVal
    END
END mouse;


PROCEDURE MouseUp* (scroll: tScroll);
BEGIN
    IF scroll # NIL THEN
        scroll.mouse := FALSE
    END
END MouseUp;


END Scroll.