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#include "config.h"
#include "ScrollbarThemeChromiumLinux.h"

#include "PlatformContextSkia.h"
#include "PlatformMouseEvent.h"
#include "RenderTheme.h"
#include "RenderThemeChromiumLinux.h"
#include "Scrollbar.h"
#include "TransformationMatrix.h"

namespace WebCore {

static const int scrollbarThicknessValue = 15;
static const int buttonLength = 14;

ScrollbarTheme* ScrollbarTheme::nativeTheme()
{
    static ScrollbarThemeChromiumLinux theme;
    return &theme;
}

int ScrollbarThemeChromiumLinux::scrollbarThickness(ScrollbarControlSize controlSize)
{
    return scrollbarThicknessValue;
}

static void drawVertLine(SkCanvas* canvas, int x, int y1, int y2, const SkPaint& paint)
{
    SkIRect skrect;
    skrect.set(x, y1, x + 1, y2 + 1);
    canvas->drawIRect(skrect, paint);
}

static void drawHorizLine(SkCanvas* canvas, int x1, int x2, int y, const SkPaint& paint)
{
    SkIRect skrect;
    skrect.set(x1, y, x2 + 1, y + 1);
    canvas->drawIRect(skrect, paint);
}

static void drawBox(SkCanvas* canvas, const IntRect& rect, const SkPaint& paint)
{
    const int right = rect.x() + rect.width() - 1;
    const int bottom = rect.y() + rect.height() - 1;
    drawHorizLine(canvas, rect.x(), right, rect.y(), paint);
    drawVertLine(canvas, right, rect.y(), bottom, paint);
    drawHorizLine(canvas, rect.x(), right, bottom, paint);
    drawVertLine(canvas, rect.x(), rect.y(), bottom, paint);
}

static SkScalar clamp(SkScalar value, SkScalar min, SkScalar max)
{
    return std::min(std::max(value, min), max);
}

static SkColor saturateAndBrighten(SkScalar* hsv,
                                   SkScalar saturateAmount,
                                   SkScalar brightenAmount)
{
    SkScalar color[3];
    color[0] = hsv[0];
    color[1] = clamp(hsv[1] + saturateAmount, 0.0, 1.0);
    color[2] = clamp(hsv[2] + brightenAmount, 0.0, 1.0);
    return SkHSVToColor(color);
}

static SkColor outlineColor(SkScalar* hsv1, SkScalar* hsv2)
{
    // GTK Theme engines have way too much control over the layout of
    // the scrollbar. We might be able to more closely approximate its
    // look-and-feel, if we sent whole images instead of just colors
    // from the browser to the renderer. But even then, some themes
    // would just break.
    //
    // So, instead, we don't even try to 100% replicate the look of
    // the native scrollbar. We render our own version, but we make
    // sure to pick colors that blend in nicely with the system GTK
    // theme. In most cases, we can just sample a couple of pixels
    // from the system scrollbar and use those colors to draw our
    // scrollbar.
    //
    // This works fine for the track color and the overall thumb
    // color. But it fails spectacularly for the outline color used
    // around the thumb piece.  Not all themes have a clearly defined
    // outline. For some of them it is partially transparent, and for
    // others the thickness is very unpredictable.
    //
    // So, instead of trying to approximate the system theme, we
    // instead try to compute a reasonable looking choice based on the
    // known color of the track and the thumb piece. This is difficult
    // when trying to deal both with high- and low-contrast themes,
    // and both with positive and inverted themes.
    //
    // The following code has been tested to look OK with all of the
    // default GTK themes.
    SkScalar minDiff = clamp((hsv1[1] + hsv2[1]) * 1.2, 0.28, 0.5);
    SkScalar diff = clamp(fabs(hsv1[2] - hsv2[2]) / 2, minDiff, 0.5);

    if (hsv1[2] + hsv2[2] > 1.0)
        diff = -diff;

    return saturateAndBrighten(hsv2, -0.2, diff);
}

void ScrollbarThemeChromiumLinux::paintTrackPiece(GraphicsContext* gc, Scrollbar* scrollbar, const IntRect& rect, ScrollbarPart partType)
{
    SkCanvas* const canvas = gc->platformContext()->canvas();
    SkPaint paint;
    SkIRect skrect;

    skrect.set(rect.x(), rect.y(), rect.x() + rect.width(), rect.y() + rect.height());
    SkScalar trackHSV[3];
    SkColorToHSV(RenderThemeChromiumLinux::trackColor(), trackHSV);
    paint.setColor(saturateAndBrighten(trackHSV, 0, 0));
    canvas->drawIRect(skrect, paint);

    SkScalar thumbHSV[3];
    SkColorToHSV(RenderThemeChromiumLinux::thumbInactiveColor(),
                 thumbHSV);

    paint.setColor(outlineColor(trackHSV, thumbHSV));
    drawBox(canvas, rect, paint);
}

void ScrollbarThemeChromiumLinux::paintButton(GraphicsContext* gc, Scrollbar* scrollbar, const IntRect& rect, ScrollbarPart part)
{
    SkCanvas* const canvas = gc->platformContext()->canvas();
    static const int widthMiddle = scrollbarThicknessValue / 2 + 1;
    static const int lengthMiddle = buttonLength / 2 + 1;
    SkPaint paint;
    enum {
        North,
        East,
        South,
        West,
    } direction;

    if (scrollbar->orientation() == HorizontalScrollbar) {
        if (part == BackButtonStartPart)
            direction = West;
        else
            direction = East;
    } else {
        if (part == BackButtonStartPart)
            direction = North;
        else
            direction = South;
    }

    // Determine if the button can be pressed.
    bool enabled = false;
    if (((direction == West || direction == North) && scrollbar->currentPos())
        || (direction == East || direction == South) && scrollbar->currentPos() != scrollbar->maximum())
        enabled = true;

    // Calculate button color.
    SkScalar trackHSV[3];
    SkColorToHSV(RenderThemeChromiumLinux::trackColor(), trackHSV);
    SkColor buttonColor = saturateAndBrighten(trackHSV, 0, 0.2);
    SkColor backgroundColor = buttonColor;
    if (part == scrollbar->pressedPart()) {
        SkScalar buttonHSV[3];
        SkColorToHSV(buttonColor, buttonHSV);
        buttonColor = saturateAndBrighten(buttonHSV, 0, -0.1);
    } else if (part == scrollbar->hoveredPart() && enabled) {
        SkScalar buttonHSV[3];
        SkColorToHSV(buttonColor, buttonHSV);
        buttonColor = saturateAndBrighten(buttonHSV, 0, 0.05);
    }

    SkIRect skrect;
    skrect.set(rect.x(), rect.y(), rect.x() + rect.width(), rect.y() + rect.height());
    // Paint the background (the area visible behind the rounded corners).
    paint.setColor(backgroundColor);
    canvas->drawIRect(skrect, paint);

    // Paint the button's outline and fill the middle
    SkPath outline;
    switch (direction) {
    case North:
        outline.moveTo(rect.x() + 0.5, rect.y() + rect.height() + 0.5);
        outline.rLineTo(0, -(rect.height() - 2));
        outline.rLineTo(2, -2);
        outline.rLineTo(rect.width() - 5, 0);
        outline.rLineTo(2, 2);
        outline.rLineTo(0, rect.height() - 2);
        break;
    case South:
        outline.moveTo(rect.x() + 0.5, rect.y() - 0.5);
        outline.rLineTo(0, rect.height() - 2);
        outline.rLineTo(2, 2);
        outline.rLineTo(rect.width() - 5, 0);
        outline.rLineTo(2, -2);
        outline.rLineTo(0, -(rect.height() - 2));
        break;
    case East:
        outline.moveTo(rect.x() - 0.5, rect.y() + 0.5);
        outline.rLineTo(rect.width() - 2, 0);
        outline.rLineTo(2, 2);
        outline.rLineTo(0, rect.height() - 5);
        outline.rLineTo(-2, 2);
        outline.rLineTo(-(rect.width() - 2), 0);
        break;
    case West:
        outline.moveTo(rect.x() + rect.width() + 0.5, rect.y() + 0.5);
        outline.rLineTo(-(rect.width() - 2), 0);
        outline.rLineTo(-2, 2);
        outline.rLineTo(0, rect.height() - 5);
        outline.rLineTo(2, 2);
        outline.rLineTo(rect.width() - 2, 0);
        break;
    }
    outline.close();

    paint.setStyle(SkPaint::kFill_Style);
    paint.setColor(buttonColor);
    canvas->drawPath(outline, paint);

    paint.setAntiAlias(true);
    paint.setStyle(SkPaint::kStroke_Style);
    SkScalar thumbHSV[3];
    SkColorToHSV(RenderThemeChromiumLinux::thumbInactiveColor(), thumbHSV);
    paint.setColor(outlineColor(trackHSV, thumbHSV));
    canvas->drawPath(outline, paint);

    // If the button is disabled, the arrow is drawn with the outline color.
    if (enabled)
        paint.setColor(SK_ColorBLACK);

    paint.setAntiAlias(false);
    paint.setStyle(SkPaint::kFill_Style);

    SkPath path;
    // The constants in this block of code are hand-tailored to produce good
    // looking arrows without anti-aliasing.
    switch (direction) {
    case North:
        path.moveTo(rect.x() + widthMiddle - 4, rect.y() + lengthMiddle + 2);
        path.rLineTo(7, 0);
        path.rLineTo(-4, -4);
        break;
    case South:
        path.moveTo(rect.x() + widthMiddle - 4, rect.y() + lengthMiddle - 3);
        path.rLineTo(7, 0);
        path.rLineTo(-4, 4);
        break;
    case East:
        path.moveTo(rect.x() + lengthMiddle - 3, rect.y() + widthMiddle - 4);
        path.rLineTo(0, 7);
        path.rLineTo(4, -4);
        break;
    case West:
        path.moveTo(rect.x() + lengthMiddle + 1, rect.y() + widthMiddle - 5);
        path.rLineTo(0, 9);
        path.rLineTo(-4, -4);
        break;
    }
    path.close();

    canvas->drawPath(path, paint);
}

void ScrollbarThemeChromiumLinux::paintThumb(GraphicsContext* gc, Scrollbar* scrollbar, const IntRect& rect)
{
    const bool hovered = scrollbar->hoveredPart() == ThumbPart;
    const int midx = rect.x() + rect.width() / 2;
    const int midy = rect.y() + rect.height() / 2;
    const bool vertical = scrollbar->orientation() == VerticalScrollbar;
    SkCanvas* const canvas = gc->platformContext()->canvas();

    SkScalar thumb[3];
    SkColorToHSV(hovered
                 ? RenderThemeChromiumLinux::thumbActiveColor()
                 : RenderThemeChromiumLinux::thumbInactiveColor(),
                 thumb);

    SkPaint paint;
    paint.setColor(saturateAndBrighten(thumb, 0, 0.02));

    SkIRect skrect;
    if (vertical)
        skrect.set(rect.x(), rect.y(), midx + 1, rect.y() + rect.height());
    else
        skrect.set(rect.x(), rect.y(), rect.x() + rect.width(), midy + 1);

    canvas->drawIRect(skrect, paint);

    paint.setColor(saturateAndBrighten(thumb, 0, -0.02));

    if (vertical)
        skrect.set(midx + 1, rect.y(), rect.x() + rect.width(), rect.y() + rect.height());
    else
        skrect.set(rect.x(), midy + 1, rect.x() + rect.width(), rect.y() + rect.height());

    canvas->drawIRect(skrect, paint);

    SkScalar track[3];
    SkColorToHSV(RenderThemeChromiumLinux::trackColor(), track);
    paint.setColor(outlineColor(track, thumb));
    drawBox(canvas, rect, paint);

    if (rect.height() > 10 && rect.width() > 10) {
        const int grippyHalfWidth = 2;
        const int interGrippyOffset = 3;
        if (vertical) {
            drawHorizLine(canvas, midx - grippyHalfWidth, midx + grippyHalfWidth, midy - interGrippyOffset, paint);
            drawHorizLine(canvas, midx - grippyHalfWidth, midx + grippyHalfWidth, midy,                     paint);
            drawHorizLine(canvas, midx - grippyHalfWidth, midx + grippyHalfWidth, midy + interGrippyOffset, paint);
        } else {
            drawVertLine(canvas, midx - interGrippyOffset, midy - grippyHalfWidth, midy + grippyHalfWidth, paint);
            drawVertLine(canvas, midx,                     midy - grippyHalfWidth, midy + grippyHalfWidth, paint);
            drawVertLine(canvas, midx + interGrippyOffset, midy - grippyHalfWidth, midy + grippyHalfWidth, paint);
        }
    }
}

bool ScrollbarThemeChromiumLinux::shouldCenterOnThumb(Scrollbar*, const PlatformMouseEvent& evt)
{
    return (evt.shiftKey() && evt.button() == LeftButton) || (evt.button() == MiddleButton);
}

IntSize ScrollbarThemeChromiumLinux::buttonSize(Scrollbar* scrollbar)
{
    if (scrollbar->orientation() == VerticalScrollbar)
        return IntSize(scrollbarThicknessValue, buttonLength);

    // HorizontalScrollbar
    return IntSize(buttonLength, scrollbarThicknessValue);
}

int ScrollbarThemeChromiumLinux::minimumThumbLength(Scrollbar* scrollbar)
{
    // This matches Firefox on Linux.
    return 2 * scrollbarThickness(scrollbar->controlSize());
}

} // namespace WebCore