cairo-beos-surface.cpp

按照官方的说法：Cairo is a vector graphics library with cross-device output support. 翻译过来

/* vim:set ts=8 sw=4 noet cin: */
/* cairo - a vector graphics library with display and print output
 *
 * Copyright © 2005 Christian Biesinger <[e-mail]>
 *
 * This library is free software; you can redistribute it and/or
 * modify it either under the terms of the GNU Lesser General Public
 * License version 2.1 as published by the Free Software Foundation
 * (the "LGPL") or, at your option, under the terms of the Mozilla
 * Public License Version 1.1 (the "MPL"). If you do not alter this
 * notice, a recipient may use your version of this file under either
 * the MPL or the LGPL.
 *
 * You should have received a copy of the LGPL along with this library
 * in the file COPYING-LGPL-2.1; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
 * You should have received a copy of the MPL along with this library
 * in the file COPYING-MPL-1.1
 *
 * The contents of this file are subject to the Mozilla Public License
 * Version 1.1 (the "License"); you may not use this file except in
 * compliance with the License. You may obtain a copy of the License at
 * http://www.mozilla.org/MPL/
 *
 * This software is distributed on an "AS IS" basis, WITHOUT WARRANTY
 * OF ANY KIND, either express or implied. See the LGPL or the MPL for
 * the specific language governing rights and limitations.
 *
 * The Original Code is the cairo graphics library.
 *
 * The Initial Developer of the Original Code is Christian Biesinger
 * <[e-mail]>
 *
 * Contributor(s):
 */

// This is a C++ file in order to use the C++ BeOS API

#include <new>

#include <Bitmap.h>
#include <Region.h>
#if 0
#include <DirectWindow.h>
#endif
#include <Screen.h>
#include <Window.h>
#include <Locker.h>

#include "cairoint.h"
#include "cairo-beos.h"

#define CAIRO_INT_STATUS_SUCCESS (cairo_int_status_t)(CAIRO_STATUS_SUCCESS)

struct cairo_beos_surface_t {
    cairo_surface_t base;

    BView* view;

    /*
     * A view is either attached to a bitmap, a window, or unattached.
     * If it is attached to a window, we can copy data out of it using BScreen.
     * If it is attached to a bitmap, we can read the bitmap data.
     * If it is not attached, it doesn't draw anything, we need not bother.
     *
     * Since there doesn't seem to be a way to get the bitmap from a view if it
     * is attached to one, we have to use a special surface creation function.
     */

    BBitmap* bitmap;


    // If true, surface and view should be deleted when this surface is
    // destroyed
    bool owns_bitmap_view;
};

class AutoLockView {
    public:
	AutoLockView(BView* view) : mView(view) {
	    mOK = mView->LockLooper();
	}

	~AutoLockView() {
	    if (mOK)
		mView->UnlockLooper();
	}

	operator bool() {
	    return mOK;
	}

    private:
	BView* mView;
	bool   mOK;
};

static cairo_surface_t *
_cairo_beos_surface_create_internal (BView*   view,
				     BBitmap* bmp,
				     bool     owns_bitmap_view = false);

static BRect
_cairo_rect_to_brect (const cairo_rectangle_fixed_t* rect)
{
    // A BRect is one pixel wider than you'd think
    return BRect(rect->x, rect->y, rect->x + rect->width - 1,
	    	 rect->y + rect->height - 1);
}

static cairo_rectangle_fixed_t
_brect_to_cairo_rect (const BRect& rect)
{
    cairo_rectangle_fixed_t retval;
    retval.x = int(rect.left + 0.5);
    retval.y = int(rect.top + 0.5);
    retval.width = rect.IntegerWidth() + 1;
    retval.height = rect.IntegerHeight() + 1;
    return retval;
}

static rgb_color
_cairo_color_to_be_color (const cairo_color_t* color)
{
    // This factor ensures a uniform distribution of numbers
    const float factor = 256 - 1e-5;
    // Using doubles to have non-premultiplied colors
    rgb_color be_color = { uint8(color->red * factor),
			   uint8(color->green * factor),
			   uint8(color->blue * factor),
			   uint8(color->alpha * factor) };

    return be_color;
}

enum ViewCopyStatus {
    OK,
    NOT_VISIBLE, // The view or the interest rect is not visible on screen
    ERROR        // The view was visible, but the rect could not be copied. Probably OOM
};

/**
 * _cairo_beos_view_to_bitmap:
 * @bitmap: [out] The resulting bitmap.
 * @rect: [out] The rectangle that was copied, in the view's coordinate system
 * @interestRect: If non-null, only this part of the view will be copied (view's coord system).
 *
 * Gets the contents of the view as a BBitmap*. Caller must delete the bitmap.
 **/
static ViewCopyStatus
_cairo_beos_view_to_bitmap (BView*       view,
			    BBitmap**    bitmap,
			    BRect*       rect = NULL,
			    const BRect* interestRect = NULL)
{
    *bitmap = NULL;

    BWindow* wnd = view->Window();
    // If we have no window, can't do anything
    if (!wnd)
	return NOT_VISIBLE;

    view->Sync();
    wnd->Sync();

#if 0
    // Is it a direct window?
    BDirectWindow* directWnd = dynamic_cast<BDirectWindow*>(wnd);
    if (directWnd) {
	// WRITEME
    }
#endif

    // Is it visible? If so, we can copy the content off the screen
    if (wnd->IsHidden())
	return NOT_VISIBLE;

    BRect rectToCopy(view->Bounds());
    if (interestRect)
	rectToCopy = rectToCopy & *interestRect;

    if (!rectToCopy.IsValid())
	return NOT_VISIBLE;

    BScreen screen(wnd);
    BRect screenRect(view->ConvertToScreen(rectToCopy));
    screenRect = screenRect & screen.Frame();

    if (!screen.IsValid())
	return NOT_VISIBLE;

    if (rect)
	*rect = view->ConvertFromScreen(screenRect);

    if (screen.GetBitmap(bitmap, false, &screenRect) == B_OK)
	return OK;

    return ERROR;
}

inline unsigned char
unpremultiply (unsigned char color,
	       unsigned char alpha)
{
    if (alpha == 0)
	return 0;
    // plus alpha/2 to round instead of truncate
    return (color * 255 + alpha / 2) / alpha;
}

inline unsigned char
premultiply (unsigned char color,
	     unsigned char alpha)
{
    // + 127 to round, instead of truncate
    return (color * alpha + 127) / 255;
}

/**
 * unpremultiply_rgba:
 *
 * Takes an input in ABGR premultiplied image data and unmultiplies it.
 * The result is stored in retdata.
 **/
static void
unpremultiply_rgba (unsigned char* data,
		    int            width,
		    int            height,
		    int            stride,
		    unsigned char* retdata)
{
    unsigned char* end = data + stride * height;
    for (unsigned char* in = data, *out = retdata;
	 in < end;
	 in += stride, out += stride)
    {
	for (int i = 0; i < width; ++i) {
	    // XXX for a big-endian platform this'd have to change
	    int idx = 4 * i;
	    unsigned char alpha = in[idx + 3];
	    out[idx + 0] = unpremultiply(in[idx + 0], alpha); // B
	    out[idx + 1] = unpremultiply(in[idx + 1], alpha); // G
	    out[idx + 2] = unpremultiply(in[idx + 2], alpha); // R
	    out[idx + 3] = in[idx + 3]; // Alpha
	}
    }
}

/**
 * premultiply_rgba:
 *
 * Takes an input in ABGR non-premultiplied image data and premultiplies it.
 * The returned data must be freed with free().
 **/
static unsigned char*
premultiply_rgba (unsigned char* data,
		  int            width,
		  int            height,
		  int            stride)
{
    unsigned char* retdata = reinterpret_cast<unsigned char*>(malloc(stride * height));
    if (!retdata)
	return NULL;

    unsigned char* end = data + stride * height;
    for (unsigned char* in = data, *out = retdata;
	 in < end;
	 in += stride, out += stride)
    {
	for (int i = 0; i < width; ++i) {
	    // XXX for a big-endian platform this'd have to change
	    int idx = 4 * i;
	    unsigned char alpha = in[idx + 3];
	    out[idx + 0] = premultiply(in[idx + 0], alpha); // B
	    out[idx + 1] = premultiply(in[idx + 1], alpha); // G
	    out[idx + 2] = premultiply(in[idx + 2], alpha); // R
	    out[idx + 3] = in[idx + 3]; // Alpha
	}
    }
    return retdata;
}

/**
 * _cairo_beos_bitmap_to_surface:
 *
 * Returns an addrefed image surface for a BBitmap. The bitmap need not outlive
 * the surface.
 **/
static cairo_image_surface_t*
_cairo_beos_bitmap_to_surface (BBitmap* bitmap)
{
    color_space format = bitmap->ColorSpace();
    if (format != B_RGB32 && format != B_RGBA32) {
	BBitmap bmp(bitmap->Bounds(), B_RGB32, true);
	BView view(bitmap->Bounds(), "Cairo bitmap drawing view",
		   B_FOLLOW_ALL_SIDES, 0);
	bmp.AddChild(&view);

	view.LockLooper();

	view.DrawBitmap(bitmap, BPoint(0.0, 0.0));
	view.Sync();

	cairo_image_surface_t* imgsurf = _cairo_beos_bitmap_to_surface(&bmp);

	view.UnlockLooper();
	bmp.RemoveChild(&view);
	return imgsurf;
    }

    cairo_format_t cformat = format == B_RGB32 ? CAIRO_FORMAT_RGB24
						: CAIRO_FORMAT_ARGB32;

    BRect bounds(bitmap->Bounds());
    unsigned char* bits = reinterpret_cast<unsigned char*>(bitmap->Bits());
    int width = bounds.IntegerWidth() + 1;
    int height = bounds.IntegerHeight() + 1;
    unsigned char* premultiplied;
    if (cformat == CAIRO_FORMAT_ARGB32) {
       premultiplied = premultiply_rgba(bits, width, height,
					bitmap->BytesPerRow());
    } else {
	premultiplied = reinterpret_cast<unsigned char*>(
					malloc(bitmap->BytesPerRow() * height));
	if (premultiplied)
	    memcpy(premultiplied, bits, bitmap->BytesPerRow() * height);
    }
    if (!premultiplied)
	return NULL;

    cairo_image_surface_t* surf = reinterpret_cast<cairo_image_surface_t*>
	(cairo_image_surface_create_for_data(premultiplied,
					     cformat,
					     width,
					     height,
					     bitmap->BytesPerRow()));
    if (surf->base.status)
	free(premultiplied);
    else
	_cairo_image_surface_assume_ownership_of_data(surf);
    return surf;
}

/**
 * _cairo_image_surface_to_bitmap:
 *
 * Converts an image surface to a BBitmap. The return value must be freed with
 * delete.
 **/
static BBitmap*
_cairo_image_surface_to_bitmap (cairo_image_surface_t* surface)
{
    BRect size(0.0, 0.0, surface->width - 1, surface->height - 1);
    switch (surface->format) {
	case CAIRO_FORMAT_ARGB32: {
	    BBitmap* data = new BBitmap(size, B_RGBA32);
	    unpremultiply_rgba(surface->data,
			       surface->width,
			       surface->height,
			       surface->stride,
			       reinterpret_cast<unsigned char*>(data->Bits()));
	    return data;
        }
	case CAIRO_FORMAT_RGB24: {
	    BBitmap* data = new BBitmap(size, B_RGB32);
	    memcpy(data->Bits(), surface->data, surface->height * surface->stride);
	    return data;
	}
	default:
	    assert(0);
	    return NULL;
    }
}

/**
 * _cairo_op_to_be_op:
 *
 * Converts a cairo drawing operator to a beos drawing_mode. Returns true if
 * the operator could be converted, false otherwise.
 **/
static bool
_cairo_op_to_be_op (cairo_operator_t cairo_op,
		    drawing_mode*    beos_op)
{
    switch (cairo_op) {

	case CAIRO_OPERATOR_SOURCE:
	    *beos_op = B_OP_COPY;
	    return true;
	case CAIRO_OPERATOR_OVER:
	    *beos_op = B_OP_ALPHA;
	    return true;

	case CAIRO_OPERATOR_ADD:
	    // Does not actually work
#if 1
	    return false;
#else
	    *beos_op = B_OP_ADD;
	    return true;
#endif

	case CAIRO_OPERATOR_CLEAR:
	    // Does not map to B_OP_ERASE - it replaces the dest with the low
	    // color, instead of transparency; could be done by setting low
	    // color appropriately.

	case CAIRO_OPERATOR_IN:
	case CAIRO_OPERATOR_OUT:
	case CAIRO_OPERATOR_ATOP:

	case CAIRO_OPERATOR_DEST:
	case CAIRO_OPERATOR_DEST_OVER:
	case CAIRO_OPERATOR_DEST_IN:
	case CAIRO_OPERATOR_DEST_OUT:
	case CAIRO_OPERATOR_DEST_ATOP:

	case CAIRO_OPERATOR_XOR:
	case CAIRO_OPERATOR_SATURATE:

	default:
	    return false;
    };
}

static cairo_surface_t *
_cairo_beos_surface_create_similar (void            *abstract_surface,
				    cairo_content_t  content,
				    int              width,
				    int              height)
{
    fprintf(stderr, "Creating similar\n");

    cairo_beos_surface_t *surface = reinterpret_cast<cairo_beos_surface_t*>(
							abstract_surface);

    if (width <= 0)
	width = 1;
    if (height <= 0)
	height = 1;

    BRect rect(0.0, 0.0, width - 1, height - 1);
    BBitmap* bmp;
    switch (content) {
	case CAIRO_CONTENT_ALPHA:
	    // Can't support this natively
	    return _cairo_image_surface_create_with_content(content, width,
							    height);
	case CAIRO_CONTENT_COLOR_ALPHA:
	    bmp = new BBitmap(rect, B_RGBA32, true);
	    break;
	case CAIRO_CONTENT_COLOR:
	    // Match the color depth
	    if (surface->bitmap) {
		color_space space = surface->bitmap->ColorSpace();
		// No alpha was requested -> make sure not to return
		// a surface with alpha
		if (space == B_RGBA32)
		    space = B_RGB32;
		if (space == B_RGBA15)
		    space = B_RGB15;
		bmp = new BBitmap(rect, space, true);
	    } else {
		BScreen scr(surface->view->Window());
		color_space space = B_RGB32;
		if (scr.IsValid())
		    space = scr.ColorSpace();
		bmp = new BBitmap(rect, space, true);
	    }
	    break;
	default:
	    assert(0);
	    return NULL;
	    
    };
    BView* view = new BView(rect, "Cairo bitmap view", B_FOLLOW_ALL_SIDES, 0);
    bmp->AddChild(view);
    return _cairo_beos_surface_create_internal(view, bmp, true);
}

static cairo_status_t
_cairo_beos_surface_finish (void *abstract_surface)
{
    cairo_beos_surface_t *surface = reinterpret_cast<cairo_beos_surface_t*>(
							abstract_surface);
    if (surface->owns_bitmap_view) {
	if (surface->bitmap)
	    surface->bitmap->RemoveChild(surface->view);

	delete surface->view;
	delete surface->bitmap;

	surface->view = NULL;
	surface->bitmap = NULL;
    }

    return CAIRO_STATUS_SUCCESS;
}

static cairo_status_t
_cairo_beos_surface_acquire_source_image (void                   *abstract_surface,
					  cairo_image_surface_t **image_out,
					  void                  **image_extra)
{
    fprintf(stderr, "Getting source image\n");