/*

File: window_transparency.c

Abstract:  Support functions to make a Carbon window transparent.

© Copyright 2005 Apple Computer, Inc. All rights reserved.

IMPORTANT:  This Apple software is supplied to you by Apple Computer,

Inc. ("Apple") in consideration of your agreement to the following

terms, and your use, installation, modification or redistribution of

this Apple software constitutes acceptance of these terms.  If you do

not agree with these terms, please do not use, install, modify or

redistribute this Apple software.

In consideration of your agreement to abide by the following terms, and

subject to these terms, Apple grants you a personal, non-exclusive

license, under Apple's copyrights in this original Apple software (the

"Apple Software"), to use, reproduce, modify and redistribute the Apple

Software, with or without modifications, in source and/or binary forms;

provided that if you redistribute the Apple Software in its entirety and

without modifications, you must retain this notice and the following

text and disclaimers in all such redistributions of the Apple Software.

Neither the name, trademarks, service marks or logos of Apple Computer,

Inc. may be used to endorse or promote products derived from the Apple

Software without specific prior written permission from Apple.  Except

as expressly stated in this notice, no other rights or licenses, express

or implied, are granted by Apple herein, including but not limited to

any patent rights that may be infringed by your derivative works or by

other works in which the Apple Software may be incorporated.

The Apple Software is provided by Apple on an "AS IS" basis.  APPLE

MAKES NO WARRANTIES, EXPRESS OR IMPLIED, INCLUDING WITHOUT LIMITATION

THE IMPLIED WARRANTIES OF NON-INFRINGEMENT, MERCHANTABILITY AND FITNESS

FOR A PARTICULAR PURPOSE, REGARDING THE APPLE SOFTWARE OR ITS USE AND

OPERATION ALONE OR IN COMBINATION WITH YOUR PRODUCTS.

IN NO EVENT SHALL APPLE BE LIABLE FOR ANY SPECIAL, INDIRECT, INCIDENTAL

OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF

SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS

INTERRUPTION) ARISING IN ANY WAY OUT OF THE USE, REPRODUCTION,

MODIFICATION AND/OR DISTRIBUTION OF THE APPLE SOFTWARE, HOWEVER CAUSED

AND WHETHER UNDER THEORY OF CONTRACT, TORT (INCLUDING NEGLIGENCE),

STRICT LIABILITY OR OTHERWISE, EVEN IF APPLE HAS BEEN ADVISED OF THE

POSSIBILITY OF SUCH DAMAGE.

*/

#include "window_transparency.h"

static EventHandlerUPP gWindowGetRegionProc = NULL;

static EventHandlerUPP gWindowContentViewDrawProc = NULL;

//---------------------------------------------------------------------

// Tells the toolbox the window's opaque region is ... nothing!

// This allows us to do transparency in a portion of the window.

//

OSStatus MyWindowGetRegionEventHandler(EventHandlerCallRef nextHandler, EventRef theEvent, void* userData)

{

    WindowRegionCode code;

    RgnHandle rgn;

    OSStatus status;

    status = GetEventParameter(theEvent, kEventParamWindowRegionCode, typeWindowRegionCode, NULL, sizeof(WindowRegionCode), NULL, &code);

    require_noerr( status, CantGetEventParameter );

    if ( code == kWindowOpaqueRgn )

    {

        status = GetEventParameter(theEvent, kEventParamRgnHandle, typeQDRgnHandle, NULL, sizeof(RgnHandle), NULL, &rgn);

        require_noerr( status, CantGetEventParameter );

        EmptyRgn(rgn);

        status = noErr; // not strictly necessary, since we have a require right above, but good to include

    }

    else {

        status = eventNotHandledErr;

    }

CantGetEventParameter:

    return status;

}

//---------------------------------------------------------------------

// Erases the contents of an HIView whenever a draw event is sent

//

OSStatus MyWindowContentViewDrawEventHandler(EventHandlerCallRef nextHandler, EventRef theEvent, void* userData)

{

    ControlRef control;

    CGContextRef context;

    CGRect cgBounds;

    OSStatus status;

    status = GetEventParameter(theEvent, kEventParamDirectObject, typeControlRef, NULL, sizeof(ControlRef), NULL, &control);

    require_noerr( status, CantGetEventParameter );

    status = GetEventParameter(theEvent, kEventParamCGContextRef, typeCGContextRef, NULL, sizeof(CGContextRef), NULL, &context);

    require_noerr( status, CantGetEventParameter );

    status = HIViewGetBounds(control, &cgBounds);

    require_noerr( status, CantGetBounds );

    CGContextClearRect(context, cgBounds);

    status = noErr; // not strictly necessary, since we have a require right above, but good to include

CantGetBounds:

CantGetEventParameter:

    return status;

}

//---------------------------------------------------------------------

// Installs proper event handlers to make the background content of a

// Carbon window transparent. Should be called before calling ShowWindow.

//

OSStatus MakeWindowTransparent(WindowRef window)

{

    EventTypeSpec eventSpec;

    HIViewRef contentView;

    OSStatus status;

    // Install a callback to set the window's opaque region to nothing

    if ( gWindowGetRegionProc == NULL )

        gWindowGetRegionProc = NewEventHandlerUPP(MyWindowGetRegionEventHandler);

    eventSpec.eventClass = kEventClassWindow;

    eventSpec.eventKind = kEventWindowGetRegion;

    status = InstallEventHandler(GetWindowEventTarget(window), gWindowGetRegionProc, 1, &eventSpec, NULL, NULL);

    check_noerr( status );

    // Find the content view of the window

    status = HIViewFindByID(HIViewGetRoot(window), kHIViewWindowContentID, &contentView);

    require_noerr( status, CantGetViewRef );

    // Install a drawing callback for the content view to make it completely transparent

    if ( gWindowContentViewDrawProc == NULL )

        gWindowContentViewDrawProc = NewEventHandlerUPP(MyWindowContentViewDrawEventHandler);

    eventSpec.eventClass = kEventClassControl;

    eventSpec.eventKind = kEventControlDraw;

    status = InstallEventHandler(GetControlEventTarget(contentView), gWindowContentViewDrawProc, 1, &eventSpec, NULL, NULL);

    check_noerr( status );

    // Make sure HIToolbox knows this is a non-opaque window

    status = HIWindowChangeFeatures( window, 0, kWindowIsOpaque );

    check_noerr( status );

    // This call forces HIToolbox to query the opaque region

    // immediately. It will actually do so on its own, but only

    // *after* the window is first displayed. This can result in

    // a quick flash of non-transparency when the window first

    // appears. Calling this before the window is first shown

    // prevents the flash.

    ReshapeCustomWindow(window);

    // On pre-10.4 systems, HIToolbox special-cased windows with

    // alpha values of 1.0 and never actually fetched the opaque

    // region at all, even when a handler was installed. As a

    // workaround, one can set the window's alpha value to 0.999,

    // which will not alter the appearance at all, but will have

    // the desired effect of causing the opaque region to be

    // queried properly. This workaround is not needed on 10.4 and

    // later systems.

    //SetWindowAlpha(window, 0.999);

    // Don't let transparency affect event processing

    status = ChangeWindowAttributes(window, kWindowOpaqueForEventsAttribute, kWindowNoAttributes);

    check_noerr( status );

CantGetViewRef:

    return status;

}