Java example source code file (CGraphicsEnv.m)

This example Java source code file (CGraphicsEnv.m) is included in the alvinalexander.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" ^TM.

Learn more about this Java project at its project page.

Java - Java tags/keywords

cgdirectdisplayid, cgdisplaycount, cgdisplayregisterreconfigurationcallback, cgdisplayremovereconfigurationcallback, cggetactivedisplaylist, cggetonlinedisplaylist, jnf_cocoa_enter, jnf_cocoa_exit, jnfexception, jnfweakjobjectwrapper, jnicall, jnienv, jniexport, null

The CGraphicsEnv.m Java example source code

/*
 * Copyright (c) 2011, 2013, Oracle and/or its affiliates. All rights reserved.
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
 *
 * This code is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License version 2 only, as
 * published by the Free Software Foundation.  Oracle designates this
 * particular file as subject to the "Classpath" exception as provided
 * by Oracle in the LICENSE file that accompanied this code.
 *
 * This code 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
 * version 2 for more details (a copy is included in the LICENSE file that
 * accompanied this code).
 *
 * You should have received a copy of the GNU General Public License version
 * 2 along with this work; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
 *
 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
 * or visit www.oracle.com if you need additional information or have any
 * questions.
 */

#import <JavaNativeFoundation/JavaNativeFoundation.h>

#import "LWCToolkit.h"
#import "AWT_debug.h"


/*
 * Class:     sun_awt_CGraphicsEnvironment
 * Method:    initCocoa
 * Signature: ()V
 */
JNIEXPORT void JNICALL
Java_sun_awt_CGraphicsEnvironment_initCocoa
(JNIEnv *env, jclass self)
{
JNF_COCOA_ENTER(env);

    // Inform Cocoa that we're multi-threaded.
    // Creating a short-lived NSThread is the recommended way of doing so.
    [NSThread detachNewThreadSelector:@selector(self) toTarget:[NSObject class] withObject:nil];

JNF_COCOA_EXIT(env);
}

#define MAX_DISPLAYS 64

/*
 * Class:     sun_awt_CGraphicsEnvironment
 * Method:    getDisplayIDs
 * Signature: ()[I
 */
JNIEXPORT jintArray JNICALL
Java_sun_awt_CGraphicsEnvironment_getDisplayIDs
(JNIEnv *env, jclass class)
{
    jintArray ret = NULL;

JNF_COCOA_ENTER(env);

    /* Get the count */
    CGDisplayCount displayCount;
    if (CGGetActiveDisplayList(MAX_DISPLAYS, NULL, &displayCount) != kCGErrorSuccess) {
        [JNFException raise:env
                         as:kInternalError
                     reason:"CGGetOnlineDisplayList() failed to get display count"];
        return NULL;
    }

    /* Allocate an array and get the size list of display Ids */
    CGDirectDisplayID displays[MAX_DISPLAYS];
    if (CGGetActiveDisplayList(displayCount, displays, &displayCount) != kCGErrorSuccess) {
        [JNFException raise:env
                         as:kInternalError
                     reason:"CGGetOnlineDisplayList() failed to get display list"];
        return NULL;
    }

    /* Allocate a java array for display identifiers */
    ret = JNFNewIntArray(env, displayCount);

    /* Initialize and return the backing int array */
    assert(sizeof(jint) >= sizeof(CGDirectDisplayID));
    jint *elems = (*env)->GetIntArrayElements(env, ret, 0);

    CGDisplayCount i;
    for (i = 0; i < displayCount; i++) {
        elems[i] = displays[i];
    }

    (*env)->ReleaseIntArrayElements(env, ret, elems, 0);

JNF_COCOA_EXIT(env);

    return ret;
}

/*
 * Class:     sun_awt_CGraphicsEnvironment
 * Method:    getMainDisplayID
 * Signature: ()I
 */
JNIEXPORT jint JNICALL
Java_sun_awt_CGraphicsEnvironment_getMainDisplayID
(JNIEnv *env, jclass class)
{
    return CGMainDisplayID();
}

/*
 * Post the display reconfiguration event.
 */
static void displaycb_handle
(CGDirectDisplayID display, CGDisplayChangeSummaryFlags flags, void *userInfo)
{
    if (flags == kCGDisplayBeginConfigurationFlag) return;

    JNFPerformEnvBlock(JNFThreadDetachImmediately, ^(JNIEnv *env) {
        JNFWeakJObjectWrapper *wrapper = (JNFWeakJObjectWrapper *)userInfo;

        jobject graphicsEnv = [wrapper jObjectWithEnv:env];
        if (graphicsEnv == NULL) return; // ref already GC'd
        static JNF_CLASS_CACHE(jc_CGraphicsEnvironment, "sun/awt/CGraphicsEnvironment");
        static JNF_MEMBER_CACHE(jm_displayReconfiguration, jc_CGraphicsEnvironment, "_displayReconfiguration", "(IZ)V");
        JNFCallVoidMethod(env, graphicsEnv, jm_displayReconfiguration,
                            (jint) display, 
                            (jboolean) flags & kCGDisplayRemoveFlag);
    });
}

/*
 * Class:     sun_awt_CGraphicsEnvironment
 * Method:    registerDisplayReconfiguration
 * Signature: ()J
 */
JNIEXPORT jlong JNICALL
Java_sun_awt_CGraphicsEnvironment_registerDisplayReconfiguration
(JNIEnv *env, jobject this)
{
    jlong ret = 0L;

JNF_COCOA_ENTER(env);

    JNFWeakJObjectWrapper *wrapper = [JNFWeakJObjectWrapper wrapperWithJObject:this withEnv:env];
    CFRetain(wrapper); // pin from ObjC-GC

    /* Register the callback */
    if (CGDisplayRegisterReconfigurationCallback(&displaycb_handle, wrapper) != kCGErrorSuccess) {
        [JNFException raise:env
                         as:kInternalError
                     reason:"CGDisplayRegisterReconfigurationCallback() failed"];
        return 0L;
    }

    ret = ptr_to_jlong(wrapper);

JNF_COCOA_EXIT(env);

    return ret;
}

/*
 * Class:     sun_awt_CGraphicsEnvironment
 * Method:    deregisterDisplayReconfiguration
 * Signature: (J)V
 */
JNIEXPORT void JNICALL
Java_sun_awt_CGraphicsEnvironment_deregisterDisplayReconfiguration
(JNIEnv *env, jobject this, jlong p)
{
JNF_COCOA_ENTER(env);

    JNFWeakJObjectWrapper *wrapper = (JNFWeakJObjectWrapper *)jlong_to_ptr(p);
    if (!wrapper) return;

    /* Remove the registration */
    if (CGDisplayRemoveReconfigurationCallback(&displaycb_handle, wrapper) != kCGErrorSuccess) {
        [JNFException raise:env
                         as:kInternalError
                     reason:"CGDisplayRemoveReconfigurationCallback() failed, leaking the callback context!"];
        return;
    }

    [wrapper setJObject:NULL withEnv:env]; // more efficiant to pre-clear

    CFRelease(wrapper);

JNF_COCOA_EXIT(env);
}