Custom title bar on macOS

[weisJ]

This relates to #2 .

Provide a custom title bar on macOS. After doing some research, this could be done by setting
the properties
fullsizecontentview and ]titlebarappearstransparent of the underlying NSWindow. (see https://stackoverflow.com/questions/54353576/colorizing-the-titlebar-in-macos-with-multiple-colors).

Communication with java would happen as in the windows version through JNI passing the request to a C++ function which in turn calls the objective-c code, that is able to set those properties.

If working the LaF should add a custom title bar (without window buttons, as those should still be present).

As I don't have access to macOS platform I can't do this myself, so help would be highly appreciated.

[vlsi]

Is it different from Frame#setUndecorated(true) ?

[weisJ]

Yes this keeps the window buttons and title text.

[vlsi]

https://bugs.openjdk.java.net/browse/JDK-8212549 which indeed works in Java 13.

JFrame frame = new JFrame();
final JRootPane rootPane = frame.getRootPane();
rootPane.putClientProperty("apple.awt.fullWindowContent", true);
rootPane.putClientProperty("apple.awt.transparentTitleBar", true);

[weisJ]

Great. At least for java version >= 12 this is a solution. Does moving the window work?

For java version below 12 there should still be a possibility to achieve this. Gladly because the jdk implementation also just sets those corresponding properties on the NSWindow the swing code can be reused and just the method of setting the window property still needs to be implemented natively.

Based on the jdk implementation it could look like this JNIDecorations.m:

#include "package_path_class.h"
#import <Cocoa/Cocoa.h>

#define OBJC(jl) ((id)jlong_to_ptr(jl))
#define FULL_WINDOW_CONTENT 1 << 14
#define TRANSPARENT_TITLE_BAR 1 << 18

JNIEXPORT void JNICALL 
package_path_class_installDecorations(JNIEnv *env, jclass obj, jlong windowPtr)
{
    NSWindow *nsWindow = OBJC(windowPtr);
    window.styleMask |= FULL_WINDOW_CONTENT | TRANSPARENT_TITLE_BAR;
}

To get hold of the window pointer Pointer.nativeValue(Native.getComponentPointer(component)) should still work on macOS.

[vlsi]

What do you think of setAccessible(true)-driven sun.lwawt.macosx.CPlatformWindow#setStyleBits(int mask, boolean value) for pre Java 12?

[weisJ]

Theoretically a good approach. The instance of the underlying CPlatformWindow can be optained as follows:

WindowPeer peer = (WindowPeer)window.getPeer();
CPlatformWindow platformWindow = (CPlatformWindow)((LWWindowPeer)peer).getPlatformWindow();

Neither CPlatformWindw nor LWWindowPeer are visible (or included) in non macOS jdk version.
All of this would need to happen through reflection or otherwise this can't be build.

[weisJ]

@vlsi could you tell me if #54 works for your? At least for the part of actually calling setStyleBits on CPlatformWindow.