RFR: 8254569: Remove hard dependency on Dispman in Monocle fb rendering [v4]

[Johan Vos]

On Thu, 5 Nov 2020 02:44:01 GMT, John Neffenger <github.com+1413266+jgneff at openjdk.org> wrote:

>> Johan Vos has updated the pull request incrementally with one additional commit since the last revision:
>> 
>>   add one more @override to process reviewer comments
>
> modules/javafx.graphics/src/main/java/com/sun/glass/ui/monocle/EGLPlatform.java line 42:
> 
>> 40:             }
>> 41:         }
>> 42:     }
> 
> I changed the constructor to the following:
> 
> import com.sun.glass.utils.NativeLibLoader;
> 
> public EGLPlatform() {
>     String lib = System.getProperty("monocle.egl.lib");
>     if (lib != null) {
>         NativeLibLoader.loadLibrary(lib);
>     }
> }
> 
> Using the `NativeLibLoader` allowed me to define my native library with `monocle.egl.lib=test01` (instead of `libtest01.so`) and drop it in the JavaFX SDK with all the other JavaFX libraries. You also get good error messages when it fails.
> 
> The current code did load the library after adding its path to the environment variable `LD_LIBRARY_PATH`, but it failed with the following message on first use:
> 
> java.lang.UnsatisfiedLinkError:
> 'long com.sun.glass.ui.monocle.EGLAcceleratedScreen
>   .nPlatformGetNativeWindow(java.lang.String)'
> 
> The call to `NativeLibLoader` solved these problems, with no `LD_LIBRARY_PATH` required.

The difference between how I'm building it and how you are building is that I combine all monocle code in 1 library (libglass_monocle.so) where you have a common monocle library and a egl-specific one -- and this is what you do with the EPD as well. For Android, we use a single library as well. At build time, the android-specific classes are added in libglass_monocle.so and dlopen() is used to load android-specific libraries at runtime.

Both approaches are valid, but can't be mixed. Hence we need to decide to either go for 1 or 2 monocle libraries (the android approach, where there is libglass_monocle only or the epd approach where there is also libglass_monocle_epd). I don't have a strong preference, but I think libglass_monocle will be really very small.

Bundling the device-specific library (in your case the one containing test01.o) with the monocle library (the general or a specific one) seems less interesting, as that means you need e.g. 4 different monocle libraries for 4 different Pi-configurations. I believe it is better to share the monocle libraries, and have a single OpenJFX library for monocle, and then platform/configuration-specific libraries.

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PR: https://git.openjdk.java.net/jfx/pull/343