DRM/KMS config: add support for specifying the primary screen

Not having a way to say that a given output should be registered as the
primary screen (meaning it comes first in the QGuiApplication::screens() list,
emits primaryScreenChanged() signal etc.) can be a problem for some systems.

The order of the outputs array in the JSON configuration file is not relevant
in this respect since screens are registered either in the original DRM connector
order, or, when the virtual desktop layout is specified via virtualIndex, in the
order specified by virtualIndex. The primary screen status is independent from this.

Therefore, add a new, optional boolean property: primary. For example, the following
forces the QScreen corresponding to the VGA output to be the primary screen on the
Renesas R-Car H2 board, even though by default it is the HDMI one that happens to
be reported first by the system.

{
    "device": "/dev/dri/card0",
    "outputs": [
        { "name": "HDMI1", "mode": "1280x720" },
        { "name": "VGA1", "mode": "1280x720", "primary": true },
        { "name": "LVDS1", "mode": "off" }
    ]
}

In addition, improve the quality of the logging output.

[ChangeLog][Platform Specific Changes] Added support for specifying the primary screen
in the JSON config file in QT_QPA_EGLFS_KMS_CONFIG when running on DRM/KMS with eglfs.

Task-number: QTBUG-57980
Change-Id: Iba490800dee3b7162c68c4d40b0822f3f6d81b69
Reviewed-by: Andy Nichols <andy.nichols@qt.io>

2 files changed, 3 insertions, 3 deletions

diff --git a/src/plugins/platforms/eglfs/api/qeglfsintegration.cpp b/src/plugins/platforms/eglfs/api/qeglfsintegration.cpp
index 0aa7a65276..73110dba61 100644
--- a/src/plugins/platforms/eglfs/api/qeglfsintegration.cpp
+++ b/src/plugins/platforms/eglfs/api/qeglfsintegration.cpp
@@ -116,9 +116,9 @@ QEglFSIntegration::QEglFSIntegration()
     initResources();
 }
 
-void QEglFSIntegration::addScreen(QPlatformScreen *screen)
+void QEglFSIntegration::addScreen(QPlatformScreen *screen, bool isPrimary)
 {
-    screenAdded(screen);
+    screenAdded(screen, isPrimary);
 }
 
 void QEglFSIntegration::removeScreen(QPlatformScreen *screen)
diff --git a/src/plugins/platforms/eglfs/api/qeglfsintegration_p.h b/src/plugins/platforms/eglfs/api/qeglfsintegration_p.h
index 080c8ed332..c288876678 100644
--- a/src/plugins/platforms/eglfs/api/qeglfsintegration_p.h
+++ b/src/plugins/platforms/eglfs/api/qeglfsintegration_p.h
@@ -103,7 +103,7 @@ public:
 
     QFbVtHandler *vtHandler() { return m_vtHandler.data(); }
 
-    void addScreen(QPlatformScreen *screen);
+    void addScreen(QPlatformScreen *screen, bool isPrimary = false);
     void removeScreen(QPlatformScreen *screen);
 
 private: