Debug output for platforms

Summary: Mostly so DRM can report if it has AMS or not

Test Plan:
Ran on my DRM setup, printed debug.
Spawned nested compositor, printed debug on that

Reviewers: #plasma, graesslin

Reviewed By: #plasma, graesslin

Subscribers: plasma-devel, kwin, #kwin

Tags: #kwin

Differential Revision: https://phabricator.kde.org/D8702

platform.cpp

@@ -477,4 +477,9 @@ void Platform::createEffectsHandler(Compositor *compositor, Scene *scene)
     new EffectsHandlerImpl(compositor, scene);
 }
 
+QString Platform::supportInformation() const
+{
+    return QStringLiteral("Name: %1\n").arg(metaObject()->className());
+}
+
 }

platform.h

@@ -383,6 +383,15 @@ public:
      **/
     virtual QVector<CompositingType> supportedCompositors() const = 0;
 
+    /*
+     * A string of information to include in kwin debug output
+     * It should not be translated.
+     *
+     * The base implementation prints the name.
+     * @since 5.12
+     */
+    virtual QString supportInformation() const;
+
 public Q_SLOTS:
     void pointerMotion(const QPointF &position, quint32 time);
     void pointerButtonPressed(quint32 button, quint32 time);

plugins/platforms/drm/drm_backend.cpp

@@ -727,4 +727,15 @@ QVector<CompositingType> DrmBackend::supportedCompositors() const
 #endif
 }
 
+QString DrmBackend::supportInformation() const
+{
+    QString supportInfo;
+    QDebug s(&supportInfo);
+    s.nospace();
+    s << "Name: " << "DRM" << endl;
+    s << "Active: " << m_active << endl;
+    s << "Atomic Mode Setting: " << m_atomicModeSetting << endl;
+    return supportInfo;
+}
+
 }

plugins/platforms/drm/drm_backend.h

@@ -120,6 +120,8 @@ public:
 
     QVector<CompositingType> supportedCompositors() const override;
 
+    QString supportInformation() const override;
+
 public Q_SLOTS:
     void turnOutputsOn();
 

workspace.cpp

@@ -46,6 +46,7 @@ along with this program.  If not, see <http://www.gnu.org/licenses/>.
 #include "rules.h"
 #include "screenedge.h"
 #include "screens.h"
+#include "platform.h"
 #include "scripting/scripting.h"
 #ifdef KWIN_BUILD_TABBOX
 #include "tabbox.h"
@@ -1425,6 +1426,11 @@ QString Workspace::supportInformation() const
         support.append(bridge->supportInformation());
         support.append(QStringLiteral("\n"));
     }
+    support.append(QStringLiteral("Platform\n"));
+    support.append(QStringLiteral("==========\n"));
+    support.append(kwinApp()->platform()->supportInformation());
+    support.append(QStringLiteral("\n"));
+
     support.append(QStringLiteral("Options\n"));
     support.append(QStringLiteral("=======\n"));
     const QMetaObject *metaOptions = options->metaObject();