kbd preview: add error description

previously we've only had the error details which is a raw dump of the
output from xkbcomp, give it some nice context so users know what's
going on

kcms/keyboard/tastenbrett/main.cpp

@@ -119,6 +119,7 @@ int main(int argc, char *argv[])
     memset(&componentNames, 0, sizeof(XkbComponentNamesRec));
     XkbRF_GetComponents(rules, &varDefs, &componentNames);
 
+    QString errorDescription;
     QString errorDetails;
     std::unique_ptr<Geometry> geometry;
 
@@ -143,6 +144,11 @@ int main(int argc, char *argv[])
         setxkbmap.waitForFinished();
         xkbcomp.waitForFinished();
 
+        errorDescription = i18nc("@label",
+                                 "The keyboard geometry failed to load."
+                                 " This often indicates that the selected model does not support a specific layout"
+                                 " or layout variant."
+                                 " This problem will likely also present when you try to use this combination of model, layout and variant.");
         errorDetails = xkbcomp.readAllStandardOutput();
     } else {
         Q_ASSERT(xkb);
@@ -172,6 +178,7 @@ int main(int argc, char *argv[])
             QCoreApplication::exit(-1);
     }, Qt::QueuedConnection);
     engine.rootContext()->setContextProperty("geometry", geometry.get());
+    engine.rootContext()->setContextProperty("errorDescription", errorDescription);
     engine.rootContext()->setContextProperty("errorDetails", errorDetails);
     engine.load(url);
 

kcms/keyboard/tastenbrett/qml/main.qml

@@ -62,6 +62,13 @@ Window {
         visible: false
         anchors.fill: parent
 
+        Label {
+            Layout.fillWidth: true
+            text: errorDescription
+            color: activePalette.text
+            wrapMode: Text.WordWrap
+        }
+
         TextArea {
             Layout.fillWidth: true
             text: errorDetails