Native style: improve debug output

Improve the debug implementation so that you don't need
to modify the application to get debug output. You
can now instead just do e.g:

QQC2_NATIVESTYLE_DEBUG="myButton output contentRect"
QQC2_NATIVESTYLE_DEBUG="combobox ninepatchmargins"
QQC2_NATIVESTYLE_DEBUG="all layoutrect"

Change-Id: I58cbcfb241bc0be20cae73735bc277d0662a476a
Reviewed-by: Jan Arve Sæther <jan-arve.saether@qt.io>

2 files changed, 55 insertions, 35 deletions

diff --git a/src/imports/nativestyle/items/qquickstyleitem.cpp b/src/imports/nativestyle/items/qquickstyleitem.cpp
index c45f0c91..4c84bf9a 100644
--- a/src/imports/nativestyle/items/qquickstyleitem.cpp
+++ b/src/imports/nativestyle/items/qquickstyleitem.cpp
@@ -328,48 +328,64 @@ void QQuickStyleItem::updatePolish()
         paintControlToImage();
 }
 
-void QQuickStyleItem::componentComplete()
+#ifdef QT_DEBUG
+void QQuickStyleItem::addDebugInfo()
 {
-    Q_ASSERT_X(m_control, Q_FUNC_INFO, "You need to assign a value to property 'control'");
+    // Example debug strings:
+    // "QQC2_NATIVESTYLE_DEBUG="myButton output contentRect"
+    // "QQC2_NATIVESTYLE_DEBUG="ComboBox ninepatchmargins"
+    // "QQC2_NATIVESTYLE_DEBUG="All layoutrect"
+
+    static const auto debugString = qEnvironmentVariable("QQC2_NATIVESTYLE_DEBUG");
+    static const auto matchAll = debugString.startsWith(QLatin1String("All "));
+    static const auto prefix = QStringLiteral("QQuickStyleItem");
+    if (debugString.isEmpty())
+        return;
 
-#ifdef QT_DEBUG
-    if (!qEnvironmentVariable("QQC2_NATIVESTYLE_DEBUG").isEmpty()) {
-        // Set objectName to "debug" pluss one or more options separated
-        // by space to show extra information about this item.
+    const auto objectName = m_control->objectName();
+    const auto typeName = QString::fromUtf8(metaObject()->className()).remove(prefix);
+    const bool matchName = !objectName.isEmpty() && debugString.startsWith(objectName);
+    const bool matchType = debugString.startsWith(typeName);
 
-#define QQC2_DEBUG_FLAG(FLAG) \
-    if (name.contains(QString(QLatin1String(#FLAG)).toLower())) m_debugFlags |= FLAG
-
-        const QString name = m_control->objectName().toLower();
-        if (name.startsWith(QString(QLatin1String("debug")).toLower())) {
-            QQC2_DEBUG_FLAG(Output);
-            QQC2_DEBUG_FLAG(ImageRect);
-            QQC2_DEBUG_FLAG(ContentRect);
-            QQC2_DEBUG_FLAG(LayoutRect);
-            QQC2_DEBUG_FLAG(InputContentSize);
-            QQC2_DEBUG_FLAG(DontUseNinePatchImage);
-            QQC2_DEBUG_FLAG(NinePatchMargins);
-            QQC2_DEBUG_FLAG(Unscaled);
-
-            if (m_debugFlags & (DontUseNinePatchImage
-                                | InputContentSize
-                                | ContentRect
-                                | LayoutRect
-                                | NinePatchMargins)) {
-                // Some rects will not fit inside the drawn image unless
-                // we switch off (nine patch) image scaling.
-                m_debugFlags |= DontUseNinePatchImage;
-                m_useNinePatchImage = false;
-            }
+    if (!(matchAll || matchName || matchType))
+        return;
 
-            if (m_debugFlags != NoDebug)
-                qDebug() << "debug options set:" << m_debugFlags;
-            else
-                qDebug() << "available debug options:" << DebugFlags(0xFFFF);
-        }
+#define QQC2_DEBUG_FLAG(FLAG) \
+    if (debugString.contains(QLatin1String(#FLAG), Qt::CaseInsensitive)) m_debugFlags |= FLAG
+
+    QQC2_DEBUG_FLAG(Output);
+    QQC2_DEBUG_FLAG(ImageRect);
+    QQC2_DEBUG_FLAG(ContentRect);
+    QQC2_DEBUG_FLAG(LayoutRect);
+    QQC2_DEBUG_FLAG(InputContentSize);
+    QQC2_DEBUG_FLAG(DontUseNinePatchImage);
+    QQC2_DEBUG_FLAG(NinePatchMargins);
+    QQC2_DEBUG_FLAG(Unscaled);
+
+    if (m_debugFlags & (DontUseNinePatchImage
+                        | InputContentSize
+                        | ContentRect
+                        | LayoutRect
+                        | NinePatchMargins)) {
+        // Some rects will not fit inside the drawn image unless
+        // we switch off (nine patch) image scaling.
+        m_debugFlags |= DontUseNinePatchImage;
+        m_useNinePatchImage = false;
     }
+
+    if (m_debugFlags != NoDebug)
+        qDebug() << "debug options set for" << typeName << "(" << objectName << "):" << m_debugFlags;
+    else
+        qDebug() << "available debug options:" << DebugFlags(0xFFFF);
+}
 #endif
 
+void QQuickStyleItem::componentComplete()
+{
+    Q_ASSERT_X(m_control, Q_FUNC_INFO, "You need to assign a value to property 'control'");
+#ifdef QT_DEBUG
+    addDebugInfo();
+#endif
     QQuickItem::componentComplete();
     connectToControl();
     polish();
diff --git a/src/imports/nativestyle/items/qquickstyleitem.h b/src/imports/nativestyle/items/qquickstyleitem.h
index ff870684..a92bc516 100644
--- a/src/imports/nativestyle/items/qquickstyleitem.h
+++ b/src/imports/nativestyle/items/qquickstyleitem.h
@@ -261,6 +261,10 @@ private:
     inline void updateGeometry();
     inline void paintControlToImage();
 
+#ifdef QT_DEBUG
+    void addDebugInfo();
+#endif
+
 private:
     QPointer<QQuickItem> m_control;
     QImage m_paintedImage;