[effects] Delay taking screenshot into next rendering cycle

Summary:
For windows the screenshot effect already delayed the rendering into the
next cycle. But for the fullscreen variants which save to a file the
Screenshot effect did try to take the shot directly.

This can be problematic as e.g. the OpenGL context might not be bound at
all. Also this makes it impossible to screenshot multiple screens
together in the Wayland case.

This change delays the DBus replies, schedules the geometry and takes
the screenshot in the next rendering pass. It does not fix the
multiscreen wayland problem yet.

Reviewers: #kwin

Subscribers: kwin

Tags: #kwin

Differential Revision: https://phabricator.kde.org/D3052

effects/screenshot/screenshot.cpp

@@ -41,6 +41,7 @@ bool ScreenShotEffect::supported()
 
 ScreenShotEffect::ScreenShotEffect()
     : m_scheduledScreenshot(0)
+    , m_replyConnection(QDBusConnection::sessionBus())
 {
     connect ( effects, SIGNAL(windowClosed(KWin::EffectWindow*)), SLOT(windowClosed(KWin::EffectWindow*)) );
     QDBusConnection::sessionBus().registerObject(QStringLiteral("/Screenshot"), this, QDBusConnection::ExportScriptableContents);
@@ -177,6 +178,11 @@ void ScreenShotEffect::postPaintScreen()
         }
         m_scheduledScreenshot = NULL;
     }
+
+    if (!m_scheduledGeometry.isNull()) {
+        m_replyConnection.send(m_replyMessage.createReply(blitScreenshot(m_scheduledGeometry)));
+        m_scheduledGeometry = QRect();
+    }
 }
 
 void ScreenShotEffect::screenshotWindowUnderCursor(int mask)
@@ -210,17 +216,62 @@ void ScreenShotEffect::screenshotForWindow(qulonglong winid, int mask)
 
 QString ScreenShotEffect::screenshotFullscreen()
 {
-    return blitScreenshot(effects->virtualScreenGeometry());
+    if (!calledFromDBus()) {
+        return QString();
+    }
+    if (!m_scheduledGeometry.isNull()) {
+        sendErrorReply(QDBusError::Failed, "A screenshot is already been taken");
+        return QString();
+    }
+    m_replyConnection = connection();
+    m_replyMessage = message();
+    setDelayedReply(true);
+    m_scheduledGeometry = effects->virtualScreenGeometry();
+    effects->addRepaintFull();
+    return QString();
 }
 
 QString ScreenShotEffect::screenshotScreen(int screen)
 {
-    return blitScreenshot(effects->clientArea(FullScreenArea, screen, 0));
+    if (!calledFromDBus()) {
+        return QString();
+    }
+    if (!m_scheduledGeometry.isNull()) {
+        sendErrorReply(QDBusError::Failed, "A screenshot is already been taken");
+        return QString();
+    }
+    m_scheduledGeometry = effects->clientArea(FullScreenArea, screen, 0);
+    if (m_scheduledGeometry.isNull()) {
+        sendErrorReply(QDBusError::Failed, "Invalid screen requested");
+        return QString();
+    }
+    m_replyConnection = connection();
+    m_replyMessage = message();
+    setDelayedReply(true);
+    effects->addRepaint(m_scheduledGeometry);
+    return QString();
 }
 
 QString ScreenShotEffect::screenshotArea(int x, int y, int width, int height)
 {
-    return blitScreenshot(QRect(x, y, width, height));
+    if (!calledFromDBus()) {
+        return QString();
+    }
+    if (!m_scheduledGeometry.isNull()) {
+        sendErrorReply(QDBusError::Failed, "A screenshot is already been taken");
+        return QString();
+    }
+    m_scheduledGeometry = QRect(x, y, width, height);
+    if (m_scheduledGeometry.isNull() || m_scheduledGeometry.isEmpty()) {
+        m_scheduledGeometry = QRect();
+        sendErrorReply(QDBusError::Failed, "Invalid area requested");
+        return QString();
+    }
+    m_replyConnection = connection();
+    m_replyMessage = message();
+    setDelayedReply(true);
+    effects->addRepaint(m_scheduledGeometry);
+    return QString();
 }
 
 QString ScreenShotEffect::blitScreenshot(const QRect &geometry)
@@ -321,7 +372,7 @@ void ScreenShotEffect::convertFromGLImage(QImage &img, int w, int h)
 
 bool ScreenShotEffect::isActive() const
 {
-    return m_scheduledScreenshot != NULL && !effects->isScreenLocked();
+    return (m_scheduledScreenshot != NULL || !m_scheduledGeometry.isNull()) && !effects->isScreenLocked();
 }
 
 void ScreenShotEffect::windowClosed( EffectWindow* w )

effects/screenshot/screenshot.h

@@ -22,13 +22,16 @@ along with this program.  If not, see <http://www.gnu.org/licenses/>.
 #define KWIN_SCREENSHOT_H
 
 #include <kwineffects.h>
+#include <QDBusContext>
+#include <QDBusConnection>
+#include <QDBusMessage>
 #include <QObject>
 #include <QImage>
 
 namespace KWin
 {
 
-class ScreenShotEffect : public Effect
+class ScreenShotEffect : public Effect, protected QDBusContext
 {
     Q_OBJECT
     Q_CLASSINFO("D-Bus Interface", "org.kde.kwin.Screenshot")
@@ -86,6 +89,9 @@ private:
     QString blitScreenshot(const QRect &geometry);
     EffectWindow *m_scheduledScreenshot;
     ScreenShotType m_type;
+    QRect m_scheduledGeometry;
+    QDBusConnection m_replyConnection;
+    QDBusMessage m_replyMessage;
 };
 
 } // namespace