[qtwin] Fix crash on pasting screenshots

Workaround for an issue with the Windows Qt version where Celestia crashes
when a copied screenshot is pasted into another application. This appears to
be because the data sent to the clipboard still contains a reference to the
data in the destructed Image object, despite the Qt documentation stating that
QClipboard::setImage causes the clipboard to take ownership of the data. This
does not occur if the QImage manages its own buffer.

src/celestia/celestiacore.cpp

@@ -4745,22 +4745,25 @@ View* CelestiaCore::getViewByObserver(const Observer *obs) const
     return nullptr;
 }
 
-Image CelestiaCore::captureImage() const
+void CelestiaCore::getCaptureInfo(std::array<int, 4>& viewport, celestia::PixelFormat& format) const
 {
-    // Get the dimensions of the current viewport
-    array<int, 4> viewport;
-    getRenderer()->getViewport(viewport);
+    renderer->getViewport(viewport);
+    format = renderer->getPreferredCaptureFormat();
+}
 
-    PixelFormat format = renderer->getPreferredCaptureFormat();
-
-    Image image(format, viewport[2], viewport[3]);
-    if (!renderer->captureFrame(viewport[0], viewport[1],
-                                viewport[2], viewport[3],
-                                format, image.getPixels()))
+bool CelestiaCore::captureImage(std::uint8_t* buffer,
+                                const std::array<int, 4>& viewport,
+                                celestia::PixelFormat format) const
+{
+    if (renderer->captureFrame(viewport[0], viewport[1],
+                               viewport[2], viewport[3],
+                               format, buffer))
     {
-        GetLogger()->error(_("Unable to capture a frame!\n"));
+        return true;
     }
-    return image;
+
+    GetLogger()->error(_("Unable to capture a frame!\n"));
+    return false;
 }
 
 bool CelestiaCore::saveScreenShot(const fs::path& filename, ContentType type) const
@@ -4774,8 +4777,11 @@ bool CelestiaCore::saveScreenShot(const fs::path& filename, ContentType type) co
         return false;
     }
 
-    Image image = captureImage();
-    if (!image.isValid())
+    std::array<int, 4> viewport;
+    PixelFormat format;
+    getCaptureInfo(viewport, format);
+    Image image(format, viewport[2], viewport[3]);
+    if (!captureImage(image.getPixels(), viewport, format))
         return false;
 
     switch (type)

src/celestia/celestiacore.h

@@ -10,6 +10,7 @@
 #ifndef _CELESTIACORE_H_
 #define _CELESTIACORE_H_
 
+#include <array>
 #include <fstream>
 #include <string>
 #include <functional>
@@ -19,6 +20,7 @@
 // #include <celutil/watchable.h>
 #include <celengine/solarsys.h>
 #include <celengine/overlay.h>
+#include <celengine/pixelformat.h>
 #include <celengine/texture.h>
 #include <celengine/universe.h>
 #include <celengine/render.h>
@@ -384,7 +386,8 @@ class CelestiaCore // : public Watchable<CelestiaCore>
     void setScriptHook(std::unique_ptr<celestia::scripts::IScriptHook> &&hook) { m_scriptHook = std::move(hook); }
     const std::shared_ptr<celestia::scripts::ScriptMaps>& scriptMaps() const { return m_scriptMaps; }
 
-    Image captureImage() const;
+    void getCaptureInfo(std::array<int, 4>& viewport, celestia::PixelFormat& format) const;
+    bool captureImage(std::uint8_t* buffer, const std::array<int, 4>& viewport, celestia::PixelFormat format) const;
     bool saveScreenShot(const fs::path&, ContentType = Content_Unknown) const;
 
     void setMeasurementSystem(MeasurementSystem);

src/celestia/qt/qtappwin.cpp

@@ -750,14 +750,16 @@ static QImage::Format toQFormat(PixelFormat format)
 void CelestiaAppWindow::slotCopyImage()
 {
     //glWidget->repaint();
-    Image image = m_appCore->captureImage();
-    QImage grabbedImage = QImage(image.getPixels(),
-                                 image.getWidth(),
-                                 image.getHeight(),
-                                 image.getPitch(),
-                                 toQFormat(image.getFormat()));
-    QApplication::clipboard()->setImage(grabbedImage);
-    m_appCore->flash(_("Captured screen shot to clipboard"));
+    std::array<int, 4> viewport;
+    celestia::PixelFormat format;
+    m_appCore->getCaptureInfo(viewport, format);
+    QImage grabbedImage = QImage(viewport[2], viewport[3],
+                                 toQFormat(format));
+    if (m_appCore->captureImage(grabbedImage.bits(), viewport, format))
+    {
+        QApplication::clipboard()->setImage(grabbedImage);
+        m_appCore->flash(_("Captured screen shot to clipboard"));
+    }
 }