Track the GL DCs we use across different threads under Windows.

A DC returned by GetDC() is only valid within the context of the calling
thread, so we need to track which tread a DC belongs to.

Reviewed-by: Kim

3 files changed, 6 insertions, 1 deletions

diff --git a/src/opengl/qgl.cpp b/src/opengl/qgl.cpp
index 3f2af9d..05dae60 100644
--- a/src/opengl/qgl.cpp
+++ b/src/opengl/qgl.cpp
@@ -1655,6 +1655,7 @@ void QGLContextPrivate::init(QPaintDevice *dev, const QGLFormat &format)
 #if defined(Q_WS_WIN)
     dc = 0;
     win = 0;
+    threadId = 0;
     pixelFormatId = 0;
     cmap = 0;
     hbitmap = 0;
diff --git a/src/opengl/qgl_p.h b/src/opengl/qgl_p.h
index eca4a29..dfbc926 100644
--- a/src/opengl/qgl_p.h
+++ b/src/opengl/qgl_p.h
@@ -347,6 +347,7 @@ public:
     QGLCmap* cmap;
     HBITMAP hbitmap;
     HDC hbitmap_hdc;
+    Qt::HANDLE threadId;
 #endif
 #ifndef QT_NO_EGL
     uint ownsEglContext : 1;
diff --git a/src/opengl/qgl_win.cpp b/src/opengl/qgl_win.cpp
index 52988b6..3f13ac4 100644
--- a/src/opengl/qgl_win.cpp
+++ b/src/opengl/qgl_win.cpp
@@ -1261,6 +1261,7 @@ void QGLContext::reset()
     }
     d->dc  = 0;
     d->win = 0;
+    d->threadId = 0;
     d->pixelFormatId = 0;
     d->sharing = false;
     d->valid = false;
@@ -1283,8 +1284,9 @@ void QGLContext::makeCurrent()
     if (d->rc == wglGetCurrentContext() || !d->valid)       // already current
         return;
 
-    if (d->win && !d->dc) {
+    if (d->win && (!d->dc || d->threadId != QThread::currentThreadId())) {
         d->dc = GetDC(d->win);
+        d->threadId = QThread::currentThreadId();
         if (!d->dc) {
             qwglError("QGLContext::makeCurrent()", "GetDC()");
             return;
@@ -1322,6 +1324,7 @@ void QGLContext::doneCurrent()
     if (d->win && d->dc) {
         ReleaseDC(d->win, d->dc);
         d->dc = 0;
+        d->threadId = 0;
     }
 }