Do not leak textures from the backing stores

Neither the default nor the eglfs-specific backingstore release the OpenGL textures
that are in use when render-to-texture widgets are involved.

The result can be fatal on embedded devices that run out of GPU memory at after showing
and closing dialogs and popups a certain number of times.

Task-number: QTBUG-49363
Task-number: QTBUG-49399
Change-Id: Ia7471b037f147bcca0a4f1db5808ca348e230547
Reviewed-by: Lars Knoll <lars.knoll@theqtcompany.com>
Reviewed-by: Andy Nichols <andy.nichols@theqtcompany.com>

2 files changed, 12 insertions, 0 deletions

diff --git a/src/platformsupport/platformcompositor/qopenglcompositorbackingstore.cpp b/src/platformsupport/platformcompositor/qopenglcompositorbackingstore.cpp
index 8ce1ed2d2b..55f8ea160c 100644
--- a/src/platformsupport/platformcompositor/qopenglcompositorbackingstore.cpp
+++ b/src/platformsupport/platformcompositor/qopenglcompositorbackingstore.cpp
@@ -67,6 +67,7 @@ QOpenGLCompositorBackingStore::QOpenGLCompositorBackingStore(QWindow *window)
     : QPlatformBackingStore(window),
       m_window(window),
       m_bsTexture(0),
+      m_bsTextureContext(0),
       m_textures(new QPlatformTextureList),
       m_lockedWidgetTextures(0)
 {
@@ -74,6 +75,14 @@ QOpenGLCompositorBackingStore::QOpenGLCompositorBackingStore(QWindow *window)
 
 QOpenGLCompositorBackingStore::~QOpenGLCompositorBackingStore()
 {
+    if (m_bsTexture) {
+        QOpenGLContext *ctx = QOpenGLContext::currentContext();
+        if (ctx && m_bsTextureContext && ctx->shareGroup() == m_bsTextureContext->shareGroup())
+            glDeleteTextures(1, &m_bsTexture);
+        else
+            qWarning("QOpenGLCompositorBackingStore: Texture is not valid in the current context");
+    }
+
     delete m_textures;
 }
 
@@ -85,6 +94,8 @@ QPaintDevice *QOpenGLCompositorBackingStore::paintDevice()
 void QOpenGLCompositorBackingStore::updateTexture()
 {
     if (!m_bsTexture) {
+        m_bsTextureContext = QOpenGLContext::currentContext();
+        Q_ASSERT(m_bsTextureContext);
         glGenTextures(1, &m_bsTexture);
         glBindTexture(GL_TEXTURE_2D, m_bsTexture);
         glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST);
diff --git a/src/platformsupport/platformcompositor/qopenglcompositorbackingstore_p.h b/src/platformsupport/platformcompositor/qopenglcompositorbackingstore_p.h
index 49d8bfd6e7..bd843e8bd9 100644
--- a/src/platformsupport/platformcompositor/qopenglcompositorbackingstore_p.h
+++ b/src/platformsupport/platformcompositor/qopenglcompositorbackingstore_p.h
@@ -83,6 +83,7 @@ private:
     QImage m_image;
     QRegion m_dirty;
     uint m_bsTexture;
+    QOpenGLContext *m_bsTextureContext;
     QPlatformTextureList *m_textures;
     QPlatformTextureList *m_lockedWidgetTextures;
 };