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-rw-r--r--src/plugins/platforms/xcb/qxcbbackingstore.cpp52
1 files changed, 41 insertions, 11 deletions
diff --git a/src/plugins/platforms/xcb/qxcbbackingstore.cpp b/src/plugins/platforms/xcb/qxcbbackingstore.cpp
index 4348ddbae9..ad8b47c25a 100644
--- a/src/plugins/platforms/xcb/qxcbbackingstore.cpp
+++ b/src/plugins/platforms/xcb/qxcbbackingstore.cpp
@@ -182,17 +182,47 @@ void QXcbShmImage::put(xcb_window_t window, const QPoint &target, const QRect &s
source.height(),
false);
} else {
- xcb_image_t *subimage = xcb_image_subimage(m_xcb_image, source.x(), source.y(), source.width(), source.height(),
- 0, 0, 0);
- xcb_image_put(xcb_connection(),
- window,
- m_gc,
- subimage,
- target.x(),
- target.y(),
- 0);
-
- xcb_image_destroy(subimage);
+ // If we upload the whole image in a single chunk, the result might be
+ // larger than the server's maximum request size and stuff breaks.
+ // To work around that, we upload the image in chunks where each chunk
+ // is small enough for a single request.
+ int src_x = source.x();
+ int src_y = source.y();
+ int target_x = target.x();
+ int target_y = target.y();
+ int width = source.width();
+ int height = source.height();
+
+ // We must make sure that each request is not larger than max_req_size.
+ // Each request takes req_size + m_xcb_image->stride * height bytes.
+ uint32_t max_req_size = xcb_get_maximum_request_length(xcb_connection());
+ uint32_t req_size = sizeof(xcb_put_image_request_t);
+ int rows_per_put = (max_req_size - req_size) / m_xcb_image->stride;
+
+ // This assert could trigger if a single row has more pixels than fit in
+ // a single PutImage request. However, max_req_size is guaranteed to be
+ // at least 16384 bytes. That should be enough for quite large images.
+ Q_ASSERT(rows_per_put > 0);
+
+ while (height > 0) {
+ int rows = std::min(height, rows_per_put);
+
+ xcb_image_t *subimage = xcb_image_subimage(m_xcb_image, src_x, src_y, width, rows,
+ 0, 0, 0);
+ xcb_image_put(xcb_connection(),
+ window,
+ m_gc,
+ subimage,
+ target_x,
+ target_y,
+ 0);
+
+ xcb_image_destroy(subimage);
+
+ src_y += rows;
+ target_y += rows;
+ height -= rows;
+ }
}
Q_XCB_NOOP(connection());