The server crashes if the remote cursor shape changes

[mykola-mokhnach]

It looks like the current implementation of cursor bitmap capture does not properly handle "locate cursor" feature which is available in the recent MacOS releases (the arrow grows in size for a moment if one shakes it for a while)

[stweil]

I cannot reproduce this issue. The cursor grows when I shake it on the Mac with macOS 10.13.6, I have OSXvnc-server -rfbnoauth running on the same Mac. A Linux vncclient ist connected. That setting works with no crash.

[stweil]

The crash dump looks like it might be related to something unexpected in your copy+paste buffer.

[mykola-mokhnach]

Sorry, the screenshot is from the other crash. The original issue was happening inside loadCurrentCursorData, free_tiny call. Unfortunately I didn't save the original stack trace and I am unable to reproduce it right now.

But anyway thanks for looking into it.

[mykola-mokhnach]

For me it looked like there was some race condition while we were trying to call free(cursorData);, but I cannot say for sure

[mykola-mokhnach]

    cursorData = (unsigned char*)malloc(sizeof(unsigned char) * cursorDataSize);
    err = CGSGetGlobalCursorData(connection,
                                 cursorData,
                                 &cursorDataSize,
                                 &cursorRowBytes,
                                 &cursorRect,
                                 &hotspot,
                                 &cursorDepth,
                                 &components,
                                 &cursorBitsPerComponent);

    //CGSReleaseConnection(connection);
    if (err != kCGErrorSuccess) {
                // maybe cursorDataSize here is not the same as it was while malloc has been executed
        free(cursorData);

[stweil]

CGSGetGlobalCursorData seems to be an undocumented function. Either we need a documented method to get the cursor image, or we simply ignore the cursor image and always use the same cursor on the VNC viewer side.

[stweil]

Some links:

• https://developer.apple.com/documentation/appkit/nscursor?language=objc
• https://stackoverflow.com/questions/8198380/how-to-get-current-type-of-mouse-cursor-in-mac-os-x

[stweil]

@mykola-mokhnach, would it be acceptable to use the default cursor on the viewer side (until someone finds working code to get the cursor image)?