Check for preview ongoing render once the thread is started not to actually hand the main thread
Removed all ScaleSlider implementation using OpenGL.
Bug fix: clamp the texture size to the region of definition of the image displayed.
OverlaysInteracts are now taking into account the RenderSafety of the plugin.
Also the plug-in mutex (for Render::Unsafe plugins) is now recursive because interacts can themselves request a redraw
Fixed ScaleSlider colors
fix conflicts