We require stdbool.h in the build environment, so we might as well use the plain bool type.
If your environment doesn't have stdbool.h, this simple replacement will suffice:
typedef signed char bool;
The flags parameter has been removed from SDL_CreateRenderer() and SDL_RENDERER_PRESENTVSYNC has been replaced with SDL_PROP_RENDERER_CREATE_PRESENT_VSYNC_NUMBER during window creation and SDL_PROP_RENDERER_VSYNC_NUMBER after renderer creation.
SDL_SetRenderVSync() now takes additional values besides 0 and 1.
The maximum texture size has been removed from SDL_RendererInfo, replaced with SDL_PROP_RENDERER_MAX_TEXTURE_SIZE_NUMBER.
If the done signal is emitted by the common event handler, the window and all of its children have already been destroyed, so don't try to render with invalid renderer objects.
Right click to create new popup menus. Clicking over an existing popup menu will create a child menu. Left click to close all menus. Hover to display a tooltip that is the child of the window below it. Closing the application closes the root window, which should automatically destroy any open popup windows and exit gracefully.
