Visual Components Library is responsible for the widgets (windowing, buttons, controls, file-pickers etc.) operating system abstraction, including basic rendering (e.g. the output device).
Welcome to the Visual Class Libraries (vcl) code
source/
+ the main cross-platform chunk of source
inc/
+ cross-platform abstraction headers / definition
vcl/
+ external headers
generic/
+ shared helper code for backends,
actually built into vcl
headless/
+ a backend renderer that draws to bitmaps
aqua/
+ OS/X backend
ios/
+ skeleton Android backend
win/
+ windows backend
unx/
+ unix specific platform backend code and its' sub-platforms
plugadapt/
+ pluggable framework to select correct unx backend
gtk/
+ gtk2 support
gtk3/
+ gtk3.2+ support
kde/
+ kde3 support
kde4/
+ kde4 support
generic/
+ raw X support
How the platform abstraction works
+ InitVCL calls 'CreateSalInstance'
+ ths is implemented by the compiled-in platform backend
+ it stores various bits of global state in the
'SalData' (inc/saldatabasic.hxx) structure but:
+ the SalInstance vtable is the primary outward facing gateway
API for platform backends
+ It is a factory for:
SalFrames, SalVirtualDevices, SalPrinters,
Timers, the SolarMutexe, Drag&Drop and other
objects, as well as the primary event loop wrapper.
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