Subject: [linux-audio-dev] LADSPA extension - Formal proposal.
From: Fons Adriaensen (fons.adriaensen_AT_skynet.be)
Date: Tue Mar 09 2004 - 22:52:58 EET
Hello list,
After much debate, I propose to extend the current LADPSA 1.1 interface
specification in the way documented below. Two new LADSPA_HINT bits are
introduced. Both can be ignored by existing hosts without any ill
consequences.
The purpose of the first new bit is to allow simple hosts that do not
need the extended information in an RDF file to display meaningfull
labels on a switch widget, as they can already do for e.g. sliders.
The second new bit allows a plugin to request that the host indicates
unconnected ports by providing a NULL pointer.
To those who have followed the debate, I changed the original name
LADSPA_HINT_ENUMERATED to LADSPA_HINT_SWITCHED. This more correctly
represents the idea, and also allows Tim to use LADSPA_HINT_ENUMERATED
for his proposal which is complementary to this one.
The text below represents those sections of ladspa.h that would be added
or modified by this proposal.
-- Fons------------8<-------------------------------------------------------
#define LADSPA_VERSION "1.2" #define LADSPA_VERSION_MAJOR 1 #define LADSPA_VERSION_MINOR 2
.....
/* This hint must be used only together with LADSPA_HINT_INTEGER. It indicates that the port corresponds to a multiway switch selecting between options that have no natural numerical value. A port using this option would typically correspond to a switch statement in the plugin code, and can be represented in a GUI by a menu, a set of radio buttons, or any '1 out of N' selection widget. For each option a label string is provided in the PortNames array (see below). These strings come after all port names. They must be listed in order of the ports using this hint bit, and for each port in order of the numerical value that represents the switch option. The number of options and strings is equal to MAX - MIN + 1, where MIN and MAX are the values of the LowerBound and UpperBound fields in the PortRangeHint struct for the port. These values must be integers. */ #define LADSPA_HINT_SWITCHED 0x400
/* This hint indicates that a host may provide a NULL pointer for this port, to indicate that it is not connected. The host must still define the port pointer, even if it is NULL. The plugin code must check ports using this bit after each call to connect_port() (see below) that may have changed the port's pointer. */ #define LADSPA_HINT_NULLPOINTER 0x800
......
#define LADSPA_IS_HINT_SWITCHED(x) ((x) & LADSPA_HINT_SWITCHED) #define LADSPA_IS_HINT_NULLPOINTER(x) ((x) & LADSPA_HINT_NULLPOINTER)
......
/* This member indicates an array of null-terminated strings describing ports (e.g. "Frequency (Hz)"). Valid indices vary from 0 to PortCount-1. If there are any ports using LADSPA_HINT_SWITCHED, then their label strings follow after all port names (i.e. the port names remain in their normal place). In this case the range of valid indices is increased by the number of labels defined. The labels are not included in PortCount. */ const char * const * PortNames;
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