From 9d3c8c0e6e1a7ba43bf3dc19350d1dca68b657a3 Mon Sep 17 00:00:00 2001 From: Chris Xiong Date: Sun, 10 Feb 2019 11:16:07 +0800 Subject: Initial commit. --- QMidiPlayer/doc/APIdoc.html | 156 ++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 156 insertions(+) create mode 100644 QMidiPlayer/doc/APIdoc.html (limited to 'QMidiPlayer/doc/APIdoc.html') diff --git a/QMidiPlayer/doc/APIdoc.html b/QMidiPlayer/doc/APIdoc.html new file mode 100644 index 0000000..ea6bfd0 --- /dev/null +++ b/QMidiPlayer/doc/APIdoc.html @@ -0,0 +1,156 @@ +

The API documentation of QMidiPlayer for plugin developers

+

This manual is not yet complete. It's only a working draft for the always-changing plugin system in QMP. Handle with care.

+

0. Overview

+

Plugin for QMidiPlayer is a dynamically-loaded library that exports the symbol qmpPluginGetInterface and qmpPluginGetAPIRev. Before starting developing your own plugin, make sure to have a look at the sample plugin in the "sample-plugin" folder.

+

1. "QMidiPlayer Plugin SDK"

+

SDK for developing QMidiPlayer plugins is merely the qmpcorepublic.hpp header found in the "include" directory in the source tree. It includes classes used by QMidiPlayer's internal plugin infrastructure.

+

2. Basics for a working plugin

+

First of all, you should make your library distinct from other libraries that are not QMidiPlayer plugins. You can achive it by exporting the symbols qmpPluginGetInterface and qmpPluginGetAPIRev. Specifically, what you should do is to add the following snipplet to somewhere of your code:

+
extern "C"{
+    EXPORTSYM qmpPluginIntf* qmpPluginGetInterface(qmpPluginAPI* api)
+    //semicolon or implementation here.
+    EXPORTSYM const char* qmpPluginGetAPIRev()
+    {return QMP_PLUGIN_API_REV;}
+}
+

The EXPORTSYM macro tells the compiler to export the following symbol. qmpPluginIntf is the abstract class which every plugin class should derive from. The parameter api provides access to QMidiPlayer's plugin API, which should be stored for future use. qmpPluginGetAPIRev helps the core to determine whether the plugin is compatible with the API it exports.

+

Next you should create your own plugin class which implements the abstract class qmpPluginIntf.

+

3. A peek into the class qmpPluginIntf

+

It has 6 public members: one default constructor, one default destructor and four methods:

+ +

Your plugin is expected to register handlers (hooks) and functionalities when init() is called by the host, and do clean-up jobs when deinit() is caled.

+

Currently plugins can register handlers for these functionalities:

+ +

...and can hooks into the following processes:

+ +

Functionalities has their own interfaces you need to implement(qmpVisualizationIntf and IMidiFileReader, respectively), while hooks uses the universal IMidiCallBack interface. Functionalities are discussed later.

+

When you register a hook, you provide the core with a instance of your class that implements the IMidiCallBack interface and your userdata to be used when the core is calling the callback. When the callback is called, it will be fed with proper callerdata generated by the core and the userdata you provided. Type of callerdata varies by hooks. Event reader and handler hooks have SEventCallBackData* as their callerdata while file read finish hook doesn't provide callerdata (NULL).

+

4. Functionalities

+

Plugins extend the host with extra functionalities. With hooks, handlers and the built-in core API, you can already do a lot of hacking. If that cannot make you satisfied, QMidiPlayer have several vacancies that are expected to be implemented by plugins. And with the introduction of the general functionality API, you can now virtually add anything to QMidiPlayer!

+

4.1 What is a functionality?

+

Have a look at the main window. By default there're three or four buttons at the bottom of it. These are functionalities. Functionalties go into two types: checkable and non-checkable. Checkable functionalities can be toggled on or off, while non-checkable functionalities have no such states. For non-checkable functionalities, only show() is called when the user invokes it. The user can arrange functionalities shown on the toolbar and the action menu to their needs.

+

4.2 Visualization

+

Visualization was once a feature of QMidiPlayer's core. But you can now write your own visualization with the Visualization interface(qmpVisualizationIntf). The methods in this interface should be self-explanatory.

+

4.3 MIDI File Reader

+

This is not strictly a "functionality", because its interface IMidiFileReader does not inherit qmpFuncBaseIntf. When the user requests to open a file, the core tries to load the file with registered file readers and accepts the first valid result. Therefore you can implement your own file reader, which may even add eXtended Module support to QMidiPlayer!

+

4.4 MIDI Output Device

+

This is not a functionality either. By implementing the interface qmpMidiOutDevice and registering it, you can add custom MIDI Devices in the built-in MIDI mapper.

+

5. Generic Considerations

+
    +
  1. If you implemented a API that returns a pointer to something, you can forget about the pointer after returning it. The core will free its memory after it is no longer used. You shouldn't extend the class pointed to because if you do so, the core will not be able to destruct it correctly. Examples include IMidiFileReader::readFile which returns a pointer to a CMidiFile class.
    2. +
  2. However if you passed a pointer to the core through a function in qmpPluginAPI, you cannot forget about the pointer later. As these pointers are mostly polymorphic, the core cannot handle their destruction. You have to delete them yourself in the deinit() function of your plugin.
    3. +
  3. Do not throw exceptions to the core. The core doesn't handle exceptions and they will crash the entire program. Use the return value to indicate failure of a procedure instead.
    4. +
+

6. Reference

+

Well, everything above is just nonsense compared to this one. The full reference of the API is here.

+

Structures & Classes

+

struct SEvent

+

Describes an MIDI event.

+ +

struct SEventCallBackData

+

A stripped down version of SEvent that is used to pass event data in APIs.

+ +

class CMidiTrack

+

Describes a single MIDI track. A MIDI track consists of multiple MIDI events.

+ +

class CMidiFile

+

Describes a MIDI file. A MIDI file consists of multiple MIDI tracks.

+ +

class IMidiCallBack

+

Generic callback function that can be used for hooking the core.

+ +

class IMidiFileReader

+

MIDI file reader interface. Use this to implement your file importer.

+ -- cgit v1.2.3