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Difference between revisions of "HOWTO-Engines"
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# Add a new directory <tt>engines/quux/</tt> | # Add a new directory <tt>engines/quux/</tt> | ||
# Add <tt>engines/quux/ | # Add <tt>engines/quux/configure.engine</tt> (looking at configure.engine files of existing engines should make it clear what you have to do). | ||
# Add <tt>engines/quux/module.mk</tt> (Again, just check out what is done for the existing engines). | |||
# Add <tt>engines/quux/quux.h</tt> and <tt>engines/quux/quux.cpp</tt>; this will contain your Engine subclass (or at least parts of it). | # Add <tt>engines/quux/quux.h</tt> and <tt>engines/quux/quux.cpp</tt>; this will contain your Engine subclass (or at least parts of it). | ||
# Add <tt>engines/quux/detection.cpp</tt>; It will contain the plugin interface code (more on that in the next section). | # Add <tt>engines/quux/detection.cpp</tt>; It will contain the plugin interface code (more on that in the next section). | ||
That's it. The difficult part is of course writing the Engine subclass. More on that in the next section! | That's it. The difficult part is of course writing the Engine subclass. More on that in the next section! | ||
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|inter.cpp, logic.cpp, script.cpp || Game logic, resp. script/bytecode interpreter | |inter.cpp, logic.cpp, script.cpp || Game logic, resp. script/bytecode interpreter | ||
|} | |} | ||
Additionally, the files saved by each engine should be consistent. | |||
* '''Saves''': These should be named <targetid>.### (where ### is the slot id) or <gameid>.###. The latter should be used when the saves can be shared across all game variants. | |||
* '''Other files''': These should be named <targetid>-<filename> or <gameid>-<filename>. Again the latter when the files can be shared acress all variants of the game (an example for these type of files would be when a minigame saves a high score record). | |||
Here, only use the <gameid> scheme if you are '''absolutely''' sure that such files can be shared across '''all''' (that is every game platform, every game language, every game patch version, every game release, etc.) versions. If you are not sure whether this is the case, then stick to the <targetid> based scheme. | |||
=== Subclassing MetaEngine === | === Subclassing MetaEngine === | ||
Let's implement the plugin interface: You'll have to create a custom MetaEngine subclass | Let's implement the plugin interface:<br> | ||
You'll have to create a custom MetaEngine subclass. This provides the information and functionality related to the engine that can be used by the launcher without loading and running the game engine, which includes detecting games, listing savegames and instancing the engine. | |||
The following example illustrates this, '''but''':<br> It is recommended that most engines should instead subclass AdvancedMetaEngine.<br> | |||
This can be found in <tt>engines/advancedDetector.*</tt> and provides a standard framework for filename and MD5 based game detection. To use this, all you will have to provide is a standard data table of ADGameDescription entries describing each game variant, which is usually placed in a separate detection_tables.h header.<br> | |||
Finally, in either case, you will then have to specify your MetaEngine class to the REGISTER_PLUGIN_* macros. | |||
=== Subclassing Engine === | === Subclassing Engine === | ||
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=== Example: engines/quux/quux.h === | === Example: engines/quux/quux.h === | ||
< | <syntaxhighlight lang="cpp"> | ||
#ifndef QUUX_H | #ifndef QUUX_H | ||
#define QUUX_H | #define QUUX_H | ||
| Line 149: | Line 159: | ||
#endif | #endif | ||
</ | </syntaxhighlight> | ||
=== Example: engines/quux/quux.cpp === | === Example: engines/quux/quux.cpp === | ||
< | <syntaxhighlight lang="cpp"> | ||
#include "common/scummsys.h" | #include "common/scummsys.h" | ||
| Line 159: | Line 169: | ||
#include "common/debug-channels.h" | #include "common/debug-channels.h" | ||
#include "common/error.h" | #include "common/error.h" | ||
#include " | #include "gui/EventRecorder.h" | ||
#include "common/file.h" | #include "common/file.h" | ||
#include "common/fs.h" | #include "common/fs.h" | ||
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QuuxEngine::QuuxEngine(OSystem *syst) | QuuxEngine::QuuxEngine(OSystem *syst) | ||
: Engine(syst) { | : Engine(syst), _console(nullptr) { | ||
// Put your engine in a sane state, but do nothing big yet; | // Put your engine in a sane state, but do nothing big yet; | ||
// in particular, do not load data from files; rather, if you | // in particular, do not load data from files; rather, if you | ||
// need to do such things, do them from | // need to do such things, do them from run(). | ||
// Do not initialize graphics here | // Do not initialize graphics here | ||
// Do not initialize audio devices here | |||
// However this is the place to specify all default directories | // However this is the place to specify all default directories | ||
| Line 239: | Line 250: | ||
} // End of namespace Quux | } // End of namespace Quux | ||
</ | </syntaxhighlight> | ||
=== Example: engines/quux/detection.cpp === | === Example: engines/quux/detection.cpp === | ||
The following example implements a custom MetaEngine instead of using the AdvancedMetaEngine. | The following example implements a custom MetaEngine instead of using the AdvancedMetaEngine. | ||
< | <syntaxhighlight lang="cpp"> | ||
#include "quux/quux.h" | #include "quux/quux.h" | ||
| Line 340: | Line 351: | ||
REGISTER_PLUGIN_STATIC(QUUX, PLUGIN_TYPE_ENGINE, QuuxMetaEngine); | REGISTER_PLUGIN_STATIC(QUUX, PLUGIN_TYPE_ENGINE, QuuxMetaEngine); | ||
#endif | #endif | ||
</ | </syntaxhighlight> | ||
=== Example: engines/quux/module.mk === | === Example: engines/quux/module.mk === | ||
< | <syntaxhighlight lang="make"> | ||
MODULE := engines/quux | MODULE := engines/quux | ||
| Line 360: | Line 371: | ||
# Include common rules | # Include common rules | ||
include $(srcdir)/rules.mk | include $(srcdir)/rules.mk | ||
</ | </syntaxhighlight> | ||
=== Example: engines/quux/configure.engine === | |||
<syntaxhighlight lang="bash"> | |||
# This file is included from the main "configure" script | |||
# add_engine [name] [desc] [build-by-default] [subengines] [base games] [deps] | |||
add_engine quux "Quux" no | |||
</syntaxhighlight> | |||