CMake: make the plugin directories used in utilities more configurable.

In particular it is now possible to override the MAGNUM_PLUGINS_DIR
variables and even specify them relative, which will make them relative
to executable location.

It's nice when everything clicks together :)

CMakeLists.txt

@@ -291,17 +291,25 @@ set(MAGNUM_PLUGINS_AUDIOIMPORTER_RELEASE_LIBRARY_INSTALL_DIR ${MAGNUM_PLUGINS_RE
 # Plugin dirs based on wheter we are in debug or release build, needed by some
 # command-line tools
 if(CORRADE_TARGET_WINDOWS)
-    set(MAGNUM_PLUGINS_DEBUG_DIR ${MAGNUM_PLUGINS_DEBUG_BINARY_INSTALL_DIR})
-    set(MAGNUM_PLUGINS_RELEASE_DIR ${MAGNUM_PLUGINS_RELEASE_BINARY_INSTALL_DIR})
+    set(MAGNUM_PLUGINS_DEBUG_DIR_INIT ${MAGNUM_PLUGINS_DEBUG_BINARY_INSTALL_DIR})
+    set(MAGNUM_PLUGINS_RELEASE_DIR_INIT ${MAGNUM_PLUGINS_RELEASE_BINARY_INSTALL_DIR})
 else()
-    set(MAGNUM_PLUGINS_DEBUG_DIR ${MAGNUM_PLUGINS_DEBUG_LIBRARY_INSTALL_DIR})
-    set(MAGNUM_PLUGINS_RELEASE_DIR ${MAGNUM_PLUGINS_RELEASE_LIBRARY_INSTALL_DIR})
+    set(MAGNUM_PLUGINS_DEBUG_DIR_INIT ${MAGNUM_PLUGINS_DEBUG_LIBRARY_INSTALL_DIR})
+    set(MAGNUM_PLUGINS_RELEASE_DIR_INIT ${MAGNUM_PLUGINS_RELEASE_LIBRARY_INSTALL_DIR})
 endif()
 if(CMAKE_BUILD_TYPE STREQUAL "Debug")
-    set(MAGNUM_PLUGINS_DIR ${MAGNUM_PLUGINS_DEBUG_DIR})
+    set(MAGNUM_PLUGINS_DIR_INIT ${MAGNUM_PLUGINS_DEBUG_DIR})
 else()
-    set(MAGNUM_PLUGINS_DIR ${MAGNUM_PLUGINS_RELEASE_DIR})
+    set(MAGNUM_PLUGINS_DIR_INIT ${MAGNUM_PLUGINS_RELEASE_DIR})
 endif()
 
+# Make these paths configurable from outside
+set(MAGNUM_PLUGINS_DEBUG_DIR ${MAGNUM_PLUGINS_DEBUG_DIR_INIT}
+    CACHE PATH "Base directory where to look for Magnum plugins for debug builds")
+set(MAGNUM_PLUGINS_RELEASE_DIR ${MAGNUM_PLUGINS_RELEASE_DIR_INIT}
+    CACHE PATH "Base directory where to look for Magnum plugins for release builds")
+set(MAGNUM_PLUGINS_DIR ${MAGNUM_PLUGINS_DIR_INIT}
+    CACHE PATH "Base directory where to look for Magnum plugins")
+
 add_subdirectory(modules)
 add_subdirectory(src)

doc/building.dox

@@ -244,6 +244,14 @@ There are also a few command-line utilities, also disabled by default:
 -   `WITH_IMAGECONVERTER` - @ref magnum-imageconverter "magnum-imageconverter"
     executable for converting images of different formats.
 
+Some of these utilities operate with plugins and they search for them in the
+default plugin locations. You can override those locations using
+`MAGNUM_PLUGINS_DIR` and `MAGNUM_PLUGINS_[DEBUG|RELEASE]_DIR` variables, much
+like when using Magnum from dependent projects -- see @ref cmake for more
+information. In particular, if you specify them as relative paths, the path
+will be taken relative to executable location, which is useful for making
+relocatable installations.
+
 Magnum also contains a set of dependency-less plugins for importing essential
 file formats. Additional plugins are provided in separate plugin repository,
 see @ref building-plugins for more information. None of the plugins is built by

src/Magnum/Text/fontconverter.cpp

@@ -119,7 +119,7 @@ FontConverter::FontConverter(const Arguments& arguments): Platform::WindowlessAp
         .addArgument("output").setHelp("output", "output filename prefix")
         .addNamedArgument("font").setHelp("font", "font plugin")
         .addNamedArgument("converter").setHelp("converter", "font converter plugin")
-        .addOption("plugin-dir", MAGNUM_PLUGINS_DIR).setHelp("plugin-dir", "base plugin dir", "DIR")
+        .addOption("plugin-dir", Utility::Directory::join(Utility::Directory::path(Utility::Directory::executableLocation()), MAGNUM_PLUGINS_DIR)).setHelp("plugin-dir", "base plugin dir", "DIR")
         .addOption("characters", "abcdefghijklmnopqrstuvwxyz"
                                  "ABCDEFGHIJKLMNOPQRSTUVWXYZ"
                                  "0123456789?!:;,. ").setHelp("characters", "characters to include in the output")

src/Magnum/TextureTools/distancefieldconverter.cpp

@@ -120,7 +120,7 @@ DistanceFieldConverter::DistanceFieldConverter(const Arguments& arguments): Plat
         .addArgument("output").setHelp("output", "output image")
         .addOption("importer", "AnyImageImporter").setHelp("importer", "image importer plugin")
         .addOption("converter", "AnyImageConverter").setHelp("converter", "image converter plugin")
-        .addOption("plugin-dir", MAGNUM_PLUGINS_DIR).setHelp("plugin-dir", "base plugin dir", "DIR")
+        .addOption("plugin-dir", Utility::Directory::join(Utility::Directory::path(Utility::Directory::executableLocation()), MAGNUM_PLUGINS_DIR)).setHelp("plugin-dir", "base plugin dir", "DIR")
         .addNamedArgument("output-size").setHelp("output-size", "size of output image", "\"X Y\"")
         .addNamedArgument("radius").setHelp("radius", "distance field computation radius", "N")
         .addSkippedPrefix("magnum", "engine-specific options")

src/Magnum/Trade/imageconverter.cpp

@@ -74,7 +74,7 @@ int main(int argc, char** argv) {
         .addArgument("output").setHelp("output", "output image")
         .addOption("importer", "AnyImageImporter").setHelp("importer", "image importer plugin")
         .addOption("converter", "AnyImageConverter").setHelp("converter", "image converter plugin")
-        .addOption("plugin-dir", MAGNUM_PLUGINS_DIR).setHelp("plugin-dir", "base plugin dir", "DIR")
+        .addOption("plugin-dir", Utility::Directory::join(Utility::Directory::path(Utility::Directory::executableLocation()), MAGNUM_PLUGINS_DIR)).setHelp("plugin-dir", "base plugin dir", "DIR")
         .setHelp("Converts images of different formats.")
         .parse(argc, argv);