Integrate online reverse image search

This makes use of our image processing capabilities in order to
turn arbitrary image files into normalized thumbnails,
upload them to a temporary host, and pass the resulting URI
to a search provider.

In future, fiv should ideally run the upload itself,
so that its status and any errors are obvious to the user,
as well as to get rid of the script's dependency on jq.

meson.build

@@ -35,12 +35,12 @@ dependencies = [
 	dependency('gtk+-3.0'),
 	dependency('pixman-1'),
 
-	# Wuffs is included as a submodule.
 	dependency('libturbojpeg'),
 	dependency('libwebp'),
 	dependency('libwebpdemux'),
 	dependency('libwebpdecoder', required : false),
 	dependency('libwebpmux'),
+	# Wuffs is included as a submodule.
 
 	lcms2,
 	libjpegqs,
@@ -251,6 +251,32 @@ if not win32
 			install_dir : get_option('datadir') / 'applications')
 	endforeach
 
+	# TODO(p): Consider moving this to /usr/share or /usr/lib.
+	install_data('fiv-reverse-search',
+		install_dir : get_option('bindir'))
+
+	# As usual, handling generated files in Meson is a fucking pain.
+	updatable_desktops = [application_ns + 'fiv.desktop']
+	foreach name, uri : {
+		'Google' : 'https://lens.google.com/uploadbyurl?url=',
+		'Bing' : 'https://www.bing.com/images/searchbyimage?cbir=sbi&imgurl=',
+		'Yandex' : 'https://yandex.com/images/search?rpt=imageview&url=',
+		'TinEye' : 'https://tineye.com/search?url=',
+		'SauceNAO' : 'https://saucenao.com/search.php?url=',
+		'IQDB' : 'https://iqdb.org/?url=',
+	}
+		desktop = 'fiv-reverse-search-' + name.to_lower() + '.desktop'
+		updatable_desktops += application_ns + desktop
+
+		test(desktop, dfv, args : configure_file(
+			input : 'fiv-reverse-search.desktop.in',
+			output : application_ns + desktop,
+			configuration : {'NAME' : name, 'URL' : uri},
+			install : true,
+			install_dir : get_option('datadir') / 'applications',
+		))
+	endforeach
+
 	# With gdk-pixbuf, fiv.desktop depends on currently installed modules;
 	# the package manager needs to be told to run this script as necessary.
 	dynamic_desktops = gdkpixbuf.found()
@@ -259,9 +285,10 @@ if not win32
 		input : 'fiv-update-desktop-files.in',
 		output : 'fiv-update-desktop-files',
 		configuration : {
-			'EXE' : get_option('prefix') / get_option('bindir') / exe.name(),
-			'DESKTOP' : get_option('prefix') / get_option('datadir') \
-				/ 'applications' / application_ns + 'fiv.desktop',
+			'FIV' : get_option('prefix') / get_option('bindir') / exe.name(),
+			'DESKTOPDIR' : get_option('prefix') /
+				get_option('datadir') / 'applications',
+			'DESKTOPS' : ' \\\n\t'.join(updatable_desktops),
 		},
 		install : dynamic_desktops,
 		install_dir : get_option('bindir'))