style: unify identifier naming per updated conventions

Automated with clang-tidy readability-identifier-naming (config added to
.clang-tidy) plus scripted passes, per the updated rules now documented
in CONTRIBUTING.md:

- types (class/struct/enum/alias/template params): PascalCase
- functions, variables, members: snake_case (incl. rational -> Rational)
- private/protected members: trailing underscore; static member
  variables likewise (instance_, available_themes_)
- constants and enum values: snake_case (kLinear -> k_linear,
  F32P -> f32p); ALL_CAPS reserved for macros
- macros: OAK_ prefix (OLIVE_ADD_TEST/OLIVE_ASSERT/OLIVE_CONFIG ->
  OAK_ADD_TEST/OAK_ASSERT/OAK_CONFIG, GL_PREAMBLE -> OAK_GL_PREAMBLE,
  include guards -> OAK_*)
- file names: all lowercase (Current/Plugin/OliveHost/OliveClip/
  OlivePluginInstance -> current/plugin/olivehost/oliveclip/
  oliveplugininstance)
- getters share the member name sans underscore, setters set_foo()
- Qt and third-party (OpenFX) virtual overrides and framework callbacks
  keep their original names (exempt in .clang-tidy)

Manual follow-ups required where automation could not reach:
- string-based QMetaObject/SIGNAL/SLOT references updated to renamed
  methods (AddTask, CreatedFile, DeleteSpecificFile, moveSelectionUp, ...)
- macro bodies referencing renamed methods (OLIVE_CONFIG,
  NODE_DEFAULT_DESTRUCTOR, MANAGEDDISPLAYWIDGET_*)
- self-shadowing locals renamed where signals/methods became same-named
  (size_changed, worker_count, selected_items, import param, filters)
- third_party OFX member/namespace usages restored (OFX::Host::*,
  _created, _clipPrefsDirty, createInstance, clearPersistentMessage)
- STL protocol aliases restored (const_iterator) with .clang-tidy
  ignore rules; qHash overloads restored

Full build and test suite pass: ctest 4/4, ~1960 gtest cases green.

tests/gtest/codec_encoder_test.cpp

@@ -11,27 +11,27 @@ public:
 	{
 	}
 
-	bool Open() override
+	bool open() override
 	{
 		return true;
 	}
 
-	bool WriteFrame(olive::FramePtr, olive::core::rational) override
+	bool write_frame(olive::FramePtr, olive::core::Rational) override
 	{
 		return true;
 	}
 
-	bool WriteAudio(const olive::SampleBuffer &) override
+	bool write_audio(const olive::SampleBuffer &) override
 	{
 		return true;
 	}
 
-	bool WriteSubtitle(const olive::SubtitleBlock *) override
+	bool write_subtitle(const olive::SubtitleBlock *) override
 	{
 		return true;
 	}
 
-	void Close() override
+	void close() override
 	{
 	}
 };
@@ -40,26 +40,26 @@ public:
 TEST(CodecEncoder, ImageSequenceFilenames)
 {
 	olive::EncodingParams params;
-	params.SetFilename(QStringLiteral("frame_[####].png"));
+	params.set_filename(QStringLiteral("frame_[####].png"));
 	params.set_video_is_image_sequence(true);
 
 	olive::VideoParams video_params;
-	video_params.set_frame_rate(olive::core::rational(24, 1));
-	params.EnableVideo(video_params, olive::ExportCodec::kCodecPNG);
+	video_params.set_frame_rate(olive::core::Rational(24, 1));
+	params.enable_video(video_params, olive::ExportCodec::k_codec_png);
 
 	TestEncoder encoder(params);
 
-	EXPECT_TRUE(olive::Encoder::FilenameContainsDigitPlaceholder(
+	EXPECT_TRUE(olive::Encoder::filename_contains_digit_placeholder(
 		QStringLiteral("frame_[####].png")));
-	EXPECT_EQ(olive::Encoder::GetImageSequencePlaceholderDigitCount(
+	EXPECT_EQ(olive::Encoder::get_image_sequence_placeholder_digit_count(
 				  QStringLiteral("frame_[####].png")),
 			  4);
-	EXPECT_EQ(olive::Encoder::FilenameRemoveDigitPlaceholder(
+	EXPECT_EQ(olive::Encoder::filename_remove_digit_placeholder(
 				  QStringLiteral("frame_[####].png")),
 			  QStringLiteral("frame.png"));
 
 	const QString filename =
-		encoder.GetFilenameForFrame(olive::core::rational(1, 24));
+		encoder.get_filename_for_frame(olive::core::Rational(1, 24));
 	EXPECT_EQ(filename, QStringLiteral("frame_0001.png"));
 }
 
@@ -67,17 +67,17 @@ TEST(CodecEncoder, MatrixGeneration)
 {
 	using Method = olive::EncodingParams::VideoScalingMethod;
 
-	QMatrix4x4 stretch = olive::EncodingParams::GenerateMatrix(
-		Method::kStretch, 1920, 1080, 1280, 720);
+	QMatrix4x4 stretch = olive::EncodingParams::generate_matrix(
+		Method::k_stretch, 1920, 1080, 1280, 720);
 	EXPECT_TRUE(qFuzzyCompare(stretch(0, 0), 1.0f));
 	EXPECT_TRUE(qFuzzyCompare(stretch(1, 1), 1.0f));
 
-	QMatrix4x4 fit = olive::EncodingParams::GenerateMatrix(Method::kFit, 1920,
+	QMatrix4x4 fit = olive::EncodingParams::generate_matrix(Method::k_fit, 1920,
 														   1080, 1024, 1024);
 	EXPECT_TRUE(qFuzzyCompare(fit(0, 0), 1.0f));
 	EXPECT_FALSE(qFuzzyCompare(fit(1, 1), 1.0f));
 
-	QMatrix4x4 crop = olive::EncodingParams::GenerateMatrix(Method::kCrop, 1920,
+	QMatrix4x4 crop = olive::EncodingParams::generate_matrix(Method::k_crop, 1920,
 															1080, 1024, 1024);
 	EXPECT_FALSE(qFuzzyCompare(crop(0, 0), 1.0f));
 	EXPECT_TRUE(qFuzzyCompare(crop(1, 1), 1.0f));
@@ -88,10 +88,10 @@ TEST(CodecEncoder, TypeFromFormat)
 	using olive::Encoder;
 	using olive::ExportFormat;
 
-	EXPECT_EQ(Encoder::GetTypeFromFormat(ExportFormat::kFormatPNG),
-			  Encoder::kEncoderTypeOIIO);
-	EXPECT_EQ(Encoder::GetTypeFromFormat(ExportFormat::kFormatDNxHD),
-			  Encoder::kEncoderTypeFFmpeg);
-	EXPECT_EQ(Encoder::GetTypeFromFormat(ExportFormat::kFormatCount),
-			  Encoder::kEncoderTypeNone);
+	EXPECT_EQ(Encoder::get_type_from_format(ExportFormat::k_format_png),
+			  Encoder::k_encoder_type_oiio);
+	EXPECT_EQ(Encoder::get_type_from_format(ExportFormat::k_format_d_nx_hd),
+			  Encoder::k_encoder_type_f_fmpeg);
+	EXPECT_EQ(Encoder::get_type_from_format(ExportFormat::k_format_count),
+			  Encoder::k_encoder_type_none);
 }