GL32 shaders and errors

- Update shaders to glsl 150
 - Objectfy errors

src/main/java/com/jozufozu/flywheel/backend/gl/GLSLVersion.java

@@ -1,8 +1,12 @@
 package com.jozufozu.flywheel.backend.gl;
 
 public enum GLSLVersion {
+	@Deprecated
 	V110(110),
+	@Deprecated
 	V120(120),
+	V150(150),
+	V330(330),
 	;
 
 	public final int version;

src/main/java/com/jozufozu/flywheel/backend/pipeline/InstancingProgramMetaData.java

@@ -29,14 +29,14 @@ public class InstancingProgramMetaData {
 		Optional<ShaderFunction> vertexFunc = file.findFunction("vertex");
 		Optional<ShaderFunction> fragmentFunc = file.findFunction("fragment");
 
-		if (!fragmentFunc.isPresent()) {
+		if (fragmentFunc.isEmpty()) {
 			ErrorReporter.generateMissingFunction(file, "fragment", "\"fragment\" function not defined");
 		}
-		if (!vertexFunc.isPresent()) {
+		if (vertexFunc.isEmpty()) {
 			ErrorReporter.generateFileError(file, "could not find \"vertex\" function");
 		}
 
-		if (!fragmentFunc.isPresent() || !vertexFunc.isPresent()) {
+		if (fragmentFunc.isEmpty() || vertexFunc.isEmpty()) {
 			throw new ShaderLoadingException();
 		}
 
@@ -64,19 +64,19 @@ public class InstancingProgramMetaData {
 		Optional<ShaderStruct> maybeVertex = file.findStruct(vertexName);
 		Optional<ShaderStruct> maybeInstance = file.findStruct(instanceName);
 
-		if (!maybeVertex.isPresent()) {
+		if (maybeVertex.isEmpty()) {
 			ErrorReporter.generateMissingStruct(file, vertexName, "struct not defined");
 		}
 
-		if (!maybeInterpolant.isPresent()) {
+		if (maybeInterpolant.isEmpty()) {
 			ErrorReporter.generateMissingStruct(file, interpolantName, "struct not defined");
 		}
 
-		if (!maybeInstance.isPresent()) {
+		if (maybeInstance.isEmpty()) {
 			ErrorReporter.generateMissingStruct(file, instanceName, "struct not defined");
 		}
 
-		if (!maybeVertex.isPresent() || !maybeInterpolant.isPresent() || !maybeInstance.isPresent()) {
+		if (maybeVertex.isEmpty() || maybeInterpolant.isEmpty() || maybeInstance.isEmpty()) {
 			throw new ShaderLoadingException();
 		}
 

src/main/java/com/jozufozu/flywheel/backend/pipeline/InstancingTemplate.java

@@ -37,9 +37,9 @@ public class InstancingTemplate extends Template<InstancingProgramMetaData> {
 	public void vertexFooter(StringBuilder template, SourceFile file) {
 		InstancingProgramMetaData data = getMetadata(file);
 
-		Template.prefixFields(template, data.vertex, "attribute", "a_v_");
+		Template.prefixFields(template, data.vertex, "in", "a_v_");
-		Template.prefixFields(template, data.instance, "attribute", "a_i_");
+		Template.prefixFields(template, data.instance, "in", "a_i_");
-		Template.prefixFields(template, data.interpolant, "varying", "v2f_");
+		Template.prefixFields(template, data.interpolant, "out", "v2f_");
 
 		template.append("void main() {\n");
 		template.append(data.vertexName)
@@ -63,7 +63,7 @@ public class InstancingTemplate extends Template<InstancingProgramMetaData> {
 	public void fragmentFooter(StringBuilder template, SourceFile file) {
 		InstancingProgramMetaData data = getMetadata(file);
 
-		Template.prefixFields(template, data.interpolant, "varying", "v2f_");
+		Template.prefixFields(template, data.interpolant, "in", "v2f_");
 
 		template.append("void main() {\n");
 		template.append(data.interpolantName)

src/main/java/com/jozufozu/flywheel/backend/pipeline/OneShotProgramMetaData.java

@@ -26,15 +26,15 @@ public class OneShotProgramMetaData {
 		Optional<ShaderFunction> maybeVertexMain = file.findFunction("vertex");
 		Optional<ShaderFunction> maybeFragmentMain = file.findFunction("fragment");
 
-		if (!maybeVertexMain.isPresent()) {
+		if (maybeVertexMain.isEmpty()) {
 			ErrorReporter.generateFileError(file, "could not find \"vertex\" function");
 		}
 
-		if (!maybeFragmentMain.isPresent()) {
+		if (maybeFragmentMain.isEmpty()) {
 			ErrorReporter.generateMissingFunction(file, "fragment", "\"fragment\" function not defined");
 		}
 
-		if (!maybeVertexMain.isPresent() || !maybeFragmentMain.isPresent()) {
+		if (maybeVertexMain.isEmpty() || maybeFragmentMain.isEmpty()) {
 			throw new RuntimeException();
 		}
 
@@ -62,13 +62,13 @@ public class OneShotProgramMetaData {
 		Optional<ShaderStruct> maybeInterpolant = file.findStruct(interpolantName);
 		Optional<ShaderStruct> maybeVertex = file.findStruct(vertexName);
 
-		if (!maybeVertex.isPresent())
+		if (maybeVertex.isEmpty())
 			ErrorReporter.generateMissingStruct(file, vertexName, "struct not defined");
 
-		if (!maybeInterpolant.isPresent())
+		if (maybeInterpolant.isEmpty())
 			ErrorReporter.generateMissingStruct(file, interpolantName, "struct not defined");
 
-		if (!maybeVertex.isPresent() || !maybeInterpolant.isPresent()) {
+		if (maybeVertex.isEmpty() || maybeInterpolant.isEmpty()) {
 			throw new RuntimeException();
 		}
 

src/main/java/com/jozufozu/flywheel/backend/pipeline/OneShotTemplate.java

@@ -32,8 +32,8 @@ public class OneShotTemplate extends Template<OneShotProgramMetaData> {
 	public void vertexFooter(StringBuilder template, SourceFile file) {
 		OneShotProgramMetaData data = getMetadata(file);
 
-		Template.prefixFields(template, data.vertex, "attribute", "a_v_");
+		Template.prefixFields(template, data.vertex, "in", "a_v_");
-		Template.prefixFields(template, data.interpolant, "varying", "v2f_");
+		Template.prefixFields(template, data.interpolant, "out", "v2f_");
 
 		template.append("void main() {\n");
 		template.append(data.vertexName)
@@ -53,7 +53,7 @@ public class OneShotTemplate extends Template<OneShotProgramMetaData> {
 	public void fragmentFooter(StringBuilder template, SourceFile file) {
 		OneShotProgramMetaData data = getMetadata(file);
 
-		Template.prefixFields(template, data.interpolant, "varying", "v2f_");
+		Template.prefixFields(template, data.interpolant, "in", "v2f_");
 
 		template.append("void main() {\n");
 		template.append(data.interpolant.name)

src/main/java/com/jozufozu/flywheel/backend/pipeline/Template.java

@@ -25,10 +25,10 @@ public abstract class Template<D> {
 
 	private final Map<SourceFile, D> metadata = new HashMap<>();
 
-	private final Function<SourceFile, D> parser;
+	private final Function<SourceFile, D> reader;
 
-	protected Template(Function<SourceFile, D> parser) {
+	protected Template(Function<SourceFile, D> reader) {
-		this.parser = parser;
+		this.reader = reader;
 	}
 
 	/**
@@ -46,11 +46,12 @@ public abstract class Template<D> {
 	public abstract Collection<ShaderInput> getShaderInputs(SourceFile file);
 
 	public D getMetadata(SourceFile file) {
-		return metadata.computeIfAbsent(file, parser);
+		// lazily read files, cache results
+		return metadata.computeIfAbsent(file, reader);
 	}
 
 	public GLSLVersion getVersion() {
-		return GLSLVersion.V120;
+		return GLSLVersion.V150;
 	}
 
 	public static void prefixFields(StringBuilder builder, ShaderStruct struct, String qualifier, String prefix) {

src/main/java/com/jozufozu/flywheel/backend/pipeline/WorldShader.java

@@ -57,7 +57,7 @@ public class WorldShader {
 				.append(template.getVersion())
 				.append('\n')
 				.append("#define ")
-				.append(type.define)
+				.append(type.define) // special case shader type declaration
 				.append('\n')
 				.append(defines != null ? defines : "")
 				.append(header)

src/main/java/com/jozufozu/flywheel/backend/source/FileResolution.java

@@ -67,11 +67,10 @@ public class FileResolution {
 		try {
 			file = sources.findSource(fileLoc);
 		} catch (RuntimeException error) {
-			ErrorBuilder builder = new ErrorBuilder();
+			ErrorBuilder builder = ErrorBuilder.error(String.format("could not find source for file %s", fileLoc));
-			builder.error(String.format("could not find source for file %s", fileLoc));
 			// print the location of all places where this file was referenced
 			for (Span span : foundSpans) {
-				builder.in(span.getSourceFile())
+				builder.pointAtFile(span.getSourceFile())
 						.pointAt(span, 2);
 			}
 			Backend.log.error(builder.build());

src/main/java/com/jozufozu/flywheel/backend/source/Index.java

@@ -27,8 +27,8 @@ public class Index {
 		Collection<SourceFile> files = sources.values();
 
 		for (SourceFile file : files) {
-			file.getStructs().forEach(knownStructs::put);
+            file.structs.forEach(knownStructs::put);
-			file.getFunctions().forEach(knownFunctions::put);
+			file.functions.forEach(knownFunctions::put);
 		}
 	}
 

src/main/java/com/jozufozu/flywheel/backend/source/SourceFile.java

@@ -13,80 +13,65 @@ import com.google.common.collect.ImmutableMap;
 import com.jozufozu.flywheel.backend.source.parse.Import;
 import com.jozufozu.flywheel.backend.source.parse.ShaderFunction;
 import com.jozufozu.flywheel.backend.source.parse.ShaderStruct;
-import com.jozufozu.flywheel.backend.source.span.CharPos;
 import com.jozufozu.flywheel.backend.source.span.ErrorSpan;
 import com.jozufozu.flywheel.backend.source.span.Span;
 import com.jozufozu.flywheel.backend.source.span.StringSpan;
-import com.jozufozu.flywheel.util.StringUtil;
 
-import it.unimi.dsi.fastutil.ints.IntArrayList;
-import it.unimi.dsi.fastutil.ints.IntList;
 import net.minecraft.resources.ResourceLocation;
 
+/**
+ * Immutable class representing a shader file.
+ *
+ * <p>
+ *     This class parses shader files and generates what is effectively a high level AST of the source.
+ * </p>
+ */
 public class SourceFile {
 	private static final Pattern includePattern = Pattern.compile("#use \"(.*)\"");
 
-	private static final Pattern newLine = Pattern.compile("(\\r\\n|\\r|\\n)");
-
 	// https://regexr.com/60n3d
 	public static final Pattern functionDeclaration = Pattern.compile("(\\w+)\\s+(\\w+)\\s*\\(([\\w,\\s]*)\\)\\s*\\{");
 
 	public final ResourceLocation name;
 
 	public final ShaderSources parent;
-	private final String source;
+	public final String source;
-	private final CharSequence elided;
+	/**
-	private final ImmutableList<String> lines;
+	 * Sections of the source that must be trimmed for compilation. Currently, it only contains the spans of imports.
+	 */
+	public final String elided;
 
-	private final IntList lineStarts;
+	public final SourceLines lines;
 
-	// Function name -> Function object
+	/**
-	private final ImmutableMap<String, ShaderFunction> functions;
+	 * Function lookup by name.
-	private final ImmutableMap<String, ShaderStruct> structs;
+	 */
+	public final ImmutableMap<String, ShaderFunction> functions;
 
-	// Includes ordered as defined in the source
+	/**
-	private final ImmutableList<Import> imports;
+	 * Struct lookup by name.
+	 */
+	public final ImmutableMap<String, ShaderStruct> structs;
 
-	// Sections of the source that must be trimmed for compilation.
+	/**
-	private final List<Span> elisions = new ArrayList<>();
+	 * Includes ordered as defined in the source.
+	 */
+	public final ImmutableList<Import> imports;
 
 	public SourceFile(ShaderSources parent, ResourceLocation name, String source) {
 		this.parent = parent;
 		this.name = name;
 		this.source = source;
 
-		this.lineStarts = createLineStarts();
+		this.lines = new SourceLines(source);
-		this.lines = createLineList(lineStarts);
 
-		this.imports = parseImports();
+		List<Span> elisions = new ArrayList<>();
+
+		this.imports = parseImports(elisions);
 		this.functions = parseFunctions();
 		this.structs = parseStructs();
 
-		this.elided = createElidedSource();
+		this.elided = elideSource(source, elisions).toString();
-	}
-
-	public String getSource() {
-		return source;
-	}
-
-	public CharSequence getElidedSource() {
-		return elided;
-	}
-
-	public ShaderSources getParent() {
-		return parent;
-	}
-
-	public ImmutableMap<String, ShaderFunction> getFunctions() {
-		return functions;
-	}
-
-	public ImmutableMap<String, ShaderStruct> getStructs() {
-		return structs;
-	}
-
-	public ImmutableList<Import> getIncludes() {
-		return imports;
 	}
 
 	/**
@@ -96,11 +81,11 @@ public class SourceFile {
 	 * @return null if no definition matches the name.
 	 */
 	public Optional<ShaderStruct> findStruct(CharSequence name) {
-		ShaderStruct struct = getStructs().get(name.toString());
+		ShaderStruct struct = structs.get(name.toString());
 
 		if (struct != null) return Optional.of(struct);
 
-		for (Import include : getIncludes()) {
+		for (Import include : imports) {
 			Optional<ShaderStruct> externalStruct = include.getOptional()
 					.flatMap(file -> file.findStruct(name));
 
@@ -117,11 +102,11 @@ public class SourceFile {
 	 * @return Optional#empty() if no definition matches the name.
 	 */
 	public Optional<ShaderFunction> findFunction(CharSequence name) {
-		ShaderFunction local = getFunctions().get(name.toString());
+		ShaderFunction local = functions.get(name.toString());
 
 		if (local != null) return Optional.of(local);
 
-		for (Import include : getIncludes()) {
+		for (Import include : imports) {
 			Optional<ShaderFunction> external = include.getOptional()
 					.flatMap(file -> file.findFunction(name));
 
@@ -142,29 +127,12 @@ public class SourceFile {
 	}
 
 	public void generateFinalSource(StringBuilder source) {
-		for (Import include : getIncludes()) {
+		for (Import include : imports) {
 			SourceFile file = include.getFile();
 
 			if (file != null) file.generateFinalSource(source);
 		}
-		source.append(getElidedSource());
+		source.append(elided);
-	}
-
-	public CharPos getCharPos(int charPos) {
-		int lineNo = 0;
-		for (; lineNo < lineStarts.size(); lineNo++) {
-			int ls = lineStarts.getInt(lineNo);
-
-			if (charPos < ls) {
-				break;
-			}
-		}
-
-		lineNo -= 1;
-
-		int lineStart = lineStarts.getInt(lineNo);
-
-		return new CharPos(charPos, lineNo, charPos - lineStart);
 	}
 
 	public String printSource() {
@@ -172,18 +140,13 @@ public class SourceFile {
 
 		builder.append("Source for shader '")
 				.append(name)
-				.append("':\n");
+				.append("':\n")
-		int i = 1;
+				.append(lines.printLinesWithNumbers());
-		for (String s : lines) {
-			builder.append(String.format("%1$4s: ", i++))
-					.append(s)
-					.append('\n');
-		}
 
 		return builder.toString();
 	}
 
-	private CharSequence createElidedSource() {
+	private static CharSequence elideSource(String source, List<Span> elisions) {
 		StringBuilder out = new StringBuilder();
 
 		int lastEnd = 0;
@@ -199,34 +162,6 @@ public class SourceFile {
 		return out;
 	}
 
-	/**
-	 * Scan the source for line breaks, recording the position of the first character of each line.
-	 */
-	private IntList createLineStarts() {
-		IntList l = new IntArrayList();
-		l.add(0); // first line is always at position 0
-
-		Matcher matcher = newLine.matcher(source);
-
-		while (matcher.find()) {
-			l.add(matcher.end());
-		}
-		return l;
-	}
-
-	private ImmutableList<String> createLineList(IntList lines) {
-		ImmutableList.Builder<String> builder = ImmutableList.builder();
-
-		for (int i = 1; i < lines.size(); i++) {
-			int start = lines.getInt(i - 1);
-			int end = lines.getInt(i);
-
-			builder.add(StringUtil.trimEnd(source.substring(start, end)));
-		}
-
-		return builder.build();
-	}
-
 	/**
 	 * Scan the source for function definitions and "parse" them into objects that contain properties of the function.
 	 */
@@ -284,8 +219,9 @@ public class SourceFile {
 	/**
 	 * Scan the source for <code>#use "..."</code> directives.
 	 * Records the contents of the directive into an {@link Import} object, and marks the directive for elision.
+	 * @param elisions
 	 */
-	private ImmutableList<Import> parseImports() {
+	private ImmutableList<Import> parseImports(List<Span> elisions) {
 		Matcher uses = includePattern.matcher(source);
 
 		List<Import> imports = new ArrayList<>();
@@ -321,11 +257,4 @@ public class SourceFile {
 		return -1;
 	}
 
-	public int getLineCount() {
-		return lines.size();
-	}
-
-	public CharSequence getLine(int lineNo) {
-		return lines.get(lineNo);
-	}
 }

src/main/java/com/jozufozu/flywheel/backend/source/SourceLines.java

@@ -0,0 +1,97 @@
+package com.jozufozu.flywheel.backend.source;
+
+import java.util.regex.Matcher;
+import java.util.regex.Pattern;
+
+import com.google.common.collect.ImmutableList;
+import com.jozufozu.flywheel.backend.source.span.CharPos;
+import com.jozufozu.flywheel.util.StringUtil;
+
+import it.unimi.dsi.fastutil.ints.IntArrayList;
+import it.unimi.dsi.fastutil.ints.IntList;
+
+public class SourceLines {
+
+	private static final Pattern newLine = Pattern.compile("(\\r\\n|\\r|\\n)");
+
+	/**
+	 * 0-indexed line to char pos mapping.
+	 */
+	private final IntList lineStarts;
+
+	/**
+	 * 0-indexed line lookup
+	 */
+	private final ImmutableList<String> lines;
+
+	public SourceLines(String source) {
+		this.lineStarts = createLineLookup(source);
+		this.lines = getLines(source, lineStarts);
+	}
+
+	/**
+	 * Scan the source for line breaks, recording the position of the first character of each line.
+	 * @param source
+	 */
+	private static IntList createLineLookup(String source) {
+		IntList l = new IntArrayList();
+		l.add(0); // first line is always at position 0
+
+		Matcher matcher = newLine.matcher(source);
+
+		while (matcher.find()) {
+			l.add(matcher.end());
+		}
+		return l;
+	}
+
+	private static ImmutableList<String> getLines(String source, IntList lines) {
+		ImmutableList.Builder<String> builder = ImmutableList.builder();
+
+		for (int i = 1; i < lines.size(); i++) {
+			int start = lines.getInt(i - 1);
+			int end = lines.getInt(i);
+
+			builder.add(StringUtil.trimEnd(source.substring(start, end)));
+		}
+
+		return builder.build();
+	}
+
+	public CharPos getCharPos(int charPos) {
+		int lineNo = 0;
+		for (; lineNo < lineStarts.size(); lineNo++) {
+			int ls = lineStarts.getInt(lineNo);
+
+			if (charPos < ls) {
+				break;
+			}
+		}
+
+		lineNo -= 1;
+
+		int lineStart = lineStarts.getInt(lineNo);
+
+		return new CharPos(charPos, lineNo, charPos - lineStart);
+	}
+
+	public int getLineCount() {
+		return lines.size();
+	}
+
+	public String getLine(int lineNo) {
+		return lines.get(lineNo);
+	}
+
+	public String printLinesWithNumbers() {
+		StringBuilder builder = new StringBuilder();
+
+		for (int i = 0, linesSize = lines.size(); i < linesSize; i++) {
+			builder.append(String.format("%1$4s: ", i + 1))
+					.append(lines.get(i))
+					.append('\n');
+		}
+
+		return builder.toString();
+	}
+}

src/main/java/com/jozufozu/flywheel/backend/source/error/ErrorBuilder.java

@@ -1,95 +1,79 @@
 package com.jozufozu.flywheel.backend.source.error;
 
+import java.util.ArrayList;
+import java.util.List;
+
 import javax.annotation.Nullable;
 
 import com.jozufozu.flywheel.backend.source.SourceFile;
+import com.jozufozu.flywheel.backend.source.SourceLines;
+import com.jozufozu.flywheel.backend.source.error.lines.ErrorLine;
+import com.jozufozu.flywheel.backend.source.error.lines.FileLine;
+import com.jozufozu.flywheel.backend.source.error.lines.HeaderLine;
+import com.jozufozu.flywheel.backend.source.error.lines.SourceLine;
+import com.jozufozu.flywheel.backend.source.error.lines.SpanHighlightLine;
 import com.jozufozu.flywheel.backend.source.span.Span;
 import com.jozufozu.flywheel.util.FlwUtil;
 
 public class ErrorBuilder {
 
-	private final StringBuilder internal = new StringBuilder();
+	private final List<ErrorLine> lines = new ArrayList<>();
 
-	public ErrorBuilder error(CharSequence msg) {
+	private final Level level;
-		internal.append("error: ")
+
-				.append(msg);
+	public ErrorBuilder(Level level, CharSequence msg) {
-		return endLine();
+		this.level = level;
+
+		lines.add(new HeaderLine(level.toString(), msg));
 	}
 
-	public ErrorBuilder note(CharSequence msg) {
+	public static ErrorBuilder error(CharSequence msg) {
-		internal.append("note: ")
+		return new ErrorBuilder(Level.ERROR, msg);
-				.append(msg);
-		return endLine();
 	}
 
-	public ErrorBuilder hint(CharSequence msg) {
+	public static ErrorBuilder warn(CharSequence msg) {
-		internal.append("hint: ")
+		return new ErrorBuilder(Level.WARN, msg);
-				.append(msg);
-		return endLine();
 	}
 
-	public ErrorBuilder in(SourceFile file) {
+	public ErrorBuilder pointAtFile(SourceFile file) {
-		internal.append("--> ")
+		lines.add(new FileLine(file.name.toString()));
-				.append(file.name);
-		return endLine();
-	}
-
-	public ErrorBuilder numberedLine(int no, CharSequence content) {
-		return line(String.valueOf(no), content);
-	}
-
-	public ErrorBuilder numberedLine(int no, int width, CharSequence content) {
-		String fmt = "%1$" + width + 's';
-		return line(String.format(fmt, no), content);
-	}
-
-	public ErrorBuilder line(CharSequence leftColumn, CharSequence rightColumn) {
-
-		internal.append(leftColumn)
-				.append(" | ")
-				.append(rightColumn);
-
-		return endLine();
-	}
-
-	public ErrorBuilder endLine() {
-		internal.append('\n');
 		return this;
 	}
 
 	public ErrorBuilder hintIncludeFor(@Nullable Span span, CharSequence msg) {
 		if (span == null) return this;
 
-		hint("add " + span.getSourceFile().importStatement() + " " + msg)
+		String builder = "add " + span.getSourceFile()
-				.in(span.getSourceFile())
+				.importStatement() + ' ' + msg;
-				.pointAt(span, 1);
 
-		return this;
+		lines.add(new HeaderLine("hint", builder));
+
+		return this.pointAtFile(span.getSourceFile())
+				.pointAt(span, 1);
 	}
 
 	public ErrorBuilder pointAt(Span span, int ctxLines) {
 
-		SourceFile file = span.getSourceFile();
-
 		if (span.lines() == 1) {
+			SourceLines lines = span.getSourceFile().lines;
 
 			int spanLine = span.firstLine();
 
 			int firstLine = Math.max(0, spanLine - ctxLines);
-			int lastLine = Math.min(file.getLineCount(), spanLine + ctxLines);
+			int lastLine = Math.min(lines.getLineCount(), spanLine + ctxLines);
 
-			int digits = FlwUtil.numDigits(lastLine);
+            int firstCol = span.getStart()
-
+                    .col();
-			int firstCol = span.getStart().getCol();
+            int lastCol = span.getEnd()
-			int lastCol = span.getEnd().getCol();
+                    .col();
 
 			for (int i = firstLine; i <= lastLine; i++) {
-				CharSequence line = file.getLine(i);
+				CharSequence line = lines.getLine(i);
 
-				numberedLine(i + 1, digits, line);
+				this.lines.add(SourceLine.numbered(i + 1, line.toString()));
 
 				if (i == spanLine) {
-					line(FlwUtil.repeatChar(' ', digits), generateUnderline(firstCol, lastCol));
+					this.lines.add(new SpanHighlightLine(firstCol, lastCol));
 				}
 			}
 		}
@@ -98,19 +82,23 @@ public class ErrorBuilder {
 	}
 
 	public CharSequence build() {
-		return internal;
+
+		int maxLength = -1;
+		for (ErrorLine line : lines) {
+			int length = line.neededMargin();
+
+			if (length > maxLength) maxLength = length;
 		}
 
-	public CharSequence generateUnderline(int firstCol, int lastCol) {
+		StringBuilder builder = new StringBuilder();
-		StringBuilder line = new StringBuilder(lastCol);
+		for (ErrorLine line : lines) {
-		for (int i = 0; i < firstCol; i++) {
+			int length = line.neededMargin();
-			line.append(' ');
+
+			builder.append(FlwUtil.repeatChar(' ', maxLength - length))
+					.append(line.build())
+					.append('\n');
 		}
 
-		for (int i = firstCol; i < lastCol; i++) {
+		return builder;
-			line.append('^');
-		}
-
-		return line;
 	}
 }

src/main/java/com/jozufozu/flywheel/backend/source/error/ErrorReporter.java

@@ -13,10 +13,8 @@ public class ErrorReporter {
 	public static void generateSpanError(Span span, String message) {
 		SourceFile file = span.getSourceFile();
 
-		ErrorBuilder builder = new ErrorBuilder();
+		CharSequence error = ErrorBuilder.error(message)
-
+				.pointAtFile(file)
-		CharSequence error = builder.error(message)
-				.in(file)
 				.pointAt(span, 2)
 				.build();
 
@@ -25,10 +23,8 @@ public class ErrorReporter {
 
 	public static void generateFileError(SourceFile file, String message) {
 
-		ErrorBuilder builder = new ErrorBuilder();
+		CharSequence error = ErrorBuilder.error(message)
-
+				.pointAtFile(file)
-		CharSequence error = builder.error(message)
-				.in(file)
 				.build();
 
 		Backend.log.error(error);
@@ -43,10 +39,9 @@ public class ErrorReporter {
 				.stream()
 				.findFirst()
 				.map(ShaderStruct::getName);
-		ErrorBuilder builder = new ErrorBuilder();
 
-		ErrorBuilder error = builder.error(msg)
+		ErrorBuilder error = ErrorBuilder.error(msg)
-				.in(file)
+				.pointAtFile(file)
 				.pointAt(vertexName, 2)
 				.hintIncludeFor(span.orElse(null), hint);
 
@@ -62,10 +57,9 @@ public class ErrorReporter {
 				.stream()
 				.findFirst()
 				.map(ShaderFunction::getName);
-		ErrorBuilder builder = new ErrorBuilder();
 
-		ErrorBuilder error = builder.error(msg)
+		ErrorBuilder error = ErrorBuilder.error(msg)
-				.in(file)
+				.pointAtFile(file)
 				.hintIncludeFor(span.orElse(null), hint);
 
 		Backend.log.error(error.build());

src/main/java/com/jozufozu/flywheel/backend/source/error/Level.java

@@ -0,0 +1,18 @@
+package com.jozufozu.flywheel.backend.source.error;
+
+public enum Level {
+	WARN("warn"),
+	ERROR("error"),
+	;
+
+	private final String error;
+
+	Level(String error) {
+		this.error = error;
+	}
+
+	@Override
+	public String toString() {
+		return error;
+	}
+}

src/main/java/com/jozufozu/flywheel/backend/source/error/lines/Divider.java

@@ -0,0 +1,18 @@
+package com.jozufozu.flywheel.backend.source.error.lines;
+
+public enum Divider {
+	BAR(" | "),
+	ARROW("-->"),
+	;
+
+	private final String s;
+
+	Divider(String s) {
+		this.s = s;
+	}
+
+	@Override
+	public String toString() {
+		return s;
+	}
+}

src/main/java/com/jozufozu/flywheel/backend/source/error/lines/ErrorLine.java

@@ -0,0 +1,19 @@
+package com.jozufozu.flywheel.backend.source.error.lines;
+
+public interface ErrorLine {
+
+	default int neededMargin() {
+		return left().length();
+	}
+
+	default Divider divider() {
+		return Divider.BAR;
+	}
+
+	default String build() {
+		return left() + divider() + right();
+	}
+
+	String left();
+	String right();
+}

src/main/java/com/jozufozu/flywheel/backend/source/error/lines/FileLine.java

@@ -0,0 +1,19 @@
+package com.jozufozu.flywheel.backend.source.error.lines;
+
+public record FileLine(String fileName) implements ErrorLine {
+
+	@Override
+	public String left() {
+		return "--";
+	}
+
+	@Override
+	public Divider divider() {
+		return Divider.ARROW;
+	}
+
+	@Override
+	public String right() {
+		return fileName;
+	}
+}

src/main/java/com/jozufozu/flywheel/backend/source/error/lines/HeaderLine.java

@@ -0,0 +1,26 @@
+package com.jozufozu.flywheel.backend.source.error.lines;
+
+import com.jozufozu.flywheel.backend.source.error.Level;
+
+public record HeaderLine(String level, CharSequence message) implements ErrorLine {
+
+	@Override
+	public int neededMargin() {
+		return 0;
+	}
+
+	@Override
+	public String build() {
+		return level + ": " + message;
+	}
+
+	@Override
+	public String left() {
+		return null;
+	}
+
+	@Override
+	public String right() {
+		return null;
+	}
+}

src/main/java/com/jozufozu/flywheel/backend/source/error/lines/SourceLine.java

@@ -0,0 +1,18 @@
+package com.jozufozu.flywheel.backend.source.error.lines;
+
+public record SourceLine(String number, String line) implements ErrorLine {
+
+	public static SourceLine numbered(int number, String line) {
+		return new SourceLine(Integer.toString(number), line);
+	}
+
+	@Override
+	public String left() {
+		return number;
+	}
+
+	@Override
+	public String right() {
+		return line;
+	}
+}

src/main/java/com/jozufozu/flywheel/backend/source/error/lines/SpanHighlightLine.java

@@ -0,0 +1,23 @@
+package com.jozufozu.flywheel.backend.source.error.lines;
+
+public class SpanHighlightLine implements ErrorLine {
+	private final String line;
+
+	public SpanHighlightLine(int firstCol, int lastCol) {
+		line = generateUnderline(firstCol, lastCol);
+	}
+
+	@Override
+	public String left() {
+		return "";
+	}
+
+	@Override
+	public String right() {
+		return line;
+	}
+
+	public static String generateUnderline(int firstCol, int lastCol) {
+		return " ".repeat(Math.max(0, firstCol)) + "^".repeat(Math.max(0, lastCol - firstCol));
+	}
+}

src/main/java/com/jozufozu/flywheel/backend/source/span/CharPos.java

@@ -3,27 +3,5 @@ package com.jozufozu.flywheel.backend.source.span;
 /**
  * A position in a file.
  */
-public class CharPos {
+public record CharPos(int pos, int line, int col) {
-
-	private final int idx;
-	private final int line;
-	private final int col;
-
-	public CharPos(int idx, int line, int col) {
-		this.idx = idx;
-		this.line = line;
-		this.col = col;
-	}
-
-	public int getPos() {
-		return idx;
-	}
-
-	public int getLine() {
-		return line;
-	}
-
-	public int getCol() {
-		return col;
-	}
 }

src/main/java/com/jozufozu/flywheel/backend/source/span/Span.java

@@ -5,7 +5,11 @@ import java.util.regex.Matcher;
 import com.jozufozu.flywheel.backend.source.SourceFile;
 
 /**
- * A span of code in a {@link SourceFile}.
+ * A segment of code in a {@link SourceFile}.
+ *
+ * <p>
+ *     Spans are used for pretty-printing errors.
+ * </p>
  */
 public abstract class Span implements CharSequence {
 
@@ -14,7 +18,7 @@ public abstract class Span implements CharSequence {
 	protected final CharPos end;
 
 	public Span(SourceFile in, int start, int end) {
-		this(in, in.getCharPos(start), in.getCharPos(end));
+		this(in, in.lines.getCharPos(start), in.lines.getCharPos(end));
 	}
 
 	public Span(SourceFile in, CharPos start, CharPos end) {
@@ -42,14 +46,14 @@ public abstract class Span implements CharSequence {
 	 * @return the string index at the (inclusive) beginning of this code segment.
 	 */
 	public int getStartPos() {
-		return start.getPos();
+		return start.pos();
 	}
 
 	/**
 	 * @return the string index at the (exclusive) end of this code segment.
 	 */
 	public int getEndPos() {
-		return end.getPos();
+		return end.pos();
 	}
 
 	/**
@@ -63,11 +67,11 @@ public abstract class Span implements CharSequence {
 	 * @return how many lines this span spans.
 	 */
 	public int lines() {
-		return end.getLine() - start.getLine() + 1;
+		return end.line() - start.line() + 1;
 	}
 
 	public int firstLine() {
-		return start.getLine();
+		return start.line();
 	}
 
 	/**
@@ -89,7 +93,7 @@ public abstract class Span implements CharSequence {
 
 	@Override
 	public char charAt(int index) {
-		return in.getSource().charAt(start.getPos() + index);
+		return in.source.charAt(start.pos() + index);
 	}
 
 	@Override

src/main/java/com/jozufozu/flywheel/backend/source/span/StringSpan.java

@@ -14,13 +14,13 @@ public class StringSpan extends Span {
 
 	@Override
 	public Span subSpan(int from, int to) {
-		return new StringSpan(in, start.getPos() + from, start.getPos() + to);
+        return new StringSpan(in, start.pos() + from, start.pos() + to);
 	}
 
 	@Override
 	public String get() {
-		return in.getSource()
+		return in.source
-				.substring(start.getPos(), end.getPos());
+				.substring(start.pos(), end.pos());
 	}
 
 	@Override

src/main/resources/assets/flywheel/flywheel/shaders/context/crumbling.glsl

@@ -26,6 +26,8 @@ void FLWFinalizeWorldPos(inout vec4 worldPos) {
 
 #elif defined(FRAGMENT_SHADER)
 
+out vec4 fragColor;
+
 vec4 FLWBlockTexture(vec2 texCoords) {
     vec4 cr = texture2D(uCrumbling, texCoords * uTextureScale);
     float diffuseAlpha = texture2D(uBlockAtlas, texCoords).a;
@@ -42,7 +44,11 @@ void FLWFinalizeColor(vec4 color) {
     color.a = a;
     #endif
 
-    gl_FragColor = color;
+    if (color.a < 0.1) {
+        discard;
+    }
+
+    fragColor = color;
 }
 
 vec4 FLWLight(vec2 lightCoords) {

src/main/resources/assets/flywheel/flywheel/shaders/context/fog.glsl

@@ -1,4 +1,8 @@
-varying float FragDistance;
+#if defined(VERTEX_SHADER)
+out float FragDistance;
+#elif defined(FRAGMENT_SHADER)
+in float FragDistance;
+#endif
 uniform vec4 uFogColor;
 uniform vec2 uFogRange;
 

src/main/resources/assets/flywheel/flywheel/shaders/context/world.glsl

@@ -34,6 +34,8 @@ void FLWFinalizeWorldPos(inout vec4 worldPos) {
 //#endif
 //#endif
 
+out vec4 fragColor;
+
 vec4 FLWBlockTexture(vec2 texCoords) {
     return texture2D(uBlockAtlas, texCoords);
 }
@@ -53,7 +55,7 @@ void FLWFinalizeColor(vec4 color) {
     }
     #endif
 
-    gl_FragColor = color;
+    fragColor = color;
 }
 
 vec4 FLWLight(vec2 lightCoords) {